Symposium Organizers
Peter Kiesel Palo Alto Research Center
David Nolte Purdue University
Xudong (Sherman) Fan University of Michigan
Martin Zillmann Millipore Corporation
PP3: Poster Session: Bio Sensors
Session Chairs
Tuesday AM, November 30, 2010
Exhibition Hall D (Hynes)
1:00 AM - PP3: BioSensors
PP3.1 Transferred to PP8.9
Show Abstract1:00 AM - PP3: BioSensors
PP3.18 Transferred to PP6.4
Show Abstract1:00 AM - PP3: BioSensors
PP3.19 Transferred to PP11.44
Show AbstractPP1: Micro-Fluidics Sensors and Devices I
Session Chairs
Monday PM, November 29, 2010
Back Bay C (Sheraton)
9:30 AM - **PP1.1
Microfluidics for Measuring Mass: From a Single Virus to a Growing Cell.
Scott Manalis 1
1 Koch Institute for Integrative Cancer Research, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe are developing micro- and nanofluidic approaches based on fluid-filled mechanical resonators that enable physical parameters such as mass, volume and density to be measured from single particles with high precision. In this talk, I will describe how these approaches are being used to: i) determine the growth properties of individual cells and how growth is related to progression through the cell cycle, ii) differentiate cells by type, disease state, and response to stimulus, and iii) weigh individual virions.
10:00 AM - PP1.2
Quantitative Selection of DNA Aptamers through Microfluidic Selection and High Throughput Sequencing.
Minseon Cho 1 , Yi Xiao 1 , Jeff Nie 2 3 , Ron Stewart 2 3 , Andrew Csordas 1 , SeungSoo Oh 1 , James Thomson 2 3 , Tom Soh 1
1 , University of california at santa barbara, Santa barbara, California, United States, 2 , University of Wisconsin, Madison, Wisconsin, United States, 3 , Morgridge Institute for Research, Madison, Wisconsin, United States
Show AbstractSELEX is an in vitro method for generating single-stranded nucleic acids, known as aptamers, with high affinity and specificity for a wide range of targets. We recently described the use of microfluidics technology to accelerate the process of aptamer selection (M-SELEX); due to multiple advantages that occur at the micro-scale, specific aptamers that bind target proteins with nanomolar affinity can be generated by M-SELEX within 1–3 rounds. However, it is difficult to identify the optimal sequences from the pool using traditional cloning and sequencing approaches, which only enable sampling of a small portion of the sequence space. Furthermore, conventional approaches do not offer the capability to track the evolution of individual sequences across multiple rounds of selection, which would provide valuable information about the enrichment process. In this work, we have integrated the microfluidic selection with high-throughput DNA sequencing technology for rapid and efficient discovery of nucleic acid aptamers. The Quantitative Selection of Aptamers through Sequencing (QSAS) method tracks the copy number and enrichment-fold of more than 10 million individual sequences through multiple selection rounds, enabling the identification of high-affinity aptamers without the need for the pool to fully converge to a small number of sequences. Importantly, our method enables the quantitative measurement of enrichment-fold of an individual sequence as a function of selection rounds, thereby discriminating those sequences that arise from experimental biases rather than true target binding.We have identified aptamers that specifically bind to platelet derived growth factor BB (PDGF-BB) protein with Kd < 3 nM within 3 rounds. Furthermore, the aptamers identified by QSAS have ~3–8-fold higher affinity and ~2–4-fold higher specificity relative to those discovered through conventional cloning methods. Given that many biocombinatorial libraries are encoded with nucleic acids, we believe that our method may be generalized for the quantitative selection of other types of libraries, including tagged small molecules, phage display, cell surface display, as well as ribosome and mRNA displays, and we extrapolate that the method may ultimately be extended for the isolation of molecules with useful functions beyond binding, such as cooperative assembly, enzymatic activity and binding-induced folding.
10:15 AM - PP1.3
A Novel Microfluidic Device for On-chip Enrichment of Tumorigenic Breast Cancer Cells via Mammosphere Culture.
Katayoon Saadin 1 , Ian White 1
1 Bioengineering, University of Maryland, College Park, Maryland, United States
Show AbstractWe will present the development of a novel microfluidic device that can be utilized for the selective culture and enrichment of highly tumorigenic cells for the purpose of improving our understanding of cancer relapse and metastasis. Cancer continues to be a deadly condition, in part because of our inability to prevent relapse and metastasis. Unfortunately, today there is a lack of understanding of the molecular mechanisms of cancer, which is impeding the ability to save patients’ lives. New low-cost, automated, high-throughput tools are needed to speed the generation of knowledge to fight cancer. Micro total analysis systems (uTAS) offer tremendous potential because of the on-chip integration of complex functions, such as cell concentration and enrichment, cell culture, drug testing assays, and molecular analysis. One critical area of study is the relationship between tumorigenicity and cancer relapse and metastasis. Much evidence exists that suggests that within a tumor, only a small percentage of cancer cells contribute to the growth and the spread of the tumor {Al Hajj, PNAS 100, 3983}. It has also been demonstrated that these highly tumorigenic cells form suspended colonies in non-adherent cell culture {Grimshaw, Breast Cancer Research 10, R52}. In the case of breast cancer cells, these colonies are referred to as mammospheres. While this technique may be a key to gaining a better understanding of how metastatic tumors form, it is limited by the difficulty of manipulating these samples in a benchtop configuration. To enable the potential for automated sample handling, increased throughput, and the integration with molecular analysis, we have developed a microfluidic device that can be utilized for on-chip mammosphere culture of breast cancer cells.Our microfluidic mammosphere culture device is fabricated using soft lithography techniques in PDMS and glass. PDMS is selected because on-chip cell culture requires a gas permeable vessel. The device contains an array of cell culture microwells 0.3 mm high and 1 mm in diameter. A 20 micron poly(ethylene glycol) hydrogel layer is located at the bottom of the microwells to prevent the epithelial cancer cells from adhering, which prompts highly tumorigenic cells to form mammosphere colonies. A novel technique was developed to locate the hydrogel layer at the bottom of the wells while also enabling the adherence of the microstructured PDMS to the glass substrate. Microfluidic channels are aligned at the top of the wells for delivery and removal of media and reagents; because the cells are in the microwells, the non-adherent cell colonies are not disturbed by the flow velocity in the microchannel. This novel microfluidic cell culture design will enable us to use the mammosphere culture technique in a uTAS chip to enrich highly tumorigenic cells for further molecular analysis, which may lead to a better understanding of cancer relapse and metastasis.
10:30 AM - PP1.4
Miniature Sensors for Detection of Airborne Biological Particles.
An-Cheng Chang 1 , Mary Beth Tabacco 1
1 , Smiths Detection, Boston, Massachusetts, United States
Show AbstractMiniature, fluorescence-based sensors are under development for detection of airborne biological agents. The sensors are composed of micron-size, gel-like spots containing reactive fluorophores. The fluorophores exhibit a significant change in optical intensity in the presence of low concentrations of airborne biological agents such as virus, bacteria, bacterial spores and toxin. The sensors have been demonstrated using a portable multi-channel LED-based bioaerosol detection system developed by Smiths Detection. The airborne biological particles are collected on the sensor surface via impaction and the particles are easily eluted from the surface for further confirmatory analysis either in the laboratory or using a portable PCR-based identifier. The sensors were initially developed for use by the military, but have also been demonstrated for monitoring airborne infectious biological particles in buildings and transportation venues.
10:45 AM - PP1.5
Investigating Cell Separation Potential – Study of Edge Tracking Behavior of Rolling HL60 Cells on μm-scale Asymmetric P-selectin Patterns.
Chia-Hua Lee 1 , Bose Suman 2 , Krystyn Van Vliet 1 , Jeffrey Karp 3 , Rohit Karnik 2
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering , MIT, Cambridge, Massachusetts, United States, 3 HST Center for Biomedical Engineering and Harvard Stem Cell Institute, Brigham and Women’s Hospital, Harvard Medical School, Cambridge, Massachusetts, United States
Show AbstractSeparation and isolation of cells from a heterogeneous population is important for diagnostic and therapeutic applications and for biomedical research. Lateral displacement of cells orthogonal to a flow stream can be realized via cell rolling on asymmetric receptor patterns, and presents a new opportunity for label-free separation and analysis of cells. Cell rolling is a physiological phenomenon involving transient receptor-ligand interactions that is involved in homing and extravasation of leukocytes, hematopoietic and mesenchymal stem and progenitor cells, and metastatic cancer cells. Characterization of cell rolling trajectories on engineered substrates with asymmetric patterns is important for design of substrates that will maximize cell separation potential. In the present work, we demonstrate control of cell rolling trajectories using μm-scale patterns of biomolecular receptors. Rolling experiments were performed by incorporating the patterned substrates in a commercial flow chamber. HL60 cells were employed as a widely used model to study leukocyte rolling. These cells express the P-selectin glycoprotein ligand-1 (PSGL-1), which binds reversibly to the receptor P-selectin and thus enables rolling along patterned P-selectin edges. We then quantified the edge tracking lengths, le, lateral displacement d and rolling velocities vp and ve (inside the patterns and along the edge, respectively) of HL60 cells along these patterned substrates at different edge inclination angle (α = 5°, 10°, 15° and 20°) and at different shear stress (τ = 0.5, 1, 1.5 and 2.0 dyn/cm2). Cells were clearly seen to roll inside the P-selectin regions, encounter an edge, and then track along the edge. The results show that increasing the edge inclination angle significantly decreased the edge tracking length, contrary to the insignificant effect of varied shear stress magnitude. Furthermore, the cumulative probability and the distribution of edge tracking length showed that detachment of rolling cells after tracking along the edge was consistent with a Poisson process of history-independent interactions. Based on these experimental distributions, we also simulated the rolling trajectories of HL60 cells in a simple device. Our work suggests that such asymmetric patterns enable quantification of cell rolling that are predictive of cell trajectories and critical to future device design.
11:00 AM - PP1: MicroFluid
BREAK
11:30 AM - **PP1.6
High Performance Materials Enabling Droplet Technologies.
Brian Hutchison 1
1 , RainDance Techologies, Inc., Lexington, Massachusetts, United States
Show AbstractCompartmentalization of various components used for research in chemistry and biology (e.g., reactants, cells, DNA, enzymes, and other biomolecules) into small discrete volumes enables very high throughput experimentation. A microfluidic device that manipulates immiscible fluids can produce picoliter-volume droplets at a rate of 10 million per hour. Each droplet is the functional equivalent of an individual test tube and can contain a single molecule, reaction, or cell. Droplet microfluidics technology can be used for high-speed workflows with minimized process-induced bias or error.The oil and surfactant materials employed to generate and stabilize individual droplets against coalescence and chemical interaction are critical elements required for this technology. Fluorocarbon oils offer uniquely appropriate chemistry for the continuous phase separating aqueous droplets. These oils are typically hydrophobic and lipophobic and they offer very low solubility for polar materials and biological reagents encapsulated within droplets. Oil-soluble surfactants are required to stabilize droplets against coalescence. Furthermore, the surfactants must be compatible with the biological or chemical processes occurring within a droplet, and the surfactants must not facilitate transport of materials between droplets.Overall, this contribution describes the interplay between materials and applications of droplet technology for advanced life sciences experiments. Specifically, this submission describes the ongoing development of amphiphilic block copolymers that are suitable for stabilization of 10-100-micron aqueous droplets in a fluorinated oil continuous phase, and which facilitate microfluidic manipulation of droplets and compatibility with a variety of biological and biochemical experiments and reactions. The synthesis, molecular characterization, and surfactant properties of a perfluoropolyether-polyethyleneglycol block copolymer have been explored. Furthermore, this submission demonstrates that the surfactant enables emulsions to meet a wide array of requirements for droplet microfluidics and specific applications. Emulsion is stabilized against coalescence during generation, reinjection, and manipulation in a microfluidic environment; for 6-12 months of storage; and also during thermal cycling (for PCR-based applications). Additionally, the oil and surfactant materials are compatible with a large variety of small molecules, DNA, proteins, cells, and beads or other dyes for fluorescent labeling, which are each important for different applications of droplet technologies in life sciences research.
12:00 PM - PP1.7
Heterogeneous Integration of Flexible Photonic Bandgap Structures with Xerogel-based Biochemical Sensors.
Huina Xu 1 , Ke Liu 1 , Kelly Yung 2 , Sung Jin Kim 1 , Frank Bright 2 , Alexander Cartwright 1
1 Department of Electrical Engineering, State University of New York at Buffalo, Amherst, New York, United States, 2 Department of Chemistry, State University of New York at Buffalo, Amherst, New York, United States
Show AbstractWe report the heterogeneous integration of a multi-functional sensor based on Polymeric Porous Photonic Bandgap (P3BG) Structures and Xerogel based luminescence sensors. The prototype xerogel based luminescence sensor element consisted of an O2-sensing material based on spin coated or pin printed tetraethylorthosilane (TEOS) composite xerogel films containing a tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) ([Ru(dpp)3]2+) luminophore was synthesized and experimentally studied. A porous polymer photonic bandgap structure was fabricated using holographic interferometry. Initially, holographic interferometry of photo-activated prepolymer syrup that included a volatile solvent as well as monomers, photoinitiators, and co-initiators was used to initiate photopolymerization. Subsequent UV curing resulted in well defined lamellae of the polymer separated by porous polymer regions that create a high quality photonic bandgap structure. The resulting porous polymer P3BG structure was then integrated with the xerogel based luminescence sensor elements to provide a fluorescent sensor element with a selective narrow band reflector to enhance the sensor sensitivity. We demonstrated enhancement of the signal-to-noise ratio of this integrated multifunctional sensor using several approaches. First, the additional TEOS in the P3BG structure provides better mechanical properties that enable the fabrication of crack-free and robust structures with an optically uniform surface that maintains excellent optical properties. Second, we developed a pre-polymer recipe incorporating a photoinitiator with absorption bands (580-600 nm) and emission bands (630-650 nm) well removed from the luminophore excitation (400 nm) and emission wavelength (620 nm) and that allowed quick-bleaching during the fabrication process, to minimize extraneous emission that can mask the desired optical fluorescence signal from the luminophore. Finally, we showed that the resulting photonic bandgap / xerogel sensor can be further patterned for multi-analyte sensing on a flexible plastic substrate. We believe that those advantages and enhancement of the integrated multifunctional sensor will enable highly sensitive and cost-effective sensor systems for biomedical applications.
12:15 PM - PP1.8
Lab-on-chip Immunoassay System with Integrated Microfluidics and Optical Detection Using Amorphous Silicon Photodiodes.
Ana Teresa Pereira 1 2 , Pedro Novo 1 , Virginia Chu 1 , Duarte Miguel Prazeres 2 3 , Joao Conde 1 3
1 , INESC MN, Lisbon Portugal, 2 , IBB-Institute for Biotechnology and Bioengineering, Lisbon Portugal, 3 Department of Chemical and Biological Engineering, Instituto Superior Técnico, Lisbon Portugal
Show AbstractMiniaturization of immunoassays to the microfluidic format has the potential to decrease the time and the quantity of reactants required, together with the potential of achieving multiplexing and portability. One of the most commonly used methods for the detection of DNA, proteins and cells in biological analysis is fluorescence. This method uses an external light source to excite the fluorophores that label the entities of interest. The integration of a fluorescence sensor with microfluidics would allow fast and real time detection of the biological recognition event, with potential increase in sensitivity and portability, and reduced costs.In this work, a lab-on-chip system incorporating a thin-film amorphous silicon photodiode microfabricated on a glass substrate integrated with a PDMS-based microfluidic network is developed for the detection of antibody-antigen recognition reactions using fluorescence. The system includes an integrated fluorescence filter based an amorphous silicon carbide (a-SiC:H) thin-film deposited directly on top of the photodiode. The model immunoassay consists of primary antibody adsorption to the microchannel walls followed by its detection by a secondary antibody labeled with a fluorescent tag (quantum dots QDots 625). The signal measured with the a-Si:H photodiode for QDots 625 is consistent with that of the fluorescence microscope and shows a linear dependence on the target antibody concentration in the nanomolar-micromolar range. Prior work with a cuvette format required a total assay time of assay of approximately 15 h. In the microfluidic format the total assay time was reduced to 2 h 30 min and currently is ~40 minutes. The detailed design and performance of the developed system will be presented, and the potential for reduction of analysis time and the level sensitivity of the miniaturized immunoassays – currently in the nanomolar range - will be discussed.
12:30 PM - PP1.9
Self-assembled Magnetic Filter for Highly Efficient Immunomagnetic Separation.
David Issadore 1 , Huilin Shao 1 , Jaehoon Chung 1 , Andita Newton 1 , Mikael Pittet 1 , Ralph Weissleder 1 , Hakho Lee 1
1 Center for Systems Biology, Massachusetts General Hospital, Boston, Massachusetts, United States
Show AbstractWe have developed a compact and inexpensive microfluidic chip, the Self Assembled Magnetic (SAM) filter, to efficiently remove magnetically tagged cells from suspension. The SAM filter consists of a microfluidic channel built directly above a self-assembled NdFeB magnet. Micrometer-sized grains of NdFeB assemble to form alternating magnetic dipoles, creating a magnetic field with a very strong magnitude B (from the material) and field gradient grad(B) (from the configuration) in the microfluidic channel. The magnetic force imparted on magnetic beads is measured to be 100-fold stronger than that from conventional magnetic sorting systems, allowing for efficient separations to be performed in a compact, simple device. The efficiency of the magnetic filter is characterized by sorting non-magnetic (polystyrene) beads from magnetic beads (iron oxide). The filter enriches the population of non-magnetic beads to magnetic beads by a factor of >10^5 with a recovery rate of 90% at 1 mL/hr. The utility of the magnetic filter is demonstrated with a microfluidic device that sorts tumor cells from leukocytes using negative immunomagnetic selection, and concentrates the tumor cells on an integrated membrane filter for optical detection.
12:45 PM - PP1.10
Microfluidic Flow Cytometer Detection Platform Based on Spatially Modulated Fluorescence Emission.
Joerg Martini 1 , Peter Kiesel 1 , Markus Beck 1 , Noble Johnson 1
1 , Palo Alto Research Center, Palo Alto, California, United States
Show AbstractWe will present an optical detection technique that delivers high signal-to-noise discrimination without precision optics to enable a flow cytometer that can combine high performance, robustness, compactness and low cost. The enabling technique is termed “spatially modulated emission” and generates a time-dependent signal as a continuously fluorescing (bio-)particle traverses a optical transmission pattern. Correlating the detected signal with the known pattern achieves high discrimination of the particle signal from background noise. The analyte’s fluidic path, the optical excitation and detection volume need to be aligned for reliable particle detection. In conventional flow cytometry, the size of the excitation and detection volume is restricted approximately to the size of the particle. Our method uses a much larger excitation volume along the fluidic channel in order to increase the total flux of fluorescence light that originates from a particle while requiring minimal optical alignment. Despite the large excitation volume, the mask patterning enables a high spatial resolution in the micron range. This allows for detection and characterization of particles with a separation (in flow direction) comparable to the dimension of individual particles. In addition, the concept is intrinsically tolerant of background fluorescence originating from fluorescent components in solution, fluorescing components of the chamber and contaminants on the surface.The fundamental advantages of the spatially modulated emission can be utilized in different ways. For a low-cost, robust, point-of-need absolute CD4+ and percentage CD4 counter for human blood, the detection technique has been extensive evaluated. By probing the same samples, we directly compared our system with a commercial instrument (BD FACSCount) and obtained excellent agreement for both absolute CD4 and percentage CD4. While for this application cost and size are crucial parameters we will also present our results on sample throughput, sheathflow-to-analyte ratio, sensitivity and multi-wavelength excitation/emission.
PP2: Micro-Fluidics Sensors and Devices II
Session Chairs
Monday PM, November 29, 2010
Back Bay C (Sheraton)
2:30 PM - **PP2.1
Miniature Mass Spectrometers: Design, Fabrication and Biological Analysis.
R. Cooks 1 , Zheng Ouyang 2 , William Chappell 3
1 Chemistry, Purdue University, West Lafayette, Indiana, United States, 2 Biomedical Engineering, Purdue University , West Lafayette, Indiana, United States, 3 Electrical & Computer Engineering , Purdue University , West Lafayette, Indiana, United States
Show AbstractMass spectrometry (MS) is recognized as an analytical technique with high sensitivity and molecular selectivity as well as wide applicability. Miniature mass spectrometer (MS) analysis systems have been developed and characterized for in situ applications to foods analysis (pesticide and melamine and other contamination), transportation security applications (monitoring of toxic and explosive compounds), and clinical analysis (therapeutics in blood). The instrumentation must be small, cheap, light and battery-operated. All these applications require direct sampling and ionization of materials in their native state as well as the ability to characterize individual compounds in complex mixtures. These requirements are met by the development of small hand portable ion trap mass spectrometers of simplified geometry, a set of new ionization methods (ambient ionization methods) that can be performed on condensed phase samples in air, capabilities for transporting ions from the sample through air into the small mass spectrometer, and tandem MS capability to allow mixture analysis without prior chromatography. A rectilinear ion trap was chosen as the mass analyzer for the miniature MS due to its capability for tandem MS, tolerance to high operation pressure and large trapping capacity. Fabrication by rapid prototyping in polymer followed by electroless metal deposition gives devices that meet the physical tolerances and thermal properties required. Close attention is also given to improved methods of interfacing atmospheric pressure ion sources with miniature mass spectrometers. A discontinuous atmospheric pressure interface (DAPI) was developed to allow analysis of ions generated in air without using a large pumping system. Three ambient sampling ionization methods, desorption electrospray ionization (DESI), low temperature plasma (LTP) probe and paper spray, were developed for fast analysis of involatile compounds in complex sample matrices without sample treatment. Miniature mass spectrometer systems (all components) of 4 kg (Mini 11) have been developed with unit mass resolution and mass range up to m/z 800. Tandem mass spectrometry capabilities were implemented for chemical structural elucidation and detection confirmation. Ambient ionization can be performed using charged sprays (desorption electrospray ionization, DESI), and by low temperature plasma (LTP) ionization. Initial attempts at transferring forensic and biological imaging MS from lab scale to handheld instruments is also discussed. The paper spray technology allows for a direct spray ionization of the chemicals on paper with a small amount of methanol/water solution and a high voltage applied on the paper. It has been applied for direct quantitative analysis of drugs in dried blood spots; excellent sensitivity and response linearity have been achieved for drugs, such as imatinib and atenolol, within their therapeutic ranges
3:00 PM - PP2.2
Nanosieving Fluidic Channels as Label Free Plasmonic Nanohole Sensors.
Ahmet Yanik 1 2 , Min Huang 1 2 , Alp Artar 1 2 , Tsung-Yao Chang 3 , Hatice Altug 1 2
1 Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States, 2 The Photonics Center, Boston University, Boston, Massachusetts, United States, 3 Electrical and Computer Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractPerformances of biosensors are often limited by the depletion zones created around the sensing area which impede the effective analyte transport. To overcome this limitation, we propose and demonstrate a novel nanoplasmonic-nanofluidic sensor with dramatic improvements in mass transport efficiency. Unlike previous approaches where the analytes simply stream pass over the surface, our platform enables targetted delivery of the analytes to the biosensor surface. Using our platform, we show 14-fold improvement in the mass transport rate constants. Considering that this rate constant appears in the exponential term, such an improvement means much superior analyte delivery to the sensing surface with respect to conventional fluidic schemes. Our detection platform is based on extraordinary light transmission effect (EOT) in suspended plasmonic nanohole arrays. The nanoholes here act as nanofluidic channels connecting the fluidic chambers on both sides of the sensors. To fabricate these nanostructures, we introduce a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography (EBL). The simplicity of this fabrication technique allows us to fabricate nanostructures with extremely high yield/reproducibility and minimal surface roughness.
3:15 PM - PP2.3
Microfluidic Chips to Detect Functional Heterogeneity of Single Cells.
Rong Fan 1
1 Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractThe highly heterogeneous nature of immune cells requires large numbers of effector molecules from single cells to be analyzed in order to assess cellular immunity against infection or tissue dysfunction. We report on an antibody-barcode array-based microfluidic platform designed for highly multiplexed measurements of secreted proteins, from a thousand single cells or small cell colonies in parallel. The platform was validated by measuring a panel of inflammatory cytokines secreted from lipopolysaccharide-stimulated human macrophage cells. We unambiguously demonstrated that multiple proteins secreted from as few as one cell can be measured. We then applied the platform towards quantitating the functional heterogeneity of T cells, via the simultaneous measurement of a dozen proteins secreted from tumor-antigen specific CD8+ T cells, collected from melanoma patients participating in an adoptive cell transfer (ACT) immunotherapy clinical trial. We observed profound cellular heterogeneity with major functional phenotypes quantitatively identified. Such multifunctional diversity is believed to contribute to enhanced potency and durability of effector T cells. This platform for the first time enables highly multiplexed single cell secretome analyses and represents a novel, informative tool for immune monitoring in the clinic.
3:30 PM - **PP2.4
New Lab-on-a-chip System for Infectious Disease Analysis.
Klaus Drese 1 , Hans Attig 2 , Rainer Dahlke 2 , Gerd Grosshauser 2 , Ralf Himmelreich 2 , Markus Jeziorski 2 , Thomas Rothmann 2 , Andy Wende 2 , Jan Claussen 1 , Eva Schaeffer 1 , Ole Wiborg 1 , Isabell Wick 1 , Marion Ritzi-Lehnert 1
1 , Institut fur Mikrotechnik Mainz GmbH, Mainz Germany, 2 , Qiagen GmbH, Hilden Germany
Show AbstractEarly diagnosis followed by personalised efficient therapy of infectious diseases (e.g. respiratory diseases, meningitis, sepsis) can lead to considerable reduction of costs in health care. Point-of-care testing can provide early detection since this kind of decentralised analysis can be done by unskilled personnel at any time. Other advantages of such automated Lab-on-a-Chip systems (LoC) are reduction of time and reagents, elimination of cross-contamination and enhanced reproducibility due to eliminated user interference. Such new Lab-on-a-Chip systems will establish themselves on market only when sensitivity and specificity meet clinical requirements. Here, an integrated cost-efficient lab-on-a-chip system is presented which allows performing all diagnostic process steps for pathogen analysis of respiratory viruses from nasopharyngeal samples. Starting with swab samples the device prepares total nucleic acids using magnetic silica beads. By reverse transcription followed by QIAplex PCR technology the purified virus RNA is amplified. Hybridised to corresponding QIAGEN LiquiChip Beads and labelled with streptavidin R-phycoerythrin the target sequences are transferred for analysis into a QIAGEN LiquiChip200 workstation. All chemicals needed are either stored freeze-dried on the disposable chip or liquid in a reagent cartridge allowing performance of 24 analyses. To realise all steps, fluidic control in terms of light barriers and turning valves including metering structures as well as magnetic stir bars for mixing are integrated into the injection moulded disposable chip. Core of the instrument is a rotating heating bar construction that allows for fast cycling, i.e. PCR times of around half an hour (30 cycles) and a volume of 120 µl make this system presently the fastest high-volume PCR-chip. To establish fast heat transfer and homogeneous mixing reactions are stirred by small magnetic foil stirrers. The functionality was proven by comparison of samples processed manually vs. automatically using the “ResPlex Panel II” for detection of respiratory viruses from nasopharyngeal samples. The LoC system performance ranges at about 30-60% compared to the manual reference experiments. Comparing the instrument performance with commercially available kits and nucleic acid preparation devices showed slightly weaker but clearly positive signal intensities obtained from the prototype even without protocol optimization. These results are promising and show an excellent basis for further development.The presented integrated lab on a chip system allows performing all diagnostic process steps for pathogen analysis of respiratory viruses from nasopharyngeal samples. The new device combines several unique solutions, among them the combined lysis and binding strategy, a novel magnetic separation principle, the “on-chip” nested multiplex amplification, and the internal processing and amplification controls. Parallel development of disposable analysis chip and corresponding instrument led to a cost-efficient LOC-system which can be adapted to identify various infectious diseases and therefore will allow opening completely new markets for in-vitro diagnostics.
4:00 PM - PP2: MicroFluid
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4:30 PM - **PP2.5
Organic Semiconductors for Integrated Optofluidic Sensing.
Uli Lemmer 1
1 Light Technology Institute, Karlsruhe Institute of Technology, Karlsruhe Germany
Show AbstractOrganic semiconductors combine the ease of processing with advantageous optical and electronic properties. A particular interesting feature of these materials is the broad optical gain spectrum allowing for the realization of widely tunable lasers. In a combination with a nanoscopic surface relief pattern, distributed feedback lasers can be realized. Tunability can be achieved, e.g, by a wedge shaped waveguide which results in a spatial variation of the local laser wavelength. Such low cost lasers are pumped by inorganic laser diodes [1] and can be used as the light source for spectroscopy systems without the need for further costly elements [2,3]. Another important feature of organic semiconductor lasers is the possibility to combine these active optoelectronic elemente with passive waveguides for integrated biomedical sensing systems. The emission from an integrated distributed feedback laser can be efficiently coupled into a waveguide in a lab-on-chip platform fabricated by hot embossing [4]. [1] C. Karnutsch, M. Stroisch, M. Punke, U. Lemmer, J. Wang, T. Weimann, Laser diode pumped organic semiconductor lasers utilizing two-dimensional photonic crystal resonators, IEEE Phot. Tech. Lett. 19, 741 (2007) [2] T. Woggon, S. Klinkhammer, U. Lemmer, Compact Spectroscopy system based on tunable organic semiconductor lasers, Appl Phys B 99, 47 (2010)[3] S. Klinkhammer, T. Woggon, U. Geyer, C. Vannahme, T. Mappes, S. Dehm, and U. Lemmer, A continuously tunable low-threshold organic semiconductor distributed feedback laser fabricated by rotating shadow mask evaporation, Appl. Phys. B 97, 787 (2009)[4] C. Vannahme, S. Klinkhammer, A. Kolew, P.-J. Jakobs, M. Guttmann, S. Dehm, U. Lemmer, and T. Mappes, Integration of organic semiconductor lasers and single-mode passive waveguides into a PMMA substrate, Microelectron. Eng. 87, 693 (2010).
5:00 PM - **PP2.6
Laser Rastering Flow Cytometry: Promise and Challenges.
Giacomo Vacca 1
1 R&D, Abbott Hematology, Santa Clara, California, United States
Show AbstractThe desire for a breakthrough in event rates in flow cytometry was one of the driving forces behind the invention of Laser Rastering (LR). This technology uses an Acousto-Optic Deflector (AOD) to rapidly sweep the interrogating laser beam across a wide, fast-flowing sample stream containing particles of interest (e.g., cells), achieving in the process far higher rates of cell counting than previously possible. Our LR prototypes routinely analyze in excess of 300,000 cells per second, compared to rates more than 10 times slower in typical on-market hematology analyzers. This dramatic enhancement in event rates is creating several new opportunities, from lysis-free assays in whole blood to efficient diagnostic detection of rare events in peripheral blood samples. In other words, the improvement in acquisition rates, more than simply speeding up existing assays, makes whole new assays possible for the first time. Concurrently, the developing technology of LR is pushing against some critical constraints, many of which are interrelated: for example, the Poisson statistics of coincident events, the optics of scattering and fluorescence excitation, the hydrodynamics of Poiseuille flow close to onset of turbulence, and the speed of beam scanning. AODs have enabled current performance milestones in our prototypes, but further sizable improvements in scanning rates (without attendant degradation in other desirable attributes, such as beam quality and uniformity of response) seem to require a different approach. A significant step in this respect could help push LR technology beyond current limitations and open up yet new fields of application.
5:30 PM - PP2.7
PDMS-CNTs Nanocomposite for PCR Device.
Marzia Quaglio 1 , Stefano Bianco 1 , Riccardo Castagna 2 , Matteo Cocuzza 3 2 , Candido Pirri 2 1
1 Center for Space Human Robotics, IIT-Italian Institute of Technology, Torino Italy, 2 Materials Science and Chemical Engineering, Politecnico di Torino, Torino Italy, 3 , CNR-IMEM, Parma Italy
Show AbstractPolymeric Lab-On-a-Chips (LOCs) for on-chip Polymerase Chain Reaction (PCR) have received great attention in the last decade [1-3]. Particularly PolyDiMethylSiloxane (PDMS) is one of the most interesting materials for such application. The low thermal conductivity of polymers is the main problem to face to design disposable PCR tools. Rapid thermocycling, as required by PCR protocols, is difficult to achieve in polymeric devices. Polymeric composites with thermally conducting nanofillers, can show a dramatic improvement in thermal response with respect to traditional polymers. Among nanocomposites, PDMS matrix filled with carbon nanotubes (CNTs) has recently shown great potentialities in different application fields [5-7]. This material combines the ease of processing and flexibility of the elastomeric matrix with the high thermal and electric conductivity of CNTs [5,6]. In the present work, we propose the fabrication and optimization of a stationary PCR device with a working volume of 15 μl, made of PDMS/CNTs nanocomposite materials with different multi-walled (MW) CNTs content. We characterized the thermal response of the material for different CNTs concentrations by means of Laser Flash measurements. Preliminary results showed a ~50% improvement in the thermal diffusivity with increasing the CNTs content up to 2% in weight.Devices for PCR protocol with a drop-shaped microfluidic reaction chamber were fabricated, both with pure PDMS and with PDMS/CNTs composite with various CNTs content. A thermocycling based on the same temperatures used in PCR protocol was performed, to test the nanocomposite response. Temperature variation was measured with a thermocouple, inserted directly into the device close to the reaction chamber, but completely surrounded by the material, to avoid external effects. A faster variation in device temperature and a better control in steady-state temperatures were demonstrated on the nanocomposite-based device, with respect to what obtained with pure PDMS. This novel approach allows us to reach a more precise thermal control in the biological reaction, with a beneficial effect on process efficiency.Finally, we validated the devices performing a PCR protocol for ABL gene amplification. The better thermal performance of the nanocomposite-based device was mirrored by a clear efficiency increasing in PCR reaction, demonstrating the direct enhancing effect of the CNTs content in the composite.[1] C. Zhang et al., Nucl. Acids Res. 35 (2007) 4223–4237[2] A.K. Jeong et al., Biochem. Eng. J. 29 (2006) 91–97 [3] C. Zhan et al., Biotechnol. Adv. 24 (2006) 243-284 [4] J. Wu et al, Biomicrofluidics 3 (2009) 012005-1_012005-7[5] C. H. Liu et al., Appl. Phys. Lett. 84 (2004) 4248-4250[6] L. Z. Chen et al., Appl. Phys. Lett. 92 (2008) 263104-1_263104-3[7] S.V. Ahir et al., Nat. Mater. 4 (2005) 491 – 495
5:45 PM - PP2.8
Generation of Microfluidic Flows in Open Environments Using Hydrodynamic Confinement.
Kevin Christ 1 , Kevin Turner 2 1
1 Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractMicrofluidic devices have shown tremendous promise for manipulating and measuring the properties of biological cells. Most of these approaches have been implemented in conventional closed-channel devices made of materials such as polydimethylsiloxane, glass, and various thermoplastics. These channel-based devices can be problematic for some studies as certain cell types are difficult to culture in small channels and cells cultured in these devices cannot be interrogated with many standard techniques. To overcome this problem, we have developed a class of devices that utilize hydrodynamic confinement to generate microfluidic flows in open environments, such as Petri dishes and multi-well plates that are traditionally used in cell culture. Hydrodynamically confined microfluidic flows are generated by positioning a microfabricated device with at least two ports in a fluid filled well a short distance (< 50 micrometers) above the bottom surface and injecting flow into one port and aspirating through the other port at a higher flow-rate. The device does not make physical contact with the bottom surface of the well and the flow is confined laterally by hydrodynamic forces alone. In the present work, we investigate the use of these devices to generate uniform microfluidics flows that can encompass several spread cells on a surface. The essential concept here is similar to previous microfluidic probes that have been reported, but a much wider-range of device geometry and flow conditions is reported here. Specifically, we have developed devices to generate uniform microfluidic flows, akin to those in a typical closed channel device, by using hydrodynamic confinement devices with optimized port shapes (e.g., rectangular, curved), arrangement, and spacing. Devices were designed using computational fluid dynamics modeling and experiments were performed using silicon devices that were made by deep reactive ion etching and bonding. An explanation of the fluid mechanics of the devices, experimental results from flow studies, and tests demonstrating the use of the devices for selective chemical treatment of cells and single-cell adhesion strength measurements will be reported. Furthermore, we demonstrate the use of pressure measurements in the devices to allow for closed-loop control of the height of the gap between the probe chip and surface of the well.
PP3: Poster Session: Bio Sensors
Session Chairs
Tuesday AM, November 30, 2010
Exhibition Hall D (Hynes)
9:00 PM - PP3.10
Rational Design of Two-dimensional Array-based Surface Plasmon Resonance Sensors with Figure of Merit > 100/RIU.
Lei Zhang 1 , Chung Yu Chan 1 , Jia Li 1 , Hock Chun Ong 1
1 Department of Physics, The Chinese University of Hong Kong, Hong Kong Hong Kong
Show AbstractSurface plasmon resonance (SPR) sensing has become a leading technology in label-free biochemical detection. Current interest in this area has been moving towards the development of hand-held, chip-scale biosensors. However, although commercially available Kretschmann type SPR sensors provide both good figure of merit (FOM ~ 70/RIU at λ = 800 nm) and resolution, they are impossible for miniaturization due to the need of a bulky prism coupler. While direct excitation is possible in metal nanoparticles, they suffer from modest performance (FOM ~ 7/RIU at λ = 700 nm and poor resolution due to broad linewidth ~100nm) and poor reproducibility that is crucial for device fabrication. Therefore, it is of importance to develop an alternative approach that on the one hand is miniaturizable while on the other hand provides supreme FOM and resolution. In this presentation, we describe our approach in rationally design two-dimensional array-based SPR sensors with FOM larger than 100/RIU. In fact, from the understanding of underlying physics of surface plasmon polaritons (SPPs) on periodic arrays, it is possible to achieve high sensitivity and strong peak profile (i.e. narrow linewidth and large peak height) by tailoring the periodicity, hole radius, and depth of the arrays, thus leading to high FOM and resolution. In particular, the peak profile is strongly associated with the interplay between the intrinsic absorption and the radiative decay of SPPs by individual holes [1]. As a result, by using hole arrays with large period and small hole radius and depth, we have demonstrated experimentally a FOM value ~ 110/RIU and good resolution at λ = 800 nm and low incident angle = 5o, which surpass those of Kretschmann and nanoparticle counterparts. 1. D.Y. Lei, J. Li, A.I. Fernandez-Dominguez, H.C. Ong, and S.A. Maier, ACS Nano 4, 432 (2010); J. Li, H. Iu, D.Y. Lei, J.T. K. Wan, J.B. Xu, H.P. Ho, M.Y. Waye and H.C. Ong, Appl. Phys. Lett. 94, 183112 (2009).
9:00 PM - PP3.11
Apta-sensor for Real-time Detection of Light Chain Botulinum Neurotoxin Type A Using Surface Plasmon Resonance.
Pavithra Janardhanan 1 , Charlene Mello 2 1 , Bal Ram Singh 1 , Shuowei Cai 1
1 Botulinum Research Center and Department of Chemistry & Biochemistry, Univ of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States, 2 Bioscience and Technology Team, US Army Natick Soldier Research, Development & Engineering Center (NSRDEC), Natick, Massachusetts, United States
Show AbstractFinding a replacement for the mouse bioassay and toxin detection has become a focal point in biosensor research. Botulinum neurotoxins (BoNTs) cause flaccid paralysis by cleaving proteins necessary for exocytosis of neurotransmitters at the peripheral cholinergic nerve terminals. We have identified 2’ fluorine modified RNA aptamers with high affinity (20-60 nM) to the zinc endopeptidase domain (light chain) of the botulinum neurotoxin type A (LC of BoNT/A) through SELEX process. Surface plasmon resonance based sensing with immobilized 2’ fluorine modified RNA aptamers is capable of detecting low levels of LC of BoNT/A (ng) in various food and clinical matrices. Sample matrices exhibit low background binding to the chip surfaces. Preliminary studies demonstrate RNA aptamer binding to LC of other BoNT serotypes such as BoNT/ B & BoNT /E, however, preferentially to LC of BoNT/A. In addition, binding to a deactivated recombinant full length BoNT/A has been observed suggesting the potential use of these aptamers in detecting the holotoxin apart from its enzymatic domain (light chain). High sensitivity, ability to quantitatively detect toxin in opaque sample matrices, robustness and the ease of sample preparation makes SPR biosensors superior to its counterparts.ACKNOWLEGEMENTSThis project is partially funded from an NIH grant (AI-30050) through Tufts University, an NIH grant (1R21AI070787-01A2) and U.S Army Natick Soldier Center grant (W911QY-09-C-0207).
9:00 PM - PP3.14
Improving Biocompatibility of Fluorescent Nano-optodes for In Vivo Glucose Monitoring.
Mary Balaconis 1 , Kevin Cash 2 , J. Matthew Dubach 1 , Heather Clark 1 2
1 Department of Bioengineering, Northeastern University, Boston, Massachusetts, United States, 2 Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, United States
Show AbstractFluorescent nanosensors have enabled the intracellular monitoring of physiological relevant analytes such as sodium, potassium, and chloride. Previously, we have reported on the extension of the ion-selective optode design of these sensors to the detection of small molecules. Our sensors were able to monitor dynamic changes in concentration of the model analyte, glucose, using all non-biological components localized in a hydrophobic core. We tailored the sensors to respond to glucose within the physiological range and we were able to demonstrate their ability to track changes in glucose levels in mice. We will present improved biocompatibility of these sensors by using biocompatible and biodegradable plasticizers and polymers for the components of the hydrophobic sensing core. The lifetime and fluorescence response of these new sensors is analogous to the sensors previously developed. These improvements will minimize the biofouling and immune responses that adversely affect the sensor function and lifetime in vivo. Improved biocompatibility will also allow repeatable long-term implantation of the sensors both as an alternative tool for monitoring glucose levels in such fields as diabetes research and as a diagnostic tool in diabetic care.
9:00 PM - PP3.16
New Mixed-monolayer Probe for Sensitive Detection of Reactive Oxygen Species.
Yiming Huang 1 , Jeremiah Miller 1 , Yujen Lin 1 , Sandra Bishnoi 1
1 Biological, Chemical & Physical Department, Illinois Institute of Technology, Chicago, Illinois, United States
Show AbstractReactive oxygen species (ROS), including hydroxyl radical, hydrogen peroxide (H2O2), and peroxynitrite (ONOO-), are generated in the cells and tissues and play an important role in pathologic process. When too much ROS are produced in cells, it will result in the alternation of DNA, membrane lipids, proteins and nucleic acids due to the oxidative stress. This is implicated in multiple diseases, including but not limited to aging, hypertension and ischemic stroke. Spectroscopic methods have been explored, such as fluorescence,luminescence, but they are limited by photo bleaching, low stability of the probes, and unwanted background contribution. The ROS sensors we designed are the nanoshells functionalized by 4-nitrobenzenethiol (4-NBT) and stabilized by poly ethylene glycol (PEG)(MW 5000), which are photo stable, easy to make and can give narrow and strong Raman peaks. We will use these Surface-enhanced Raman Scattering (SERS) probes to identify and quantify the ROS, based on the characteristics and the intensity of Raman spectrum and we will also localize the ROS by analyzing the intensity variations of Raman mapping.
9:00 PM - PP3.17
TEM Characterization of the Shell Distribution on NaYF4/NaGd F4 Core/Shell Nanocrystals.
Carmen Andrei 1 , Keith Abel 2 , John-Christopher Boyer 2 , Frank van Veggel 2 , Gianluigi Botton 1
1 Brockhouse Institute for Materials Research and Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario, Canada, 2 Department of Chemistry, University of Victoria, Victoria, British Columbia, Canada
Show AbstractLanthanide-based nanocrystals (NCs) have attracted a lot of attention due to their potential in a wide range of applications including lasers, display devices and biological imaging probes [1]. More recently, a new subgroup of these materials has shown the ability to upconvert low energy near-infrared (NIR) radiation into higher energy visible luminescence. Use of NIR excitation permits deep tissue penetration and also minimizes autofluorescence. By incorporating Gd3+, the NCs can be used as contrast agents for magnetic resonance imaging applications [2, 3]. Controlling the mechanism of the shell growth is a common way to improve the luminescence efficiency [4]. Standard transmission electron microscopy (TEM) techniques are unable to differentiate between the core and the shell structure due to the similarity of the lattice parameters.In this study advanced TEM techniques such Electron Energy Loss Spectroscopy (EELS), Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning Transmission Electron Microscopy (STEM) showed that NaYF4/NaGd F4 NCs are core/shell structures.High-angle annular dark field (HAADF) images showed clearly contrast between the shell (higher atomic number) and the core (lower atomic number). EELS line scans were acquired across either a single particle or two neighboring particles and showed Gd residing predominantly in the shell. The average size of the core/shell NCs was determined to be 23 ± 3 nm in diameter by averaging over the long and short axis. The original NaYF4 core NCs had a diameter of 16 ± 1 nm. The increase in overall size suggests successful growth of NaGdF4 on to the NaYF4 cores, with an average shell thickness of 3.5 nm. The Y signal could not be detected in EELS. EDS line scan showed clearly the Y in the core and Gd located in the shell.The shell was not uniformly distributed on all particles suggesting certain faces of the core are more reactive than others.Futher improvements in synthetic procedure will likely improve shell quality. Also high resolution STEM on NCs might give more insights about the growth orientation of the shell.References:[1] Chan, W. C. W.; Nie, S. Science 1998, 281, 2016.[2] Abel, K. A.; Boyer, J.-C.; van Veggel, F. C. J. M. J. Am. Chem. Soc. 2009, 131, 14644.[3] Wang, F.; Han, Y.; Lim, C. S.; Lu, Y.; Wang, J.; Xu, J.; Chen, H.;Zhang, C.; Hong, M.; Liu, X. Nature 2010, 463, 1061[4] Boyer, J.-C.; Gagnon, J.; Cuccia, L. A.; Capobianco, J. A. Chem. Mater. 2007, 19, 3358.
9:00 PM - PP3.20
Sharp Silicon Nano-needles Based on Boron Etch-stop in TMAH Solutions.
Sheping Yan 1 , Yang Xu 1 , Junyi Yang 1 , Huiquan Wang 1 , Zhonghe Jin 1 , Yuelin Wang 1
1 Department of Information Science and Electronic Engineering, Institute of Microelectronics and Optoelectronics, Hangzhou China
Show AbstractOperations on biological living cells and molecular devices have driven research towards implementation of high-aspect-ratio nano-needles. In this work, we develop a simple method to fabricate repeatable and IC-compatible nano-needles based on boron etch-stop in TMAH solutions, in which the needle angles can be accurately controlled. The whole process starts from an n-type (100) SOI wafer with top Si of 2000 Å and buried oxide of 4000 Å. While the middle part of the beam is protected, boron ions implantation (with a dose of 1E15cm-2 and an accelerator voltage of 50 keV) is performed in the unprotected (or exposed) region. Impurity doping induces internal stress to the silicon, which results in the decreased etching rate of silicon in TMAH solution with increasing boron doping concentration. A group of suspended silicon needles with thickness t = 25 nm, angle θ = 3.1°, and lengths in microns, have been formed on an n-type SOI wafer after TMAH etching. Modeling the etching evolution and formation of needle angles have been established and theoretical analysis has been conducted. By choosing boron doping concentration and thermal silicon oxide thickness, we can obtain silicon needles with required angles, thickness, and lengths. The suspended nano-needles can be used as cantilevers to develop highly sensitive sensors.
9:00 PM - PP3.21
Miniemulsion for Passive Cellular Loading of Fluorescent ion Detecting Nanodroplets.
Matt Dubach 1 2 , Kevin Cash 2 , Katie Balaconis 1 2 , Heather Clark 2
1 Bioengineering, Northeastern, Boston, Massachusetts, United States, 2 Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, United States
Show AbstractNanoparticle optodes have been used to image intracellular ion concentrations that cannot be reliably detected using commercially available molecular dyes, such as sodium. The particles, however, must be injected into the cytoplasm as they will remain trapped in cellular compartments if they enter the cell through endocytosis. Here we demonstrate the use of an oil in water miniemulsion to deliver nanodroplets of functional ion sensors into the cytosol. The miniemulsion was made by sonication of dilute oil in water with nanometer to submicron sized droplets being formed. Plasticizers were used as the oil phase and all the recognition and optical components were entrapped in the nanodroplets based on hydrophobicity. The type of plasticizer and chemical components were optimized to respond to intracellular ion concentration levels. The emulsion can be stabilized using surfactant and highly hydrophobic molecules to prevent coalescence and Ostwalt ripening, respectively. However, while surfactants stabilize small droplets, they prevent interaction of these droplets with cellular membranes. Additionally, the droplets must be on the order of a 100 nm in diameter to passively diffuse through the plasma membrane. Here we use minimal surfactant concentrations at the emulsion interface to create unstable miniemulsions with nanometer sized droplets. Over time the size of the droplet will increase to microns in diameter. However, the surfactant allows the nano-sized droplets with high Laplace pressure to be stable for a long enough time to reach the plasma membrane. Also, there is not enough surfactant at the nanodroplet surface to prevent hydrophobic interaction with the plasma membrane. Therefore fluorescent nanosensors for ions such as sodium can be passively loaded into cells over the course of minutes without traveling through the endocytotic pathway. This may provide a simple way to measure membrane ion channel activity and inhibition in cell culture.
9:00 PM - PP3.22
Extension of the Underlying Plasmonic Properties of Triangular Silver Nanoplate Sols to the Scaling of Electromagnetic Field Enhancement Phenomena Including LSPR Biomedical Sensing.
Denise Charles 1 , Damian Aherne 1 , Deirdre Ledwith 3 , Matthew Gara 2 , John Kelly 2 , Wermer Blau 1 , Margaret Brennan-Fournet 3
1 School of Physics, Trinity College, Dublin 2 Ireland, 3 School of Physics, National University of Ireland, Galway Ireland, 2 School of Chemistry, Trinity College , Dublin Ireland
Show AbstractNoble metallic nanostructures are becoming powerful building blocks for new and emergent fields, such as optical frequency metamaterials, nanoantennanas, and refractive index biosensing. Many metallic nanostructure functionalities and applications arise from nanoscale electromagnetic field enhancements governed by the particle’s localized surface plasmon resonances (LSPR) meaning that a thorough understanding of the underlying plasmonic behaviour of the nanostructure is necessary in order to find the optimal structural characteristics required for enhanced LSPR response.Solution phase triangular nanoplates are herein presented as tunable, highly sensitive, localized surface plasmon resonance (LSPR) sensors with excellent potential for versatile highly responsive biosensing. We will show that these TSNP sols have high LSPR sensitivities and will highlight how the aspect ratio of these nanoplate structures behaves as a key parameter for the enhancement of their LSPR sensitivities. We demonstrate reduced radiation damping in TSNP sols at sizes above that which quasistatic theory predicts it to dominant, enabling longer plasmon dephasing times and a more coherent oscillation in these larger edge length nanoplates. Using DDA calculated absorption and scattering spectra we show how the aspect ratios of these nanoplate structures enable a coherent oscillation of the plasmon while confining its electromagnetic field to the surface resulting in an aspect ratio dependent enhanced LSPR sensitivity to surface conditions. Advances in the functionalization and alteration of the surface chemistry of these TSNP will show how these alterations result in increased stability under physiological conditions thus enabling exploitation of their high sensitivities in biological applications. Low volume Dark Field Microscopy techniques which are currently explored are finally introduced to further analyze the potential these solution phase nanostructures hold for potential applications in a range of bio-analytical technologies.
9:00 PM - PP3.23
Electrical Detection of IgE Protein Using Single Conducting Polymer Nanowire-based Aptasensor.
Jiyong Huang 1 , Xiliang Luo 2 , Yushi Hu 1 , Innam Lee 1 , Xinyan Cui 2 , Minhee Yun 1 2
1 Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show Abstract In the past decade, nanostructured conducting polymers have been successfully demonstrated as promising candidates for biological sensor because of their biocompatibility, environmental stability, and controllable processing. Notably, biomolecules can be incorporated into the conducting polymer in one step during the polymerization, which simplifies the bio-functionalization process significantly. Furthermore, comparing with antibodies, aptamers are more favorable due to their high selectivity, specificity, and affinity. Therefore it is advantageous to employ aptamers doped conducting polymer nanowires as biosensors. The anti-IgE aptamers doped PPy nanowires were electrochemical deposited in polymethylmethacrylate (PMMA) nano-channels patterned between two Au electrodes. Fluorescent day labeled aptamers were used during the polymerization, and the fluorescence microscopy image confirms that the aptamers were successfully doped into the PPy nanowires. The real-time IgE detection in phosphate salt buffer (PBS) solution with aptasensor was further carried out using Keithley system. A droplet of PBS solution was placed on the aptasensor. The conductance of the nanowire was monitored as several solutions were then added to the solution above the aptasensor. A droplet of nontarget bovine serum albumin (BSA) solution was added, and followed by several droplets of IgE solution with different concentrations. For the aptasensor, non appreciable changes in the curve were observed upon the addition of BSA droplets, which indicates the excellent selectivity and specificity of the aptasensor. This is further confirmed by the responses on the negative control of PPy nanowire corresponding to BSA and IgE solutions. In contrast, the response of the aptasensor increased significantly after being exposed to IgE solutions. The sensitivity of the aptasensor was measured using varying IgE concentrations. The aptasensor was very sensitive with around 1% change in conductance even at the lowest tested IgE concentration of 20 ng/ml. This result is about 3 times of the sensitivity obtained from aptamer doped PPy film. Further, this aptasensor had a wide dynamic range from 20 ng/ml to 200 μg/ml. This result was consistent with recent work on aptamer doped PPy film biosensor. In conclusion, we have successfully demonstrated the aptamers dopted PPy nanowire aptasensor for real-time and label-free detection of IgE protein with high sensitivity and specificity. Remarkably, the lowest IgE concentration (20 ng/ml) tested in this work is much lower than the suitable lever for human testing (300 ng/ml), which promises the potential of this aptasensor for clinical application. Additionally, more medially relevant aptasensors can be obtained by employing other monomers such as aniline and thiophene that can be electropolymerized, or other aptamers that are specific to certain proteins, which can advance the research in biomedical area and health care greatly.
9:00 PM - PP3.24
The Studies in the Mechanisms of the Penetration of Functionalized Nanoparticles Using Two-photon Microscopy.
Tsung-Rong Kuo 1 , Chia-Chun Chen 1 , Hsin-Yuan Tan 3 , Chen-Yuan Dong 2 , Sung-Jan Lin 3
1 Chemistry, National Taiwan Normal University, Taipei Taiwan, 3 Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei Taiwan, 2 Department of Physics, National Taiwan University, Taipei Taiwan
Show AbstractIn this study, we succeed in combining autofluorescence of the stratum corneum and the second harmonic generation of ZnO nanoparticles to image the transdermal pathway of ZnO nanoparticles with chemical enhancers, using two-photon microscopy. In addition to qualitative imaging, the microtransport properties of ZnO nanoparticles were quantified to give the vehicle-to-skin partition coefficient, the second harmonic generation intensity gradient and the effective diffusion path length. The results suggested that the multilamellar lipid regions between the corneocytes were the pathways for ZnO nanoparticles delivery. Furthermore, we also demonstrated that corneal epithelium played an important role for preventing the penetration of functionalized nanoparticles using two-photon microscopy. Once the barrier was damaged, nanoparticles penetrated into cornea, interacted with corneal stromal cells, and retained within cornea a relatively long period. Bovine cornea was used as an experimental model to study the detail mechanisms of the penetration and distribution.
9:00 PM - PP3.25
IRIS - Interferometric Reflectance Imaging Sensor for High-throughput Detection and Sizing of Individual Nanoparticles
Abdulkadir Yurt 1 , George Daaboul 2 , Xirui Zhang 2 , Bennett Goldberg 2 3 4 , M. Selim Unlu 2 4
1 Material Science and Engineering, Boston University, Boston, Massachusetts, United States, 2 Biomedical Engineering , Boston University, Boston, Massachusetts, United States, 3 Physics, Boston University, Boston, Massachusetts, United States, 4 Electrical and Computer Engineering , Boston University, Boston, Massachusetts, United States
Show AbstractFast, high-throughput and cost-effective characterization of nanoparticles is essential in materials science, biomedical and national security applications. Optical and photonics-based detection schemes are promising due to their inherent sensitivity and label-free detection capabilities. However, discrete photonic device techniques are low-throughput, and spectroscopic solutions are bulky and expensive, limiting their range of applications. Here we report a new interferometric technique based upon phase imaging on a reflecting surface which is capable of detecting as well as sizing polystyrene nanoparticles down to 35nm radius. We use a high NA telescopic 4f imaging system with a single LED source in Kohler configuration illuminating a mixture of particles immobilized on a patterned SiO2 – Si layered media surface. The wavelength of the LED source and thickness of the SiO2 layer are co-optimized to maximize the interferometric signal for the smaller particles of interest. In addition to phase imaging and basic detection, we further determine the sizes of individual particles by fitting the interferometric visibility at each particle as a function of defocusing. As the focal plane is vertically stepped, the relative phase between reference and scattered fields changes between 0 and 2π and thus interferometric signal exhibits local maxima and minima at distinct defocusing distances. The interferometric visibility can be recorded with just a few steps and yields an accurate fingerprint of the size of particle. We demonstrate the detection and sizing capability of our technique by means of both EM simulation and experimental results using polystyrene beads. The imaging modality allows us to perform detection and size quantification of thousands of individual particles simultaneously in less than a minute, demonstrating that our approach offers a high-throughput, robust and cost-effective solution to nanoparticle characterization problems in various research fields.
9:00 PM - PP3.26
Liquid State Inertial Sensor for the Prosthesis of Human Vestibular System.
Hansong Zeng 1 , Yi Zhao 1
1 Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
Show AbstractPatients suffering from vestibular disorders have symptoms like blurred vision, vertigo and increased risks to fall. Clinical statistics shows more than 6.2 million American adults have ever reported chronic balance problems and more than 3.1 million senior people are prone to develop dysfunctional vestibular organs. In order to accomplish the prosthesis, a motion sensing device possessing comparable function as human vestibular system is required. In this work, we propose a fluidic system composed of a liquid droplet and a curved channel. Mimicking the vestibular system, relative movement between the droplet and channel is used to indicate the acceleration. The liquid state inertial sensor is expected to possess comparable dynamic responses to human vestibular system and therefore can be an alternative for its prosthesis. The sensing principle is briefed here. Initially, the droplet locates at the bottom of the channel due to its gravity. When an external acceleration is applied, the inertial force moves the droplet upwards along the channel. Displacement of the droplet indicates the magnitude of the external acceleration. Besides the inertial force, the droplet movement is also influenced by its gravity, the friction at the interface and air damping around the droplet. To validate the sensing concept, a sensing prototype is designed, fabricated and characterized. The circular channel is fabricated by photolithography of the photoresist, SU-8, with a radius of 4mm. The droplet is made up of mercury coated with a layer of copper nanoparticles. After placing the droplet in the circular channel, the channel is sealed by glass to prevent liquid evaporation. The frequency response of a single sensor under forced oscillations with three different amplitudes is obtained. The amplitudes of the accelerations are 0.05g, 0,08g and 0.1g, respectively. The angular displacement of each oscillation is measured from 7Hz to 11Hz. The result shows that the resonance frequencies are 8.7Hz at 0.05g, 8.6Hz at 0.08g, and 8.7Hz at 0.1g. After characterizing a single sensor, a pair of sensors is assembled perpendicularly to measure the random acceleration in the lateral plane. Statistical study of the measurement shows the sensing system can predict the acceleration with good accuracy, with the error around 5milli g. In summary, a liquid state inertial sensor is investigated. Typical parameters influencing the dynamic behavior are examined. Experimental results show that the resonance frequency of the liquid-state sensor can be controlled below 10Hz, which is within the range of the body motion. Two dimensional measuring can be accomplished by assembling two sensors in the perpendicular way. The work is the first study of its kind and will provide insights into design and development of next generation liquid-state inertial sensors with desired frequency responses.
9:00 PM - PP3.27
pH Sensitivity in Nanowire-based Devices with Various Dielectric Layer Coatings.
Ming-Pei Lu 1 , Cheng-Yun Hsiao 2 , Wen-Tsan Lai 2 , Yuh-Shyong Yang 2 1
1 , National Nano Device Laboratories, Hsinchu Taiwan, 2 , Institute of Biological Science and Technology, National Chiao Tung University, Hsinchu Taiwan
Show AbstractIn this work, n-type polycrystalline silicon nanowires (NWs), used as one-dimensional conducting channels to study the ph sensitivity of NW biosensors, were fabricated using fully complementary metal–oxide–semiconductor (CMOS) compatible processes. In order to perform the electrical characteristics of NW devices in the solution environment, a home-made solidification poly (dimethylsiloxane) (PDMS) microfluidic channel bonded onto the NW device was fabricated in order to sequentially deliver the solutions into this sensing system. The devices were measured by using a gold microwire serving as the liquid-gate electrode for modulating the conductance of NW. The pH sensitivity of NW devices coated with different dielectric layers, such as SiO2 and Al2O3,were investigated for use to the pH sensing applications. The surface potential change at the solution–dielectric layer interface, due to protonation/deprotonation process, was also extracted for different dielectric layer-coating cases. Experimentally, the highest pH sensitivity can be observed for device operated in the subthreshold regime. An equivalent capacitive model of the liquid-gate biosensor system was carried out to explore the dependence of the sensitivity on the liquid-gate voltage, which was contributed by the capacitive competition between the nanowire capacitance and the thin dielectric capacitance. This study opens a window to physically understand how to modulate the pH sensitivity of device by the liquid-gating fashion and dielectric layer-coating, indicating the promising application of this work to the fields of biological and chemical biosensors.
9:00 PM - PP3.28
Electrogenerated Chemiluminescent Anion Sensing: Selective Recognition and Sensing of Pyrophosphate.
Se Won Bae 1 , Ik-Soo Shin 1 , Jong-In Hong 1
1 Department of Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractRecently, significant advances have been made independently in electrogenerated chemiluminescence (ECL) analysis and supramolecular anion sensing. Herein, we demonstrate a new proof of concept for ECL-based pyrophosphate (PPi) sensing, where the emission intensity is changed by electrochemical turn-on. The conventional PPi detection is based on fluorescent or bioluminescent approaches which necessarily accompany bulky and expensive analytical instruments. Considering the important and ubiquitous roles of PPi in biology and environment, there is an urgent need to develop an ECL sensor that would enable highly sensitive and selective detection of PPi with minimizing additional equipments (without light source and additional separation tools). The ECL PPi sensor (1-2Zn) consists of two orthogonally bonded moieties: boron dipyrromethene (ECL reporter) and a phenoxo-bridged bis(Zn2+-dipicolylamine) complex (PPi receptor). The presence of PPi is confirmed from the change in the intensity of green ECL generated from the former when PPi is selectively recognized by the latter. During PPi recognition, changes of ECL intensity are caused in the electronic states of the receptor, and this stimulates the attenuation of ECL. The preferential sensing ability of 1-2Zn to PPi in the presence of other phosphate-containing anions, such as ATP, ADP, AMP and phosphate allows sensitive, compact, simple, and chip-based luminescence detection. The electrochemical “on-off” triggering of light emission upon anion binding forms the basis of a new anion sensing strategy. Also, we expect that green-colored ECL sensing would offer an advantage to current ECL analysis.
9:00 PM - PP3.29
FET-based Biosensor Incorporating a Conductimetric Bioreceptor.
Andres Vercik 1
1 Basic Sciences Department ZAB/FZEA, University of São Paulo, Pirassununga - SP Brazil
Show AbstractA biosensor combines a bio-recognition element in contact with a transducer which converts biochemical event in an electrical signal. Usually, these devices operate according to different principles such as electrochemical, mechanical, piezoelectric or optical techniques. Electrochemical detection strategies, particularly amperometric biosensors are most widely used, followed by the potentiometric devices, mainly those based on field effect transistors. Different strategies or elements are combined frequently to achieve more sensitive or selective devices, aiming a good compatibility with standard microelectronic technologies, for better integration of the sensor with the electronic components for signal conditioning, amplification and displaying, in a compact device. Several materials and structures exhibiting conductance changes in the presence of a chemical or biological species have been used in biosensors, such as arrays of capped metallic nanoparticles or organic films containing nanoparticles and catalytic agents such as enzymes for different target analytes. A possible approach to construct biosensors is the combination of conductimetric element in the biasing circuit of Metal-Oxide-Semiconductor-Field-Effect-Transistor (MOSFET). In this work we proposed the use of a conductimetric element in series with a tunnel-MOSFET, to provide conductance dependent electrical signals. Simulations are performed to show the feasibility of the propose device and the linear range of operation. According to the results, a linear dependence of the gate voltage on the conductivity is observed. The linear dependence spreads over the whole range of conductivities used in this simulation. On the other hand, the drain current exhibits a linear dependence for higher conductivities, before its saturation. Thus, two different detection strategies of detection can be defined: measure the gate voltage for very low conductivities or measure drain current for higher conductivities.
9:00 PM - PP3.3
Adsorption of Poly-L-Lysine on Platinum Electrodes as a Function of Applied Potential.
Sara Nilsson 1 , Mats Fahlman 1 , Fredrik Bjoerefors 1 , Nathaniel Robinson 1
1 The Department of Physics, Chemistry and Biology, Linköpings Universitet, Linköping Sweden
Show AbstractElectronic measurement and stimulation of biological tissue in vivo and in vitro is usually inhibited by the system’s own defense systems. The biocompatible polyelectrolyte poly-L-lysine (PLL) has previously been investigated within areas such as e.g. surface coatings and modification assays as a protein repellent coating for hard materials such as metal electrodes. The goal of these studies is to develop electrodes for stimulating and monitoring e.g. nerve cells for extended periods of time.Many studies concerning the adsorption of PLL on various substrates deal with variables such as pH and ionic strength while fewer reports the effect of the underlying substrate potential. However, it has been demonstrated that the weakly basic cation PLL adsorbs continuously on the conducting substrate indium tin oxide (ITO) when applying a potential and using optical techniques. In addition to the continuous adsorption, no limitations regarding the adsorption rate was observed during film growth.We examine the rate-limiting step of the deposition of PLL on platinum electrodes (since platinum is a commonly used electrode material), by employing the electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) together with cyclic voltammetry (CV). This combination is very powerful in the simultaneous measurements of the change in frequency, dissipation and current in response to the potential applied, hence emphasizing the value of applying a potential to the underlying substrate while adsorbing PLL. To further investigate the properties of the resulting film, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements have been made to further corroborate the EQCM-D and CV results.
9:00 PM - PP3.30
Nanostructured Dendritic LbL Films as Plataform to ENFET Biosensors.
Nirton Vieira 1 , Alessandra Figueiredo 1 , Edson Fernandes 1 , Alvaro de Queiroz 2 , Valtencir Zucolotto 1 , Francisco Guimaraes 1
1 , IFSC-USP, São Carlos, São Paulo, Brazil, 2 , ICE-UNIFEI, Itajubá, Minas Gerais, Brazil
Show AbstractThis study presents a new Enzyme Field Effect Transitors (ENFET) based on dendrimers and metallophtalocyanines (MPcs) in the form of Layer-by-Layer (LbL) films assembled on indium tin oxide (ITO) as gate platforms. MPcs may act as artificial enzymes due to its catalytic properties and ionic selectivity. The dendrimer layers offer a nanoporous environment, which may be permeable to H+ ions improving the sensibility as modified electrodes for (bio)sensing. Furthermore, NH3+ groups from dendrimer allow electrostastic interactions or covalent bonds with redox based enzymes. Upon detection of specific analytes, the sub-products of the enzymatic reaction may change the pH locally, affecting the electrical properties of the ENFET. Here, a Separative Extended Gate-FET (SEGFET) was used as an alternative structure to isolate the field effect transistor (FET) from the chemical environment, formed by an ITO plate connected to the input pin of instrumentation amplifier AD620 used as unity gain buffer. Ag/AgCl electrode was connected in the reference pin of AD620. Glucose oxidase was imobilized on the ITO in conjunction with poly(propylene imine) dendrimer (PPID) generation 3 and nickel tetrasulfonated phthalocyanine (NiTsPc) layers. The systems were able to detect glucose at concentrations down to 10 mg/dL, which is below the typical concentrations in the human body. The ENFET platforms also allowed the immobilization of tyrosinase, for phenolic compounds detection. This set of nanostructured platforms may be useful for fabrication of low-cost, highly sensitive biosensors for point-of-care analyses
9:00 PM - PP3.31
Diamond Micro Electrode Array (MEA) for Recording and Stimulating Neuronal Tissue Toward New Retinal Implants.
Lionel Rousseau 1 , Alexandre Bongrain 2 , Amel Bendali 3 , Emmanuel Scorsonne 2 , Gaelle Lissorgues 1 , Blaise Yvert 4 , Philippe Bergonzo 2 , Serge Picaud 3
1 Service for Microelectronics and Microsystems, ESIEE-Paris, Noisy Le grande cedex France, 2 LIST Diamond Sensor Laboratory, CEA/Saclay, Gif-sur-Yvette France, 3 Institut de la Vision, , INSERM UMRS-968, UPMC, Paris France, 4 Centre de Neurosciences Intégratives et Cognitives (CNIC), CNRS & Univ. Bordeaux1, Bordeaux France
Show AbstractMicro Electrode Arrays (MEAs) offer an elegant way to probe the neuronal activity distributed over large populations of neurons either in vitro or in vivo. They enable to deliver specific electrical stimulations to neuronal networks. Today the interests for MEAs are rapidly growing since they provide a mean to record the activity of many cells simultaneously over large networks in order to follow cell information exchanges. Specific MEAs can be also used to build neural prosthesis or implants to compensate function losses due to lesions or degeneration of part of the Central Nervous System (CNS) such as for Parkinson disease treatment, or for cochlear or retinal implants. One critical problem encountered when using metallic microelectrodes is the narrow potential window they offer before medium direct ionisation. This implies that high currents may degrade the electrodes and alter the tissue itself. This paper describes a new approach involving the use of a non conventional material, namely Boron Doped Diamond (B-NCD) to fabricate MEAs composed of 64 electrodes. The technological route implies either (i) the local growth of diamond on metal electrodes (Titanium) and using Si3N4 for insulation, or (ii) homogeneous growth and annular metallic contacts. All passivation is ensured using SU8. Here two preparations were used for tests : (i) cultures of ganglion cells (CGC) and (ii) organotypic cultures of mouse spinal cords. The tests demonstrated that no difference could be observed with respect to glass control. Also, no proteinic coating was found to be necessary to ensure cell growth. We show that B-NCD offers several advantages when compared to metallic materials. Its carbon surface offers high biocompatibility, and the B-NCD potential window is about twice that of Pt. Fabricated MEAs were characterized using electrochemical measurements (cyclic voltametry and Electrochemistry Impedance Spectrocscopy (EIS)) and their performances compared with that of Pt identical devices. In-vitro 64 B-NCD MEA were tested with retina of rat and spinal cords. We recorded spontaneous activity (local field potential (LFP) and spikes. Stimulation was also achieved and the possibility to inject higher current levels was demonstrated using B-NCD than with Pt. The local pH variations were probed in the vicinity of these microelectrodes during electrical stimulation and we observed strong improvements of the charge injection capabilities (up to x40) over conventional platinum microelectrodes. Finally, flexible B-NCD implants were fabricated using this approach for retinal prosthesis. Such implants were based on 16 electrode systems and were tested in-vivo on rats. Preliminary results demonstrated a significant reduction of glial cells appearance for diamond electrodes when compared to metallic electrodes, thus demonstrating that B-NCD MEAs provide new promising routes for the design of robust neural prosthesis for long term interfacing of complex nervous systems.
9:00 PM - PP3.32
Equivalent Circuit Analysis of Impedance Spectroscopy in Human Trabecular Meshwork Endothelium.
Wenwen Gu 1 2 , Yi Zhao 1
1 Biomedical Engineering, Ohio State University, Columbus, Ohio, United States, 2 , Chongqing University, Chongqing China
Show AbstractAqueous humor is generated by ciliary body and leaves the eye at the anterior chamber. The elevated resistance in aqueous humor outflow is believed the main cause of the increased intraocular pressure (IOP), which leads to primary open-angle glaucoma (POAG), one of the leading causes of blindness. In the past two decades, research on outflow resistance of aqueous humor has focused on trabecular meshwork (TM) and Schlemm’s canal (TM) endothelial lining. Current technologies include morphological and immunochemical characteristiions, protein and DNA assay, and perfusion. Nonetheless, little is yet known about the exact loci that are responsible for the resistance increase, or the key factors that govern the outflow resistance. In addition, many aforementioned technologies are time-consuming and labor-extensive. Impedance spectroscopy is a promising and non-invasive alternative, which quantifies cell behavior through cell-electrode interaction. Here, we analyze the equivalent circuit of TM endothelium to pave the way for impedance spectroscopy based outflow determination.First, an analogy between hydraulic resistance and electrical impedance is developed. In perfusion, the fluidic flow rate through TM endothelium under a given hydraulic pressure is a measure of the hydraulic resistance. Assuming the concentration of conductive ions (the main charge carrier) is homogeneous, the hydraulic pressure can be positively correlated to the electrical impedance across the endothelium.An equivalent circuit of the TM endothelium is developed. Each TM cell is modeled as two capacitors (cell membrane) and one resistor (cytoplasm) connected in series. The cells are connected in parallel with a resistor representing extracellular matrix (ECM). Spectrum analysis is performed using PSpice by systematically changing the electrical resistivity of the cytoplasm, the electrical resistivity of the ECM, and the cell number index.The result shows that appropriate electrode area is necessary for achieving discernable impedance changes due to resistivity changes of cytoplam and ECM, and for differentiating them from each other. In particular, under a low frequency on the order of a few hundred Hz, the impedance is more responsive to ECM resistivity change; while under a high frequency on the order of a few MHz, the impedance is more responsive to the cytoplasm resistivity change. The cell number index does not seem to be a critical control factor. Its influence on the impedance can be seen within the range of a few tens kHz. The beauty of this work lies in the differentiation capacity of transcellular resistivity through the cell body and paracellular resistivity through the ECM. As known, the aqueous humor outflow has both transcellular and paracellular transports. The understanding of the contribution of each passway and their evolution under glaucomatous conditions is expected to bring insights for new therapies towards POAG.
9:00 PM - PP3.33
Design and Fabrication of a Multi-patch Recording Unit for Electrophysiological Studies on Neural Networks.
Onyekachi Odoemene 1 , Aeraj ul Haque 2 , D.Marshall Porterfield 2 1
1 Biological Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Agricultural and Biological Engineering, Purdue University, West Lafayette , Indiana, United States
Show AbstractPresented is the design and fabrication of a next-generation electrophysiology tool for whole-cell recordings on many cells of a biological neural network. The device, fabricated on a silicon substrate, consists of a circular array of through-holes (patch pores) interconnected to backside microfluidic channels produced via Deep Reactive Ion Etching (DRIE). The silicon substrate is integrated with PDMS channels with provision for insertion of microtubing for suction and Ag/AgCl microelectrodes for measurement. The fabricated biochip is interfaced with custom signal processing and data acquisition system to yield a complete technology for high throughput electrophysiology. This multiple patch-clamp microsystem is a promising research tool for studying communication in neuronal networks such as in the retina or auditory cortex, and can potentially serve as a standard electrophysiology tool for cell signaling research.
9:00 PM - PP3.34
Development of a Nanoscale Optical Fiber Biosensor Assays to Detect and Differentiate Staphylococcus Aureus and Methicillin-resistant S. Aureus.
James Heflin 1 , Thomas Inzana 2 , Ziwei Zuo 1 , Aloka Bandara 2 , Michaelenka Anne 2
1 Physics, Virginia Tech, Blacksburg, Virginia, United States, 2 Biomedical Sciences and Pathobiology, Virginia Tech , Blacksburg, Virginia, United States
Show AbstractStaphylococcus aureus (SA) is a dynamic and adaptable bacterium that is demonstrated to exhibit a great efficiency for quick antibiotic resistance. It is well known that SA is a dominant source of a range of skin, soft-tissue and systemic infections. Methicillin-resistant S. aureus (MRSA) has emerged as a major health problem beyond the health care setting. Reports from various community settings regarding MRSA infections indicate up to 33% of patients due to bacteremia. A call for rapid diagnosis to enable early effective therapeutics is highly needed. Therefore, there is a demand for culture-free diagnostic tests that are both highly sensitive and specific, and can be implemented in basic facilities without professional guidance. We present results utilizing a novel optical fiber biosensor with nanoscale self-assembled film affinity coatings. Ionic self-assembled multilayer (ISAM) films are a burgeoning class of materials that allow precise thickness control at the nanoscale level combined with simple, rapid, and inexpensive fabrication. Optical fibers with long-period gratings (LPGs) exhibit exceptional sensitivity of the transmitted intensity at specific wavelengths due to adsorption of ISAMs on the surface of the fiber cladding. The goal of our work is to combine the LPG-ISAM system as a culture-free, rapid diagnostic assay to detect and differentiate SA and MRSA. The LPG-ISAM was treated with monoclonal antibody (MAb) to the penicillin-binding-Protein 2a that is positively specific to MRSA isolates, while negatively to methicillin-sensitive SA (MSSA) isolates. The MAb bound LPG-ISAM was then reacted with serial dilutions of irradiated whole cells of MRSA strain 1556 or MSSA strain 29213. The transmission power was significantly attenuated as a result of MRSA strain 1556 binding to the LPG-ISAM, which is able to sense the existence of MRSA strain 1556 down to the range of 100 cells/ml. The transmittance for the light in fiber at the wavelength of 1550 nm was reduced by 23% in the presence of 440 cells/ml, and 48% in the presence of 4.4 x 10^3 cells/ml, while transmittance changes of 1% can be reliably measured. These results demonstrate that the LPG-ISAM system provides a promising culture-free assay that can be operated by non-specialist personnel and allow accurate determination of MRSA with minimal sample treatment. Work is currently underway to evaluate the capability and specificity of this system to MRSA in infected tissues from mice.
9:00 PM - PP3.35
Ultrathin Film Resonators Excited by Ultrafast Light Pulses and Their Application to Label-free Biosensors.
Hirotsugu Ogi 1 , Tetsuya Kawamoto 1 , Nobutomo Nakamura 1 , Youhei Nakamichi 1 , Masahiko Hirao 1
1 , Osaka University, Toyonaka, Osaka Japan
Show AbstractFocusing on the principle of the quartz-crystal microbalance (QCM) biosensor, we propose a novel label-free biosensor using ultrathin film resonators. A QCM biosensor detects adsorbed proteins on receptor proteins immobilized on the quartz surface through the decrease in the mechanical resonance frequency, realizing a label-free monitoring of the binding reaction. Its sensitivity significantly increases with the decrease of the oscillator thickness, because the mass of adsorbed proteins relatively increases with the decrease of the mass of the oscillator. The picosecond ultrasound spectroscopy allows measuring through-thickness vibrations of ultrathin films and makes it possible to develop an ultrahigh-sensitive oscillator biosensor. We use 100-nm silicon-nitride free-standing thin films and 16-nm Pt thin films on glass substrates. Their fundamental resonance frequencies are 45 and 132 GHz, respectively. Ultrashort light pulses were focused onto thin films to excite standing-wave vibrations within the films. After the excitation, probing light pulses detect their vibrations through the optoelastic effect. We used anti human-immunoglobulin G antibody and Staphylococcus aureus protein A as receptors and immobilized them on the film surfaces. The surface-modified sensor chip was set in a flow-cell, where a carrier solution flowed along the sensor-chip surface. The back surface of the substrate was exposed to atmosphere, from which the light pulses entered for the vibration measurement. The hIgG solutions were injected by a micropump, and we monitored the vibrational amplitude and frequency of the ultrathin films during the binding reaction between hIgG and receptors. Significant decreases in the amplitude and the frequency were observed even for analytes with concentrations below 1 ng/ml, showing high potential as highly sensitive biosensors.
9:00 PM - PP3.36
A Mechanical Model for Soft Tissue Elastic Modulus Computation.
Xiaodong Zhao 1 , Baoxiang Shan 2 , Assimina Pelegri 3
1 Mechanical and Aerospace Engineering, Rutgers - The State University of New Jersey, Piscataway, New Jersey, United States, 2 Mechanical and Aerospace Engineering, Rutgers - The State University of New Jersey, Piscataway, New Jersey, United States, 3 Mechanical and Aerospace Engineering, Rutgers - The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractA number of biomechanics-based imaging techniques have been developed based on the difference in mechanical properties or responses of biological tissues under external loading and stimulus. To ensure stimulus effectiveness, focused acoustic radiation forces (FARF) are increasingly being used as the externally-applied excitations. FARF methods may generate a localized oscillation point-by point directly within the targeted region. Harmonic motion imaging (HMI) is a technique that uses point-focused ultrasound waves to generate a periodic, sinusoidal excitation force at specific points in the target tissues. It was applied in a 2D fashion using raster-scanning technique for tissue mapping and 3D displacement imaging. Raster scanning measures displacements at a multiple equilibrium configurations instead of a single equilibrium configuration as occurs in traditional experimental and computational methods. A mechanical model and computational procedure are developed in this study to estimate the elastic modulus of soft tissue in HMI, which could model the multiple equilibrium configurations and reconstruct the global elasticity from the localized displacement measurements.The multiple equilibrium configurations during raster-scanning experiments could be modeled as a series of localized measurements. In each measurement, the dynamic displacement is estimated by using 1D cross correlation methods. The local displacement field is then estimated based on the superposition principle. The concept of dipole loadings is also introduced in the superposition calculation. The localized acoustic radiation force distribution and boundary conditions are considered and satisfied with a model of dipole loading in infinite medium. Then an estimated inverse function is built which relates the elastic modulus with the dynamic displacement amplitude measured by HMI and raster-scanning techniques. The localized computation of elastic modulus of soft tissue could be reconstructed to get the global elasticity of the whole model. The analytical results are compared with experimental data and are found in good agreement.
9:00 PM - PP3.37
WITHDRAWN 12/21/10 Plasmon-integrated Photodiode Mechanism for Label Free Detection of Mycobacterium Tuberculosis Complex.
Burak Turker 1 4 5 , Hasan Guner 1 , Nihan Guvener 2 , Sencer Ayas 1 , Okan Ekiz 1 , Handan Acar 1 , Mustafa Guler 1 , Erhan Piskin 2 3 , Aykutlu Dana 1
1 UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara Turkey, 4 Biomedical Engineering, Afyon Kocatepe University, Afyon Turkey, 5 Electronics and Communication Engineering, Yildiz Technical University, Istanbul Turkey, 2 Chemical Engineering Department and Bioengineering Division, Hacettepe University, Ankara Turkey, 3 R&D Center for Bioengineering and Biyomedtek, Hacettepe University, Ankara Turkey
Show AbstractIn this work we use a plasmon-integrated photodiode substrate which has been developed for biomolecular sensing in microfluidic systems [1]. The sensing mechanism is composed of planarly integrated three layers. In between is the patterned and then metalized transparent polymer which functions as the grating coupler. At the bottom there is the integrated photodiode substrate to detect transmitted light intensity in terms of photocurrent and at the top there exists the integrated fluidic channel for biomolecular interactions to take place. Extending the study presented in [1], in this work it is proposed that the sensing mechanism can be turned into a biomolecular affinity sensor for the label free detection of Mycobacterium tuberculosis (MTB) complex [2]. Tuberculosis is considered a widely spread infectious disease with a significant social impact around the world with over 10 million incident cases and 13.7 million prevalent cases in 2007 (the WHO global tuberculosis control report, 2009). In order to detect the presence of MTB complex with the proposed sensing mechanism, the sensor platform is planned to be prepared as in the following steps: (1) immobilization of the MTB probe in the presence of surface blocking agent, (2) hybridization with the MTB target sequence and finally, (3) observation of the non-specific interaction by the immobilization of non-tuberculosis bacteria (mycobacterium gordonae) to the specified sensing platform. A single-strand oligodeoxynucleotide, carrying a thiol end group, which is complementary of the target characteristic sequence of MTB complex and Mycrobacterium gordonae is used as the “probe” and immobilized onto the sensor surface by using a direct immobilization method based on the self-assembled over-layer formation. Plasmon enhanced transmission is employed as a sensitive refractive index (RI) sensing mechanism for the label free detection scheme. By tuning the angle of incidence of a collimated beam to the sharp plasmon resonance condition, enhanced transmission of light is monitored at the integrated photodiode. Slight changes of the effective refractive index (RI) shift the resonance angle resulting in a change in the photocurrent.The developed sensing mechanism promises high specificity, sensitivity and sensor reproducibility with its formerly proven sensing abilities (an equivalent RI noise of 6.3x10E-6 RIU/sqrt(Hz) compared to a shot-noise limited theoretical sensitivity of 2.2x10E-8 RIU/sqrt(Hz)) for the solution based (i.e. distilled water and 5 % NaCl solution) detection of the small changes in the refractive indices. It also promises rapid and cost effective solutions for label free detection schemes.[1] Turker B., Guner H., Ayas S., Ekiz O. O., Acar H., Guler M. O. and Dana A., Lab On Chip, DOI: 10.1039/b000000x, 2010 (under review).[2] Duman M., Caglayan M. O., Demirel G., Piskin E., Sensor Letters, 7, 1-8, 2009.
9:00 PM - PP3.38
Probing Interactions of CdSe/ZnS Quantum Dots with Anti-porcine Parvovirus Antibody.
Shan Huang 1 , Maude Boisvert 2 , Peter Tijssen 2 , Dongling Ma 1
1 , University of Quebec, Institut National de la Recherche Scientifique, Varennes, Quebec, Canada, 2 , University of Quebec, Institut National de la Recherche Scientifique, Laval, Quebec, Canada
Show AbstractCurrently, semiconductor quantum dots (QDs) have attracted great attention in the field of biomedicine due to their superior and unique photophysical properties. For example, they have been explored to serve as probes in certain biological processes that are critical for the diagnosis and treatment of viral infections. To realize the high potential of QDs in biomedical applications, the investigation of the QD-biomolecule interaction is of high significance. Although the interaction between QDs and proteins has been studied, the results appear not universal and depend on the nature of the biomolecules. Here, we report our most recent work on the interaction between water-soluble CdSe/ZnS QDs of different capping agents and anti-porcine parvovirus (PPV) antibody. The anti-PPV antibody is a mouse monoclonal antibody and could bind specifically to the icosahedral capsid of PPV which is one of the small viruses of the Parvoviridae that can infect several types of animals. Both covalent coupling and simple mixing strategies were applied to form the QD-antibody bioconjugate structures. An array of photophysical measurements has been performed to quantify the interaction of QDs with the antibody. After systemic investigations, we found that the interaction of the antibody with QDs highly depends on the type of the capping agents on the QDs surface. For instance, the photoluminescence of mercaptoacetic acid-capped QDs are severely quenched by the antibody and the quenching dynamics appear quite different at different pH values. The quenching can be significantly reduced by using polyethylene glycol (PEG)-based molecules, although is not totally eliminated. The possible mechanisms for antibody adsorption on and photoluminescence quenching by the antibody to the QDs with varying capping agents are investigated and will be presented herein.
9:00 PM - PP3.39
Study of Synthesis of Gold Deposited Fluorescent Silica Nanoparticles for Biosensor Application.
Kyoung G. Lee 1 2 , Rinbok Wi 2 , Tae Jung Park 3 , Jae Beom Lee 4 , Seok Jae Lee 1 , Do Hyun Kim 2
1 NEMS-Bio team, Natioanl Nanofab Center, Daejeon Korea (the Republic of), 2 Department of Chemical & Biomolecular Engineering, KAIST, Daejeon Korea (the Republic of), 3 Bioprocess Engineering Research Center, KAIST, Daejeon Korea (the Republic of), 4 Department of Nanomedical Engineering, Pusan National University, Miryang Korea (the Republic of)
Show AbstractRecently, gold and silica nanoparticles have brought interests in bioanalysis applications due to high surface area and chemical and mechanical stability with high biocompatibility. Several methods have been employed to synthesize and modify both gold and silica nanoparticles for further applications. However, almost all the previously reported synthesis and deposition methods of gold nanoparticles on silica particles are required extra steps to modify silica particles. In addition, the synthesized gold nanoparticles have a wide size distribution with various shapes. In order to solve these problems, the use of sonochemical method will provide a unique condition to fabricate gold nanoparticles and modification of silica nanoparticles. In this study, the unifom size and shape of fluorescent silica nanoparticles with deposition of highly monodisperse gold nanoparticles were synthesized using both water-in-oil (W/O) microemulsioin method and intensive ultrasound irradiation. Triton X-100 and n-hexanol are used as surfactants to form water pools inside of cyclohexane. Individual water pools are served as reactor to hydrolysis of tetraethyl orthosilicate (TEOS) to form silica network and encapsulate fluorescent dye molecules. The encapsulated fluorescent dyes were protected by silica matrix from the outer environment to maintain the fluorescent properties. The diameter of produced fluorescent silica nanoparticles is in the range of 58-60 nm. The fabricated fluorescent silica nanoparticles were dispersed in the water and gold(III) chloride trihydrate (HAuCl4-3H2O) was added to the mixture then applied ultrasound with present of ammonium hydroxide for the deposition of gold nanoparticles on the silica. The diameter of deposited gold nanoparticles is in the range of 1-2 nm. One biosensor applications of gold-doped red fluorescent silica nanoparticles was demonstrated through the attachment of gold binding polypeptide-avian influenza viral surface antigen (GBP-AIa) and the subsequent interaction with anti-avian antibody. This application indicated that the gold-deposited fluorescent silica nanoparticles with a large surface area for binding can be an important material in the development of the new detection tool of biomolecules, such as viruses, with high selectivity and reproducibility. It is expected that current fabrication of gold-deposited fluorescent silica nanoparticles will extend its potential in various biological applications, such as multiplex bioanalysis, fluorescent imaging and biomolecular separation. Transmission electron microscope and scanning electron microscope were used to investigate the morphology of both fluorescent silica nanoparticles and gold-coated fluorescent silica nanoparticles. X-ray photon spectroscopy and Fourier-Tranform infrared spectrometer were employed to characterize the fabricated fluorescent silica nanoparticles and gold nanoparticles.
9:00 PM - PP3.4
Fabrication of Thick Cell Sheet via Electrochemical Reactions on Porous Membrane Culture Substrate.
Naoto Mochizuki 1 , Hiroaki Suzuki 1 , Junji Fukuda 1
1 , Graduate School of Pure and Applied Sciences University of Tsukuba, Ibaraki Japan
Show AbstractThis study describes that a porous membrane substrate modified with a synthetic oligopeptide, CCRRGDWLC, can be used to grow thick cell sheets, and subsequently detach them along with electrochemical desorption of the oligopeptide and stack each other. The oligopeptide was designed to contain an arginine-glycine-aspartate (RGD) domain in the center and cysteine at both ends. Since cysteine contains a thiol group, the oligopeptide was chemically adsorbed onto a gold layer on a porous membrane via the formation of a gold-thiolate bond. Fibroblasts seeded on the membrane were grown to form a thick cell layer. Then, by applying a negative potential, the gold-thiolate bonds were reductively cleaved, and the cell sheet was detached along with the desorption of the peptide. To evaluate the cell detachment quantitatively, cells were attached to the membrane substrate at a low density, and the detached cells were counted after the application of the potential. Over 90% of the cells detached within 5 min. Fibroblast sheets grown on the porous membrane were reached to a 50-µm-thick cell sheet at 14 days of culture, which was significantly thicker than that on a conventional culture dish due to higher oxygen supply. The proposed approach was further employed to stack the detached cell sheets to obtain 200–300 µm thick multilayered sheets. This cell sheet engineering approach could be a promising tool for tissue engineering and regenerative medicine applications.
9:00 PM - PP3.40
Protein-microparticles: Folding/Unfolding Thermodynamics.
Vamsi Mudhivarthi 1 , Inoka Deshapriya 1 , Densie Lee 1 , Challa Kumar 1
1 Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractDetailed thermodynamic studies of enzymes bound to solid supports are needed to design strategies for improving the bound enzyme stability. In this study, we describe our first attempts to characterize the thermodynamic folding & unfolding of a small set of representative protein, which are encapsulated in co-precipitated ZnCO3 microparticles. Thermal denaturation of Hb, lipase, GO & HRP occur in a very short range of temperature compared to that the protein in solution. While cooling proteins encapsulated in the ZnCO3 microparticle showed exothermic transitions even at a high scan rate of 2°C/min, which is in contrast with proteins in solution, which do not show any transition at this rate. Unlike protein in solutions, encapsulated proteins retained transitions in the 2nd heating scan. These transitions were observed all the way up to 6th heating scan. Proteins encapsulated showed no effect of scan rate on the melting temperature. HRP and lipase retained the peroxidase and esterase activity, respectively. Isolated encapsulation of the protein in the microparticle helps in the reversible unfolding of the protein, and efforts will be focused in further understanding this phenomenon. Biocatalysis, biosensors, gene delivery might be few of the many potential applications.
9:00 PM - PP3.41
Novel, Simple, Versatile Synthesis and Properties of Nanoparticles Made from Proteins, Nucleic Acids and Other Materials.
Challa Kumar 1 , Inoka Deshapriya 1 , Michael Duff 1 , Brett Blakeley 1 , Denise Haye 1
1 , University of Connecticut, Storrs, Connecticut, United States
Show AbstractAbstract: A new, simple, and versatile method was developed to prepare protein nanoparticles, for the first time, and the approach was extended to prepare organic, inorganic, and biological nanomaterials. For example, nanoparticles of met-hemoglobin and glucose oxidase are readily prepared by contacting a fine spray of aqueous solutions of the proteins to an organic solvent such as methanol or acetonitrile. The protein nanoparticles retained the secondary structure and the biological activities to a significant extent. The synthesis was extended to prepare nanoparticles of nucleic acids, ion exchange materials, transition metal complexes, organic molecules and organic polymers. Particle size depended on reagent concentration, pH, and the solvent used, and the particle sizes were controlled from 20 nm to 200 nm by adjusting reaction conditions. In each case, the particle sizes and size distributions were determined by dynamic light scattering and confirmed by electron microscopy, in a reproducible manner. Addition of appropriate electrolytes stabilized the particles against aggregation or crystallization, and the particles were found to be stable over months of storage at 4 °C. Nanoparticles of met-hemoglobin, glucose oxidase, and calf thymus DNA indicated retention of their native-like structures, as evidenced from the circular dichroism spectra. Enzyme nanoparticles retained their catalytic activities to a significant extent. For example, peroxidase-like activity of met-hemoglobin nanoparticles suspended in methanol was 0.3 μM-1s-1, while in aqueous buffer (pH 7) the specific acitivity of the free biocatalyst has been 1.0 μM-1s-1. Nanoparticles of anthracene indicated extensive excitonic coupling due to inter-chromophore interactions. The current method of nanoparticle synthesis is rapid, simple, versatile, reproducible and resulted in the formation of nanoparticles from a variety of matierials, for the first time.
9:00 PM - PP3.42
Highly Sensitive Single-walled Carbon Nanotubes Based Gas Sensors on Plastic Substrates.
Xinghui Li 1 , Selvapraba Selvarasah 1 , Yu Liu 1 , Chih-Feng Yang 1 , Mehmet Dokmeci 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractGas sensors are widely used in many applications including environmental safety, gas alarms and controlling manufacturing processes. Traditional gas sensors have limitations as being large, bulky and less sensitive. Miniature, low cost, highly sensitive and fast response gas sensors are of particular interest at present. Single walled carbon nanotubes (SWCNTs) are promising candidates as active materials in sensor applications due to their small size, large surface area-to-volume ratio and fast response. Being a light-weight, stress-free, transparent and inert film, Parylene-C does not produce any out-gassing and also has very low permeability against moisture and gases which makes it an ideal flexible substrate for flexible devices. In this paper, a miniature, sensitive SWCNT gas sensor with a fast response fabricated on parylene-C thin films is demonstrated. The SWCNTs based sensors can detect ppm level target molecules at room temperature in several seconds with very good reproducibility. 2D and 3D microelectrode-pair assembly platforms are fabricated on polymeric substrates. The fabrication starts by depositing a 10μm thick parylene-C layer on a silicon wafer. Then, sputter deposition, optical photolithography, lift-off and reactive ion etching process are utilized to form Ti/Au electrode pairs served as elevated microplatforms for assembling CNT devices. To realize 3D structure, a thin parylene-C layer was used as the dielectric between the two microelectrodes. Dielectrophoretic assembly is used to place SWCNT bundles on to the electrode pairs which form the sensor structure. Finally parylene substrates containing sensor units are peeled off from the silicon substrate which conclude the fabrication process. The measurements indicate an obvious resistance change between SWCNTs connected electrode pairs when the sensors are exposed to various gas vapors (isopropanol and methanol). Detection of methanol vapors is demonstrated using the SWCNT sensors, where the sensors easily distinguished a large range of different concentrations from 4.26ppm to 1.32×105ppm, which corresponded to a resistance variation of 4.8% and 69.6% respectively. DNA decoration on CNTs enhanced the sensitivity of the sensors. After DNA decoration, the sensors displayed a larger response to the gas vapors which were 12.3% and 131% respectively. In addition, the sensors also showed good reproducibility and fast response rate. When exposed to an ambient containing methanol vapors, the sensor had a fast response which rose from its initial value to half saturation value in less than 30 seconds. Meanwhile, the response also recovered its initial value very rapidly when put back in a nitrogen atmosphere. Several reproducibility measurements were conducted and there was no apparent variation or drift between measurements. Our results demonstrate a promising technology for SWCNT based flexible gas sensors in emerging monitoring applications.
9:00 PM - PP3.43
Effects of ZnO Nanowire Internalization into Individual Cells.
Deepti Sharma 1 , Rizwan Khan 1 , Bora Kang 1 , Jin-Tae Kim 1 , Yeon Ho Im 1
1 Chemical Engineering, Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractThe new field of nanomedicine integrates advanced nanomaterials (nanowire (NW) arrays and nanoparticle) with biomolecules and cells, in order to develop novel platforms for applications such as biosensing, drug screening, and drug delivery. As a part of the efforts for studying complex cellular process, direct interconnection of the cells to the external world by interfacing nanomaterials will be very useful to monitor biological processes occurring inside the cells, across the membranes, and between neighboring cells. We present the direct interface of ZnO NWs with mammalian cells THLE-3 (ATCC No. CRL-11233) cell lines and liver cancerous (HLK-2) cells without any external force. The ZnO NWs to be used for this study were grown by a vapor-liquid-solid (VLS) process in a horizontal tube furnace. The internalization of the ZnO NWs into individual cells naturally occurred during the cell incubation. The MTT assay results showed that the ZnO nanowires are completely biocompatible and biosafe after internalized into the cells. The optical and confocal images showed that in comparison to the control cells, most of the cells treated with ZnO NWs were rounded and less elongated, indicating some change in there morphology. After the specific surface modifications with plasma treatment, the NWs were found to provide less stressful environment to the mammalian cells culture upon internalization.
9:00 PM - PP3.44
Direct Sensing of Biomolecular Interactions Using Optically Responsive Probes Based on ZnSe Quantum Dots.
Jun Wang 1 , Ling Shen 2 , T. Mountziaris 1
1 Chemical Engineering, University of Massachusetts, Amherst, Massachusetts, United States, 2 CVIP, University of Massachusetts, Amherst, Massachusetts, United States
Show AbstractWe report the development and testing of a new class of nanoscale fluorescent biomolecular probes consisting of a ZnSe quantum dot (QD) capped with a layer of stabilizing bi-functional organic molecules and covalently linked to a single probe biomolecule, such as ssDNA, antibody, protein, etc., having an affinity to a specific biological target. These probes enable instantaneous direct sensing of biomolecular interactions by monitoring changes in the fluorescence emission intensity of the QDs induced by the binding of the probe to its specific biological target. We studied the hybridization of QD-ssDNA probes to a variety of target ssDNA sequences and found that the observed changes in fluorescence emission intensity of the QDs depend on the length and location of the hybridized segment. We designed and tested a probe by linking ZnSe QDs to 5’-Amine-AGACTTCTCCTCAGGAGTCAG, a sequence found in the healthy hemoglobin beta (HBB) gene, and studied its hybridization with two targets in solution: (a) the complementary sequence 5’-CTGACTCCTGAGGAGAAGTCT and (b) the mutated sequence 5’-CTGACTCCTGTGGAGAAGTCT, which includes a single-base mismatch corresponding to a common mutation in the HBB gene that causes sickle-cell anemia. The probe was able to differentiate between the two targets based on measurable variations of the QD emission intensity that were detected upon probe-target hybridization. A homogeneous assay was developed for quantitative detection of target oligonucleotides in solution. In another set of experiments, the rapid quantitative detection of human serum albumin (HSA) was demonstrated by employing a QD-HSA probe in a competitive homogeneous assay, performed by dosing a sample containing HSA with equimolar amounts of probe and anti-HSA antibody. A direct assay for rapid quantitative detection of fibroblast growth factor (FGF) using a QD-anti-FGF probe was also developed and tested. The stability, robustness, and sensitivity of these probes are being studied to enable the development of commercial applications.
9:00 PM - PP3.46
All-natural Synthesis and Nanoimprinting of GFP-silk for Fluorescent Enhancement.
Konstantinos Tsioris 1 , Jessica Mondia 1 , David Kaplan 1 , Fiorenzo Omenetto 1
1 BME, Tufts U., Medford, Massachusetts, United States
Show AbstractWe present here recombinant molecular- and cell biology based strategies for functional material synthesis with the objective of developing an all-natural process for optically functional materials.In this approach, chimeric proteins with various functionalities can be designed in a semi rational fashion at the DNA level. These new fusion materials are then conveniently expressed downstream in the cellular machinery of prokaryotic cells (i.e. Escherichia coli) and ultimately incorporated in a suitable environment for the development of a new class of micro- and nanostructured devices.We have chosen green fluorescent protein (GFP), and silk fibroin from the silk worm Bombyx mori for our model material system. The Super Folder GFP (sfGFP) variant was chosen for its excellent fluorescence properties (a quantum yield of 0.65 and a relative brightness of 1.6 in comparison to Enhanced GFP) and high protein expression yield. Silk fibroin was selected for its excellent optical characteristics (> 95 % transmission over the visible) and its mechanical properties that allow us to fabricate nanopatterned thin films. As a proof of principle we have successfully doped silk with GFP (GFP content < 1 %) to demonstrate combined material functionality.As a practical demonstration of an all natural derived functional biomaterial application, we have spincast GFP doped silk films. The films were subsequently nanoimprinted with suitable photonic lattices designed to enhance the fluorescent properties of this new material and we have characterized the resulting enhancement. The dimensions of the imprinted lattices are on the lengthscale of the fluorescent emission wavelength (lambda = 510 nm). These results pave the way for future applications where fusion of the GFP and silk protein are performed to show the functionality of the recombinant biomaterial. This approach provides a large variety of functionalities and consequently the generation of novel biomaterials with unprecedented combination of functions.
9:00 PM - PP3.47
Background-free Fluorescence Detection of Biomolecules Using Hydroxylated Nanocrystals.
Seung Koo Shin 1 , Yongwook Kim 1 , Wonjung Kim 1 , Hye-Joo Yoon 1
1 Chemistry, POSTECH, Pohang Korea (the Republic of)
Show AbstractMaking nanocrystals biocompatible without nonspecific bindings to background molecules is essential for long-term imaging and multiplexed assays of biomolecules using fluorescent semiconductor nanocrystals. Herein, we report the bioconjugation of small-sized, hydroxylated nanocrystals, enabling highly-sensitive detection of various biomolecules with little or no nonspecific binding. 3-Mercapto-1-propanol (MPO) was used to passivate the surface of zinc-blende CdSe/ZnS nanocrystals and the hydroxyl group was activated to amine-reactive succinimidyl carbonate derivatives to covalently link to amine-functionalized biomolecules, such as biotin, DNA, and hemagglutinin peptide, by forming a carbamate linkage. For comparison, 3-mercaptopropionic acid (MPA) was used to passivate the CdSe/ZnS nanocrystals and the carboxyl group was activated to O-succinimide esters to conjugate with aminated biomolecules. Photoluminescence properties of organic, water-soluble, and bioconjugated nanocrystals were characterized. Significantly, the bioconjugates of hydroxylated (CdSe/ZnS-MPO) nanocrystals exhibited brighter photoluminescence with longer lifetimes than those of carboxylated (CdSe/ZnS-MPA) nanocrystals. Specific and nonspecific interactions between nanocrystals and biomolecules were examined by incubating nanocrystal-bioconjugates with avidin-agarose beads, anti-hemagglutinin-affinity matrix, DNA-glass slide, or avidin-glass slide. CdSe/ZnS-MPO nanocrystals showed little or no nonspecific binding to both agarose beads and glass slides, whereas CdSe/ZnS-MPA nanocrystals exhibited significant nonspecific binding due to the carboxyl–amine interactions. Notably, CdSe/ZnS-MPO-bioconjugates yield much brighter images than CdSe/ZnS-MPA-bioconjugates in both DNA hybridization and biotin-streptavidin binding. Furthermore, CdSe/ZnS-MPO-DNA probes enable the detection of a DNA chip at the sub-attomole level. Hydroxylated nanocrystals are small, bright and photostable in physiological conditions and their bioconjugates afford background-free detection of specific biomolecular interactions, positioning them for an ideal fluorescent probe to biological settings.
9:00 PM - PP3.49
Surface Functionalization of Gold Nanoparticles for Dual Optical and Electrochemical Detection of Pathogens.
Clara Adams 1 , Hamdi Baccar 2 , Adnane Abdelghani 2 , Sherine Obare 1
1 Department of Chemistry, Western Michigan University, Kalamazoo, Michigan, United States, 2 Department of Physics, University of 7 November, Tunis Tunisia
Show AbstractSynthetic procedures that produce gram-scale, well defined and monodisperse metallic and bimetallic nanoparticles in the 1-4 nm size range is a continuing challenge in nanoscale science. We have developed new organic ligands that when used as stabilizers for metal nanoparticles, provide the ability to gain control of the particle size in one-step synthetic procedures. We have synthesized and characterized monodisperse metallic gold and bimetallic alloys of gold nanoparticles. Within the 1-4 nm size regime the nanoparticles exhibit unique electrochemical and optical properties. We have investigated the electrochemical quantized double-layer (QDL) charging differences of these metallic nanoparticles. Within this size range, the electronic properties transition from a bulk-like continuum of electronic states to molecule-like, discrete electronic orbital levels. Such properties provided evidence that the nanoparticles were ideal for biosensing applications. Studies that demonstrate the appropriate functionalization of the nanoparticles for the detection of pathogens will be presented.
9:00 PM - PP3.5
Electrochemical Control of Cell Density and Motility Gradients on Conducting Polymer Surfaces.
Alwin Wan 1 , Esma Ismailova 3 , Abdurrahman Gumus 1 , Daniel Brooks 2 , Delphine Gourdon 1 , Christopher Ober 1 , Claudia Fischbach 2 , George Malliaras 1 3
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 3 Centre Microélectronique de Provence, Ecole Nationale Supérieure des Mines de Saint Etienne, Gardanne France, 2 Biomedical Engineering, Cornell University, Ithaca, New York, United States
Show AbstractThe interface between electronic materials and biological systems is central to governing the behaviour of bioelectronics systems. To this end, learning how to control the interaction between cells and conducting polymers would aid the design and implementation of numerous biomedical devices ranging from sensors to prosthetics. Our work focuses on the design and fabrication of organic electronic devices, and how they interact with a variety of cell types and biomolecules. The devices have electrochemically-active surfaces that range in size from large-area macroscopic stripes to micron-scale pixels. We have been studying the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluenesulfonate (TOS) or polystyrenesulfonate (PSS), and its interactions with tumour cells (MDA-MB231), fibroblasts (3T3-L1), and neurons (NG108-15). By applying a voltage gradient across a PEDOT stripe, we have established gradients in cell density and motility by locally modulating the strength of cell adhesion on our “active” growth substrate. To study single-cell behaviour, we have patterned micron-scale pixelated surfaces where individual pixels can be electrically switched between two states: one that promotes cell adhesion, and one that does not. We discuss the differences in cell behaviour as a function of voltage; namely, that the cell types we have studied adhere more densely and with greater strength to oxidized PEDOT surfaces, as compared to reduced surfaces. We also discuss an underlying mechanism based on redox-dependent changes in the molecular conformation of fibronectin (both surface-adsorbed and cell-deposited), measured with Förster Resonance Energy Transfer (FRET) imaging. Finally, we discuss the dynamics of cell-hopping in the pixelated system, and the effectiveness of such a system in deterministically placing cells and directing their migration.
9:00 PM - PP3.52
Shape-memory Anchoring System for Bladder Sensors.
Iaci Pereira 1 2 3 , Fabrice Axisa 3 , Rodrigo Orefice 1 , Jan Vanfleteren 3 , Hercules Neves 4
1 Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 2 , Federal Center of Technological Education of Minas Gerais, Timoteo, Minas Gerais, Brazil, 3 Interuniversity Microelectronics Centre , IMEC-INTEC/TFC, Zwijnaarde Belgium, 4 Interuniversity Microelectronics Centre , IMEC, Leuven Belgium
Show AbstractBladder diseases can be prevented or predicted by observing abnormal syndromes of bladder urine pressure variations. Sensors may be built stretchable over a polyimide (PI) film and encapsulated in silicone that protects the sensor from attack by urine. The built pressure sensor would be implanted through catheters into the bladder with minimal pain and stress for the patient. However, as the sensor becomes smaller, it has become more difficult to keep the sensor implanted and to control its tendency to be expelled along with urine. In the present work, we propose the use of shape-memory polymer that would be able to change shape while in the body to provide an anchoring system for the bladder sensor. This polymer was made of a biomedical biodegradable waterborne polyurethane (PU). The electronic system was simulated by a PI film containing copper patterning. In the first stage, waterborne PU dispersion was synthesized by reacting poly(caprolactone diol) and isophorone diisocyanate in water. To guarantee a strong interface between PU and PI film, the PU area that interfaces the PI film was subjected to surface modification. Afterwards, the sensor was encapsulated in silicone. Mechanical tests were employed to evaluate adhesion between PU and PI film and adhesion in the ensemble on silicone. The shape recovery was simulated at 37°C, immersing the prototype in artificial urine (SURINE) and DI water. Bond strength between PU and PI film was 26.1 KPa. Prototype tension tests showed good maximum load. Shape recovery in synthetic urine and DI water was slightly different, 92.7 % and 95.2 % respectively. Mechanical tests after hydrolytic degradation indicated that sensor expulsion by the body may occur due to erosion of highly degradable material in SURINE. Biodegradable shape memory polymer is an appropriate anchoring system for a miniaturized bladder sensor.
9:00 PM - PP3.53
Flexible Parylene C-based Microdevice for Multichannel EMG Recordings.
Cinzia Metallo 1 , Robert D. White 2 , Barry A. Trimmer 3
1 Neuroscience Department, Tufts University , Boston, Massachusetts, United States, 2 Mechanical Engineering Department, Tufts University , Medford, Massachusetts, United States, 3 Biology Department, Tufts University , Medford, Massachusetts, United States
Show AbstractWe present the development, fabrication and testing of a flexible and minimally invasive parylene C-based microdevice intended for long term in vivo acquisition of electromyographic (EMG) signals. Parylene C was used as a structural substrate to take full advantage of its unique mechanical, electrical and physical properties. In particular, the device is extremely flexible. This provides, at the same time, a highly conformal coverage of the muscle surface and some degree of strain relief against the forces of micro-motion between the electrode and the surrounding tissues. Since a more uniform electrical contact is established at the electrode-tissue interface, the SNR is significantly improved. To yield high signal selectivity, the design of our multi-electrode array has been custom tailored to match the muscle anatomy of different living systems.The multichannel microdevice presented here offers the opportunity to study motor coordination in a vast range of invertebrate systems that are presently poorly understood. Furthermore, its design parameters are currently being implemented to record myoelectric activity in vertebrates.
9:00 PM - PP3.54
Effective Separation of Tumor Cells Using Surfaces Functionalized with a Biomimetic Combination of Adhesive Proteins.
Ja Hye Myung 1 , Khyati Gajjar 1 , Cari Launiere 2 , David Eddington 2 , Seungpyo Hong 1 2
1 Biopharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, United States, 2 Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractEffective detection of circulating tumor cells (CTCs) is of clinical importance in diagnosis/prognosis of cancer metastasis. However, CTCs are estimated as few as one tumor cell in the background of 10^6-10^9 normal blood cells even for late-stage metastatic cancer patients. The rareness of the cells has made effective separation and enumeration of CTCs from blood extremely difficult. We have investigated a novel separation method of tumor cells from cell mixtures in vitro using surfaces with biomimetic combinations of adhesive proteins, i.e. anti-epithelial-cell adhesion molecule (anti-EpCAM) and E-selectin. It was known that E-selectin and anti-EpCAM involve in the initial physiological interactions between CTCs and endothelium, which includes concurrent rolling and stationary binding steps. The specific capturing and potential enrichment of CTCs using anti-EpCAM and E-selectin, respectively, inspire a biofunctionalized surface that mimics biological complexity may detect and isolate target cells at a greater sensitivity and specificity. To prove this concept, we investigated the following: i) two proteins with distinct biofunctions can be co-immobilized; ii) a combined rolling and stationary binding via the mixture of the adhesive proteins can induce the separation of a CTC model cell; and iii) the biomimetic combination enhances overall capture efficiency of the surface, compared with that of the functionalized surface solely with anti-EpCAM. The co-functionalization of the surface by immobilization of various combinations of the two adhesive proteins was characterized using x-ray photoelectron spectroscopy and fluorescence microscopy using fluorophore-conjugated proteins such as APC-anti-EpCAM and fluorescein-anti-E-selectin. The surfaces were tested using in vitro cell lines (MCF-7 cells as a CTC model and HL-60 cells as a leukocyte model) under flow. Cell mixtures of MCF-7 and HL-60 were injected into a flow chamber that was assembled with a protein-immobilized slide, followed by microscopic observations of the cell behaviors on various surfaces. E-selectin caused both cells to roll, and anti-EpCAM induced stationary adhesion of MCF-7 cells exclusively. More importantly, the combination of dynamic rolling and stationary binding significantly enhanced MCF-7 cell isolation by 3-fold as compared to the anti-EpCAM-functionalized surface. This combination technique may be translated into a device with enhanced separation and detection of CTCs.
9:00 PM - PP3.55
PS-b-PAA Block Copolymer-Based Electrical Immunosensor for the Detection of Escherichia coli O157:H7.
Cho-Kyung Joung 1 , Han-Nah Kim 1 , Young-Rok Kim 1
1 Graduate school of Biotechnology, Kyung Hee University, Yongin Korea (the Republic of)
Show AbstractThe development of biosensors for the detection of pathogenic microorganisms is driven by the needs to increase the sensitivity and speed. Label-free biosensors using nanoporous membranes as the sensing elements have recently been gaining attention. Herein we demonstrate a nanoporous membrane biosensor for the detection of E. coli O157:H7 by implementing the nanopores with specific antibody. E. coli O157:H7 is one of the most harmful pathogenic bacteria that may causes life-threatening diseases. Nanoporous membrane was built through self-assembly of amphiphilic polystyrene-b-polyacrylic acid (PS-b-PAA) block copolymer on gold electrode and subsequent solubilization of PAA moiety. Anti- E. coli O157 antibody was immobilized on the surface of nanoporous membrane through EDC/NHS chemistry. Placed in a fluidic chamber, the gold electrode coupled with nanoporous membrane and specific antibody generated characteristic electrical signals that showed a good correlation with the concentration of target microorganisms in tested sample. The measurement was based on the regression equation for the normalized impedance change (NIC) and current change versus concentraion of E. coli O157:H7 This new feature of the nanoporous structure showed a potential for a simple and powerful analytical tools for pathogen detection.
9:00 PM - PP3.58
Organic Electrophoretic Delivery Devices for Modulating Molecular Rhythms in Hypothalamic Brain Slices.
Karin Larsson 1 , Gabriella Schmitz Lundkvist 1 , Agneta Richter-Dahlfors 1
1 Swedish Medical Nanoscience Center, Neuroscience, Karolinska Institutet, Stockholm Sweden
Show AbstractSignaling molecules and ion fluxes are key players in cell communication. Detailed studies in this field are hampered, as current technologies do not provide precise spatio-temporally controlled delivery of the bio-stimuli. Taking advantage of the combined electronic and ionic conductivity of conjugated polymers, we have established a novel technology platform to achieve precise, spatio-temporal control of cell signaling. The conducting organic polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) form the basis for this device, the organic electrophoretic “ion pump” (OEIP) (Isaksson J et al. 2007 Nature Materials, Tybrandt K et al. 2009 Advanced Materials). This device does not rely on aqueous flow, but rather translates electronic signals into ion fluxes. This enables cell addressing without convective disturbances. The OEIP can deliver positively charged ions (e.g. Na+, K+, Ca2+) and bio-molecules (e.g. acetylcholine, glutamate) in short-term experiments. Calcium plays an important role as an intracellular signaling molecule that regulates numerous intracellular processes in many cell types. This includes the gene transcription of so called “clock genes”, for instance Period 1 and 2, which maintain the circadian rhythm generation in mammalian pacemaker neurons located in the master brain clock, the suprachiasmatic nucleus. Circadian molecular rhythms can be studied in real-time using transgenic PERIOD2::LUCIFERASE mice. Here, we report on the development of the OEIP for delivery of ions and neurotransmitter to hypothalamic brain slices obtained from transgenic PERIOD2::LUCIFERASE mice in long-term experiments and describe current experiments regulating and phase shifting PERIOD2 rhythms.
9:00 PM - PP3.59
Real-time, Step-wise, Electrical Detection of Protein Molecules Using Dielectrophoretically Aligned SWNT-film FET Aptasensors.
Sei Kwang Hahn 1 , Taechang An 2 , Ki Su Kim 1 , Geunbae Lim 2
1 Advanced Materials Sciences and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Korea (the Republic of), 2 Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Korea (the Republic of)
Show AbstractAptamers are oligonucleotides which can specifically bind to target molecules such as small molecules, peptides, proteins, cells, and other biomolecules. Aptamer biosensors, so called aptasensors, have been developed using various nano-materials such as conducting polymers, graphenes and silicone nanowires for real-time electrical detection of biomolecules. However, the aptasensors still had several problems such as difficulties in fabrication and spatial control, reproducibility, a long detection time, insignificant electrical signals, and an unproportional sensitivity to the concentration of target molecules. In this work, aptamer functionalized addressable SWNT-film arrays between cantilever electrodes were successfully developed for biosensor applications. Dielectrophoretically aligned SWNT suspended films made possible highly specific and rapid detection of target proteins with a large binding surface area. Thrombin aptamer immobilized SWNT-film FET biosensor resulted in a real-time, label-free, and electrical detection of thrombin molecules down to a concentration of ca. 7 pM with a step-wise rapid response time of several seconds. The novel addressable dielectrophoretically aligned SWNT-film FET aptasensor will be investigated further for various diagnostic applications with biomarker-specific aptamers.
9:00 PM - PP3.6
Vapor Sensors Using Olfactory Proteins Coupled to Carbon Nanotubes.
Mitchell Lerner 1 , Brett Goldsmtih 1 , Joe Mitala 1 , Bohdana Discher 1 , A.T. Charlie Johnson 1
1 , University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractWe have constructed bio-nano devices which combine mammalianolfactory proteins with carbon nanotubes to create a new class of vapor sensors. Olfactory proteins are a specific class of G-protein coupled receptors, and require a cell membrane or similar environment for proper function. Functionalization procedures have been developed to meet the challenges of routinely coupling such membrane proteins to nanotubes, while preserving the function of the protein. We have successfully isolated olfactory proteins and attached them to carbon nanotube transistors, which provide fast, all-electronic readout of analyte binding by the olfactory receptor. Several different olfactory proteins have been tested, each showing a different sensing response. This work opens the way for future coupling of biology to nanoelectronics and improved biomimetic chemical sensing.This work is supported by the DARPA RealNose Project and theNano/Bio Interface Center
9:00 PM - PP3.60
Functional Polymeric Nanocoatings in Microfluidic Devices for Biological Applications.
Jingjing Xu 1 , Karen Gleason 1
1 Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States
Show AbstractModification with specific organic groups is critical for controlling the functionality of the surface. The initiated chemical vapor deposition (iCVD) method has shown great promise as a surface modification technique, and it has successfully been used to create many distinct homopolymers, random copolymers, and alternating copolymers using free radical polymerization. It is chemically comparable to solution-phase polymerization but is environmentally friendly, able to achieve good conformality, and able to maintain the chemical functionality in the monomers.Amine-functionalized iCVD surfaces have not yet been reported. Selection of a monomer is challenging because many candidates have low vapor pressures as a result of hydrogen bonding between amine groups. In this work, poly(4-aminostyrene) (PAS) thin films were synthesized via iCVD, representing the first time that a library of iCVD functional groups has been extended to amine moieties. The retention of the pendent amine chemical functionality was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photo-electron spectroscopy (XPS). Scanning electron microscope (SEM) reveals that the iCVD PAS coatings are conformal over nonplanar structures.The high amine density of the iCVD films enables the formation of a robust nanoadhesive with complementary epoxy functional groups. Prototype microfluidic structures were fabricated using the low-temperature and zero-outgassing reaction between the amine groups in iCVD PAS and the epoxy groups in iCVD poly(glycidyl methacrylate) (PGMA). Bonded devices were able to withstand pressure higher than 150 psi. While the traditional plasma sealing methods are specific for sealing glass or Si wafers to polydimethylsiloxane (PDMS), this new bonding method is compatible with a wide variety of polymeric materials. Additionally, the all-iCVD nanoadhesive bonding process displays high resistance against hydrolytic degradation. We've successfully grown both E-coli and myocytes in the iCVD-bonded chips and the chips lasted throughout the whole growth and over 2 weeks. Within the channels of the bonded devices, the reactive epoxy and amine groups remain available for subsequent functionalization for biological applications. The further functionalization of amine groups has been pursued in collaboration with Professor Swager’s group in the chemistry department. Research in Swager’s group has focused extensively on the application of conjugated polymers (CPs) such as poly(phenylene ethynylene)s (PPEs) to detect biological and chemical species. CPs has the ability to create much larger signal amplification than small molecule-based sensors and they can be attached to the amine-functionalized microchannels by carbonyl-amine reactions. Successful integration of amplified fluorescent polymers (AFPs) detection schemes into iCVD functionalized microfluidic systems has been achieved.
9:00 PM - PP3.61
Ion-beam-drilled Nanopore Arrays for Single-molecule DNA Sequencing Applications.
Ruby dela Torre 1 , Alon Singer 1 , Amit Meller 1
1 Biomedical Engineering, Boston University, Boston, Massachusetts, United States
Show AbstractFabrication of nanopore arrays using ion-beam drilling and atomic layer deposition is shown to be a viable method for high throughput DNA sequencing applications using optical detection. High-density nanopore arrays were drilled using Focused-Ion-Beam (FIB) and Atomic Layer Deposition (ALD) was used to decrease the pore size of the nanopore by adding layers of aluminum oxide. The FIB dwell time and current were optimized for our applications. Deposition of aluminum oxide improves the signal-to-background of our optical sensing scheme and decreases the surface charge induced by ion-beam drilling, which is advantageous for DNA capture in the nanopore.
9:00 PM - PP3.7
Nanosensors and Breath Analyzers for Point-of-care Diagnostics.
Perena Gouma 1
1 Center for Nanomaterials and Sensor Development, SUNY Stony Brook, Stony Brook, New York, United States
Show AbstractThe detection and monitoring of gases in exhaled human breath up to date has been limited by the lack of appropriate materials and technologies that could rapidly and selectively identify the presence and monitor the concentration of trace levels of specific analytes-biomarkers. We present novel metal oxide-based nanosensors that are highly specific to biomarkers such as ammonia and acetone gas in breath-simulating environments at low part-per-billion concentrations. The design of a MEMS-based handheld breath analyzer for gas detection in exhaled human breath is described and examples are given for urea monitoring and diabetes detection. Semiconducting ceramics are presented as suitable sensor materials for easy and affordable noninvasive diagnostics.
9:00 PM - PP3.9
Grating Coupled Waveguide Biosensor Based on Porous Silicon.
Xing Wei 1 , Sharon Weiss 1
1 Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractPorous silicon is an attractive material for biosensing applications due to its large internal surface area, which enables the possibility of immobilizing a large number of biomolecules. Porous silicon waveguide structures have the additional advantage of strong electric field confinement in the porous waveguide film layer where the biomolecules are captured, resulting in more sensitive detection of small molecules compared to evanescent wave based biosensors that rely on surface-based biomolecule capture. Here we demonstrate a grating coupled waveguide structure made entirely of porous silicon as a new portable platform for biosensing. The porous silicon waveguide is fabricated by electrochemical etching. The porous silicon grating is formed using two different methods. In one case, electron beam lithography is used to define photoresist gratings on top of the waveguide followed by reactive ion etching to transfer the grating patterns into the porous silicon underneath. Residual photoresist is removed. In the second case, the porous silicon gratings are formed by a new direct imprinting method where a silicon grating stamp is used to locally deform the porous silicon film. In both instances, the gratings are simple, reproducible and permanent couplers that are especially beneficial for integrated sensing applications. A discussion of the relative advantages and disadvantages of each grating fabrication method will be provided. Simulations and experimental measurements are performed to demonstrate the capabilities of the grating coupled porous silicon waveguide biosensors. When light is incident on the biosensor, the gratings can couple the light into the waveguide at a specific incident angle. Biomolecular attachment in the waveguide causes the porous silicon waveguide refractive index to change; this process can be monitored by measuring the corresponding angular change in the grating coupling condition. We demonstrate that the grating coupled porous silicon waveguide sensors can distinguish specific DNA sequences with a selectivity of approximately 6 : 1 when functionalized appropriately. Rigorous coupled-wave analysis gives good agreement with experiment results.
Symposium Organizers
Peter Kiesel Palo Alto Research Center
David Nolte Purdue University
Xudong (Sherman) Fan University of Michigan
Martin Zillmann Millipore Corporation
PP4: Electrical Bio Sensors
Session Chairs
Tuesday AM, November 30, 2010
Back Bay C (Sheraton)
9:30 AM - PP4.1
Biologically-switchable Gate Semiconductor for Bio-functional Analysis.
Toshiya Sakata 1
1 Department of Materials Engineering, The University of Tokyo, Tokyo Japan
Show AbstractBiosensing techniques, which enable simple detection and diagnosis, realize precisely and simply the elucidation of various diseases such as cancer, Alzheimer's disease, and circulator disease and the development of adequate drugs, although biological function is obviously complex. In our laboratory, we are studying and developing biosensing techniques to analyze and monitor simply and easily biomolecules or cell functions, which is reenacted on substrates in vitro as same as in vivo possible. Moreover, we focus on direct detection of ions or ionized molecules with charges, for example sodium or potassium ions through ion channel at cell membrane, which are closely related to cell-cell communication, and DNA molecules also have intrinsic molecular charges based on phosphate groups. In order to detect directly ion or molecular charges, we have used semiconductor-based biosensing devices. Using the semiconductor-based biosensing devices for direct detection of biomolecules and cell behaviors, we can utilize the principle of field effect based on semiconductor device technology. We have basically utilized metal-oxide-semiconductor (MOS) transistor but devised to trust energization to biological phenomena on the gate sensing surface in solutions, which we call “Biologically-Switchable Gate Semiconductor”. Most of biomolecules such as DNA, protein or ions through ion channel at cell membrane electrostatically interact with electrons in silicon crystal across thin gate insulator resulting in change of drain-source current at channel in silicon, because they have intrinsic charges in solutions. Thus, we can obtain easily and noninvasively biological phenomena such as DNA molecular recognition events, antigen-antibody reaction, cell behaviors. In real-time measurement of cell functions for the prolonged culture, particularly, we have to consider the control of cell culture environment such as temperature, and atmosphere. Recently, we have succeeded in real-time and noninvasive monitoring of respiration activity of cancer cells, mouse embryos and iPS cell colonies for the prolonged cell culture. Our cell analysis system have both functionalities of real-time measurement of electrical signals by use of semiconductor-based biosensing devices and real-time observation of cell movement by use of microscopy in incubation system. Also, microfluidic system has been prepared as a matter of course. Using the established detection and observation system, we have been able to detect and monitor easily and accurately “Live and Dead” cells. The real-time and noninvasive analysis of “Live” cell is very valid for transplantation of cell to patients, while you can realize the high-throughput and accurate measurement of the effect of drugs on cancer cells and so on, which means the detection of “Dead” cell, that is programmed cell death – Apoptosis, in field of drug discovery.
9:45 AM - PP4.2
Cell/Semiconductor Signal Transduction Interface for Cell Death Detection
Toshiya Sakata 1
1 Department of Materials Engineering, The University of Tokyo, Tokyo Japan
Show AbstractRecently, many types of biochip/biosensor have been developed for biological and clinical research, medical application and pharmaceutical lead discovery. In our group, we have succeeded in the non-label and non-invasive electrical detection of bio-molecular recognition events for the genetic and the cell-functional analyses using a biologically coupled field effect transistor (bio-FET). The principle of bio-FET is based on the potentiometric detection of charge density change which is induced at a gate insulator/solution interface by specific bio-molecular recognition. The highly sensitive and selective detection of ion or molecular charges through membrane proteins such as ion channel, ion pump and transporter at cell membrane by use of the bio-FET enable to analyze cell function clearly. In this study, we investigate signal transduction interface between cell/semiconductor for highly sensitive and selective detection of cell function. In particular, we develop cell/semiconductor interface which can selectively detect potassium ion release through the ion-channel based on programmed cell death, apoptosis.We used n-channel depletion mode FET with Ta2O5/SiO2 layer as the gate insulator and made functional membrane sensitive to potassium ion at the gate insulator using 18-crown-6 ether derivative. In order to investigate the electrical characteristics of FET, we used a semiconductor parameter analyzer and a custom-made real-time analyzer. The analysis of surface structure was performed using X-ray photoelectron spectroscopy (XPS).The chemically modified 18-crown-6 derivative was confirmed at the gate insulator by XPS analysis. The bio-FET with the functional monolayer showed the detection selectivity to potassium ion and detected electrically the variation of potassium ion concentration. In addition, to investigate the possibility of electrical measurement by the bio-FET under cell culture, we cultured Hela cells at 37 °C and 5% CO2 on the functional membrane made on the gate insulator of bio-FET. Hela cells were adhered and extended on the gate insulator with the functional membrane. Moreover, potassium ion release through the ion-channel caused by apoptosis could be detected electrically by use of the bio-FET with the functional membrane.In this study, we could show the possibility to analyze the ion channel behavior selectively using the bio-FET modified by the functional membrane. The platform based on the bio-FET in combination with the functional bio-interface is suitable for noninvasive, real-time and high-throughput monitoring of apoptosis for drug discovery. We are going to develop the functional polymer membrane for more highly sensitive and selective detection, and would like to discuss with its effect on the electrical detection of cell function in the conference.
10:00 AM - PP4.3
CMOS Inverter Mmine/Ammonia Sensors.
Noah Tremblay 1 2 , Howard Katz 1 , Patrick Breysse 2
1 Materials Science & Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractIt is well-known that ammonia diminishes the performance of organic p-type semiconductors by way of decreasing current levels by lowering mobility. We have investigated the effect of ammonia as well as other amines on p-type materials in the development of amine sensors. Depending on the carrier energy level of the semiconductor and the size of the amine, amines in the ppb to ppm range either reversibly decrease mobility by factors of 2-5, or irreversibly decrease mobility by orders of magnitude. Conversely, we have also discovered a response by n-type organic semiconductors to amines that increases current levels and electron-mobilities. Using both p-type and n-type sensitive materials, we have developed sensitive CMOS inverters to accomplish increased sensitivity (exploiting the difference between the two types of responses) and increased range of sensitivity. Both these highly sensitive sensors and sensors with wide response ranges will lead to highly selective integrated sensor arrays (exploiting the wealth of diversity of different semiconductors responding to amines of various types) over individual semiconductor devices.
10:15 AM - PP4.4
SOIFET-based Nanoribbon Sensors for Ultra-low Biomolecule Detection.
Poornika Fernandes 1 , Oliver Seitz 2 , Richard Chapman 2 , Harvey Stiegler 2 , Huang-Chun Wen 3 , Yves Chabal 2 , Eric Vogel 1 2
1 EE, University of Texas at Dallas, Richardson, Texas, United States, 2 MSE, University of Texas at Dallas, Richardson, Texas, United States, 3 , Texas Instruments, Inc., Dallas, Texas, United States
Show AbstractFor over 30 years, field effect transistors (FETs) have been used as ion sensors [1] and their potential impact on biomedical applications have been explored. Recently, functionalized silicon nanowires have been used to detect a variety of species including proteins and single viruses [2]. Fabricating nanowires for use in CMOS-compatible processes still pose a major challenge in terms of large-scale manufacturability. Bottom-up nanowires suffer from metal contamination, poor size controllability and pick-and-place alignment, whereas top-down nanowires require device by device e-beam lithography for patterning. Sensors based on planar FET structures are more compatible with existing manufacturing processes. In this paper, we show that planar micron-width nanoribbon sensors can be used for ultra-low detection of biological molecules similar to that demonstrated using nanowire sensors.We have developed a well-controlled platform for sensing. Issues such as damage-free surface cleaning of sensor oxides, SAM stability [3] and salt contamination of FET oxides in buffers have been addressed [4]. Base-line studies as pH sensors have also been performed and coupling effects due to back-gate biasing of the SOI-based structure have been investigated [5]. Using this platform, we show electrical measurements of protein sensing on planar sensors using the well known biotin-streptavidin system. We also demonstrate that ultra-low detection down to the femto-molar range can be achieved using micron scale devices. Simulations of the biosensor to corroborate electrical results will also be presented and FTIR physical characterization will be presented which confirm the attachment of the biomolecules [6].REFERENCES:[1] P. Bergveld, Sensors and Actuators B, vol. 88, pp. 1-20, 2003.[2] F. Patolsky, G. Zheng, O. Hayden, M. Lakadamyali, X. Zhuang, and C. M. Lieber, Proc. Nat. Acad. Sci., vol. 101, no. 39, pp. 14019, 2004.[3] O. Seitz, P. G. Fernandes, R. Tian, H. -C. Wen, H. J. Stiegler, R. A. Chapman, E. M. Vogel, Y. J. Chabal, to be submitted to Langmuir[4] P. G. Fernandes, O. Seitz, R. A. Chapman, H. J. Stiegler, H. -C. Wen, Y. J. Chabal, and E. M. Vogel, accepted at Applied Physics Letters[5] P. G. Fernandes, O. Seitz, R. A. Chapman, H. J. Stiegler, H. -C. Wen, Y. J. Chabal, and E. M. Vogel, submitted to Applied Physics Letters[6] N. A. Lapin and Y. J. Chabal, J. Phys. Chem. B, vol. 113 , pp. 8776, 2009
10:30 AM - PP4: ElecBio
BREAK
11:00 AM - PP4.5
Chemo-resistive Gas Sensors for Easy Diagnosis of Diabetes by Breath Analysis.
Marco Righettoni 1 , Antonio Tricoli 1 , Sotiris Pratsinis 1
1 Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Zurich, Switzerland
Show AbstractThe rising costs of medical care are pushing toward a rationalization and reorganization of medical services including daily hospital care and diagnostic methods. For the latter, standard detection of illnesses such as blood analysis, gastroscopy, endoscopy, and ultrasonic imaging have reached the limit of further economization as trained human resources are required. New methods such as non-invasive diagnostics by human breath analysis (1) bear the potential of drastically reducing such diagnostic costs as a greater amount of automatization is possible (2). Furthermore, breath analysis has the potential for early stage detection and monitoring of several illnesses allowing a prompt medical treatment with higher chances of patient recovery and better quality of life.Acetone in the human breath is an important marker for non-invasive diagnosis of type-1 diabetes. Here, novel chemo-resistive detectors have been developed that allow rapid measurement of ultralow acetone concentrations (down to 20 ppb) with high signal-to-noise ratio in ideal (dry air) and realistic (up to 90% rh) conditions. The detector films consist of (highly sensitive) pure and Si-doped WO3 nanoparticles (10 - 13 nm in diameter) made in the gas phase and directly deposited onto interdigitated electrodes. Their sensing properties (selectivity, limit of detection, response, and recovery times) have been investigated as a function of operating temperature (325 - 500 °C), relative humidity (rh), and interfering analyte (ethanol or water vapor) concentration. The Si-doping increases and stabilizes the acetone-selective epsilon-WO3 phase while increasing its thermal stability and, thus, results in superior sensing performance with an optimum at about 10 mol% Si content (3). Furthermore, increasing the operation temperature decreased the detector response to water vapor, and above 400 °C, it was always below (<0.7) the threshold (10.6) for fake diabetes detection in ideal conditions. At this temperature and at 90% rh, healthy humans (<900 ppb acetone) and diabetes patients (>1800 ppb) can be clearly distinguished by a remarkable gap (40%) in sensor response (2). As a result, these solid state detectors may offer a portable and cost-effective alternative to more bulky systems for non-invasive diabetes detection by human breath analysis.References:(1) Cao, W. Q.; Duan, Y. X. Clin. Chem. 2006, 52, 800-811.(2) Righettoni, M.; Tricoli, A.; Pratsinis, S. E. Anal. Chem. 2010, 82, 3581-3587.(3) Righettoni, M.; Tricoli, A.; Pratsinis, S. E. Chem. Mater. 2010, 22, 3152-3157.
11:15 AM - PP4.6
Continuous Monitoring of Glucose and Lactate Using Minimally Invasive Sensors.
Jakub Trzebinski 1 2 , Anna Radomska - Botelho Moniz 1 , Konstantinos Michelakis 1 , Sanjiv Sharma 1 , Krishna Burugapalli 2 , Anthony Cass 1
1 Institute of Biomedical Engineering, Imperial College London, London United Kingdom, 2 Brunel Institute for Bioengineering, Brunel University, Uxbridge United Kingdom
Show AbstractMaintaining the isoglycemic state through an intensive self treatment regime is the most effective method of reducing the risk of complications that are associated with type I diabetes. Commercially available glucose sensors for diabetes require patients to sample blood by pricking their finger at least 5-7 times a day. Another approach towards monitoring glucose levels includes the use of a subcutaneously implanted sensor which is painful and also necessitates calibration. Similar problems are encountered in the case of athletes monitoring lactate level, a key biomarker for controlling their training regime. We present minimally invasive enzyme based platform able to detect lactate or glucose concentration in interstitial fluid. Gold coated microspike arrays were fabricated on a flexible SU8 layer and were capable of penetrating the skin thereby enabling a pain free monitoring of the analyte of interest. Polydimethysiloxane (PDMS) was spin coated leaving the tips of microspikes exposed and thus insulating the underlying gold layer. The gold tips were functionalised using self assembly monolayer (SAM) technique with thiomalic acid (TMA) which was then catalysed using 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) to form amide bounds between TMA carboxylic groups and enzyme amine groups. These platforms were then further incubated in the glucose oxidise (GOD) or lactate oxidise (LOD) enzyme in presence of poly-lysine. In order to reduce the amount of interfering agents and make enzyme reaction oxygen independent, tetrathiafulvalene (TTF) mediator was incorporated into an epoxy based polyurethane (PU) mass transport limiting membrane. Such prepared sensors were tested in vitro and on microfluidics platform.The microspike based sensors exhibit linear response in the clinically relevant range (from 2-25mM concentration), with an average sensitivity of 10nA/mM and are able to detect the analyte for at least 12h. When incorporated into a microfluidics platform it was also confirmed that TTF is not leaching out and that the response of such sensors is diffusion limited.
11:30 AM - PP4.7
Organic Electrochemical Transistors with Ionic Liquids for Enzymatic Sensing.
Sang Yang 1 , Fabio Cicoira 1 , Robert Byrne 2 , Fernando Benito-Lopez 2 , Dermot Diamond 2 , Dion Khodagholy 3 , Roisin Owens 3 , George Malliaras 3 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Centre for Sensor Web Technologies, Dublin City University, Dublin Ireland, 3 Centre Microelectronique de Provence, Ecole Nationale Superieure des Mines de Saint Etienne, Gardanne France
Show AbstractRecently, interest in organic electronics has extended into bioelectronics because it has been demonstrated that organic semiconductors show great compatibility with biological systems. In particular, organic electronics have a key role to play in bioelectronics for biosensing devices; i.e. devices that enable the monitoring of biological events through changes in an associated electronic signal. Organic electrochemical transistors (OECT) based on poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) conducting polymer have shown to be promising in this regard, as these devices convert the biological event such as an analyte/enzyme reaction to an electrical current modulated through electrochemical gating. The enzymatic sensing systems with PEDOT:PSS OECT described above usually employ an aqueous electrolyte such as phosphate buffered saline (PBS) to prepare the analyte and enzyme solutions. However, the aqueous media, in other word, the existence of many water molecules around enzyme can provide chances to assist the denaturation of enzymes. To overcome this limitation of aqueous based devices, ionic liquids have gained significant interest as an alternative electrolyte in bioelectronics. Room temperature ionic liquids (RTILs) are molten salts which are entirely composed of ions that are in the liquid state at ambient conditions. Recently, RTILs have gained considerable interest from biologists as enzymes have been found to retain their selectivity, stability and in some cases enhance their catalytic activity in a RTIL medium. In this study, we demonstrate the integration of an all-plastic PEDOT:PSS OECT with a RTIL to yield an enzymatic sensor. Hydrophilic RTIL was used as the immobilization medium for both enzyme glucose oxidase and mediator ferrocene. An enzyme/mediator solution in RTIL was patterned on the surface of OECT by using patterned hydrophobic monolayer to control the surface energy. PEDOT:PSS OECT glucose sensor provided glucose detection down to the micromolar range (analyte detection range: 10^-7 ~ 10^-2 M) and long-term stability of sensing performance by virtue of the enzyme stability in RTIL medium. Good miscibility of RTIL immobilization medium with aqueous solution is one of the important factors to achieve the homogenous environment for the effective enzyme redox reaction in this system. The concept of this work can pave a new way for the development of various RTIL related electrochemical devices in organic bioelectronics when devices are coupled with the appropriate selection of RTILs for the specific enzymes.
PP5: Nano Sensors I
Session Chairs
Tuesday PM, November 30, 2010
Back Bay C (Sheraton)
11:45 AM - PP5.1
Optical Heating and Sensing with Plasmonic Gold Shell and Phosphorescent Core Nanoparticle.
Sudheendra Lakshmana 1 , Ian Kennedy 1
1 Mechanical and Aerospace Engineering Department, University of California, Davis, Davis, California, United States
Show AbstractNanoparticles with a rare-earth doped, up-converting phosphorescent core and plasmonic gold shell were synthesized by a modified sol-gel method and were employed to demonstrate optical heating and temperature sensing. The up-converting phosphor consisted of an Er3+emitter with Yb3+sensitizer in a NaYF4 matrix. The typical sizes of the nanoparticle were 20-50 nm and the thickness of the gold shell was 5-8 nm [1,2]. Optical heating and sensing from this novel core-shell architecture was achieved by employing two lasers. The heating of the shell was accomplished by 10 nS pulsed laser with an average energy ranging from 1-10 mJ per pulse. The wavelength was either a visible light that excited the surface plasmon resonance of the gold shell centered around 532 nm or a near infrared (NIR) 1064 nm that directly heated the shell.The temperature was measured by a low power picosecond pulsed laser or a continuous laser operating at 980 nm. The nanoparticles were immobilized on a solid matrix and the emission spectrum from Er3+ at 520 nm and 540 nm were analyzed. The ratio of the two green lines gives a quantitative estimate of temperature within one degree of accuracy.References1. L. Sudheendra, Jin-Hee Han and I. M. Kennedy Proc. of SPIE Vol. 7576, 75760Y (2010).2. L. Sudheendra, Volkan Ortlan, Sanchita Dey, Nigel Browning, I.M. Kennedy, Manuscript under review.
12:00 PM - PP5.2
Gold Nanoparticle Enlargement Coupled with Fluorescence Decrease for Highly Sensitive Detection of Analytes.
Seong Yoon Lim 1 , Jae Hong Kim 1 , Joon Seok Lee 1 , Chan Beum Park 1
1 Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractWe present a versatile and facile route for highly sensitive detection of analytes through coupling the enlargement of gold nanoparticles (Au NPs) with fluorescence decrease. The fluorescence intensity of dye molecules (e.g., fluorescein or rhodamine B) significantly decreased with the increasing concentration of reducing agents, such as hydrogen peroxide and hydroquinone. The sensitivity for the detection of reducing agents was much higher than other detection methods based on the absorbance measurement of enlarged gold nanoparticles or quantum dot-enzyme hybridization. We could successfully detect acetylthiocholine with the detection limit of several nM orders, using an enzymatic reaction by acetylcholinesterase, a key route for the detection of toxic organophosphate compounds. The fluorescence decreasing approach described in this work requires only a simple addition of fluorescence dye to the reaction solution without any chemical modification. The strategy of fluorescence decrease coupled with nanoparticle growth will be applied on the fluorescent substrate to develop detection templates for highly sensitive optical biosensor.Author's related publications1. S. Y. Lim, J. S. Lee, and C. B. Park, In situ growth of gold nanoparticles by enzymatic glucose oxidation within alginate gel matrix, Biotechnology and Bioengineering, 2010, 105, 210-214.2. S. Y. Lim, J. H. Kim, J. S. Lee, and C. B. Park, Gold nanoparticle enlargement coupled with fluorescence quenching for highly sensitive detection of analytes. Langmuir, 2009, 25, 13302-13305.3. J. H. Kim, S. Y. Lim, D. H. Nam, J. Ryu, S. H. Ku, and C. B. Park, Self-assembled photoluminescent peptide hydrogel as a versatile platform for enzyme-based optical biosensors, Biosensors and Bioelectronics, 2010, In press.
12:15 PM - **PP5.3
Integrated Nanodevices for Medical Diagnostics and Battlefield Therapeutics.
David Erikson 1
1 Mechanical Engineering, Cornell University, Ithaca, New York, United States
Show AbstractIn this talk I will discuss my groups recent work on the development of both optically and electrically based devices for in-vitro medical diagnostics and in-vivo battlefield therapeutics. For the former of these, I will describe our attempts to combine microfluidic concentration with optically resonant nanosensors to enable high fidelity, highly parallel, detection of rare biomarkers diagnostic of both the presence and severity of a variety of diseases. We show how variations on these microfluidic devices can also be combined with novel plasmonic surfaces to elucidate information on early stage protein folding disorders by examining changes in Raman signatures. In the second half of this talk I will discuss our work on extending this in-vitro work to highly integrated “self-reliant” in-vivo microsystems for diagnosis of late phase hemorrhagic shock and autonomous treatment. I will discuss the challenges of integrating nanowire based biosensing with electrokinetically driven drug delivery in order to regulate vasopressin levels in the bloodstream. Significant attention will also be paid to the ability of the system to self-power by harvesting energy from glucose using an abiotic fuel cell.
12:45 PM - PP5.4
Size Control for Fluorescent Polymeric Nanosensors.
Kevin Cash 1 , J. Matthew Dubach 2 , Mary Balaconis 2 , Heather Clark 1 2
1 Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, United States, 2 Program in Bioengineering, Northeastern University, Boston, Massachusetts, United States
Show AbstractRecent years have shown the incredible versatility and utility of polymeric nanosensors. Sensors have been developed for a wide variety of ionic analytes (e.g. sodium, potassium, pH) as well as nonionic analytics (e.g. glucose) and have been applied for challenging research fields such as detection of sodium sparks in live cardiomyocytes. This field of research has yielded new knowledge on cellular metabolism and function. Additionally, these sensors can be applied in vivo, through implantation in or under the skin in animals; showing potential as a research tool for continuous monitoring of analyte concentrations without the need for direct samples to be taken from the animal. The size control of these nanosensors is an important parameter in successful applications. For in vitro research in cell lines, the use of smaller sensors is preferred for improved distribution throughout the cell as well as to minimize clogging of the micropipette tip during injection. However, for in vivo applications, larger sensors are desirable in order to minimize sensor migration away from the injection site. Methods to affect sensor size over both a small and large range will be discussed for both in vitro and in vivo applications. This work was supported by a grant from the National Institutes of Health National Institute of General Medical Sciences (R01 GM084366).
PP6: Nano Sensors II
Session Chairs
Tuesday PM, November 30, 2010
Back Bay C (Sheraton)
2:30 PM - PP6.1
Iron Oxide Nanoparticle T1 MR Contrast Agents and Their Application In-vivo.
Ulrich Tromsdorf 1 , Barbara Freund 2 , Michael Kaul 3 , Caroline Jung 3 , Markus Heine 5 , Oliver Bruns 4 , Heinrich Hohenberg 4 , Horst Weller 1
1 Institute of Physical Chemistry, University of Hamburg, Hamburg Germany, 2 IBM II: Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg Germany, 3 Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg Germany, 5 Anatomie II, University Medical Center Hamburg-Eppendorf, Hamburg Germany, 4 , Heinrich-Pette Institute, Hamburg Germany
Show AbstractSuperparamagnetic iron oxide nanoparticles (SPIONs) are widely used in biomedicine. As a result of their tunable magnetic properties, SPIONS act as excellent contrast enhancers in Magnetic Resonance Imaging (MRI). Recently, we developed an optimized positive (T1) MR contrast agent based on ultrasmall SPIONs [1]. Here, we demonstrate the in-vivo use of these particles exemplary as a blood pool contrast agent in MR Angiography. Via radioactive labelling strategies, the in-vivo behaviour, in particular blood half-life and organ distribution are investigated. Moreover, cryo electron microscopy and tomography provide detailed insights into the dispersion state of the nanoparticles in blood serum, thus allowing a close correlation of in-vivo imaging with direct microscopic techniques.[1] U.I. Tromsdorf, O.T. Bruns, S.C. Salmen, U. Beisiegel, H. Weller Nano Letters 2009, 9, 4434.
2:45 PM - **PP6.2
Miniaturization of Biomedical Sensing Platforms.
Axel Scherer 1
1 Electrical Engineering, California Institute of Technology, Pasadena, California, United States
Show AbstractThe opportunity of highly accurate definition of microdevices and their precise alignment to one another holds tremendous promise for radically increasing the complexity and functionality of optical communications, microfluidic, and magnetic systems. Moreover, it is possible to “print” very complex integrated optical, mechanical, magnetic or fluidic systems with excellent accuracy and resolution if the devices can be designed around standard planar fabrication capabilities. For example, by integrating nonlinear optical materials with lithographically fabricated silicon waveguides, extremely high optical fields can be obtained, and spectroscopic measurements can be conducted on very small sample volumes. Lithographically defined fluidic systems can also be integrated with optical and electronic systems for the purpose of efficient device cooling on a micro-device scale. Moreover it is now possible to construct useful medical diagnosis tools through integration of electronics, optics and fluidics. Indeed, biomedical devices today can be constructed by two- and three-dimensional soft and hard lithography approaches, in which pico-Liter volumes can be manipulated and analyzed. Compact and efficient immuno-assay chips, cell and bacterial analysis chips and pathogen identification systems have evolved. In the near future, we can expect similar success from lithographically integrated opto-fluidic, optomechanical, magneto-optical and magneto-fluidic systems. Here, the opportunities for integrating nanoscale electronic, photonic, magnetic and fluidic devices in lithographically printed and aligned biomedical diagnostic systems will be described.
3:15 PM - PP6.3
Integrating Colloidal Quantum Dots With Porous Silicon For High Sensitivity Biosensing.
Girija Gaur 1 , Dmitry Koktysh 2 , Sharon Weiss 1
1 Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, United States, 2 Department of Chemistry, Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractWe aim to utilize the large surface area of a porous silicon matrix coupled with quantum dot (QD) amplifiers for ultrasensitive optical detection of small biomolecules. QDs offer several advantages for biosensing stemming from their unique photophysical properties such as size-tunable emission, large absorption and narrow emission spectra, high quantum yields, stability, and resistance to photobleaching. In our system, the QDs are attached to the target biomolecules and serve as signal amplifiers by providing an additional refractive index increase beyond that of the smaller target molecule, and by generating a strong photoluminescence (PL) signal. To first understand the infiltration efficiency of QDs into the porous silicon matrix, PbS QDs of different sizes were coupled to porous silicon films having different pore morphology, porosity, thickness and pore size. To simulate a specific biological binding event on the pore walls, the QDs were attached to the walls via a chemical linking molecule. A rinsing step was utilized to ensure that unbound QDs were removed from the porous silicon matrix. QD binding was monitored by measuring the reflectance signal at near normal incidence. QD attachment on the pore walls increases the effective refractive index of the porous silicon matrix thereby causing a shift in the Fabry-Perot fringe pattern of the reflectance spectra. At a wavelength of 1000nm, shifts in the fringe pattern ranging from 5nm to 35nm were measured. Simulation results indicate corresponding QD coverages of approximately 0.01% to 15% of the total porous surface area depending upon the fabricated porous film morphology. For biosensing experiments, 5nm CdTe QDs were selected due to their strong visible PL. The CdTe QDs were infiltrated into a porous silicon film with parameters chosen based on our initial experiments. Both reflectance and PL measurements confirm QD attachment in the pores and suggest a maximum surface coverage of 10%, corresponding to approximately 3E15 QDs per square cm. Studies were conducted to determine the minimum resolvable reflectance and PL signals, and determine the corresponding minimum number of molecules that can be detected. Our QD coupled porous silicon sensors have the potential to be utilized for multiplexed detection through the use of QDs with different peak emission wavelengths attached to different types of molecules.
4:00 PM - PP6.4
Identification of Microorganisms with Magnetic Relaxation Switches.
David Alcantara 1 , Lee Josephson 1
1 Center for Nuclear Medicine and Molecular Imaging, MGH-Harvard Medical School, Charlestown, Massachusetts, United States
Show AbstractNanomaterials with precise biological functions have considerable potential for use in biomedical applications. Point of care (POC) sensors developed in our group are an important part of the preparation for possible pandemics such as that created by avian influenza.1 NMR based magnetic relaxation switches (MRS) are attractive for this application because they are indifferent to light and involve no immobilization of materials on vessel walls.2, 3 MRS consists of magnetic nanoparticles (NP’s) to which biomolecules have been conjugated. Depending on the presence of target analytes the NP's switch between a dispersed and clustered state. 4-6 The change in dispersion state decreases T2 because the clustered magnetic nanoparticles are more potent relaxation enhancing agents. T2 is the spin-spin relaxation time of water protons, a basic parameter determined in MR imaging. MR relaxometers are practical as POC sensors since their requirements for magnetic field strength, volume and homogeneity are minimal. Traditional methods for microbial identification require the recognition of differences in morphology, growth, enzymatic activity, and metabolism to define genera and species. On the other hand, the 16S rRNA gene contains regions well conserved in all organisms that are ideal for primer design, polymerase chain reaction (PCR) or sequencing, and sequence alignment. While the current MRS system has been used to measure a variety of different analytes, it has not been used to measure rRNA from microorganisms. In this presentation we’ll show the preliminary results of model microorganism (E.Coli) identification with a new designed MRS sensor targeting the bacterial rRNA. Selected bacterial rRNA oligonucleotide sequences have been identified with good sensibility using T2 magnetic relaxation experiments. These results demonstrate that our system can be a good alternative to traditional detecting methods. 1.Koh, I.; Hong, R.; Weissleder, R.; Josephson, L., Sensitive NMR sensors detect antibodies to influenza. Angew Chem Int Ed Engl 2008, 47 (22), 4119-21.2.Sun, E. Y.; Weissleder, R.; Josephson, L., Continuous analyte sensing with magnetic nanoswitches. Small 2006, 2 (10), 1144-7.3.Weissleder, R.; Kelly, K.; Sun, E. Y.; Shtatland, T.; Josephson, L., Cell-specific targeting of nanoparticles by multivalent attachment of small molecules. Nat Biotechnol 2005, 23 (11), 1418-23.4.J. Manuel Perez, L. J., Terrence O'Loughlin, Dagmar Högemann & Ralph Weissleder, Magnetic relaxation switches capable of sensing molecular interactions. Nature Biotechnology 2002, 20, 816-820.5.Zhao, M.; Josephson, L.; Tang, Y.; Weissleder, R., Magnetic sensors for protease assays. Angew Chem Int Ed Engl 2003, 42 (12), 1375-8.6.Josephson, L.; Perez, M.; Weissleder, R., Magnetic nanosensors for the detection of oligonucleotide sequences. Angew. Chem. (Int Ed.Engl.) 2001, 40, 3204-3206.
4:15 PM - PP6.5
Development of Biosensors for In-situ Detection of Pathogenic Species in Liquid with High Sensitivity and Capability to Seek the Target Species.
Zhongyang Cheng 1 , Kewei Zhang 1 , Liling Fu 1
1 , Auburn University, Auburn, Alabama, United States
Show AbstractBiosensors with high sensitivity and work well in liquid are highly desirable. However, there is a challenge for the sensors with high sensitivity in the sample with low concentration due to the time needed for the target species to be brought into the sensor since the sensors are usually small, Magnetostrictive particles (MSPs) were recently developed as sensor platforms that exhibit a sensitivity and at the same time have the capability to bring the target species into the sensor. The antibody and phage have been immobilized onto the MSPs to form biosensors for the in-situ detection of bacteria and spores in water based samples. The unique advantages of this approach over others are discussed. The principle and fabrication issues of the biosensors are presented. The results for in-situ detection of three bacteria in water samples are reported. A sensitivity of less than 50 cfu/ml is observed for the in-situ detection.
4:30 PM - **PP6.6
Materials Considerations for Programmable Bio-Nano-Chip Sensor Systems.
John McDevitt 1
1 Bioeineering & Chemistry, Rice University, Houston, Texas, United States
Show AbstractThe programmable bio-nano-chip (PBNC) synergizes components and achievements from nanotechnology, clinical chemistry, bioinformatics, microfluidics, optics, image analysis, and pattern recognition to create a powerful new integrated measurement approach in a small device footprint. The PBNC ensemble employs a size-tunable network of nanometer-scale fibers (“nano-net”) within agarose microspheres or a polymer membrane and a fluorescent signal arising from nanoparticles (nano) to isolate and quantify biologically important analytes (bio) from complex matrices within a closed, miniaturized system (chip). The PBNC features a flexible assay design and has a diverse collection of validated analyte subtypes. The PBNC’s modular design elements allow for rapid inclusion of tests for new biomarker signatures; assays for nucleic acids, proteins, and cells are arranged in the PBNC to create analytical test modalities specific to different disease types. Collectively, the modularity, flexibility, and ability to process and learn new biomarker signatures is here referred to as “programmability”. This presentation features the materials considerations related to the PBNC system. This tailored materials base allows for high fidelity testing which has enabled the more efficent collection of research, clinical validation and clinical implementation results all on the same platform. As such, this universal detection modality is now moving through the simultaneous completion of 6 clinical trials in the area of HIV immune function (number one global humanitarian issue), cardiac heart disease (number one killer on a global basis) and three types of cancers (oral, ovarian, prostate).
PP7: Artificial Scaffolds for Cell Growth
Session Chairs
Tuesday PM, November 30, 2010
Back Bay C (Sheraton)
5:00 PM - PP7.1
Chemical Vapor Deposition of Topographically Biomimetic Cell Culture Scaffolds.
Courtney Pfluger 1 , Rebecca Carrier 1
1 Chemical Engineering, Northeastern University, Boston, Massachusetts, United States
Show AbstractSurface topography of cell culture substrates has been shown to influence protein expression and potentially induce phenotype (e.g., morphology) more similar to that of cells in vivo. Many topographically modified substrates roughly mimic in vivo topography, in the form of random surface roughness or ridges/grooves, for example. Chemical Vapor Deposition (CVD) on fixed, dehydrated tissue is being used to develop polymeric substrates presenting complex, multi-scale, irregular topography precisely mimicking micron and sub-micron topography found in vivo. CVD allows for the deposition of thin polymer films on complex geometries and chemistry that can be easily manipulated to enhance cell culture properties. CVD deposition of Parylene has been developed to recast a negative mold of the intestinal basement membrane surface. The small intestine epithelium has an intricate, complextopography at the micron and sub-micron scales; cell phenotype and expression vary with position relative to this topography. SEM images indicate replication of micron (e.g., villi, crypts, pores) and sub-micron (fibrous texture) scales after tissue removal from the polymer film. CVD depositions of biocompatible poly 2-hydroxyethyl methacrylate (pHEMA) with different degrees of cross-linking on these Parylene molds enables fabrication of a positive intestinal basement membrane replica for cell culture. Optimization of pHEMA CVD process parameters was performed to increase deposition rate to allow for thicker (micron-scale) films amenable to separation from the Parylene mold and handling for cell seeding and culture. Separation of pHEMA films from Parylene molds, residual polymer adherence, and the influence of surface treatment with surfactant on separation were investigated on flat and complex geometries. Maintenance of topographical features of structurally biomimetic pHEMA films was explored in aqueous media, as the ultimate goal is to obtain a biocompatible pHEMA cell culture scaffold for cell culture and potentially intestinal tissue engineering.
5:15 PM - PP7.2
Rapid Prototyping of Nano- and Micro-patterned Substrates for the Control of Cell Neuritogenesis by Topographic and Chemical Cues.
Cristina Lenardi 1 5 , Ajay Singh 2 3 , Lasma Gailite 2 3 , Varun Vyas 2 3 , Stefania Forti 2 , Michela Matteoli 4 5 , Paolo Milani 2 5
1 CIMAINA, Dipartimento di Scienze Molecolari Applicate ai Biosistemi, Universita' di Milano, Milano Italy, 5 , Fondazione Filarete, Milano Italy, 2 CIMAINA, Dipartimento di Fisica, Universita' di Milano, Milano Italy, 3 European School of Molecular Medicine (SEMM), IFOM-IEO Campus, Milano Italy, 4 Dipartimento di Farmacologia, Chemioterapia e Tossicologia Medica, Universita' di Milano, Milano Italy
Show AbstractThe investigation in vitro of complex inter- and intra-cellular signaling mechanisms increasingly rely on methods for precisely manipulating cell deposition and maintenance through sophisticated substrate modifications which allow to control specific cell properties. Physical and chemical patterning of surfaces at the nano- and microscale is used to understand and control cell adhesion, proliferation, differentiation and phenotype expression. A particularly interesting and challenging system is represented by neuronal cells (NC), where micro and nanoenvironment stimuli trigger the activation of complex pathways, leading to differentiation, neurite growth and eventually formation of synaptic connections.PC12 cells represent a convenient model for the study of neuronal differentiation thanks to the vast availability of data about their response to exogenous signals such as growth factors, neurotrophins and hormones, which induce the formation of neurites and the acquisition of neuronal-like properties. While the intracellular signaling pathways related with PC12 differentiation have been largely explored, relatively few studies have been devoted to elucidate the role that surface topography plays in neuronal differentiation. Studies on the role of substrate topography report almost exclusively on the analysis of alignment of neurites over different micro-nanopatterned substrates. Several micro/nanofabrication techniques have been proposed to mimic in vitro the physical and chemical signaling experienced by neuronal cells in vivo. These are based on complex and multistep processes. Nanosphere lithography (NSL) is a simple and high throughput fabrication technique capable of producing a large variety of structures and well-ordered 2D nanoparticle arrays. Recently we demonstrated that cluster-assembled nanostructured TiOx films produced by supersonic cluster beam deposition (SCBD) in combination with lift-off technique can be used for micro- and nanostructuring of chemically functionalized substrates for cell culture [1]. Nanostructured TiOx films, resulting from a random stacking of nanoparticles, are characterized, at the nanoscale, by a granularity and porosity mimicking those of ECM structures making cluster-assembled TiOx films a remarkably efficient substrate for the adsorption of proteins and for the maintenance in vitro of different cell lines and primary cultures [2].Here we describe a fabrication approach, consisting in coupling NSL with SCBD that allows the rapid prototyping of micro and nanopatterned TiOx substrates with topographic and chemical cues for the study of cell neuritogenesis. We demonstrate the growth and enhanced neuritogenesis of PC12 cells cultured on these geometrically, morphologically and chemically defined patterns on length scales ranging from the nanometer to the microscale.[1] Singh AV, et al. J Micromech Microeng 2009; 19(11): 115028-115035.[2] Carbone R et al. Biomaterials 2006;27(17):3221-9.
5:30 PM - PP7.3
Micro and Nano Fabricated Hydrogels for Tissue Engineering.
Alessandro Tocchio 1 2 , Federico Martello 2 , Cristina Lenardi 2 3 , Paolo Milani 2 4
1 , European School of Molecular Medicine, Milan Italy, 2 , Fondazione Filarete, Milan Italy, 3 C.I.Ma.I.Na. - Dipartimento di Scienze Molecolari Applicate ai Biosistemi, Università degli Studi di Milano, Milan Italy, 4 C.I.Ma.I.Na. - Dipartimento di Fisica, Università degli Studi di Milano, Milan Italy
Show AbstractOrgan failure is one of the most serious problems faced by the healthcare industry in developed nations. To address this problem, the field of tissue engineering and regenerative medicine has emerged with the aim at repairing damaged tissue in vivo or growing tissues and organs in vitro in order to implant them in the body. This revolutionary technology has the potential to develop therapies for previously untreatable diseases and conditions including diabetes, heart diseases and renal failure, osteoporosis and spinal cord injuries. Virtually any disease that results from malfunctioning damaged or failing tissues may be potentially cured through regenerative medicine therapies [1]. One of the major challenges of engineering tissues in vitro is the lack of a proper vascularization [2]. The development of an artificial microvasculature is critical to move tissue-engineered organs into the clinics to benefit patients with end-stage organ failure. In fact, oxygen and other nutrients can only diffuse within a short distance before being consumed and without an intrinsic capillary network the maximal thickness of engineered tissue is smaller than clinically relevant dimensions, limiting the ability for in vivo integration. Nowadays the most successful tissue engineering applications in clinics are skin and cartilage, which have relatively low requirements for nutrients and oxygen and rely on vascularization from the host to provide permanent engraftment and mass transfer of oxygen and nutrients [3]. However, such techniques encounter difficulties when applied to thick and complex tissues, particularly those comprising the large vital organs such as liver, kidney, and heart [2].With the aim at solving this limitation we have engineered a porous synthetic scaffold based on biocompatible hydrogels [4], characterized by an embedded three-dimensional micro-channels network. The scaffold mimics the complexity of native tissue microenvironment increasing cell viability and tissue expansion. These results are allowed by the vascularization, achievable by cell co-culturing in the embedded micro-channels network and within the porous structure, that provide a proper transfer of oxygen and nutrients to the cells and a more homogeneous shear stress distribution within the scaffold. Moreover the use of synthetic material, for scaffold manufacturing, guarantees a cost reduction and enhanced aptitude for clinical applications compared to animal origin material. In conclusion this technology would permit to engineer ex-vivo tissues with the normal biomechanical and metabolic functions and with clinically relevant dimensions overcoming the state of art’s limit. [1] Langer et al., (1993) Science, 260:920-6.[2] Borenstein et al., (2002) Biomedical Microdevices, 4:167-175.[3] Fidkowski et al., (2005) Tissue Eng, 11:302-9.[4] Jacchetti et al., (2008) Journal of Nanobiotechnology, 6:14.
Symposium Organizers
Peter Kiesel Palo Alto Research Center
David Nolte Purdue University
Xudong (Sherman) Fan University of Michigan
Martin Zillmann Millipore Corporation
PP8: Label-Free Detection I
Session Chairs
Wednesday AM, December 01, 2010
Back Bay C (Sheraton)
9:30 AM - **PP8.1
Nanomechanical Sensing with Molecular Selectivity.
Thomas Thundat 1
1 , ORNL, Oak Ridge, Tennessee, United States
Show AbstractNanomechanical sensors have attracted considerable attention over the last decade because of their potential as a highly sensitive sensor platform for high-throughput, multiplexed, label-free detection of chemicals. Although nanomechanical sensors enable chemical and biological sensing with unprecedented sensitivity using variations in mass and stress, obtaining selectivity still remains as a crucial challenge. Selectivity in small molecule detection, using immobilized selective layers that rely on weak chemical interactions, provides only partial selectivity. Biological detection using immobilized probes provides very high selectivity, but poor reproducibility due to challenges faced with immobilization techniques. However, the low thermal mass of the sensor allows integration of nanomechanics with photothermal, photoacoustic, and calorimetric techniques for increased selectivity. The thermomechanical phenomena produce unique responses that can be used for analyte specific detection without losing sensitivity or reversibility. Controlled heating of the sensors with adsorbed molecules can produce unique, adsorbate specific mechanical and thermal responses for achieving very high specificity. It is also possible to achieve chemical and biological selectivity by exposing the adsorbate-covered micromechanical structures to optical/infrared excitation. These thermo-mechanical techniques have the advantage of obtaining signals from picogram quantities of adsorbed analytes. Various thermomechanical techniques as well as signal transduction techniques for achieving improved selectivity will be discussed.
10:00 AM - PP8.2
Large Scale Metal Nanowire Arrays for Combined Electrical and Optical Biosensing Applications.
Bernd Dielacher 1 , Robert MacKenzie 1 , Corrado Fraschina 1 , Takumi Sannomiya 1 , Birgit Paivanranta 2 , Andreas Langner 2 , Janos Voros 1
1 , Laboratory of Biosensors & Bioelectronics, ETH Zurich, Zurich Switzerland, 2 , Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute (PSI), Villigen Switzerland
Show AbstractNanowires are attractive building blocks for future sensor devices since their large surface to volume ratio makes them extremely sensitive to surface perturbations. In contrast to the focus on semiconducting materials a novel metal nanowire array platform is presented which combines the advantages of electrical and optical sensing techniques. Extreme Ultraviolet Interference Lithography was used to produce large-scale arrays of nanoline patterns with dimensions down to 20 nm. The resulting structures were further processed into metal nanowires either using a semi-conventional evaporation method or an unconventional self-assembling approach of metal nano colloids. Each nanowire array was electrically connected and the entire chip was mounted on a special transparent electrochemical flow cell. This allows the simultaneous monitoring of the nanowires' electrical and optical properties upon various surface binding actions. Optical characterization based on Localized Surface Plasmon Resonance (LSPR) has shown a bulk sensitivity up to 114.6 nm/RIU (Refractive Index Unit) and limits of detection as low as 4.5 x 10-5 RIU. This sensing performance is already beyond initial predictions but the combination with electrochemistry is unique. Peak shifts in LSPR spectrum of over 4 nm have been observed while gating the potential of the electrochemical cell. In this configuration the nanowires themselves are acting as working electrode allowing the controlled adsorption and desorption of ions and molecules. In addition simultaneous electrical measurements across the nanowire arrays have shown a change in the nanowires' resistance of more than 3% (peak-to-peak). These results and ongoing measurements with various molecules clearly demonstrate the potential of our novel nanowire array platform and strengthen the claim that metal nanowires are feasible for (bio-) electrochemical sensing applications.
10:15 AM - PP8.3
SPR in Metallized Ultrathin Porous Membranes for Biological and Chemical Sensing.
Krishanu Shome 1 , Maryna Kavalenka 2 , David Fang 2 , Philippe Fauchet 2 1
1 Institute of Optics, University of Rochester, Rochester, New York, United States, 2 Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States
Show AbstractSurface Plasmon Resnonance (SPR) sensors are widely used in biochemical sensing techniques. SPR sensors based on the collinear transmission mode provide a simpler setup and smaller probe area than the widely used prism based SPR techniques. Here we demonstrate a new collinear SPR platform which involves depositing a thin (~ 15 nm) continuous gold film onto a free standing porous ultrathin nanocrystalline silicon membrane [1]. These silicon membranes are 15 nm or 30 nm in thickness and contain holes formed spontaneously upon annealing with an average diameter ranging from 5 nm to 50 nm. The thickness of the metal deposited is such that it does not completely block of the pores in the membranes [2]. Compared to previous work [3], these metallized membranes are free standing and the metal thickness is much smaller than that of nanoholes in optically thick metal films. Two arrangements have been investigated, one where the metal is deposited on the Si membranes and another where the membranes are first oxidized before the metal is deposited. 3D finite difference time domain simulations were performed to calculate scattering cross sections, transmission spectra and mode profiles for a single metallized hole. Measurements were performed using a spectrophotometer and an integrating sphere to collect all the light transmitted through and reflected by the metallized membranes. In preliminary experiments performed with methanol and isopropyl alcohol the SPR peak was seen to blueshift by 10 nm and 27 nm with respect to air respectively giving a sensitivity of 350 nm/RIU. This shows that the metallized ultrathin porous silicon membranes can effectively act as a simple biochemical sensor.This work was supported by the CEIS Bio Imaging Program of the New York State and by SiMPore Inc.[1] C.C. Striemer, T.R. Gaborski, J.L. McGrath, and P.M. Fauchet, Nature 445, 749–753 (2007). [2] K. Shome, M. Kavalenka, D.Z. Fang, and P.M. Fauchet, in Frontiers in Pathogen Detection: From Nanosensors to Systems, edited by P.M. Fauchet and B.L. Miller (SPIE, San Francisco, California, USA, 2010), pp. 75530F-9.[3] L. Pang, G.M. Hwang, B. Slutsky, and Y. Fainman, Appl. Phys. Lett. 91, 123112 (2007).
10:30 AM - PP8.4
Metal Substrate Induced Control of Ag Nanoparticle Plasmon Resonances for Tunable SERS Substrates.
Pieter Kik 1 , Amitabh Ghoshal 1 , Manuel Marquez 2 , Min Hu 3
1 CREOL, The College of Optics and Photonics, UCF-CREOL, Orlando, Florida, United States, 2 , YNano LLC, Midlothian, Virginia, United States, 3 Information and Quantum Systems Laboratory, Hewlett-Packard Laboratories, Palo Alto, California, United States
Show AbstractControl of the surface plasmon resonance of nanometallic structures is crucial for biosensing applications such as surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS). In this presentation we discuss an experimental study of the tunability of the silver nanoparticle localized plasmon resonance in close proximity to a gold film. It is shown that broadband tuning of the silver particle plasmon resonance from blue wavelengths into the near-IR region can be achieved as a result of strong electromagnetic coupling between the nanoparticle and the metal film. We discuss how this method can be extended to related material systems.Silver nanoparticles with a mean diameter of 60nm are deposited on SiO2 films grown on a 50nm thick gold film. Single particle spectroscopy of over 250 isolated silver nanoparticles show evidence for the excitation of both horizontal and vertical nanoparticle plasmon modes. Distinct resonance features observed in the scattering spectra are assigned to specific modes based on a dipole-dipole interaction model. The plasmon resonance frequency is found to redshift dramatically with decreasing SiO2 thickness. The recorded scattering spectra demonstrate reproducible frequency controlled resonances at wavelengths between 450-700nm as the silver-gold spacing is decreased from 40nm – 0nm. The experimental results suggest that low-loss silver nanoparticles can be used in surface enhanced spectroscopy studies throughout the entire visible spectrum. The use of frequency tuned spherical metal nanoparticles on solid substrates could lead to thermally stable substrates for a wide variety of plasmon enhanced biosensing applications.
10:45 AM - PP8: Label-Free
BREAK
11:15 AM - PP8.5
Pore-spanning Lipid Membrane and Protein Biosensing with Plasmonic Nanopore Arrays.
Hyungsoon Im 1 , Nathan Wittenberg 1 , Antoine Lesuffleur 1 , Nathan Lindquist 1 , Sang-Hyun Oh 1
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractIntegration of solid-state biosensors and lipid bilayer membranes is important for membrane protein research and drug discovery. In these sensors, it is critical that the solid-state material does not have adverse effects on the conformation or functionality of membrane-bound molecules. In this work, we present periodic nanopore arrays in free-standing Au/Si3N4 films as surface plasmon resonance (SPR) biosensors to detect the incorporation of a transmembrane protein, α-hemolysin (α-HL), into a pore-spanning membrane and also to detect subsequent antibody binding. Pore-spanning lipid membranes were formed using vesicle rupture facilitated by conformal encapsulation of the gold sensing surface with a 20-nm-thick silica layer deposited by atomic layer deposition. Part of the lipid membrane is thus suspended over the nanopores as a lipid “drum” and is accessible from both sides, more closely mimicking natural cell membranes. Three-dimensional finite-difference time-domain (FDTD) calculations show that strong field intensities due to SPs can be observed over the nanopores and near their edges, suggesting high sensitivity at the area where a pore-spanning lipid membrane forms. A polydimethylsiloxane (PDMS) microfluidic channel and a thin PDMS membrane sealed the top and bottom sides of nanopore chip, allowing both sides of the chip, the nanopores, and the lipid membrane to be immersed in aqueous solution. After lipid membrane formation, a fluorescence recovery after photobleaching (FRAP) technique was used to confirm the formation of a continuous lipid membrane on the substrate. In the FRAP experiments, a small circular area of the membrane was photobleached with an intense laser beam at a wavelength of 405 nm. Diffusion of unbleached fluorescence in the lipid membrane back into the previously bleached area indicates a continuous membrane layer. The ability to perform kinetic assays with a transmembrane protein is demonstrated with α-hemolysin (α-HL) and its subsequent binding with anti-α-HL. The affinity constant, KD, is determined from real-time kinetic measurements with different concentrations (50, 100, and 200 nM) of anti-α-HL. Subsequent fluorescence imaging reveals that the antibodies primarily bind to the nanopore regions, indicating that α-HL incorporation preferentially occurs into areas of pore-spanning lipid membranes. The detection of anti-α-HL binding on α-HL-incorporated lipid membranes demonstrates the functionality of an integrated platform for lipid membrane SPR sensing.
11:30 AM - PP8.6
Dual Detection Platform with Refractive Index and SERS Sensing Based on Colloidal Gold Functionalized Porous Silicon Substrates.
Yang Jiao 1 , Dmitry Koktysh 2 , Sharon Weiss 1
1 Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, United States, 2 Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractWe report a new dual-mode sensor based on porous silicon (PSi) impregnated with colloidal gold nanoparticles (Au NPs) that supports both molecular fingerprinting via surface enhanced Raman scattering (SERS) and quantification of molecular binding via reflectance measurements. PSi has attracted much attention for label-free small molecule detection due to its large internal surface area for molecule binding and capability for size-selective molecular filtering. Typically PSi sensors operate in a single mode. For example, very small changes in the refractive index of PSi, due to molecules attachment, can be detected and quantified optically using reflectance, transmittance, or photoluminescence measurements. PSi has also been shown to be a promising substrate for SERS-based sensing due to its nanostructured surface. Our dual-mode sensor, consisting of a 2 μm-thick single layer PSi film with 50-60 nm diameter pores coated with 5 nm colloidal Au NPs, combines the advantages of the SERS and refractive index methods for molecular identification and quantification. The PSi film was formed electrochemically using an aqueous hydrofluoric acid-based electrolyte. A sacrificial layer was etched first to create a rough surface with small corrugations and to ensure that the pore openings were sufficiently wide to allow the Au NPs and target molecules to infiltrate into the pores. The Au NPs were then impregnated into the PSi surfaces using a 3-APTES linker. The infiltration of the Au NPs into the PSi matrix was monitored by spectral reflectance measurements at near normal incidence. A blue-shift of the spectrum was observed upon NPs infiltration. Dual-mode sensing was tested by exposing the Au-PSi sensor to benzenethiol. A consecutive red-shift of the reflectance spectrum was observed, indicating that molecules were absorbed on the Au-PSi sensor. Subsequent SERS measurements enabled unique identification of the benzenethiol molecules based on analysis of the set of measured Raman peaks. Experimental results showed that our Au-PSi structure provided a <1 μM molecule detection sensitivity and approximately 6-7 fold SERS signal enhancement compared to that of the conventional nano-porous gold SERS template. We believe a large fraction of the SERS signal was originating from the Au-PSi surface corrugations while the reflectance shift was primarily due to the refractive index change caused by molecular infiltration inside the pores. A discussion of the roles of the PSi pore diameter and Au NPs size for refractive index and SERS sensitivity will be discussed. A key advantage of our sensor is that the SERS signal strength across the colloidal Au-coated PSi surface is uniform. Therefore, there is no need in our case to search for a hot spot, which is a common problem for many SERS sensor platforms.
11:45 AM - PP8.7
Angle-resolved Surface Enhanced Raman Scattering (SERS) for Rationally Designing Two-dimensional Hole Arrays as High Performing SERS Substrates.
Chung-yu Chan 1 2 3 , Hock-chun Ong 1 , Jian-bin Xu 2 , Miu-yee, Mary Waye 3
1 Physics, The Chinese University of Hong Kong, Shatin Hong Kong, 2 Electronic Engineering, The Chinese University of Hong Kong, Shatin Hong Kong, 3 Biomedical Sciences, The Chinese University of Hong Kong, Shatin Hong Kong
Show AbstractBecause of its high specificity, surface-enhanced Raman scattering (SERS) is a promising technique for molecular identification. Unfortunately, this technique so far has only been proven to be of limited use due to a major drawback: lack of reliable SERS substrates that produce stable Raman signals. The Raman active sites found in metal colloid and rough metal surface are usually very irregular that they suffer from large spatial and temporal fluctuation. To obtain strong and stable SERS, one must controls the size, shape, and position of the metallic nanostructures with high precision. In fact, recent attention has been slowly shifted to the use of periodic metallic arrays due to their well-defined structure that provides more stable localized field. However, knowing that the plasmonic effect is so geometry dependent that slight modification of the structure can lead to large variation in the outcome, it is of importance to optimize the geometry (size, shape, depth and period) of periodic arrays in order to produce the strongest possible SERS. In this presentation, we have systematically studied the dependence of SERS on the geometry of two-dimensional circular hole arrays. In particular, we employ angle-resolved reflectivity and Raman spectroscopy to map out the dispersion relations of all resonance modes arising from the arrays and to study their contributions to the Raman enhancement individually. As a result, both the excitation and emission enhancements induced by Bloch-like propagating and localized waveguide modes can be identified and studied quantitatively. More importantly, we find that, for a given mode, the resulting SERS is strongly associated with its decay lifetime and coupling efficiency; shorter lifetime and stronger coupling efficiency lead to stronger SERS. In the end, we will lay out a general scheme on how one can rationally design high sensitive and stable SERS substrates based on periodic arrays.[1] C.Y. Chan, J.B. Xu, M.Y. Waye, H.C. Ong, Appl. Phys. Lett. 96, 033104 (2010).
12:00 PM - PP8.8
Real-time Monitoring of Biological Interactions with Chemically-modified Graphene FETs.
Rory Stine 1 , Jeremy Robinson 1 , Paul Sheehan 1 , Cy Tamanaha 1
1 , Naval Research Lab, Washington, District of Columbia, United States
Show AbstractSensitive detection of biological molecules without the need for secondary labeling has been a longstanding goal in the biosensor community. Eliminating the need for a secondary label simplifies sensor operation, reduces operating cost, and allows the examination of biomolecular interactions in real time. Surface plasmon resonance has long been the gold standard for such devices, and recent work with silicon nanowire and carbon nanotube FETs have shown significant promise. Still, there remains significant room for improvement, as these platforms continue to experience problems with sensitivity, specificity, reproducibility, cost, and portability. Here, we examine the use of field effect transistors made from chemically-modified graphene as a platform for label-free biodetection. Devices made from both reduced graphene oxide and plasma modified graphene will be discussed, showing successful detection of multiple targets including DNA, proteins, and small molecules.
12:15 PM - PP8.9
Optimization of Biosensors Using Selective Chemistry.
Oliver Seitz 1 , Poornika Fernandes 1 , Huang-Chun Wen 2 , Harvey Stiegler 1 , Richard Chapman 1 , Eric Vogel 1 , Yves Chabal 1
1 , University of texas at Dallas, Richardson, Texas, United States, 2 , Texas Instrument Inc., Dallas, Texas, United States
Show AbstractThere is currently a strong need to develop sensitive and reliable biosensors, based on electronic detection, such as field-effect transistors (FET). Most of the focus has been on improving sensitivity by decreasing the FET channel size, using nanowires instead of similar devices on planar silicon. Issues of silicon functionalization, important for device reliability have been mostly ignored. In this work, we present a robust approach to functionalize the channel region of a SOI wafer, thus achieving better reliability and sensitivity to very low analyte concentrations. The process leads to attachment of active SAM on oxide-free (H-terminated) silicon through formation of a Si-C bond on the channel. Combining IR absorption (IRAS) and X-ray photoelectron (XPS) spectroscopies, photoluminescence, atomic force microscopy (AFM) and electrical measurements, we find that this configuration results in a stable device where the active SAM is more strongly attached to the Si than silane molecules do on oxides. This functionalization is achieved by immersion in carboxylic acid (COOH)-terminated alkene molecules to functionalize the H-terminated channel. After processing, XPS and IRAS confirm that the channel remains oxide-free, that the packing of the SAM on the channel is dense. Photoluminescence measurements confirm the high quality of the interface on the channel where non-radiative recombination (interface states) is not detected. The AFM pictures confirm that active molecules attach to the channel (imaged by attachment of nanoparticles). Electrical measurements, on these improved devices, indicate excellent response for both pH and protein sensing with sensitivity at least as good as the one of similar structure with a uniform SAM functionalization (i.e. using oxidized Si channels).
PP9: Label-Free Detection II
Session Chairs
Wednesday PM, December 01, 2010
Back Bay C (Sheraton)
2:30 PM - PP9.1
Glucose Concentration Measurements by Cavity Enhanced Sensing.
Joerg Martini 1 , Marek Smolarczyk 1 , Michael Recht 1 , Jeffrey Roe 1 , Francisco Torres 1 , Peter Kiesel 1 , Richard Bruce 1
1 , Palo Alto Research Center, Palo Alto, California, United States
Show AbstractOur refractive index (RI) cavity sensor consists of a double chamber Fabry-Perot etalon that measures the differential RI between a reference chamber and a measurement chamber. The etalon chambers have wavelength dependent transmission maxima which are linearly dependent on the RI inside them. In our device, an RI difference of Δn = 1.5*10^-6 changes the spectral position of a transmission maximum by 1 pm. We sweep the wavelength of a single-mode VCSEL linearly in time (1kHz, nominal central wavelength is 850 nm) and detect the maximum transmission times of the etalon. Thereby we achieve an RI accuracy of Δn = ±3.5*10^-6 in the Δn = 0…1.75*10^-4 and a 2% accuracy in the Δn = 1.75*10^-4…9.8*10^-4 RI-difference detection range. The accuracy is primarily limited by our reference measurement. The temperature stability of the measurement was determined by varying the temperature between 32 C and 42 C. The standard deviation of a RI measurement under these conditions is typically Δn = ±1.4*10^-6. We are working towards a continuous glucose monitor for subcutaneous long term implantation. The size of the tethered prototype sensor that includes a laser and detectors is suitable for implantation (12mm x 2.5mm x 8mm).The RI difference between the etalon chambers can be made specific to glucose by competitively and reversibly releasing dextran from immobilized Concanavalin A (Con A). Con A and dextran bound to it, is positioned outside the optical detection path. Dextran that has been released from the receptor by glucose, diffuses into the optical path and changes the RI of the detection chamber. At the same time other factors, for example buffer variations and temperature changes, affect the RI in measurement and detection chamber equally. Therefore, we have created a label-free, glucose specific concentration measurement on the basis of our cavity sensor platform. We will present our current results and calculations about the release of different variations of Con A, response times of the measurement, sensitivity and specificity.
2:45 PM - PP9.2
Digital Holographic Label-Free Drug Screening in Three Dimensional Tissue Culture.
Kwan Jeong 1 , Ran An 2 , John Turek 3 , David Nolte 2
1 Physics, Korean Military Academy, Seoul Korea (the Republic of), 2 Physics, Purdue University, West Lafayette, Indiana, United States, 3 Basic Medical Sciences, Purdue University, West Lafayette, Indiana, United States
Show AbstractMotility contrast imaging (MCI) is an alternative drug screening technology that has higher throughput and provides higher content than conventional proliferation-based tissue assays. MCI is a three-dimensional imaging technology that uses the functioning motions inside of cells as its imaging contrast to capture the behavior of cells embedded in their native three-dimensional environment, far from surface effects [1]. The ability to image cells in such an environment provides data that are more representative of cellular and tissue response to applied drugs than traditional high-throughput methods. Broad-area and low resolution tissue-scale imaging supports high-throughput screening (HTS), while the detailed subcellular dynamics provides high content screening (HCS). In MCI, speckle is sectioned from a fixed depth as deep as 1 mm inside tissue using short-coherence light and coherence gating through digital holography. Differential spectrograms capture the response as a function of time as drugs affect the internal functions of the cellular processes. Different perturbations produce time-frequency differential spectrograms that act as specific fingerprints for the mode of action. By creating a library of drug response spectrograms for known drugs, the spectrograms from unknown drug candidates can be matched to known drugs through fingerprint similarity analysis. In addition to elucidating modes of action, the state of health of the tissue can be monitored for general toxicity to drug candidates, providing an approach to early toxicity testing in drug discovery.This presentation describes the protocols and libraries that will form the bioinformatics foundation of MCI for drug screening as we correlate MCI drug response spectrograms with known modes of drug action. The primary application is for early assessment of drug candidate efficacy and toxicity. [1]K. Jeong, J. J. Turek, and D. D. Nolte, "Imaging Motility Contrast in Digital Holography of Tissue Response to Cytoskeletal Anti-cancer Drugs,," Optics Express, vol. 15, pp. 14057, 2007.
3:00 PM - PP9.3
Ferromagnetic Core and Superparamagnetic Shell Nanoparticles with Unique Magnetization Mechanism.
Hakho Lee 1 , Taejong Yoon 1 2 , Huilin Shao 1 , Ralph Weissleder 1 3
1 Center for Systems Biology, Massachusetts General Hospital / Harvard Medical School, Boston, Massachusetts, United States, 2 Department of Applied Bioscience, CHA University, Seoul Korea (the Republic of), 3 Systems Biology, Harvard Medical School, Boston, Massachusetts, United States
Show AbstractFerromagnetic metals, rather than their corresponding oxides, have been suggested as an ideal constituent for magnetic nanoparticles (MNPs) for their superior magnetization. Unfortunately, monometallic MNPs typically require protective layers to prevent progressive oxidation, which often results in reduced magnetization per particle. Here we present a new approach to preparing highly magnetic, monometallic MNPs. The particles consisted of an elemental iron core and an artificial ferrite-shell. The iron cores were enlarged into a thermally stable ferromagnetic state to increase the overall magnetization. Subsequently, protective ferrite shells were grown onto the cores and metal-doped to further enhance magnetization. The resultant particles displayed a unique magnetic feature, the presence of hysteresis with negligible coercivity. Further analysis revealed a novel magnetization process wherein the shell effectively reduces the coercivity of the ferromagnetic cores by leading the magnetization process at small magnetic fields. The resulting MNPs attain high saturation magnetization but with negligible remanence, and are free of inter-particle aggregations. The utility of the particles was demonstrated through the highly sensitive detection of proteins in the pico-molar ranges and of single cancer cells. The mechanism and MNP featured here could serve as a new strategy in preparing stable, highly magnetic and yet dispersible nanoparticles from ferromagnetic crystals.
3:15 PM - PP9.4
Molecular Interferometric Imaging of Prostate Specific Antigen on the BioCD.
Ming Zhao 2 , Xuefeng Wang 1 , David Nolte 1
2 Optical Sciences, University of Arizona, Tuscon, Arizona, United States, 1 Physics, Purdue University, West Lafayette, Indiana, United States
Show AbstractThe BioCD is an interferometric biosensor that detects protein captured by antibody arrays [1]. It has intrinsic scalability of surface-normal interferometric detection with capacity for hundreds or thousands of assays per disc. The interferometric detection allows repeatable surface height sensitivity to below 50 picometers. These simple attributes provide the potential for high-speed label-free multi-analyte assays with future applications in diagnostics, prognostics and drug discovery.The imaging is performed using a common-path interferometric configuration that is stable and sensitive to sub-monolayer coverage of captured protein [2]. Surface biolayers are detected using phase quadrature that converts phase to intensity modulation using local generation of signal and reference to lock the relative phase of the waves. The interferometric surface is a thermal oxide on silicon that is 3/8 of a wavelength thick, presenting a quadrature condition for the interferometry of surface-captured molecules.We have detected prostate specific antigen (PSA) in multiple configurations on the BioCD. Endpoint assays using spinning disc interferometry (SDI) and molecular interferometric imaging (MI2) provide calibrated concentration response curves with a high affinity equilibrium constant around 10 ng/ml and a limit of detection down to 1 ng/ml. Real-time binding assays provide kinetic coefficients for the association of antigen with antibody. Antibody immobilization is achieved either through direct printing onto functionalized surfaces, of by capture of the Fc portion of the antibody by the fusion protein A/G. Assays were performed in spiked buffer, spiked female serum and in cancer patient sera. Detection in patient sera was achieved down to 4 ng/ml.[1]D. D. Nolte, "Review of centrifugal microfluidic and bio-optical disks," Review Of Scientific Instruments, vol. 80, pp. 101101, 2009. [2]X. Wang, M. Zhao, and D. D. Nolte, "Common-Path Interferometric Detection of Protein on the BioCD," Appl. Opt., vol. 46, pp. 7836-7849, 2007.
3:30 PM - PP9.5
Prediction of the Mass Sensitivity of Phage-coated Magnetoelastic Biosensors for Detection of Single Pathogenic Bacteria.
Shin Horikawa 1 , Suiqiong Li 1 , Valery Petrenko 2 , Bryan Chin 1
1 Department of Mechanical Engineering, Auburn University, Auburn, Alabama, United States, 2 Department of Pathobiology, Auburn University, Auburn, Alabama, United States
Show AbstractMagnetoelastic (ME) materials are ferromagnetic amorphous alloys that undergo deformation in response to magnetic forces. When an ME material is placed in a time-varying magnetic field, the material oscillates and possesses characteristic resonance frequencies. Hence, ME materials can be used as mass-sensitive resonance sensor platforms. With a bio-recognition layer interfaced, ME sensors are capable of performing wireless, real-time detection of target biological substances. In recent years, phage-coated ME biosensors have attracted much attention in the food safety and bio-security fields. One of the ultimate goals established for such ME biosensors is detection of single pathogenic bacteria. Although the detection principle for ribbon-shaped ME biosensors has been well documented, conventional theories are applicable only to the case where attached masses are uniformly distributed over ME biosensors. For non-uniformly distributed masses, the mass sensitivity of ribbon-shaped ME biosensors depends largely on the longitudinal location of the attached masses. To address the issue, resonance frequency measurements of phage-coated ME biosensors immobilized with localized masses were performed. The mass sensitivity was found to be very low when a mass was located in the middle of the ME biosensor. By contrast, the maximum value of the mass sensitivity was obtained for the placement of a mass at the ends of the biosensor. In addition, three-dimensional finite element (FE) analysis was performed, and close agreement with the experimental results was obtained. The FE model was then used to predict the mass sensitivity of varying sizes of phage-coated ME biosensors immobilized with a single bacterial mass at different longitudinal locations. The results showed that sigmoidal curves had the best fit to the longitudinal mass sensitivity values of the ME biosensors.
3:45 PM - PP9: LabelFree
BREAK
PP10: Surface Functionalization I
Session Chairs
Wednesday PM, December 01, 2010
Back Bay C (Sheraton)
4:15 PM - PP10.1
Characterization of Immobilized DNA on Sulfur Passivated InAs Surfaces.
EunKyung Cho 1 , Pae Wu 2 , Minhaz Ahmed 2 , April Brown 2 , Thomas Kuech 1
1 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States
Show AbstractInAs is one of the few semiconductors that possess a Fermi level at the surface typically positioned above the conduction band edge. This leads to the presence of a quasi-two-dimensional electron gas at the surface that can be easily modulated by adsorbed species and binding events. Thus, the material is a premier candidate for a variety of sensing applications. Here, we look to the immobilization of DNA on the surface as the basis of a nucleic-acid affinity-based sensing platform. The immobilization of DNA on passivated n-type InAs (100) surfaces have been studied using X-ray and ultraviolet photoelectron spectroscopy. The thiolated ssDNA probe used in this study has a 25-base oligonucleotide. The 3’ end of the ssDNA was modified with fluorinated adenosine (A) to verify the existence of DNA on the InAs surface since there is no fluorine atom on the InAs surface or oligonucleotides. The benefits of sulfur passivation using ammonium sulfide solutions (NH4)2S for DNA immobilization were examined. The XPS/UPS data carried out on non- functionalized and the functionalized surfaces demonstrate that the DNA probes were reacted with passivated InAs surface. The XPS data in combination with later fluorescently-tagged DNA indicate at that the sulfur passivation process leads to a higher and more uniform attachment of DNA over the surface. In addition, the XPS spectra of As 3d core-levels immediately after passivation shows that there are only negligible amount of As-Ox and As-Sx observed after exposing the aqueous DNA probe solution for 20 hours. Based on literature [1], the potential oxidation pathways would be provided by displacement of sulfur by oxygen. These pathways appear to be kinetically or sterically hindered by the presence of sulfur on the surface and the high areal density of attached ssDNA. This system forms the basis of a DNA sensing system. While chemically passivating the surface against oxidation and facilitating probe attachment, the changes in Fermi level position was also monitored, when possible, by UPS.
4:30 PM - PP10.2
Biomolecular Material Systems with Encapsulated Interface Bilayers.
Stephen Sarles 1 , Donald Leo 1
1 Mechanical Engineering, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractMany of the transduction mechanisms that exist in living cells occur at the boundary of the cell, whereby the selective blockage or passage of chemical species through the cell membrane is used to detect and transmit information and energy into and out of the cell. Since the structure and composition of the cell membrane is a crucial part of the sensing process, the ability to construct artificial cell membranes, known as lipid bilayers, and incorporate functional proteins into these structures enables a wide variety of in vitro studies of both membrane material properties and transmembrane protein transduction, respectively. As a result, devices that feature lipid bilayers are of interest in developing new material platforms for performing high throughput drug screening, DNA sequencing, and analyte sensing related to personal health monitoring and environmental toxin detection. Unfortunately, many of methods used to form lipid bilayers require a skilled scientist and produce fragile membranes with limited use in laboratory environments and short durations. The droplet interface bilayer (DIB) method that was recently developed demonstrated that durable networks of lipid bilayers can be formed at the liquid interfaces of lipid-encased aqueous droplets contained in immiscible oil.We have developed a new method for the in situ formation of encapsulated interface bilayers (EIBs) within durable polymeric substrates (e.g. PDMS, PU) that increases the usability and versatility of biomolecular assemblies such as lipid bilayers. The encapsulating solid substrate features compartments for containing both liquid phases and is designed such that an applied mechanical force to the substrate is used to open and close apertures that divide adjacent wells. This technique, called the regulated attachment method (RAM), relies on the substrate to both support and locally manipulate the lipid-encased aqueous volumes to initiate bilayer formation and control bilayer size. A key feature of EIBs is that the size of the bilayer is controlled by the dimensions of the substrate, rather than the sizes or shapes of the connected aqueous volumes. Electrical recordings verify that EIBs exhibit values of electrical resistance greater than 10GΩ, permitting single channel recordings of transmembrane protein gating, yet demonstrate increased durability and portability through encapsulation within a durable substrate.Our current research efforts focus on the use of encapsulated interface bilayers with transmembrane proteins as the transduction elements for developing new types of biomedical sensors and energy-harvesting platforms. One such idea includes the fabrication of substrates that feature external “hairs” to create biologically-inspired hair cells, where mechanical deformations of the hair are coupled to the transport properties of EIBs contained within the substrate.
4:45 PM - PP10.3
Uniform Beads with Controllable Pore Sizes for Biomedical Applications.
Sung-Wook Choi 1 , Yi-Chun Yeh 1 , Yu Zhang 1 , Hsing-Wen Sung 2 , Younan Xia 1
1 Biomedical Engineering, Washington University in St. Louis, Saint Louis, Missouri, United States, 2 Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractUniform, porous poly(D, L-lactide-co-glycolide) (PLGA) beads with controllable pore sizes were prepared using an unstable water-in-oil (W-O) emulsion and a simple fluidic device. Optical micrographs revealed that the unstable emulsion phase-separated into two phases: the top layer rich in large water droplets and the bottom layer rich in small water droplets. When a syringe with a luer tip offset from the barrel was used, we could selectively introduce each layer of the phase-separated emulsion as a discontinuous phase into the fluidic device while a poly(vinyl alcohol) (PVA) solution was used as the continuous phase. The resultant water-in-oil-in-water (W-O-W) droplets evolved into PLGA beads with pores both in the interior and on the surface after the organic solvent had evaporated. Porous beads prepared using the top layer exhibited larger pores and windows interconnecting the pores than the beads obtained from the bottom layer. To show the effect of pore size on cell growth, we cultured fibroblasts in the beads with small and large pores. Fluorescence micrographs and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay confirmed a high density of viable cells in the beads with large pores. These results suggest that the beads with large pores could provide a more favorable environment for cells and thus be potentially useful for tissue engineering and cell delivery applications.
5:00 PM - PP10.4
Antimicrobial Peptides as Pathogen Biosensors: Understanding Surface Structure and Selective Binding to Lipopolysaccharide and Whole Cells.
Joshua Uzarski 1 2 , Abla Tannous 2 , Xiaofeng Han 3 , Zhan Chen 3 , Charlene Mello 1 2
1 Bioscience and Technology Team, US Army Natick Soldier Research, Development, and Engineering Center, Natick, Massachusetts, United States, 2 Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, United States, 3 Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe threat of biological infection is a persistent and daunting challenge for the medical community. One of the more effective strategies at preventing the spread of infection is, rather than antibiotic administration post-infection, detection of the causative microorganism prior to contamination. An ideal pathogen biosensor will be both sensitive and accurate and provide a fast response in an easy-to-use and portable device. Currently, many state-of-the-art pathogen biosensors rely on antibodies and large proteins as the detection element; however these molecules are often unstable under non-ideal conditions and offer poor long term stability. To circumvent many of the issues inherent to antibody-based detection platforms, we have focused on using a family of more robust peptides as potential capture agents for a multiplex pathogen biosensor.Antimicrobial peptides are produced by most organisms to help prevent microbial infection. A number of the peptides have shown discriminatory binding behavior to both bacterial strain and species, and the basis of the observed binding behavior is hypothesized to occur as a result of the peptide structures. While many peptide structural studies have been performed, the majority of them were conducted in solution or focused on antibacterial activity and not binding. The structure of covalently immobilized peptides and dependent binding/activity effects might be significantly different than those of solution-based peptides.Our efforts have been to both obtain a better understanding of the surface structure of immobilized antimicrobial peptides and the relationship to pathogen binding, as well as to develop a better substrate for peptide immobilization and subsequent pathogen binding studies. We have used the model peptide cecropin P1 modified with a terminal cysteine to facilitate binding to gold and maleimide-derivatized substrates. Here we will report on our major findings: 1) the location of the terminal cysteine residue influences the average orientation of the immobilized peptides, which consequently influences binding behavior, and, 2) a self-assembled monolayer composed of mixed oligo(ethylene) glycol-containing thiols offers a superior platform for binding analyses than the previously reported carboxymethyl dextran based substrates. Our binding analyses have focused on lipopolysaccharide (LPS), which are constituent molecules of the gram negative outer cell envelope as well as whole cells. We expect to observe a correlation between the LPS and whole cell binding, and our study is one of the first to demonstrate such a relationship. Our current and future efforts will continue to enhance our understanding of antimicrobial peptide structure and relationship to cell binding. By broadening our comprehension of immobilized peptides, we will be able to carefully design and construct a multi-array peptide based pathogen biosensor to aid in the early detection of a potential disease outbreak.
5:15 PM - PP10.5
Chemically Functionalized Carbon Nanotube Label for Immunoassay.
Adeyabeba Abera 1 , Jin-Woo Choi 1 2
1 Department of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, Louisiana, United States, 2 Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana, United States
Show AbstractA recent approach in disease diagnosis and viral epidemics is aimed at point-of-care tests that could be administered near the patient rather than time-consuming processes involving centralized laboratories. Point-of-care devices provide rapid results in simple and low-cost manner requiring only small sample volumes. These devices will strongly benefit from advanced materials and fabrication methods to improve their efficiency and sensitivity. This abstract presents a microfabricated immunosensor using carbon nanotube label for a simple and easy-to-use point-of-care application. Carbon nanotube label is prepared through suitable modification of the carbon nanotube surface to anchor biomolecules. The method involves the partitioning functionalization of multi-walled carbon nanotubes (MWCNTs) by surfactant adsorption and antibody attachment. First, the carboxylic acid treated MWCNTs are uniformly dispersed with polyvinylpyrrolidone (PVP) by sonication in aqueous solution. PVP partially wraps around the carbon nanotubes and exposes the surface of the nanotubes for further functionalization. PVP is non-toxic and water soluble, and low-power sonication minimizes defects to the structure of the MWCNTs that could alter their properties. The MWCNTs were then conjugated with human immunoglobulin G (IgG) using EDC/Sulfo-NHS coupling chemistry, where the antibodies occupied sites not covered by PVP. SEM and TEM characterization revealed the stability of the MWCNT dispersion before and after antibody attachment. TEM images also accounted for the attachment of antibodies and the organic coverage of PVP on the MWCNTs. The successful functionalization of the MWCNTs and reactivity of the covalent attached antibodies were demonstrated for specific antigen binding on the microelectrode device. The sensing device was composed of gold interdigitated microelectrodes with 20 µm spacing, where capture human IgG was immobilized. Anti-human IgG was used as model analyte and was applied on the electrodes to form antibody-antigen binding reaction. The MWCNT-human IgG conjugate was then introduced to form a sandwich complex. Consequently, the conjugated MWCNTs formed a conducting network bridging the electrodes enabling real-time electrical measurements proportional to the amount of captured antigens. This carbon nanotube-based detection mechanism could be tailored for screening various analyte specific molecules. Furthermore, this technique could easily be integrated in various microfluidic and lab-on-a-chip devices for the development of functional electronic sensors providing quantitative, sensitive, and low-cost detection in point-of-care setup.
5:30 PM - PP10.6
Passive Transfer Masking and Dry Etching of Active Silk Fibroin Meta Materials.
Konstantinos Tsioris 1 , Hu Tao 1 , David Kaplan 1 , Fiorenzo Omenetto 1
1 BME, Tufts U., Medford, Massachusetts, United States
Show AbstractSilk fibroin from the silk worm Bombyx mori (B.mori) is used as a material for high technology applications in the physical- and biomedical sciences. These applications include biopolymer based photonic crystals, and implantable and biodegradable microelectrodes. Silk was chosen as a material for these applications due to its biocompatibility, excellent optical properties (> 95 % transmission in the visible spectrum), and mechanical properties that allow fabrication of micro- and nanosize features.Reactive ion etching (RIE) is a major tool used in planar fabrication and yet, it has barely found usage with biopolymer micro manufacturing. Our objective is to demonstrate passive metal mask transfer, and RIE to fabricate active functional silk based meta materials (MM).Appropriate masking of the etch material is one of the critical steps in high quality RIE. We have developed a novel metal shadow masking and silk stenciling transfer method which allows patterning of silk biopolymer films in an easy and elegant single step. The metal patterns can be used for RIE masking or as active metal elements in the silk hybrid micro devices. The resulting biocompatible MM structures can then be used for sensing applications in various schemes. The combination of silk material properties and its affinity to biological species creates an excellent platform for potential high resolution biodetection.
PP11: Poster Session: Bio Material Interfaces
Session Chairs
David Nolte
Martin Zillmann
Thursday AM, December 02, 2010
Exhibition Hall D (Hynes)
9:00 PM - PP11.1
Selective Lectin Recognition by Mannose-modified Hyperbranched Conjugated Polymer in Aqueous Solution.
Dai Geun Kim 1 , Geun Seok Jang 2 , Seong Won Seo 2 , Minjung Lee 3 , Taek Seung Lee 2
1 Department of Nanotechnology, Chungnam National University, Daejeon Korea (the Republic of), 2 Department of Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejeon Korea (the Republic of), 3 Department of Oriental Medicine and Food Biotechnology, Joongbu University, Kumsan-gun Korea (the Republic of)
Show Abstract Dendritic molecules, including dendrimers and hyperbranched molecules, are gaining ever increasing attention for their potential applications in electronics, sensors, and medicine, with their unique and beneficial properties, such as improved solubility, efficient intramolecular energy transfer, easier and versatile functionalization on the multiple end groups, and so on. The search for artificial light-harvesters has triggered intense studies of conjugated dendritic molecules, including phenylacetylene and thiophene dendrimers, for efficient intramolecular energy transfer based on the global molecular shapes. Carbohydrate-protein interactions, which are found in interactions of proteins, viruses, and bacteria, are among the most important events or mechanisms in biological systems. Lectin is carbohydrate-binding proteins that mediate important biological processes such as cell growth, the inflammatory response and viral infections. Many lectin sensors have been developed over the years. The optical sensing of lectin is particularly relevant. Indeed, a number of optical sensors for lectin have been developed using different principles in the sensor design. Among them, fluorescence-based lectin sensors have been utilized a sugar-containing probe molecule. In this study, we have designed and synthesized water-soluble conjugated polymer containing mannose group for use as a lectin sensor. These polymers are studied using 1H NMR, elemental analysis, UV-vis absorption, and photoluminescence. We studied change of emission intensity of hyperbranched conjugated polymer by mannose and lectin. When mannose was added in polymer solution, emission intensity of polymer slightly decreased. This polymer in the presence of mannose revealed a selective fluorescence enhancement type signaling behavior in response to lectin in 100% aqueous solution.
9:00 PM - PP11.10
Layer by Layer Deposition of Polymer Spheres for Pesticide Biosensors.
Alexandra Snyder 1 , Lia Stanciu 1
1 Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractLatex microspheres were used as a template for layer by layer deposition of polyelectrolytes with opposite surface charges. The latex was coated with three alternating layers of polyacrylic acid (PAA) and poly(allylamine hydrochloride) (PAH). Scanning electron microscopy and zeta potential measurements verified the deposition of the polyelectrolyte layers. Acetylcholinesterase (AChE) was immobilized onto the surface of the polymer spheres by electrostatic forces and hydrogen bonding. Screen printed electrodes were coated with the immobilized AChE in order to measure current response and stability of the enzyme. Enzyme concentration, pH, and applied voltage were optimized for each system. Higher current response was observed when AChE was immobilized onto polymer spheres with a terminal PAA layer, despite the fact that both the polyelectrolyte and the enzyme are negatively charged. This can be attributed to positively charged PAH molecules blocking the negatively charged active site of the enzyme during immobilization. Inhibition tests will be done to measure the paraoxon detection limit of these biosensors and long term stability of the electrodes will be observed.
9:00 PM - PP11.11
Biosensing Using Voltage Control of Droplet-interface-bilayers.
Sri Punnamaraju 1 , Andrew Steckl 1
1 Nanoelectronics Laboratory, University of Cincinnati, Cincinnati, Ohio, United States
Show Abstract Droplet-interface-bilayer (DIB) lipid membranes are formed at the interface of phospholipid monolayer-coated aqueous droplets. Lipid-monolayer coated droplets are obtained by dispensing aqueous droplets in dodecane-lipid oil. The DIB approach to form artificial lipid bilayers has several attractive characteristics: versatile aqueous droplet volume, ranging from picoliters to microliters; mechanical overlap control of DIB dimensions; formation of various types of droplet networks; easy reformation. We report on the use of voltage enabled control over the DIB dimensions. This allows fine control and sensing of molecular transport through the DIB membrane. Both AC and DC voltages applied between adjacent droplets are shown to effectively modulate the DIB area and the current flow between droplets. Voltage-induced changes in interfacial tension modulated the DIB-oil contact angle and the membrane contact length, which provided control of membrane dimensions. Experimental results indicate substantial similarities between the DIB overlap control mechanism and that of electrowetting on dielectric. The process is reversible, robust and reproducible. Ion channel transport through the DIB was studied by incorporating the transmembrane protein alpha hemolysin (αHL). Experiments were conducted as a function of voltage and αHL concentration. A smaller (larger) DIB region results in the insertion of fewer (more) ion channels and, in turn, results in lower (higher) currents being measured. The voltage control of the DIB dimensions enables a fine control on the number of αHL ion channels available in the lipid bilayer membrane and, thus, ion channel studies can be carried out with greater flexibility.
9:00 PM - PP11.12
Surface Modification to Control Biomaterial-adherent Macrophage Activation.
Kyung Park 1 , James Bryers 1
1 Bioengineering, University of Washington, Seattle, Washington, United States
Show AbstractIn biomaterial-associated infections, the presence of foreign bodies is known to impair the local host immune function, rendering the implant surface vulnerable to bacterial infections. The goal of this research was to create model biomaterial surfaces that would enhance the immune response of adherent macrophage cells. A series of immunomodulatory biomaterial surfaces were developed, characterized, and tested in vitro for their ability to modulate adherent macrophage activation and improve macrophage defense against Staphylococcus epidermidis challenge. Glass substrates were covalently grafted with a mixture of methoxy- and biotin-terminated silanated polyethylene glycol (biotin-PEG-silane), to provide a non-fouling base layer with attachment sites for macrophage-activating ligands. Interferon-γ (IFN-γ) and/or lipopolysaccharide (LPS), ligands known to induce the highly microbicidal classical (M1) activation state in macrophages, were biotinylated and immobilized onto the PEG/biotin-PEG base layer via biotin/streptavidin chemistry. Macrophage cytokine and nitric oxide (NO) response to the fabricated surfaces was quantified in vitro using the murine macrophage cell line J774A.1. Then, surface-adherent macrophages were challenged with the bacterium, S. epidermidis, and the extent of phagocytosis was determined. Ligand-presenting surfaces were shown to successfully modulate adherent macrophage activation. IFN-γ-presenting surfaces primed adherent cells for classical activation upon stimulation with a secondary microbial signal (e.g., LPS), while LPS-presenting surfaces elicited a limited, pro-inflammatory activation state, characterized by high pro-inflammatory cytokine expression but low NO production. Surfaces presenting a combination of IFN-γ and LPS elicited full classical activation of the adherent cells. When challenged with bacteria, surfaces presenting IFN-γ, but not those presenting LPS alone, were shown to enhance macrophage phagocytosis of S. epidermidis. Results suggest that surface modification to modulate the immune response may be a promising approach for designing anti-infective implant materials.
9:00 PM - PP11.13
Quantitative Analysis of Protein Adsorption onto Materials for Biomedical Application.
Maria Holmberg 1 , Xiaolin Hou 2
1 Department of Micro- and Nanotechnology, Technical University of Denmark, Roskilde Denmark, 2 Risø DTU, Technical University of Denmark, Roskilde Denmark
Show AbstractIn this study radioactive labeling and Atomic Force Microscopy (AFM) is used to investigate protein adsorption onto materials aimed for biomedical application. Combining AFM performed in liquid with radioactive labeling, were the different proteins are labeled with isotopes that emit gamma radiation with different energies, creates a unique platform for quantitative analysis of protein adsorption onto materials in an aqueous environment on both nano-, micro- and macro-level. Addressing protein adsorption onto materials intended for biomedical application is important since contact between material and biological sample (for example blood, plasma and urine) inevitably results in protein adsorption onto the surface of the material, and this unspecific protein adsorption is often regarded as non-wanted. For example, high level of unspecific protein adsorption in miniaturised biomedical systems, such as lab-on-a-chip, can have a large impact on functionality and efficiency of the device. Narrow channels and small chambers can easily be clogged by adsorbed material and adsorption of small amount of protein to sensor surfaces can disturb analysis of subsequent samples. Generally, monolayer adsorption is assumed when analyzing protein adsorption onto materials used in biomedical devices, for example polymer and glass surfaces. However, results from radioactive labeling experiments, both from simple protein solutions and more complex solutions, often show adsorption levels that are higher than expected for monolayer adsorption. Additionally, results from adsorption of albumin and fibrinogen onto polymer and glass surfaces indicates that fibrinogen can adsorb on top of albumin, and that pre-adsorbed proteins are not easily replaced by other proteins during competitive adsorption. Tapping Mode AFM analysis of polymer and glass surfaces with adsorbed proteins show no protein aggregates or island formation on the surface, and instead the adsorbed proteins seem to be homogeneously spread over the surface. Thus, the results imply that proteins can adsorb in a multilayer fashion, a characteristics that should be considered when fabricating and developing materials for biomedical applications.By using the combination of quantitative radioactive labeling experiments with AFM in liquid it is possible, not only to detect how much protein you have adsorbed on a surface and to study competitive protein adsorption from complex solutions such as human serum and plasma, but also to evaluate the structure, topography and characteristics of the formed protein layer. The information and knowledge obtained from the analysis are important when interaction between proteins and materials is evaluated with reference to optimize materials for biomedical applications.
9:00 PM - PP11.14
Kinetics of Crystallization of Biodegradable PHA Cpolymers: A Combined X-ray Scattering, Micro-indentation, Small-angle Light Scattering and Polarized Microscopy Study.
Maraolina Dominguez-Diaz 1 3 , Araceli Flores 2 , Angel Romo-Uribe 1 , Rodolfo Cruz-Silva 3
1 Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos, Mexico, 3 Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Cuernavaca, Morelos, Mexico, 2 Instituto de Estructura de la Materia, C. S. I. C., Madrid Spain
Show AbstractWide Angle X-ray scattering (WAXS) and indentation hardness have been used to study the kinetics of crystallization at room temperature of biodegradable poly(hydroxybutyrate) (PHB) and its copolymers with hydroxyvalerate (PHB/HV) containing 5% and 12% of valerate. Amorphous samples were obtained by quenching from the molten state (200C) in ice water. X-ray scattering and indentation studies were carried out immediately after the quenching process and expanded over a period of more than 2 months. WAXS showed that the crystallization of the PHB-based polymers initiated within the first minute at room temperature, and the copolymer with higher content of valerate (12%) displayed the highest rate of crystallization. The degree of crystallinity reached a plateau value within the first hour of crystallization, for all samples. However, crystallinity continued increasing even after two months. Concurrently to the development of crystallinity, microhardness values clearly rose as crystallization occurred. A correlation between nanostructure and mechanical properties is found at all stages of the crystallization process. The evolution of micron-scale morphology from the as-quenched glassy state was also studied using small-angle light scattering (SALS) and polarized optical microscopy (POM). In the light of these results, a discussion on the possible mechanisms responsible for the changes usually observed in the nanostructure and the mechanical properties of PHB-based polymers, when stored at room temperature, is offered.
9:00 PM - PP11.15
The Relevance of Piezoelectricity of Poly (L-lactic) Acid on Protein Adsorption and Bone Cells Activity.
Paula Vilarinho 1 , Nathalie Barroca 1 , Maria Fernandes 1 , Alexei Gruverman 2 , Pedro Gomes 3 , Maria Fernandes 3
1 Dep. of Ceramics and Glass Engineering, University of Aveiro, Aveiro Portugal, 2 Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 3 Faculty of Dental Medicine, University of Porto, Porto Portugal
Show AbstractSince the discovery of the piezoelectric character of the bone by Fukada in the sixties, some attempts to repair the bone using piezoelectric materials such as PVDF, collagen and poly(L-lactic)acid have been performed. The few in vivo studies proved that piezoelectric materials have the ability to accelerate bone regeneration but the underlying mechanism was not untangled until now. A better understanding of the process starts with the knowledge of the relation between the self-polarizable piezoelectric material and the in vivo environment at the early stages of material implantation, which consists in the adsorption of proteins. The protein adsorption is a decisive stage because it mediates cells attachment and subsequent tissue growth around the implant material.Until now, no works have reported the effect of the polar activity of a piezoelectric material and the tissue growth process. In a previous study using piezoelectric PLLA thin films poled by piezoresponse force microscopy we have demonstrated, that a human serum protein (fibronectin) showed a preferential adsorption in a polarized surface comparing with a non polarized ones. The enhanced adsorption of proteins was related with the higher density of charges accumulated in the poled areas of PLLA films although no marked differences were visualized between the positively and negatively poled films. For a further understanding, in the present study the effect of the polarization of PLLA films on the process of cell adhesion is studied. PLLA thin films were prepared by solvent casting using 1% wt PLLA solution on Pt/TiO2/SiO2/Si substrate and subsequently submitted to a thermal annealing to crystallise. Films were heated at 190°C for 30 minutes, maintained at the crystallization temperature (80°C) for 15 minutes to induce some crystallization and finally frozen. Fibronectin adsorption was allowed for 30 minutes on the surfaces of the films macroscopically polarized (positively and negatively). And finally the different surfaces were exposed to MG-63 osteoblast-like cells. The ability of the different surfaces to allow cell adhesion, proliferation and correct phenotypic expression are compared and discussed.
9:00 PM - PP11.18
Direct Microfabrication of Topographical and Chemical Cues for the Guided Growth of Neural Cell Networks on Polyamidoamine Hydrogels.
Cristina Lenardi 1 2 , Gabriel Dos Reis 2 3 , Paolo Milani 2 3
1 CIMAINA, Dipartimento di Scienze Molecolari Applicate ai Biosistemi, Universita' di Milano, Milano Italy, 2 , Fondazione Filarete, Milano Italy, 3 CIMAINA, Dipartimento di Fisica, Universita' di Milano, Milano Italy
Show AbstractThe capability of controlling cell culture microenvironment is fundamental to better understand cell biology, build cell models and develop high throughput cell-based arrays. In this work we present the microscale fabrication of topographical and chemical cues on a novel class of biocompatible and biodegradable hydrogels for neural cell growth. Poly(amidoamine) (PAA) hydrogels are a family of synthetic polymers able to absorb a tissue-like water content and can be easily functionalized during the cross-linking with biomolecules to enhance and control major cell processes such adhesion, proliferation, and differentiation. We produce patterned microstructures on dry cross-linked PAAs using direct-write electron-beam exposure. This new approach allows to preserve the patterned features after rehydration and swelling scaled according to the designed structural properties of the material. The fine control of patterning process with the electron beam enables to produce microsized structures with a spatial control down to the submicrometric scale. We find that proteins preferentially adhere on the irradiated area as a function of the exposure dose. Moreover we observe that PC12 cells adhere only on the exposed area and, in the presence of neural growth factor (NGF), show neurite outgrowth guidance only along the microfabricated channels [1].[1] G. Dos Reis, F. Fenili, A. Gianfelice, G. Bongiorno, D. Marchesi, P. Scopelliti, A. Borgonovo, A. Podestà, M. Indrieri, E. Ranucci, P. Ferruti, C. Lenardi, P. Milani, “Direct microfabrication of topographical and chemical cues for the guided growth of neural cell networks on polyamidoamine hydrogels”, Macromolecular Bioscience 2010, 10.
9:00 PM - PP11.2
Biological Properties for Nitrogen-doped Hydrogenated Amorphous Carbon Film Coated Inner Wall of Artificial Heart Blood Pump.
Hotaka Sera 1 , Atsuko Toriu 1 , Yasuharu Ohgoe 2 , Ali Alanazi 3 , Kenji Hirakuri 1 , Yasuhiro Fukui 2
1 Electrical and Electronic Engineering, Tokyo Denki University, Tokyo Japan, 2 Division of Electrical and Mechanical Engineering,, Tokyo Denki University, Saitama Japan, 3 Biomedical Engineering, King Saud University, Riyadh Saudi Arabia
Show AbstractHydrogenated amorphous carbon (a-C:H) films including diamond-like carbon (DLC) films have attractive properties, which are attractive properties high hardness, anticorrosion, low friction, chemical stability and biocompatibility. Therefore, a-C:H film coatings have attracted much attention for biomedical applications. Recently, it is reported that the cellular affinity improves by the nitrogen of nitrogen addition in the a-C:H film. For the long period to use them in human body, stability of these instruments and the reduction of the hemolysis are expected by the a-C:H film with nitrogen.In this experiment, nitrogen-doped amorphous carbon (a-C:H:N) films were coated inner wall of artificial heart blood-pump and a cellular affinity is estimated. a-C:H:N film on an artificial heart blood pump was deposited by the RF plasma CVD system with a special 3-dimensional type electrode. Methane gas and nitrogen were used for source and dopant gas, respectively. The effect of nitrogen addition for the a-C:H film surface were estimated by Raman microscopy (Raman), contact angle measurement, X-ray photoelectron spectroscopy (XPS) and an atomic force microscopy (AFM). Additionally, the cytocompatibility of a-C:H:N film has been investigated under cell culture by in-vitro studies using fibroblast of mouse origin (NIH-3T3). In case of initial inner wall of artificial heart blood-pump, no significant change is observed in the cell incubation experiment. On the other hand, a number of cell is dramatically increased by a-C:H:N coating inner wall of artificial heart blood-pump. As a result, addition of nitrogen to the a-C:H film showed the improvement of the cellular affinity. The growth process of cells are observed by a scanning electron microscope (SEM).
9:00 PM - PP11.20
Design and Production of Biofunctional Surfaces Based on Hierarchically Structured Nanomaterials and Printing Processes.
Guenter Tovar 1 2
1 Interface and Material Sciences, Fraunhofer IGB, Stuttgart Germany, 2 Institute for Interfacial Engineering, University of Stuttgart, Stuttgart Germany
Show AbstractA key question of nanomaterials designed for use in life sciences and environmental technology is how to meet the needs of the interface between the technical and the living world: Whereas biological surfaces generally expose highly dynamic attributes – such as adsorption, reorientation, regeneration – the situation at a technical surface must be relatively steady, e.g. to ensure a sufficient shelf-life of a finalized product. How a nanostructured surface should be designed for providing its functionalities for the envisaged life time and which aspects must be taken into account for the processing of the nanomaterials will be discussed in the talk. We understand increasingly the complex interaction of biosystems with technical surfaces. In this talk we look at complex biosystems such as the human body or complex parts of it such as body fluid, and even the environment with its biosphere. A human body might be confronted with the technical surface of an implanted medical device such as a coronary stent or a transplant such as an artificial skin. A complex body fluid such as blood or blood serum is brought in contact with a technical device used as a diagnostic instrument which applies an advanced technology taken from the world of electronics, optics, or photonics. In our environment, nanostructured surfaces may help to provide solutions for water decontamination from bioactive substances which are currently not removed during the water management.
9:00 PM - PP11.21
Vapor Reactive Coatings as Platforms for Biomolecular Binding Studies.
Aftin Ross 1 , Di Zhang 2 , Xiaopei Deng 3 , Seiwon Laura Chang 4 , Joerg Lahann 1
1 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 , Washington University in St. Louis, St. Louis, Missouri, United States, 3 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractSurface-biomolecule interactions influence many biological fields from sensing applications to controlling the cellular microenvironment. While numerous techniques exist to determine the extent of these interactions, few provide spatially-resolved, quantitative data. Imaging ellipsometry used in conjunction with surface plasmon resonance (SPR) addresses these limitations. However, the use of these techniques to probe biologically relevant inquiries is hindered by the accessibility of versatile binding substrates. Vapor-based reactive polymer coatings made by chemical vapor deposition (CVD)polymerization of functionalized [2.2]paracyclophanes are promising candidates as flexible binding substrates for biomolecular immobilization. [2.2]paracyclophanes, also known as poly-p-xylylenes incorporate a wide range of reactive species including aldehydes, anhydrides, amines, and active esters which can be utilized to immobilize various proteins and biomolecules. In addition, these polymers can serve as initiators for atom transfer radical polymerization (ATRP) of hydrogels. This work will show the efficacy of CVD thin films as platforms for imaging ellipsometry/SPR biomolecular sensing. In addition, the influence of film properties on sensing capabilities and biomolecular adsorption will be highlighted via ellipsometry, atomic force microscopy, electrical impedance spectroscopy, fluorescence microscopy, and ELISA.
9:00 PM - PP11.22
Shear-induced Adhesion in Mussel Foot Proteins Films for Biomedical Applications.
Rebecca Schur 1 , Roberto Andresen-Eguiluz 1 , Delphine Gourdon 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractMussels adhere permanently to a variety of surfaces under extreme saline conditions by depositing a highly specific ensemble of 3,4 dihidroxyphenyl-L-alanine (DOPA) containing proteins. Using an atomic force microscope (AFM) in buffer solution, we have investigated the adhesive and friction properties of Mytilus Edulis foot protein-1 (mfp-1) films deposited onto mica and glass substrates. The normal (adhesion) and lateral (friction) forces were monitored as a function of shearing cycles, shearing velocity, applied pressure, and mfp-1 film thickness. Our results indicate that shearing globally increases the ‘superficial’ adhesion of the protein film. This effect was attributed to the ability of the AFM tip to progressively rearrange the mfp-1 molecules at the film surface hence exposing highly adhesive DOPA groups. This shear-enhanced adhesion was found reversible and more pronounced in thin rather than thick mfp-1 films: prolonged shearing of thick films eventually led to the detachment of weakly bound proteins (found in the upper film layer) and to the consequent contamination of the AFM tip by mfp-1, promoting low (and constant) adhesion and friction. Complementary intermittent contact AFM imaging of the films was performed to confirm shear-induced rearrangement (alignment) but no removal of the tightly bound proteins in thin films while thick films exhibited accumulation of detached proteins at the periphery of the sheared areas. The chemical (specific role of DOPA) and physical reasons for the “tunable” adhesive properties of mfp-1 films as well as the potential use of mussel foot proteins based surfaces for biomedical applications such as surgical or dental restoration techniques are discussed.
9:00 PM - PP11.23
Synthesis of Compact and Biocompatible Quantum Dots with a Zwitterionic Polymer Coating.
Hee-Sun Han 1 , Jungmin Lee 1 , John Martin 1 2 , Peter Allen 1 , Jain Rakesh 2 , Moungi Bawendi 1
1 Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Cambridge, Massachusetts, United States
Show AbstractWe present a new class of zwitterionic polymer ligands to yield derivatizable, bright, compact, stable and biocompatible water soluble quantum dots (QDs). In this study, RAFT mediated polymerization was used to synthesize random co-polymers with low polydispersity employing imidazole monomers for stable multi-dentate binding, zwitterionic monomers for water solubilization with low protein adsorption and compact size, and amine or biotin terminated monomers for further functionalization. Zwitterionic terminated nanoparticles are expected to have a more compact size when compared to traditional poly(ethylene glycol) coatings, low non specific binding to proteins, and high stability in concentrated buffers. We probe physical properties of these zwitterionic QDs such as surface charge by zeta potential analysis and hydrodynamic diameter by dynamic light scattering and gel filtration chromatography. In addition, we also present preliminary results of their use for in vivo and in vitro biological imaging.
9:00 PM - PP11.24
Hydrogel/Bioceramic Composite System for Coating Orthopaedic Implants.
Kyung-Ah Kwon 1 , Judith Juhasz 1 , Serena Best 1
1 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom
Show AbstractMetallic implants are used widely in orthopaedics due to their high strength, biocompatibility and corrosion resistance. However, these materials are relatively stiff compared to natural bone, which may result in stress shielding and are unable to form a suitable bond with the adjacent bone. To circumvent these problems a bioactive, low modulus coating material, which can be applied to the metallic implant, has been developed and characterised, with the intention that the coating will act as a soft interface with the bone tissue while encouraging bone repair.A hydrogel/bioceramic composite was produced as the coating material with bioceramic filler weight fractions in the range; 0, 5 and 10 wt.%. Nano-sized carbonated hydroxyapatite (nCHA) was prepared as the bioceramic filler by a wet precipitation method and the polymer matrix was produced by mixing a hydrophilic polymer (polyhydroxyethylmethacrylate; PHEMA) with a hydrophobic polymer (polycaprolactone; PCL) at a 4 to 1 ratio. This hydrogel/bioceramic composite attached well to titanium alloy (Ti-6Al-4V) substrates, creating a homogeneous and smooth coating surface. Scanning electron microscopy with energy-dispersive spectroscopy analysis (SEM-EDS) revealed that the coating was uniform and continuous with approximately 60 μm to 80 μm thickness and that the bioceramic nanosized particles were evenly distributed throughout the hydrogel polymer network. The surface topology was evaluated using atomic force microscopy (AFM) under both dry and wet conditions. AFM results illustrated that wetting a sample had a significant effect on the surface topology, and thereby the surface roughness, especially for 10 wt.% CHA content.The mechanical stability of coating was characterised using nanoindentation, which was performed both in dry and wet environments. In dry conditions, increasing the bioceramic filler content increased the modulus and the hardness of the coating in a near linear fashion from 126.8 MPa and 2.54 MPa for 0 wt.% CHA sample to 735.7 MPa and 8.15 MPa for 10 wt.% CHA sample. However, no similar significant increases in modulus and hardness were noted with increasing filler content in wet conditions. Preliminary in-vitro evaluation was performed using SBF testing and a marked reduction in the required time to form an apatite layer was noted on the CHA samples as compared to the pure hydrogel samples. Overall, nCHA incorporation in the hydrogel polymer network improved not only the bioactivity but also the indentation resistance of the coating. These coatings appear to offer excellent potential as a soft interface between the orthopaedic metallic substrates and bone tissue.
9:00 PM - PP11.25
Redefining In-Sight: Effective MRI Contrast Agents in Biodegradable Polymeric Drug Delivery Vehicles.
Ragy Ragheb 1 , Arunima Bandyopadhyay 1 , Halima Chahboune 1 , Jason Criscione 1 , Tarek Fahmy 1
1 Biomedical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractNon-invasively imaging the dynamics and anatomical localization of biodegradable drug delivery vehicles would give insight into subsequent pharmacokinetics and biodistribution. This would afford early diagnosis and monitoring of disease progression. Superparamagnetic iron oxides (SPIOs), specifically magnetite, have been widely used as diagnostic agents for magnetic resonance imaging (MRI) in various platforms including tumor therapy and cardiovascular disease. Incorporating magnetite into poly(lactide-co-glycolide) (PLGA) nanoparticles improves both the imaging effects while facilitating drug delivery. Conventional hydrophilic magnetite incorporation into polymer nanoparticles via water-oil-water emulsion leads to inefficient loading and increased susceptibility for leakage. Hydrophobic magnetite was synthesized allowing for efficient loading of magnetite in the organic polymer phase during nanoparticle formation. Hydrophobic magnetite-loaded PLGA nanoparticles were prepared via an oil-in-water emulsion technique with and without the incorporation of an Avidin-fatty acid conjugate. MRI phantom studies of magnetite-loaded PLGA with and without avidin showed increased relaxivities (r2) and improved contrast in comparison with commercial SPIOs (Molday Ion). Avidin-functionalized magnetite-PLGA nanoparticles produced strong negative contrast of labeled macrophages with an increased rate of relaxation, R2. Extensive in vitro investigations have shown that the PLGA nanoparticles can be effectively internalized by macrophages with and without targeting. Uptake of these particles did not affect the function or viability of the macrophages.Thus these nanosystems can be effectively used as a platform for imaging diseases such as arthesclerosis as well as serve as excellent drug delivery vehicles.
9:00 PM - PP11.26
Effect of Fluid Shear Stress upon Cell Adhesion to Patterned Stainless Steel Surfaces.
Rose Spear 1 , George Sykes 1 , Vera Malheiro 1 , Jorge Sobral 2 , Kun Li 1 , Athina Markaki 1
1 Department of Engineering, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom, 2 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Show AbstractSuccessful integration of an orthopaedic implant with bone is often approached via modification of the bone/implant interface by either chemical or topographical means. This work relates to the effect of surface topography on proliferation and adhesion of human osteoblast cells on 316L austenitic stainless samples. A pulsed fibre laser was used to create terracing on the samples. The topography of the patterns produced by the laser were characterised using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). X-Ray Photoelectron Spectroscopy (XPS) was employed to study the surface composition before and after the laser treatment. The AlamarBlue™ and CyQUANT assays were used to assess cell viability and proliferation respectively. The AlamarBlue assay is based on quantification of the reducing environment of cell metabolic activity, while the CyQUANT assay measures dye fluorescence upon binding to cellular nucleic acids. The beginning of osteoblastic differentiation was determined using a classical osteoblastic marker: alkaline phosphatase (ALP). To characterise cell adhesion, a centrifugal field was used to detach the cells from the substrates. Testing was carried out with the cell-substrate interface oriented parallel to the acceleration direction, so that shear forces were developed. At high rotational velocities (60,000g), the results indicate a distinct difference in the reduction of cell metabolic activity between samples. There was a significantly larger drop in cell metabolic activity on the as-received samples compared to the patterned ones. We conclude that interactions and adhesion of human osteoblast cells with metallic implant surfaces can be improved through terraced surface patterning.
9:00 PM - PP11.27
A Library of Synthetic Polypeptides for Biomedical Applications.
Amanda Engler 1 , Anita Shukla 1 , Daniel Bonner 2 , Hilda Buss 1 , Paula Hammond 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSynthetic polypeptides have received a significant amount of attention because of their unique structural properties and biocompatibility. Synthetic polypeptides, like their naturally-occurring analogues, can exhibit pH-responsive secondary structures in solution. Our group has developed a general synthesis for functionalized polypeptides.1 We have developed a synthetic scheme for the production of polypeptides that combines the ring opening polymerization (ROP) of the N-carboxyanhydride (NCA) of γ-propargyl-L-glutamate with click chemistry to form a library of new polypeptides with near quantitative functionalization. We have explored several different applications for this synthesis including the formation of brush polymers, antimicrobial polypeptides, and pH responsive polymers for drug and gene delivery. We have successfully synthesized brush polymers using a “grafting onto” strategy with a grafting efficiency higher than 95%. The antimicrobial polypeptides are able to kill both gram positive and gram negative bacteria. The pH responsive polymers are able to adapt both a random coil conformation and an α-helical conformation depending on solution pH and side group functionality. These charged polymers successfully complex with siRNA and DNA. The combination of NCA ROP and click chemistry provides a versatile synthetic approach to develop complex macromolecules for many different biomedical applications.1.Engler, A. C.; Lee, H. I.; Hammond, P. T., Highly Efficient "Grafting onto" a Polypeptide Backbone Using Click Chemistry. Angew. Chem.-Int. Edit. 2009, 48 (49), 9334-9338.
9:00 PM - PP11.28
Photo Sensitive Film Forming Polymers for Tissue Engineering Applications.
Monica Apostol 1 , Tatiana Mironova 1 , Miriam Rafailovich 1 , Nan-loh Yang 1
1 , Stony Brook University, Stony Brook, New York, United States
Show Abstract An improved substrate for cell culture is presented. The substrate consists of a rigid base, such as a Si wafer or glass coverslip, upon which a light sensitive polymer coating is spun cast. Exposure to light for short periods of time is then shown to release adherent cells non-enzymatically. This method allows for layer by layer tissue deposition, as well as producing patterned tissue constructs. Examples are shown using keratinocyte and dermal fibroblast cells constructs.
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Study of Cellular Motility on Patterned Polyeletrolyte Multilayer Films.
YooJin An 1 , SungYun Yang 1
1 , Chungnam National University, Daejeon Korea (the Republic of)
Show Abstract Cells exhibit a wide range of movement including migration of cells along a surface, tissue or movement of components within cells. Recently, more studies of cell movement have been conducted in many different fields. Polymeric surfaces would be suitable candidates to study cellular motility because one can control various properties including physical morphology as well as chemical functionality. Especially, their thicknesses can be controlled by means of film processes. Layer-by-Layer deposition (LbL) is one of the convenient methods to create such thin films. Moreover, the functional groups of deposited film by this process are still remained reactive, therefore, allow further chemical reactions such as the polymer micro patterning and the selective crosslinking. In this paper, we utilized LbL deposition method to form polyelectrolyte multilayer films on the surface of the substrate and we used ink-jet printing to create micropatterns. Polyelectrolyte mutilayer films comprised of weak polyelectrolytes such as poly(allylamine hydrochloride)(PAH), poly(acrylic acid)(PAA), hyaluronic acid(HA) exhibit different surface properties as they were assembled at different pH condition. Also, we used PAH as the ink of ink-jet printing to test cellular interaction. Cell-interatctive ligands were immobilized on the patterns by a subsequent coupling reaction. As the results, cells show more directional movement on the patterned surface than isotropic surface.
9:00 PM - PP11.3
Protein-polymer Conjugates for Use as Hybrid Functional Materials.
Victoria Briand 1 , Vindya Thilakarathne 1 , Yuxiang Zhou 1 , Rajeswari Kasi 1 , Challa Vijaya Kumar 1
1 Chemistry , University of Connecticut, Storrs , Connecticut, United States
Show AbstractProtein-polymer conjugates synergistically improve the biological and functional properties of proteins and polymers. By covalently attaching polymers, the stability, solubility and immunogenicity of proteins can be improved. In this study, hemoglobin (Hb) was chosen due to its reversible oxygen binding capabilities and functionalizable prosthetic heme groups. Hemoglobin is a tetramer consisting of 2 α and 2 β subunits with each subunit contains a prosthetic heme. Outside of red blood cells, hemoglobin’s structure loses stability and the tetramers dissociate. By attaching polymers to the tetrameric globular structure, we aim to stabilize the structure while retaining oxygen binding. Two approaches have been taken to modify hemoglobin a) random bulk attachment and b) well-defined attachment. Poly(acrylic acid) (PAA) and cholesterol-modified polyacrylates have been attached to hemoglobin and the prosthetic hemes. The bulk attachment sample consists of a high molecular weight PAA randomly attached to Hb at various amine groups. TEM has showed that bulk attachment of PAA to Hb can lead to a network structure. The protein retained its structure and redox activity while embedded in the polymer network. A second conjugate was synthesized using a well-defined approach. The conjugate was synthesized by cleavage, modification and reconstitution of the heme from hemoglobin. The effect of modified heme and influence of polymer on hemoglobin activity was investigated. The characterization of the conjugates was done by UV-vis spectroscopy, gel electrophoresis, transmission electron microscopy, and circular dichroism. The synthesized conjugates have potential uses in sensing and biomedical applications.
9:00 PM - PP11.30
Ti-based Metallic Glasses for Partial Denture.
Jeong-Jung Oak 1 , Junji Saida 1 , Inoue Akihisa 2
1 Tohoku University, Center for Interdisciplinary Research, Sendai Japan, 2 Tohoku University, WPI-AIMR, Sendai Japan
Show AbstractWe have successfully observation of newly designed Ti-based metallic glasses with plastic deformation under fracture behavior. Due to the mechanical properties is very important to use in utility. It is well known that Ti-based alloys have various phases, e. g., α phase, α+β phase or β phase, were used for utilization purpose. Especially, β phase Ti-based alloys exhibit high specific strength for lightweight, low elastic modulus as well as excellent workability for being applied to biomedical structure materials. Meanwhile, the typified as metallic glasses, these materials are well known by outstanding properties, i.e., specific strength with low elastic moduli, excellent corrosion resistance, good workability as well as large elastic deformation. Especially, in case of fracture behavior of typical bulk metallic glasses skip the process of plastic deformation. In this study, we have attempted improvement of mechanical property (comparable the level of Ti-6Al-4V alloys and Ti-Ni alloys) by development of Ti-based metallic glasses for partial denture at buccal cavity. Obtained results exhibit good mechanical properties compared with those of typical metallic glasses. The studied metallic glasses reveal large plastic deformation after elastic deformation around 2% for length of test sample in compressive test. The result might be recognized as a hot issue in novel materials science in Ti-based alloys because of the improvement of machining-workability and the possibility of further application as like common alloys. In addition, the object metallic glasses exhibit high bulk forming ability, and exclusive Al and Ni elements which have high potential to be toxic in human body as well as high corrosion resistance in SBF at 310 K. It will be revealed the upgraded mechanical properties for Ti-based metallic glasses in detail.
9:00 PM - PP11.31
Fiber-particle Composite Scaffolds In-situ Prepared by Electrohydrodynamic Co-jetting.
Harim Bae 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang university, Seoul Korea (the Republic of)
Show AbstractDespite intense investigation in recent years, non-woven fabric or particulate scaffold system alone has serious limitations in guiding cell differentiation and controlling the release of growth factor. ECM-mimetic structure is considered as a solution for the current limitations, for which the engineering technology of particle/fiber hierarchical structures is a key. Herein, electrohydrodynamic jetting of countercharged nozzles was developed to combine fibers with particles based on the neutralization phenomenon between electrospun fibers and eletrosprayed droplets. Because the surfaces of the fibers and the particles have opposite charges, the two different materials uniformly combined each other. Otherwise, simple electrospraying of particles onto fibers could not result in efficient conjugation. Electrospun PLA fibers provided physical cues that could direct tissue formation when seeded with cells without disrupting scaffold mechanical properties. Vascular endothelial growth factor (VEGF) was encapsulated within electrosprayed PLGA nanoparticles combined with fibers, which controlled the release rate of VEGF. SEM observation showed that the particles were well dispersed on the surface of fibers, and confocal laser scanning microscopy showed that VEGF was distributed evenly in the microparticles. With these scaffolds, VEGF could be released in a sustained manner separately from the degradation of fibers. This fiber-particle conjugation would improve the maturation of such constructs and add additional functionality to the systems both in vitro and in vivo.
9:00 PM - PP11.32
Hydrogels based on Nanoclay-Fucoidan Interactions.
Sunae Hwang 1 , Sona Lee 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractHydrogels have been intensively investigated due to their potential in a myriad of applications, such as drug delivery, wound dressing, artificial cartilage, superabsorbants, microfluidics, electroconducting smart materials, and contact lenses, each of which requires specific mechanical properties. Fucoidan refers to a type of anionic polysaccharide containing substantial percentages of fucose and sulfate ester groups, largely derived from brown seaweed. We found effective physical gelation between nanoclay and fucoidan, and pH-sensitive semi-InterPenetrating Network (semi-IPN) hydrogels based on acryl amide, nanoclay, and fucoidan were successfully prepared by photo-crosslinking with controlling both chemical and physical crosslinking to engineer biomimetic structures. The mechanical properties of hydrogels were characterized using compression, tensile, and fracture tests. The elastic modulus, strain hysteresis and essential work of fracture of semi-IPN could be controlled through changing the concentration of fucoidan. The swelling ratio and drug release of semi-IPN hydrogels reflects the internal structures of hydrogels revealed by SEM.
9:00 PM - PP11.33
Controlling Human Dermal Fibroblast Morphology by Micro-patterned Fibronectin and Its Biological Behaviors.
Jong Hwa Lee 1 , Sang Jun Park 1 , Yong Jae Jin 1 , Chun-Ho Kim 1
1 Jong Hwa Lee, Korea Institute of Radiological & Medical Sciences, Seoul Korea (the Republic of)
Show AbstractIt is thought that topography can influence cellular responses from initial attachment to migration through differentiation and production of new tissue. To study the cell cytoskeltal responses to topography and the effect of cell cytoskeltal on its biological behaviors such as adhesion, proliferation, and differentiation, we designed a pattern of self-assembled monolayers (SAMs) with fibronectin by microcontact printing. An elastomeric stamp (PDMS, Polydimethylsiloxane), containing line features on the micrometer scale, was used to imprint gold surfaces with specific patterns of SAMs of methyl-terminated alkanethiols. The remaining bare gold regions were derivatized with a polyethylene glycol-terminated alkanethiol; SAMs of this alkanethiolate resist adsorption of proteins such as laminin, fibronectin, etc. Through this technique, methyl-terminated alkanethiols regions of defined size that supported protein adsorption were produced on otherwise nonadhesive gold surfaces. The exposure of this substratum to the purified extracellular matrix (ECM) protein, fibronectin, resulted in the formation of protein coated lines of defined geometry and distribution that corresponded precisely to the patterns formed from SAMs of methyl-terminated alkanethiolate. The various patterns were fabricated by controlling the space length between fibronectin coated SAMs lines. Space length is 5,11,20 micrometer and patterns’s area is 0.7 x 0.3 mm. Human dermal fibroblast attached preferentially to the adhesive, fibronectin-coated SAMs lines and showed peculiar cytoskeleton by different space ength. The adhered HDF showed different their cytoskeleton, attachment amount, proliferation rate, and differentiation on different space lengths. As result, there is optimum space length for enhancement of cell’s adhesion, proliferation and migration.This work was supported by the Ministry of Knowledge Economy(MKE) (10035291) and the Korea Science and Engineering Foundation(KOSEF) (grant code: 2010-0005408)
9:00 PM - PP11.34
Polypeptide Macromers with Tunable Secondary Structure as Components of a Modular Synthetic ECM.
Abigail Oelker 1 , Linda Griffith 2 3 , Paula Hammond 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIt is widely reported that cellular functions including DNA synthesis, migration, and differentiation are co-regulated by both the stiffness of the extracellular matrix (ECM) and the presence of soluble signaling molecules (growth factors, cytokines, hormones, etc). Parsing the effects of ECM stiffness and permeability on cellular behavior requires an in vitro system in which these parameters can be tuned independently. The purpose of this research is to synthesize and characterize a set of functionalizable polypeptides with tunable secondary structure as part of a hydrogel toolkit for modeling cell-matrix interactions. The polypeptides of interest were synthesized via ring-opening polymerization of N-carboxyanhydride derivatives of γ-propargyl L- and/or D-glutamate. These macromers were found to exhibit low polydispersity and become water soluble after a cycloaddition reaction between the alkyne moieties along the polymer backbone and azide-terminated poly(ethylene glycol) chains. Preliminary circular dichroism spectroscopy data demonstrate that stereoregular polyglutamate (containing only L-glutamate monomers) exhibits α-helix secondary structure in solution, whereas polyglutamate composed of both D and L monomers adopts a random coil conformation. These macromers can readily be designed to adopt either α-helix (more stiff) or random coil (less stiff) secondary structure and functionalized with adhesion ligands, affinity probes, and macromolecular permeability modifiers then crosslinked to form hydrogels with which to study fundamental parameters of cell-matrix interactions.
9:00 PM - PP11.35
Thermally Regulated Microwells for Retrieval of Cell Aggregates.
Halil Tekin 1 2 , Michael Anaya 2 3 , Claire Nauman 2 4 , Robert Langer 3 5 , Ali Khademhosseini 2 5
1 Department of Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Medicine, Center for Biomedical Engineering, Brigham and Women’s Hospital, Harvard Medical School, Cambridge, Massachusetts, United States, 3 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe generation of cell aggregates with a controlled geometry has a number of applications in biological research and tissue engineering experimentation. Previous research has established the utility of microwells formed from photocrosslinkable poly(ethylene glycol) in the formation of cell aggregates. The glass bottomed microwells is often useful in stable formation of aggregates due to the adhesive regions of the glass substrate. The utility of such aggregates could be substantially increased by a reliable method of retrieving the aggregates from these microwells, for use in other experiments or to construct more elaborate tissue structures. Such retrieval from glass bottomed microwells is often difficult, necessitating the use of digestive enzymes or distorting the desired geometry of the aggregates in the process. The process described in this study uses responsive microwells to consistently form cell aggregates, then retrieve the aggregates by exploiting the temperature dependant properties of the polymer. The polymer structure of the microwell arrays responds to thermal conditions, allowing changeable microwell diameters that mechanically facilitate aggregate retrieval. The resultant aggregate retrieval from these dynamic microwells represents a significant improvement over static microwells, and is scalable to high throughput systems. As such, this method may be of value in research fields that make use of uniform cell structures, such as tissue engineering, drug discovery, stem cell differentiation.
9:00 PM - PP11.36
Bottom-up Process of Electrosprayed Fibers to Develop Cell-glued 3D Scaffold for Tissue Regeneration.
Jong Kyu Hong 1 , Sundararajan Madihally 1
1 Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, United States
Show AbstractTissue engineering or regeneration focuses on restoring, maintaining, and enhancing tissue and organ function. In tissue engineering, biodegradable scaffolds are used to support and guide cells to proliferate, organize and produce their own extracellular matrix. Electrospinning technique has recently emerged as a novel technique for tissue regeneration because it allows fabrication of nano and micro size fibers, similar to the characteristic of natural extracellular environment. However, a major problem in electrospinning is the lack of generating structural features necessary for building 3D tissues. The pore sizes are less than 10 µm, while human cells are typically greater than 10 µm in size. Hence, cell growth is restricted to the surface only. In this study, we introduce bottom up process to develop thicker 3D scaffold using thin layers of novel electrosprayed fibers with large pore sizes.Polycaprolactone (Mw =43,000) was used to fabricate electrosprayed fibers. The setup of electrospraying consists of a syringe pump, syringe, needle tip, high voltage power supply, earth grounding, and the novel collector or a conventional one. The physical properties of fibers made by novel and conventional collectors were compared using SEM, CCD camera, and Sigma Scan Pro software. Load and extension curve was also confirmed using INSTRON 5542 and Merlin software. Cell culture study of human fibroblast was carried out in single and multiple layers using layer-by-layer assembly technique. The cells were cultured in serum media for 1, 4, 7, and 30 days, immobilized, and stained with Alexa phalloidin and DAPI, or hematoxylin and eosin (H & E) for histology analysis. Then, cell morphology was confirmed using inverted microscopy, fluorescent confocal microscopy, and SEM.Three pairs of fibers (Fiber A and B, C and D, and E and F) were fabricated under the same conditions except for exchanging novel (A, C, and E) and conventional (B, D, and F) collectors. Physical properties of each pair of fibers were very similar except pore sizes. The pore sizes were 61.75 and 9.95 μm for A and B, 104.83 and 6.35 μm for C and D, 9.14 and 3.21 μm for E and F. The diameters of fibers were 3.18 and 3.37 μm for A and B, 1.80 and 2.97 μm for C and D, and 100 and 350 nm for E and F. After cell culture using human fibroblast and Fiber C, cell morphology at day 1, 4, and 7 showed that cells were growing not only horizontally but also vertically in single and three layers of fibers. After 30 day cell culture, three layers of fibers were merged into one stable 3D scaffold because cells acted as a glue to attach each layers. The shape of the 3D scaffold was tailored using scissors because cells stabilized the merged scaffold. Thus, bottom up process of electrosprayed fibers with large pore size will expand its implication to develop thicker tissues and organs using various biomaterials and cells for tissue regeneration.
9:00 PM - PP11.37
Three Dimensional Polymer Patterning for Ordered Cellular Networks.
Maria Dinescu 1 , Alexandra Palla-Papavlu 1 , Valentina Dinca 1 , Iurie Paraico 2 , James Shaw-Stewart 3 4 , Matthias Nagel 3 , Thomas Lippert 4
1 Lasers, NILPRP, Bucharest Romania, 2 Department of Cellular and Molecular Medicine, “Carol Davila” Medical University, Bucharest Romania, 3 Laboratory for Functional Polymers, EMPA, Swiss Federal Laboratories for Materials Testing and Research , Dübendorf Switzerland, 4 General Energy Research Department, Paul Scherrer Institute, Villigen Switzerland
Show AbstractThe precisely two-dimensional (2D) and three-dimensional (3D) patterning of functional surfaces is arguably an important step toward future micro and nano-systems. We report the formation of well-defined 2D and 3D patterns of polyethylene imine (PEI), polyisobutylene (PIB) and polyepichlorhydrine (PECH) on simple or poly(ethylene glycol) (PEG) coated glass, fused silica and silicon surfaces by using laser induced forward transfer (LIFT). An important opportunity arises from the propensity of PEI, PIB and PECH to accommodate and coordinate cell growth. We envisioned that by means of 2D and 3D organization of different polymer patterns well-ordered cultured cells (neuronal cells, fibroblasts and keratinocites) might constitute in vitro networks positioned with micrometer precision. The ability to obtain in vitro functional networks on patterned polymers at different length scales is important for research fields including cell biology, tissue engineering and medicinal science.To this end, challenges and future directions are discussed from the point of view of both applicability and strategies for cell growth on 2D and 3D polymer patterns.Keywords: patterns, 3D, LIFT, in vitro, cell culture
9:00 PM - PP11.38
Metal-enhanced Fluorescence to Quantify Bacterial Adhesion.
Kangwon Lee 1 2 , Lewis Hahn 1 , William Yuen 1 2 , Hera Vlamakis 3 , Roberto Kolter 3 , David Mooney 1 2
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States, 3 Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States
Show AbstractCurrent methods to examine bacterial adhesion, a key step in biofilm formation, are based on qualitative observations of the physical proximity of the cells to a surface, and provide little information regarding the mechanism of adhesion. We have developed a new optical technique, based on metal-enhanced fluorescence, to monitor and probe the adhesion of individual bacterium, and demonstrate the possibility of obtaining precise information regarding the three-dimensional cell distribution as they come into contact with a surface. A gold surface with comparable roughness to a glass surface (control) was prepared by electron beam lithography and deposition technique. A prominent enhancement of fluorescence intensity was observed by electronic coupling of the gold surface and fluorescently-labeled cells upon close contact (< 70 nm) to the gold surface. Bacteria within this distance from the adhesion substrate formed stable adhesions on the surface, allowing fluorescence enhancement to be utilized as a real-time, non-invasive measure of cell adhesion. The utility of this method to study the influence of substrate chemistry, soluble factors, and cell structure on cell adhesion is demonstrated. In summary, this new technique is likely to be of utility in many studies of bacterial adhesion, and may also be applied to studies of mammalian cell adhesion.
9:00 PM - PP11.39
Guided 3-dimensional Cell Growth in Agarose Hydrogel Scaffold via X-ray Irradiation.
Kyu Hwang Won 1 , KyungShin Kang 2 , Dong-Woo Cho 2 , JungHo Je 1
1 materials science and engineering, Pohang University of Science and Technology, Pohang, Kyungbuk, Korea (the Republic of), 2 Mechanical Engineering, Pohang University of Scinece and Technology, Pohang, KyungBuk, Korea (the Republic of)
Show Abstract3-dimensional (3D) scaffold of natural polymer such as hydrogel, in spite of its importance in the cell growth in an environment analogous to natural condition, has been rarely reported. Here, we propose a x-ray ablation method [1] to fabricate 3D micropatterned network scaffold of agarose hydrogel without any photoinitiators, by irradiating synchrotron X-rays (10-60 keV) to the hydrogel through a Ni micropatterned mask for more than 2 min. The ablation rate of the hydrogel by X-ray irradiation was very high as 1.5 mm/min. Interestingly, the reduction of the irradiation time to less than 2 min decreased the stiffness of the hydrogel instead of the ablation. Specifically we were able to tune the stiffness locally by controlling the irradiation time, as characterized by rheometry. The reduction rate of the stiffness was 5 times faster than that by UV exposure in synthetic polymers.[2] Furthermore, 3D micropatterned networked scaffolds fabricated from cell embedded agarose hydrogels showed guided 3D cell growth along microchannels. We believe that the x-ray ablation method would be a good platform to fabricate 3D network micropatterned scaffolds for guided 3D cell growth in natural polymers.Reference1.Weon B M, Chang S, Yeom J, Hahn S K, Je J H, Hwu Y, Margaritondo G, Journal of Applied Physics 2009; 106:0535182.Kloxin A M, Tibbitt M W, Kasko A M, Fairbairn J A, Anseth K S, Advanced Materials 2009; 21:1-6
9:00 PM - PP11.4
Study of Water Vapor and Surfactant Absorption by Lipid Model Systems Using Quartz Crystal Microbalance.
Guojin Lu 1 , Timothy Gillece 1 , David Moore 1
1 R&D/Materials Science, International Specialty Products, Wayne, New Jersey, United States
Show AbstractIt is widely established that environmental exposure to surfactants can cause damage to the outer epidermis, the stratum corneum (SC), by denaturing proteins and disrupting the organization of SC lipids. A consequence of this damage is to make the SC dry and flaky, compromising its physiological barrier function, and allowing surfactant molecules to penetrate into the SC inducing skin irritation. Damage to the skin barrier is particularly problematic for individuals with sensitive skin (i.e., inherently poorer skin barrier function) or those continually exposed to surfactants whether due to cleansing requirements (medical personnel) or occupational exposure. To address skin damage induced by cleansing it is clearly desirable to modify topical cleansing formulations with materials that will mitigate or alleviate surfactant related damage to the outer epidermis, including protein denaturation and lipid disruption. As part of the process to develop such technologies, it is essential to develop in vitro and in vivo quantitative measurement methods to predict, evaluate, and demonstrate the effect of these technologies on surfactant-related skin interactions. In this article, water vapor uptake and surfactant absorption onto skin barrier lipid model films were quantitatively studied using a technique based on the piezoelectric effect, the quartz crystal microbalance. This approach is straightforward and reliable in providing subtle surface-interface related mass change information with high resolution and sensitivity. Lipid model thin films of specific molar ratios of free fatty acids (FFA), ceramides (CER) and cholesterol (CHO), which are designed to mimic the SC skin barrier composition, were deposited onto quartz crystals from solution. The lipid-coated crystals were then exposed to water vapor in a humidity chamber, or to surfactant solutions, to study the permeability and penetration by those molecules into the lipids. Factors such as lipid composition, thickness of the lipid film, and surfactant concentration were systematically studied for their impact on absorption of water vapor and surfactant molecules onto the lipid film. The results show that abnormal lipid composition (deviating from the equimolor ratio between the three main lipid components associated with healthy SC) leads to poor water binding and more surfactant absorption and penetration. Surfactant absorption is concentration dependent even beyond its CMC.
9:00 PM - PP11.40
Design and Properties of Polymeric Biomaterials Based on Polyurethane and Chitosan for Ophthalmology Application.
Yerkesh Batyrbekov 1 , Zaure Utelbaeva 2 , Tursunkul Botabekova 2 , Bulat Zhubanov 1
1 , Institute of Chemical Sciences, Almaty Kazakhstan, 2 , Kazakh Institute of Eye Diseases, Almaty Kazakhstan
Show AbstractPolymer-based biomaterials are becoming increasingly important in ophthalmology due to considerable advantages of improving drug availability and decreasing side effects compared to conventional therapeutic methods. In the present study the design and properties of polymeric biomaterials based on segmented polyurethane and chitosan for ophthalmology application in the treatment age-related macular degeneration have been described. Polyurethanes with different content of hard and soft segments were prepared by a two-step polymerization using a number of polyethylene and propylene glycols and 2,4-tolylene-diisocyanate. These polyurethanes were used for the fabrication of thin films immobilized by prostaglandin analog vazaprostan. The drugs release behaviour from segmented polyurethane into modelling biological media was studied. All the release data show the typical pattern for a matrix controlled mechanism. The process is controlled by the dissolution of the drug and by its diffusion through the polymer. The total amount of vazaprostan is released in 10–12days and depends of polyurethane structure and contents of high segments in polymer. The chitosan gels and films containing different doses of mexidole were developed. The release of drug from chitosan biomaterials was studied in vitro experiments. It was established that process of release occurs on the mechanism of diffusion and erosion with reduction of rate. Polymeric biomaterials were used for treatment of age-related macular degeneration at 24 patients. The experimental and clinical tests show that implantation of films to suprahoroidal area did not cause the pathological changes in the membrane of eyes and help to activate the formation of vascular anastomoses in 1 month. The positive effect is prolonged up to 6 month in 63 %. The results obtained in the present work have shown the perspectives of use polymeric biomaterials based on segmented polyurethane and chitosan as a matrix for prostaglandins delivery for application in ophthalmology for the treatment age-related macular degeneration.
9:00 PM - PP11.41
Electrical Power Generation in Blood Vessel toward Medical Applications.
Takeo Miyake 1 2 , Yohei Yatagawa 1 , Syuhei Yoshino 1 , Keigo Haneda 1 , Tatsuya Takahashi 1 , Ryo Takahashi 1 , Matsuhiko Nishizawa 1 2
1 , Tohoku.Univ, Sendai Japan, 2 , CREST, Tokyo Japan
Show AbstractWe have been developing miniature biofuel cells toward a power source of implantable medical devices. Implantable biofuel cells require following three properties: blood-compatibility, miniature electrode, and safety electrocatalysts, in addition to power density and stability. Here, we present anti-biofouling coating of the electrode surfaces, fabrication of the needle-type miniature electrodes, and immobilization of the safety electrocatalysts. The enzymatic biofuel cells is appropriate for biomedical applications, especially for the power generation directly from biofluids, tissue fluids and blood, containing glucose (ca. 5 mM), lactate (ca. 1 mM) and oxygen (0.1 mM in arterial blood) due to their high reaction selectivity and absolutely-safe. There may be many types of medical devices with each levels of invasiveness, from the low invasive skin-patch devices for health monitoring and drug delivery to the highly invasive devices such as cardiac pacemakers, all of which require sufficient stability and safety in addition to the power generation property. We have studied the bioanode modified with bio-adaptive Vitamin K3-pendant polymer and an enzyme membrane for glucose oxidation. We have also studied the microfluidic biofuel cell for quantitatively evaluating the fuel cell performances in the regulated flow. Following two topics will be presented. 1). In order to obtain biocompatible surface, bioelectrode surface is coated with bioinert MPC-polymer. A MPC-treated bioanodes showed biocompatible ability, while blood clot is formed on an untreated anode surface when immersed in human blood for 2 hours. And then, LLC (lyotropic liquid crystal) molecules are modified on the electrode surface to inhibit the invasion of uric acid molecule. 2). A prototype of needle type biofuel cell (for inserting into subcutaneous or blood vessels) was fabricated. In order to avoid the peel-off of an enzymatic catalyst, we tried to immobilize an enzyme within a needle. At first, a disposable injection needle (inner diameter is 0.5 mm) was insulated by electrodeposition of an insulating paint. A gold wire, which used as a current collector, was inserted in the insulated needle. Finally, carbon particle and enzyme membrane were packed. The performance of the needle-type biofuel cells are evaluated in a rabbit ear vein.
9:00 PM - PP11.42
Viscoelastic Properties of PDMS in the Frequency Domain.
Ping Du 1 , I-Kuan Lin 1 , Hongbing Lu 2 , Xin Zhang 1
1 Mechanical Engineering, Boston University, Boston, Massachusetts, United States, 2 Mechanical Engineering, University of Texas at Dallas, Richardson, Texas, United States
Show AbstractPolydimethylsiloxane (PDMS) has been widely used in bio-MEMS devices to exploit the intrinsic cellular mechanical forces. The accuracy of these devices relies on choosing an appropriate material constitutive model to convert the measured structural deformations into corresponding reaction forces. Previous studies have introduced the viscoelastic property in the time domain to take into account the modulus changes with loading rates and elapsed time. However, the actual cell traction will induce loading conditions much more complicated than the simple constant rate conditions. The cell is more likely to behave periodic motions in the frequency domain. As is well known, any periodic signal can be decomposed into a sum of simple oscillating functions by Fourier analysis. Therefore it is practical to study the viscoelastic properties in the frequency domain. Two types of PDMS specimens were used in this report: thin films and microfabricated pillars. A Dynamic Mechanical Analyzer (DMA), model RSA α (Rheometric Scientific), with 1 mN load resolution and temperature range of -100 °C~100 °C, was used in the measurement of the complex moduli of PDMS films. Because the DMA can only reach a frequency up to 16 Hz, the temperature-frequency superposition principle was employed to obtain master curves that could cover a wide range of frequency (0~260 Hz).For the PDMS micropillars, a MTS Nano Indenter XP system was used in nanoindentation tests to acquire load-displacement data. In order to measure the viscoelastic functions, a dynamic indentation loading history needs to be applied. The dynamic load can be realized by superimposing a harmonic oscillation upon a quasi-static carrier load, such as a constant rate load or a pseudo step load. Formulas were derived to determine both storage and loss moduli in terms of amplitudes of the harmonic load and displacement, and the out-of phase angle. The results were compared with data obtained from DMA to validate the method presented, and a good agreement was reached.In summary, the experimental methodologies and theoretical framework developed in this work can be readily applied to other type of polymer or composite materials for various MEMS applications.
9:00 PM - PP11.43
Enhanced Sensitivity of the Self-similar Cantor Heterostructures Made From Nanostructured Porous Silicon.
Jose Escorcia-Garcia 1 , Luis Gaggero-Sager 2 , Fabiola Balderas-Valadez 3 , Gabriela Palestino 3 , Vivechana Agarwal 1
1 Materials, CIICAp-UAEM, Cuernavaca, Morelos, Mexico, 2 Physics, Facultad de Ciencias-UAEM, Cuernavaca, Morelos, Mexico, 3 Chemistry, Facultad de Ciencias Químicas-UASLP, San Luis Potosí, San Luis Potosí, Mexico
Show AbstractIn this work we have studied and tested the sensitivity of the porous silicon (pSi) Cantor heterostructures as biosensors as compared to the microcavity structures. An enhanced sensitivity is demonstrated by immobilizing an enzyme Glucose Oxidase (GOX), used for the determination of free glucose in body fluids. Any Cantor multilayer is characterized by two fundamental parameters, the generator G=3,5,7,... and the generation number M=1,2,3,... Here we consider the triadic Cantor construction (G=3) for which the initiator is a porous layer A and the generator consists of removing its Rth (R>1) central part, and replacing it with a porous layer B; iterating this generation procedure M times produces a fractal Cantor set [1]. Cantor structures were prepared by electrochemical etching process of a p-type crystalline Si wafer [2]. During the electrochemical etching, the current density and anodization time were varied in order to produce a layered structure consisting of alternating layers whose optical thicknesses and refractive indices are chosen according to the Cantor set fractal construction. The functionalization of the Cantor structures was realized in the similar way as reference [3]. Changes of the confined resonant modes in the reflectivity spectra were monitored during each modification step. Apart from these Cantor structures, microcavity multilayers were fabricated in order to compare the sensitivity in their optical response after functionalization. Our results demonstrate that Cantor heterostructures exhibit an enhanced sensitivity. The change of the optical response (Δλ) for the Cantor structure was found to be 72 nm with respect to the 53 nm for the microcavity multilayers. This increase is attributed to the characteristic distribution of the porous layers that conform the Cantor structure which improves a better infiltration of the molecules. Furthermore, the optical response (Δλ) of the Cantor structures is found to depend on the order of the generation M, i.e. the stage at which the algorithm of Cantor is growth (3 layers of M=1, 7 layers for M=2, 15 layers for M=3, and so on), showing a better behavior for a value of M=3. The optimum value of M depends of the refractive indices utilized for the Cantor structure.References1. S.V. Zhukovsky and A.V. Lavrinenko, Photonics and Nanostructures 3, 129 (2005).2. J. Escorcia-García, V. Agarwal and P. Parmananda, Appl. Phys. Lett. 94, 133103 (2009).3. G. Palestino, V. Agarwal, R. Aulombard, E. Pérez, and C. Gergely, Langmuir 24, 13765 (2008).
9:00 PM - PP11.44
Gold Nanoparticles Used in the Genetic Diagnostics.
Iliana Medine-Ramirez 1 , Maribel Gonzelaz-Garcia 1 , Jingbo Liu 2
1 Chemistry, Universidad Autónoma de Aguascalientes, Aguascalientes Mexico, 2 Chemistry, Texas A&M University-Kingsville, Kingsville, Texas, United States
Show AbstractComposite of noble metal and polymer based genetic diagnostics draw significant attention to medical (such as cancer diagnosis), pharmaceutical (drug delivery), and analytical applications. We hypothesize that specific interaction of noble metal gold (Au) and targeted deoxyribonucleic acid (DNA) plays the most important roles. In this study, the aim is to understand the morphological and optical intensity changes of composite of Au-targeted DNA (pBluescript KS) and its electrochemical behavior. Therefore, a series of colloidal Au was synthesized through reducing hydrated HAuCl4 by a green reducing agent, ascorbic acid. The Au colloidal suspension was then impregnated into pBluescript KS (+) plasmid buffered solution, which was prepared using alkaline lysis plasmid preparation procedure. Several advanced instrumentation techniques have been applied to characterize the compiste and to understand the interaction between immobilized DNA and Au, such as scanning electron microscopy (SEM), and ultra-violet and visible spectroscopy (UV-Vis) and Raman spectroscopy. From the analytical results, it can be seen that mono-dispersed Au colloid was prepared from sol-gel method; and this sol-gel derived Au nano-particles were highly crystallized and its crystallite size ranged from 5 to 7 nm corresponding to the fabrication variable. Pure gold displays strong capability to scatter light at wavelength of 550 nm when ultraviolet visible spectroscopy is used. The gold particles coincide with the particles’ surface plasmon resonances. When Au-colloid was used to bind pBluescript KS (+) plasmid, the red shift of the Au absorbance occurred from spectroscopic (UV-Vis and Raman) data, which has been explored for in-vivo biological and chemical application, such as determination of diseased tissues. It was also found that Au-nanoparticles (NPs) display high intensity so that gold can be used in development of contrast agent for optical imaging. When Au was used to target pBluescript KS (+) plasmid, the composite formed and nanostructure was destroyed. According to this intensity increase (including the peak splitting), it was confirmed that Au was bi-conjugated with pBluescript KS through the intermolecular forces. In addition to the optical activity, gold is electrochemically active at various applied potentials, which causes the oxidation number of gold change from Au3+ to Au0 or vice versa. Based on this redox reaction, the phenomenon of blue-gray pigmentation was observed. These phenomena allowed us to visualize the pBluescript KS (+) plasmid being bioconjugated with Au-NPs. Using optical and electrochemical properties as complementary approaches, the efficiency and accuracy of the conjugation between Au and pBluescript KS (+) plasmid will be advanced.
9:00 PM - PP11.5
Effect of Lipid Composition on Its Permeability and Structure: A QCM, DSC, and FT-IR Spectroscopy Study.
Guojin Lu 1 , Donald Koelmel 1 , Xiaohong Bi 2 , David Moore 1
1 R&D/Materials Science, International Specialty Products, Wayne, New Jersey, United States, 2 Dept. of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractThe stratum corneum (SC) is the outermost layer of human skin. It is generally accepted that SC lipid organization functions as the primary permeability barrier and plays a critical physiological role in regulating water loss and uptake through the skin, as well as protecting the organism from the environmental milieu and external physical and chemical insults. SC lipid membranes are comprised of three major components: free fatty acids (FFA), ceramides (CER) and cholesterol (CHO). Because of the complicated structure of SC model lipid system are widely employed to probe the fundamental biophysical and materials properties of SC. These models consist of FFA, CER, and CHO in an equimolar ratio when mimicking a normal (healthy) SC lipid barrier. Lipid composition (different molar ratios between these three main components), especially the amount of ceramide, is of paramount importance for SC organization and its barrier properties. In fact, it is known that lipid composition in the SC varies with anatomical skin sites and, more importantly, is altered as a function of skin damage and disease. For complex lipid mixtures, variation in lipid composition will modify the material properties of the membranes and, therefore, their phase behavior. This in turn will affect the water holding capability and barrier properties of the lipid system. In pathological conditions, when lipid composition is changed, a reduced capacity to hold water and increased trans-epidermal water loss (TEWL) is observed. Ternary SC lipid models of different molar ratios were studied using the quartz crystal microbalance (QCM), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy. QCM absorption results (with both water vapor and surfactant molecules) show that abnormal lipid composition leads to poor water binding and more surfactant absorption and penetration. The barrier function of lipid models with relatively less ceramide and cholesterol is poorer and these membranes are more vulnerable to water swelling than the SC lipid model of healthy skin. Furthermore, the perturbation of lipid organization by surfactant molecules is greater in the case of the lipid models of compromised skin. DSC data and FT-IR spectroscopy results show the fatty acid components in these altered models separate into more ordered, crystalline domains (higher Tm and enhanced orthorhombic lipid packing) when there is more FFA in the lipid model samples. The Tm of the fatty acid increases with amount of FFA in the sample while the Tm of ceramide decreases with FFA concentration in the lipid model.
9:00 PM - PP11.7
Fabrication of New Biocompatible and Non-fouling PEG Thin Films Using the CCP-CVD Method and Their In Vitro and In Vivo Applications.
Changrok Choi 1 , Donggeun Jung 2 , Eun Joong Kim 3 , Taek Dong Chung 3 , Yun Mi Kang 4 , Moon Suk Kim 4 , Dae Won Moon 1 , Tae Lee 1
1 Center for Nano-Bio Technology, Korea Research Institute of Standards and Science, Daejeon, Chungnam, Korea (the Republic of), 2 Department of Physics, Sungkyunkwan University, Suwon, Kyongki, Korea (the Republic of), 3 Department of Chemistry, Seoul National University, Seoul, Kyongki, Korea (the Republic of), 4 Department of Molecular Science and Technology, Ajou University, Suwon, Kyongki, Korea (the Republic of)
Show AbstractNon-fouling films have surfaces that are resistant to protein adsorption and cell adhesion. Among non-fouling films, polyethylene glycol (PEG) thin films have been popular in various biological applications such as diagnostic assays, sensors, drug deliveries, and in vivo implants because of their hydrophilic and non-toxic properties. In this work, a new plasma-polymerized polyethylene-glycol (PP-PEG) thin film was fabricated onto various substrates by using the capacitively coupled plasma chemical vapor deposition (CCP-CVD) method and PEG monomer (MW=200) as a precursor. Our PP-PEG thin film not only has characteristics similar to PEG polymer thin films but also has characteristics similar to plasma polymer thin films such as uniformity, reproducibility and strong adhesion to the surface. Moreover, PP-PEG thin films can be used in nano- and micro-patterning of proteins and cells by using photolithography and the CVD method with a shadow mask, respectively. For in vivo applications of PP-PEG film, its biocompatibility was studied by implanting into Fisher rats polyethylene (PE) that had been coated with PP-PEG on both sides, and examining the histological staining of tissues within and near the implanted PP-PEG coated PE film after 1 week and 4 weeks post-implantation. Our results confirmed a good in vivo biocompatibility. We are optimistic that our PP-PEG film can be used for various in vitro and in vivo bio-applications.
9:00 PM - PP11.8
Engineered Immunity: Targeting of Gram-positive Bacteria to Phagocytes by Artificial Antibodies Constructed from Multivalent Conjugates of Poly(L-lysine)-graft-poly(ethylene glycol) with Vancomycin and Human IgG-Fc.
Kristy Katzenmeyer 1 , James Bryers 1
1 Bioengineering, University of Washington, Seattle, Washington, United States
Show AbstractHospital-acquired infections remain a leading cause of death in the United States. Unfortunately, the emergence of antibiotic-resistant bacterial strains has rendered traditional antibiotic therapy ineffective. Furthermore, many of the causative bacteria, such as staphylococci, are surrounded by a protective polysaccharide capsule which allows them to evade the host’s immune system. For this reason, novel antibody therapies, including passive and active immunization, also have little efficacy. In an effort to enhance the body’s natural immune response to infection, we have developed multivalent artificial antibodies to promote the recognition, phagocytosis, and destruction of pathogenic bacteria by human phagocytes. The structure of our artificial antibodies consists of multiple copies of both bacterial and phagocyte recognition molecules attached to a poly(L-lysine)-graft-poly(ethylene glycol) polymeric support. Human immunoglobulin G (IgG) Fc antibody fragment serves as the phagocyte recognition molecule and is recognized by the Fcγ cell surface receptors universally expressed on human phagocytic cells. Binding of the IgG-Fc leads to cell activation to elicit the powerful antimicrobial functions of the phagocytes. For bacterial recognition, we have employed a novel application for the glycopeptide antibiotic vancomycin as a high affinity targeting molecule. Our approach utilizes vancomycin’s inherent ability to bind to multivalent structures naturally present in the cell wall of Gram-positive bacteria. Conjugation of vancomycin to PLL-g-PEG prevents its action as an antibiotic and allows it to function solely as a recognition molecule. Notably, we have found that our approach has efficacy against virulent multi-drug-resistant and polysaccharide-encapsulated bacteria which are notoriously difficult to treat, including a vancomycin-resistant strain of Staphylococcus aureus. In addition, the artificial antibodies themselves are designed to be non-bactericidal, thereby minimizing or even eliminating the chance that bacteria would develop resistance mechanisms.
9:00 PM - PP11.9
Enantioselectivity of Chiral Molecules on a Chiral Copper Surfaces.
Lars Thomsen 1 2 , Michael Gladys 2
1 , Australian Synchrotron, Clayton, Victoria, Australia, 2 School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia
Show AbstractThe study of chirality can be of fundamental significance for applicative purposes in device technology and also in biological processes but especially in the pharmaceutical industry where many new drugs are developed that contain chiral molecules and where a molecule with the ‘wrong’ chirality can often have harmful consequences living organisms. To separate a set of enantiomers the industry currently utilize homogeneous catalysis where catalyst reactants as well as the product are all in liquid form however this leaves the issue of eliminating the reactants from the solution product without damaging the final product. The goal of the future is to focus on either separating the two chiral pairs, or through a reaction to produce only a single enantiomer on the surface of a heterogeneous catalyst.It is known that a chiral surface can act as such a heterogeneous catalyst as it can display enantioselectivity with regards to chiral adsorbents [1-5] however the mechanism behind this selectivity is still somewhat elusive. The use of a heterogeneous catalyst would circumvent the majority of separation problems that exist. In our research we hypothesize that the correct chiral interface can act as a ‘lock’ (a active site) so that only one of the enantiomers, the reactant or ‘key’ will fit, i.e. the surface will recognize the chirality of the molecule and hence making one molecule of a chiral pair separable from the other. A heterogeneous catalyst is easily removed from the product solution and avoids the intrinsic problems associated with current homogeneous catalysis.In this paper I discuss Near Edge X-ray Adsorption Fine Structure (NEXAFS) and X-ray Photoelectron Spectroscopy (XPS) results gained from synchrotron radiation of chiral amino acids such as Alanine, Cysteine and Methionine on Cu(421) and Cu(531). These results are part of a greater effort to characterize chiral molecules on chiral interfaces using synchrotron light.1.G. Held and M. J. Gladys, Top. Catal. 48 (2008) 128.2.Y. Huang and A. J. Gellman, Catal Lett. 125 (2008) 177–182.3.S. M. Barlow and R. Raval, Surf. Sci. Rep. 50 (2003) 201.4.K. Soai, S. Osanai and K. Kadowaki, J. Am. Chem. Soc 121 (1999) 11235.5.G. A. Attard, A. Ahmadi, J. Feliu, A. Rodes, E. Herrero, S. Blaise and G. Jerkiewicz, J. Phys. Chem. B 103 (1999) 1381.
Symposium Organizers
Peter Kiesel Palo Alto Research Center
David Nolte Purdue University
Xudong (Sherman) Fan University of Michigan
Martin Zillmann Millipore Corporation
PP12: Surface Functionalization II
Session Chairs
Thursday AM, December 02, 2010
Back Bay C (Sheraton)
9:30 AM - PP12.1
Metal Assisted Plasma Etching of Silicon- A One-step Method for Fabrication of Microfluidic Devices, Membranes and Sensors.
Teena James 1 , Shivendra Pandey 1 , Chih-Chieh Chan 1 , Harrison Schwartz 1 , David Gracias 1 2
1 Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractWe describe the unusual characteristics of metal assisted plasma etching of silicon that can be used to precisely structure microchannels, wells and membranes for a wide range of biomedical applications. The etch characteristics with respect to different metals, geometry and plasma parameters will be discussed. In addition, we will describe two specific applications of the process: one involving the creation of nanoparticles coated microfluidic channels to precisely localize biomolecules within them while at the same time retaining their bioactivity. Here, we describe the mechanism for the spontaneous Au nanoparticle coated microchannel formation and explore its utility in biomolecular patterning and sensing applications. We also describe the fabrication of porous membranes using this process and describe their utility as immunoisolation membranes.
9:45 AM - PP12.2
A Weak Affinity Dynamic Microarray for Glycan Profiling: Potential Platform for Optimal, High-throughput Screening and Profiling of Glycoproteins.
Nigel Reuel 1 , Jin-Ho Ahn 1 , Michael Strano 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractMicroarrays of carefully selected lectins have been proposed as high-throughput platforms for profiling and screening glycoproteins. Rather than constructing a traditional protein array, where each glycan group has a highly-specific lectin pair, we introduce the concept of a Weak Affinity Dynamic Microarray (WADM) to utilize the entire affinity spectrum and achieve profiling with a smaller set of lectins. Lectins, having much weaker affinities yet broader interaction spectrums, can potentially fingerprint glycosylated proteins with higher resolution by dynamically monitoring the on and off binding rates of a target glycan. This can be realized with several emerging nanosensor platforms that allow for single protein adsorption dynamics to be recorded in real time. The dynamic use of these weakly-affined lectins may reduce the complexity and increase the robustness of proposed lectin microarrays. We use binding constants obtained from a public database of 113 lectins and 442 glycan groups to design several aspects of such WADM. By employing a Kinetic Monte Carlo model we predict the optimal number of lectin types as well as best operating spaces (number of transducers and glycoprotein concentration) for three prototypical glycan profiling applications: 1) screening protein therapeutics, 2) differentiating arthritic disease, and 3) complete profiling of glycoproteins without a priori knowledge of their synthesis pathway. It was found that a subset of 28 lectins was sufficient for clear profiling of proteins with two glycosylation sites. Our calculations also provide design constraints for instrumentation necessary to realize a lectin WADM for glycoprotein profiling and screening.
10:00 AM - PP12.3
Laser Rapid Prototyping of Microstructured Devices for Transdermal Drug Delivery.
Roger Narayan 1 , Shaun Gittard 1 , Philip Miller 1 , Anand Doraiswamy 1 , Aleksandr Ovsianikov 2 , Boris Chichkov 2
1 , North Carolina State University, Raleigh, North Carolina, United States, 2 , Laser Zentrum Hannover, Hannover Germany
Show AbstractMicroneedles are devices that may be utilized for delivery of protein-based and nucleic acid-based pharmacologic agents through the stratum corneum layer of the skin. These miniaturized hypodermic needle-shaped, lancet-shaped, or thorn-structures possess at least one dimension under 500 micrometers in length. Two photon polymerization is an additive fabrication process that may be used to create individual microneedles as well as arrays of microneedle devices with a wider range of geometries than conventional lithography-based technologies, including reactive ion etching and lithography-electroforming-replication. In this technique, photoinitiator molecules within a photosensitive resin release free radical molecules upon absorption of photon energy above a given threshold. These free radical molecules enable free radical polymerization and solidification of material within the resin. Unpolymerized material is removed by means of an appropriate solution. Individual microneedles and microneedle arrays were created by polymerization of the photosensitive resin along a laser trace, which was moved in three dimensions. Two photon polymerization differs from stereolithography in that it enables three-dimensional processing of a photosensitive resin in a single step. Two photon polymerization has been used for direct fabrication of hollow microneedles with a wide variety of geometries out of organically modified ceramic materials and polymers. Fabrication and in vitro testing of silver-coated microneedles is discussed; such antimicrobial microneedles may reduce the risk of infection associated with stratum corneum perforation. Our results indicate that two photon polymerization is a promising technique for creating a wide variety of microstructured and nanostructured medical devices.
10:15 AM - PP12.4
Electrodeposition and Characterization of Thin-film Platinum Iridium Alloys Used in Neural Implants.
Artin Petrossians 1 , Florian Mansfeld 1 , James Weiland 1 , John Whalen 1
1 , USC/Doheny Eye Institute, Los Angeles, California, United States
Show AbstractAbstractAn efficient platinum-iridium electrodeposition method with high surface area is reported. The goal is to modify microelectrodes with conventional platinum smooth surfaces to improve the charge injection properties for neural stimulation applications. The platinum-iridium thin films were electrodeposited onto smooth platinum microelectrodes using a potentio-dynamic approach. Effects of electroplating temperature and potential on the deposition rate and chemical composition of the electrodeposited films were investigated, respectively. Thin film properties were characterized using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS) and electrochemical properties were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Visual inspection with SEM showed a highly roughened surface. WDS showed 43% of iridium in electrodeposited films composition. Capacitance measured by EIS increased nearly 250 times compared to the unplated electrode, which was confirmed qualitatively by CV data. Tests support a lowering of impedance of the surfaces by up to 70%. In a chemical sensing application, a significant decrease in the limit-of-detection (LOD) was observed in 4 out of 8 electrodes, which supports enhanced electrochemical performance. Voltage transient was measured in response to current stimulus. Voltage response was used to determine the charge-injection capacity of the Pt-Ir electroplated microelectrodes. Charge transfer of 2.5 mC/cm2 was achieved within safe limits of stimulation (before hydrolysis), representing a 7X improvement in accepted limits for smooth platinum. These results suggest that electrodeposited, high-surface area microelectrodes may be advantageous for neural stimulation.
10:30 AM - PP12.5
Betaine-modified Polyurethanes Demonstrate Long-term Anti-microbial and Anti-thrombotic Efficacy in Whole Plasma.
Zheng Zhang 1 , Jun Li 1 , Chad Huval 1 , Abby Deleault 1 , Abbe Miller 1 , Joshua Kaitz 1 , Christopher Loose 1
1 , Semprus BioSciences, Cambridge, Massachusetts, United States
Show AbstractFor blood-contacting medical devices such as chronic catheters, it is highly desirable to resist both bacteria-related infection and thrombosis for multi-month periods. Significant proof-of-concept data has been generated to-date on betaine polymer surface modifications which reduce protein fouling and decrease biofilm and thrombus formation. This research is the first long-term study demonstrating constant anti-biofilm and anti-thrombotic performance after 56 day whole plasma exposure to simulate chronic device use. Leaching antimicrobial coatings have had limited success in >30 day applications and suffer from potential toxicity and generation of drug-resistant strains. Heparin-based coatings reduce thrombus formation, but limited duration of activity and risk of allergic reactions cause concern. Polysulfobetaine was grafted on a medical grade polyurethane substrate (Carbothane® with 20 wt % BaSO4) through a surface-initiated polymerization. The structure of the polymer layer was well-controlled resulting in a surface with a fibrinogen adsorption of less than 15 ng/cm2. The modification was adapted to a double-lumen dialysis catheter where both outer surfaces and inter-luminal surfaces, and septa were homogenously modified. In order to mimic the clinical setting, samples were stored in 100% citrated human plasma (CHP) for one day or 56 days prior to the evaluation of biofilm or thrombosis formation. To assess anti-biofilm performance, Staphylococcus epidermidis was used in a modified CDC system following plasma preconditioning. Reductions in adherent bacteria from the modified substrates and polyurethane controls were quantified by sonication and plating. Betaine modified substrates demonstrated a mean reduction of 96.8% after 1 day in plasma and a mean reduction of 96.8% after 56 days of storage in plasma, demonstrating consistent performance over extended exposure to a clinically relevant environment. For the anti-thrombosis evaluation, samples were tested in a third party flow loop thrombosis model. Modified and control substrates were subjected to heparinized fresh bovine blood for two hours, and thrombus was measured both visually and quantitatively using radio-labeled platelet counts. After 56 days of storage in plasma, the betaine-modified substrates exhibited a 99% reduction in platelet attachment relative to control, equivalent to performance before plasma exposure. This data demonstrates dual anti-microbial and anti-thrombotic characteristics from a single betaine modification after 56 days of human plasma exposure, enabling a range of chronic medical and industrial applications.
10:45 AM - PP12.6
A Tunable, Hydrogel-quantum Dots Based Multifunctional Nanoscale Platform for ``Theranostics".
Santaneel Ghosh 1 , Somesree GhoshMitra 2 , Tong Cai 3 , Nathaniel Mills 2 , DiAnna Hynds 2
1 Department of Physics and Engineering Physics, Southeast Missouri State University, Cape Girardeau, Missouri, United States, 2 Department of Biology, Texas Woman's University, Denton, Texas, United States, 3 Department of Physics, University of North Texas, Denton, Texas, United States
Show AbstractHydrogel based Quantum dots (QDs) have become an interesting subject of study for labeling and drug delivery in biomedical research due to their unique responses to the external stimuli. Uncoated QDs made of CdTe core are toxic to cells because of release of Cd2+ ions into the cellular environment. This problem can be partially solved by encapsulating QDs with polymers, like poly(N-isopropylacrylamide) (PNIPAM) or poly(ethylene glycol) (PEG). The toxicity of uncoated QDs is known; however, we are unaware of any study especially designed to assess the toxicity inside the intracellular environment caused by the remotely tunable hydrogel encapsulated QD nanospheres, capable of delivering both therapeutic and diagnostic agents (theranostics) to the targeted cells. Since PNIPAM shell acts as the reservoir of the drug molecules plus a tunable polymer matrix around the QDs, and thus controls the distance between the adjacent dots inside the nanospheres, idea of external modulation to bring the dots close enough that is ideal to cause Forster Resonance Energy Transfer (FRET) makes it an attractive alternative that overcomes traditional difficulties in actuating conventional micro- or nanostructures by chemical, mechanical or magnetic excitations. In this work, we present the design and assessment of dose dependent cytotoxicity of a novel, FRET based multifunctional nano-scale system at the cellular and molecular level on a neuronal model. Tunable QD-hydrogel nano-spheres were synthesized at different QD packing densities encapsulated with PNIPAM biopolymers. Temperature sensitive volumetric transition behavior and controlled release of model drug from the luminescent nanovectors indicate diverse therapeutic potential; however, for the nanospheres to be useful in biomedical applications, it must be relatively non-toxic and non-bioreactive, thereby allowing precise derivatization to manipulate diverse biological functions. Live/Dead assay indicated that the toxicity was far less than reported for bare or silanized QDs. High resolution scanning electron micrographs indicated that exposure to non-toxic levels did not inhibit the elaboration of neurites and the formation of intracellular contacts, an indication that the formation of synaptic contacts is not affected. Texas Red phalloidin labeling of filamentous actin and fluorescent tagged antibody labeling for βIII tubulin showed no apparent differences in actin filament or microtubule structure in nanosphere treated cells compared to cells not exposed to nanospheres. It is also observed that the nanospheres were internalized efficiently by the PC12 cells and nuclear morphology was unaffected. These data indicate that the nanospheres have the qualities that hold great promise for sustained release of pharmaceuticals to the targeted cells in clinical practice, and coupled with tunable QD packing density, have the potential of efficient and early detection of the damaged cells.
11:00 AM - PP12: SurfFunct
BREAK
11:30 AM - PP12.7
Polymeric Nanostructure-based Targeted Delivery of Biomolecules for Modulating Cancer and Stem Cell Fate.
Birju Shah 1 , Cheoljin Kim 1 , Prasad Subramaniam 1 , Aniruddh Solanki 1 , Shreyas Shah 1 , Ki-Bum Lee 1
1 , Rutgers University, Piscataway, New Jersey, United States
Show AbstractAdvances in the realm of molecular biology and genetics have triggered a surge in development of genetic manipulation-based therapies for cancer as well as for controlling stem cell fate. Such therapeutic approaches involve either silencing the expression of the aberrant gene or augmenting the expression of a therapeutic gene. However, the potential of these approaches is greatly dependent on the intracellular uptake and localization of the therapeutic modalities like nucleic acids, proteins, small molecules. Current delivery approaches involve the use of cationic polymers like polyethyleneimine and polyamidoamine, which have great potential for delivering genetic material because of their flexible chemistry, biocompatibility and robustness. However, there still exists a clear need to develop efficient delivery vehicles designed to overcome the numerous barriers associated with translocation from the site of uptake to the membrane, cytoplasm or nucleus of the target cells. To address this issue, we focused on developing a multimodal delivery platform consisting of polyamine backbone with pendant β-cyclodextrin (CD) moieties capable of simultaneous delivery of (i) negatively charged nucleic acids via electrostatic interactions with primary/tertiary amine groups and (ii) hydrophobic drug moieties or hydrophobic ligand-functionalized nanoparticles via host-guest interactions with β-CD. Our synthetic approach allowed us to tune the number of amine groups and cyclodextrin moieties present, thereby providing a handle to optimize the transfection efficiency, drug loading capacity and cytotoxicity in different cell-lines such as cancer and stem cells. We hypothesize that the delivery of two orthogonal therapeutic moieties via a single platform can not only achieve synergistic results, but can potentially simplify clinical applications by allowing a single administration. As a model study, we have chosen glioblastoma, an extremely aggressive and difficult-to-treat form of brain cancer and aimed at down-regulating the PI3K signaling cascade, which is implicated in cancer cell proliferation and apoptosis via simultaneous delivery of anticancer drugs and siRNA against a key oncogene. Furthermore, we have demonstrated successful translocation of our delivery system and subsequent knockdown of target genes in stem cells, which are a more challenging cellular model as compared to cancer cells. This talk will be mainly focused on demonstrating the capability of our multimodal delivery platform to deliver a wide variety of cargo like nucleic acids, proteins, small molecules in cancer and stem cells to achieve synergistic influence on cell fate.
11:45 AM - PP12.8
Bone Cell Response to 444 Ferritic Stainless Steel Surfaces.
Vera Malheiro 1 , Rose Spear 1 , Roger Brooks 2 , Athina Markaki 1
1 Department of Engineering, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom, 2 Orthopaedic Research Unit, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Show AbstractOne of the most serious issues with total joint replacement operations is the failure of an implant surface to integrate with the adjacent bone cells. One solution to this problem proposed by A.E. Markaki, T.W. Clyne [1] is based on the exploitation of bonded arrays of ferromagnetic fibres that when subjected to an external magnetic field are capable of imposing mechanical strains that can potentially stimulate bone cells adhesion and growth. However the use of such ferromagnetic materials needs to be evaluated in terms of their biocompatibility. Therefore, the aim of the present study was to assess the response of osteoblasts to 444 ferritic stainless surfaces. A comparison is made between 316L, the non-magnetic austenitic stainless steel in common use for implants, and 444, a magnetic ferritic stainless steel. To limit the variability between the two stainless steel grades, both substrates were ground to the same surface finish.Profilometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle techniques were used to characterise the morphology and chemistry of the surfaces. Human Foetal Osteoblasts (hFOBs) were used to evaluate the cell response to the aforementioned materials. Cellular proliferation, metabolism, morphology and early osteoblastic differentiation were examined, using the CyQuant® assay, alamarBlue®, SEM imaging and an alkaline phosphatase (ALP) activity assay, respectively. Additionally, gene expression of osteogenic markers (collagen type I (COL I), osteopontin (OP) and osteocalcin (OC)) was investigated by real-time Reverse Transcription Polymerase Chain Reaction (RT-PCR). To quantify the effect of chemistry on cell attachment, a centrifugal field was used to detach the cells from the substrates.The results obtained from the biological studies show that osteoblast cells respond successfully when in contact with 444 ferritic stainless steel surfaces and consequently that this material holds potential to be used in advanced bone applications.References: 1. A.E. Markaki and T.W. Clyne, Biomaterials, 2004, 25(19): 4805-4815.Acknowledgements: Financial support for this work comes from the European Research Council (ERC) and from the Portuguese Foundation for Science and Technology (FCT).
12:00 PM - PP12.9
Self-cleaning Sensor Membranes Based on Thermoresponsive Nanocomposite Hydrogels.
Melissa Grunlan 1 , Ruochong Fei 1 , Jason George 1
1 Biomedical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractMembrane biofouling severely limits the lifetime and efficacy of implanted biosensors. Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels undergo reversible deswelling when heated above its volume phase transition temperature (VPTT, ~33 °C). Thermal modulation of PNIPAAm hydrogels has been shown to be useful for the controlled detachment of cultured cells. Extending the utility of PNIPAAm hydrogels as robust “self-cleaning” membranes for implanted biosensors requires enhancement of mechanical properties as well as swelling/deswelling kinetics to removed adhered proteins and cells. Here, we demonstrate that incorporation of polysiloxane nanoparticles (average diameters of ~200 and 50 nm) produce modest increases in mechanical properties as well as swelling/deswelling kinetics. Furthermore, upon utilizing a double network (DN) PNIPAAm matrix rather than a traditional “single network, SN” PNIPAAm matrix, significant enhancement in mechanical properties were achieved. PNIPAAm crosslink density as well as polysiloxane nanoparticle size, concentration, and location in first or second network were systematically altered to produce various hydrogel membranes. The effect of these compositional variables on morphology, mechanical properties and swelling/deswelling behavior were evaluated. The release of cells upon thermal modulation was also studied.
12:15 PM - PP12.10
Nanoengineered Self-assembled Monolayers for Biosensor Applications.
Jing-jiang Yu 1
1 , Agilent Technologies, Inc., Chandler, Arizona, United States
Show AbstractSelf-assembled monolayers (SAMs) have attracted tremendous attention due to their highly ordered structure, stability and rich terminal group chemistry and they offer very promising applications in development of biocompatible materials, solid-phase bioanalytical techniques and biosensors. Particularly, nanometer-scaled mixed self-assembled monolayers are better systems than pure SAMs in mimicking biomembranes because of the presence of segregated domain structures and variety of surface functionalities. In nature, the collective properties and biofunctionalities of these ensembles depend not only on the individual molecular unit but also on the organization at the molecular or nanoscopic level. It has been demonstrated that high-resolution nanofabrication of mixed SAMs with sub-10 nm precision can be achieved readily using either lithography or natural growth approaches.1 These artificially engineered organic thin films with both desired surface chemistry and designed spatial distribution provide a unique scaffold to investigate bioinspired molecular recognition in the fields of biosensors and immunoassays. For example, HIV infection of CD4 negative cells is initiated by the binding of the viral envelope glycoprotein gp120 to galactosylceramide (GalCer), a glycosphingolipid that serves as the cellular receptor for viral adhesion. By constructing a series of GalCer nanostructures with various geometries via AFM-based lithography and using high-resolution AFM imaging as an in situ, real-time and label-free detection approach to directly monitor the subsequent binding of recombinant gp120 molecules to those engineered carbohydrate ligand nanostructures, the polyvalent interactions between HIV-gp120 protein and GalCer nanostructures are revealed both qualitatively and quantitatively and a better understanding of HIV viral infection process at single molecular level is gained.2 In addition, our recent studies on advanced strategies to generate thiol-exposing SAMs3,4 that can serve as highly selective bio-platforms and exhibit the great potential for development of immunobiosensor will be presented. Reference:1. Yu et al. A Nanoengineering Approach to Regulate the Lateral Heterogeneity in Mixed Self-Assembled Monolayers. J. Am. Chem. Soc. 2006, 128, 11574-11581.2. Yu et al. Polyvalent Interactions of HIV-gp120 Protein and Nanostructures of Carbohydrate Ligands. NanoBiotechnology 2005, 1,201-210.3. Yu et al. Nanografting versus Solution Self-Assembly of α,ω-Alkanedithiols on Au(111) Investigated by AFM. Langmuir 2008, 24, 11661-11668.4. Li et al. Engineering the Spatial Selectivity of Surfaces at the Nanoscale Using Particle Lithography Combined with Vapor Deposition of Organosilanes. ACS Nano 2009, 7, 2023- 2035.
12:30 PM - PP12.11
A Fluorescent Superparamagnetic Nano-carrier System for Cancer Diagnosis and Treatment: Drug Storage, Targeting, and Imaging.
Donglu Shi 1 2 , Hoon Sung Cho 1 , Chris Huth 1 , Zhongyun Dong 3 , Giovanni Pauletti 4 , Rodney Ewing 5 , Hong Xu 6 , Hongchen Gu 6
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States, 2 The Institute for Advanced Materials and Nano Biomedicine, Tongji University, Shanghai China, 3 Internal Medicine, University of Cincinnati, Cincinnati, Ohio, United States, 4 James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, United States, 5 Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States, 6 Med - X , Institute, Shanghai Jiao Tong University, Shanghai China
Show AbstractFor early cancer diagnosis and treatment, a nano carrier system is designed and developed with key components uniquely structured at nano scale according to medical requirements. For imaging, quantum dots with emissions near infrared range (~800 nm) are conjugated onto the surface of a nano composite consisting of a spherical polystyrene matrix (~100 nm) and the internally embedded, high fraction of superparamagnetic Fe3O4 nanoparticles (~10 nm). For drug storage, the chemotherapeutic agent paclitaxel (PTX) is loaded onto the surfaces of these composite multifunctional nano-carriers by using a layer of biodegradable poly(lactic-co-glycolic acid) (PLGA). A cell-based cytotoxicity assay is employed to verify successful loading of pharmacologically active drug. Cell viability of human, metastatic PC3mm2 prostate cancer cells is assessed in the presence and absence of various multifunctional nano-carrier populations using the MTT assay. PTX loaded composite nano-carriers are synthesized by conjugating anti-Prostate Specific Membrane Antigen (anti-PSMA) for targeting. Specific detection studies of anti-PSMA-conjugated nano carrier binding activity in LNCaP prostate cancer cells are carried out. LNCaP cells are targeted successfully in vitro by the conjugation of anti-PSMA on the nano carrier surfaces. To further explore targeting, the nano carriers conjugated with anti-PSMA are intravenously injected into nude tumor bearing mice. Substantial differences in fluorescent signals are observed ex vivo between the targeted- and non-targeted tumor regions, indicating considerable targeting effects due to anti-PSMA functionalization of the nano carriers.
PP13: Resonance Based Sensors – Refractive Index
Session Chairs
Thursday PM, December 02, 2010
Back Bay C (Sheraton)
2:30 PM - **PP13.1
Optical Microcavity Biosensors.
Frank Vollmer 1
1 Rowland Institute, Harvard University, Cambridge, Massachusetts, United States
Show AbstractOptical microcavities are photonic structures that confine coherent light for a prolonged time in a micro- or nano- scale modal volume where it interferes constructively. Almost immune to damping in a liquid such miniature optical resonators are ultra-sensitive biosensors: specific binding of single virus particles can be detected from discrete resonance frequency shifts without requiring any labeling of the particle. I will give an overview of microcavity structures that exhibit record high Q factor and record-low modal volume. I will then report on our progress in the application of such miniature optical devices for label-free chip-scale biodetection, for the study of nanoparticle interactions at a photonic interface, as optical tweezers and as a platform for bioinspired photonics engineering.
3:00 PM - **PP13.2
Photonic Crystal Microcavities for Label-free Multiplexed Biosensing.
Philippe Fauchet 1 , Benjamin Miller 1 , Sudeshna Pal 1
1 , University of Rochester, Rochester, New York, United States
Show AbstractWe have developed and demonstrated a novel family of label-free biosensors that consist of 2-D photonic crystal microcavities coupled to waveguides and fabricated on silicon-on-insulator (SOI) wafers. The detection principle relies on a shift of the microcavity resonant mode wavelength due to a change in the local refractive index resulting from the capture of biological targets. The key to designing ultrasensitive yet robust devices is to increase the quality factor of the microcavity without making it too susceptible to random environmental fluctuations and to concentrate the electric field on resonance to below (λ/n)^3 by decreasing the modal volume. Multiple implementations of such device structures have been investigated theoretically and experimentally. We will compare various microcavity designs, including large or small defects and slotted defects, and microcavities in line with a conventional waveguide or coupled to a photonic crystal waveguide to allow multiplexing. We will report on device performance upon capture of human IgG and various other proteins, single inorganic nanoparticles, and individual viruses. In all cases, the measured device performance compares well with FDTD modeling. Various figures of merit will be discussed, including the refractive index sensitivity, which easily reaches in the 100's of nm/RIU, and the lower limit of detection, which can be well below 1 pg.
3:30 PM - PP13.3
Integration of Optofluidics and Colorimetric Signatures of Deterministic Aperiodic Metal Nanoparticle Arrays.
Sylvanus Lee 1 2 , Svetlana Boriskina 2 , Fiorenzo Omenetto 4 5 , Luca Dal Negro 2 3
1 Department of Mechanical Engineering, Boston University, Boston, Massachusetts, United States, 2 Department of Electrical and Computer Engineering & Photonic Center, Boston University, Boston, Massachusetts, United States, 4 Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 5 Department of Physics, Tufts University, Medford, Massachusetts, United States, 3 Division of Materials Science and Engineering, Boston University, Boston, Massachusetts, United States
Show AbstractIn this paper, we study the integration of colorimetric optical sensing with microfluidics technology by investigating light scattering from deterministic aperiodic metal nanoparticle arrays in a microfluidic device. Periodic and aperiodic arrays consisting of metallic nanoparticles on quartz substrates were fabricated using electron beam lithography and integrated in a microfluidic channel for the first time. We show that, unlike periodic gratings, aperiodic nano-patterned surfaces feature a broadband frequency response with wide angular intensity distributions and that these colorimetric fingerprints are ideally suited as a novel transduction mechanism for optical biosensing in a microfluidic environment [1]. Our previous work has demonstrated that metallic Gaussian prime nanoparticle arrays are ideally suited to detect protein monolayers with attomolar sensitivity by monitoring distinctive structural color modifications using autocorrelation analysis of scattered fields [2]. The integration of this sensitive technique with microfluidics technology may result in the engineering of novel integrated, multiplexed, optofluidic lab-on-a-chip platforms for bio-chemical detection.1. Svetlana V. Boriskina, Sylvanus Y. Lee,Jason J. Amsden, Fiorenzo G. Omenetto and Luca Dal Negro "Formation of colorimetric fingerprints on nano-patterned deterministic aperiodic surfaces", Optics Express (to be published)2. S. Y. Lee, J. J. Amsden, S. V. Boriskina, A. Gopinath, A. Mitropoulos, D. L. Kaplan, F. G. Omenetto, and L. Dal Negro, "Spatial and spectral detection of protein monolayers with deterministic aperiodic arrays of metal nanoparticles," Proc. Natl. Acad. Sci. USA (to be published).
3:45 PM - **PP13.4
LED-Interferometric Reflectance Imaging Sensor for Nanoscale Label-free Detection of Pathogens.
George Daaboul 1 , Priscilla Renda 2 , Russell Graef 2 , Abdulkadir Yurt 3 , Xiriu Zhang 1 , Carlos Lopez 3 , John Connor 4 , Grace Hwang 2 , M. Selim Unlu 1 3
1 Biomedical Engineering, Boston University, Boston, Massachusetts, United States, 2 , The MITRE Corporation, Bedford, Massachusetts, United States, 3 Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States, 4 Microbiology, Boston University, Boston, Massachusetts, United States
Show AbstractNear real-time detection of pathogens is essential to protecting the population in the case of bioterrorist attack or naturally occurring epidemics. Current detection of viral pathogens relies on time-consuming ELISAs and PCR techniques. We present here a parallel, label-free detection technology, LED-Interferometric Reflectance Imaging Sensor (LED-IRIS), which monitors biomolecular binding interactions on a reflective, layered silicon substrate with a thin oxide top layer. Four LEDs with wavelengths spanning the visible to near-infrared spectral region serially illuminate a field-of-view (~500x500 μm^2 surface) comprising several biologically-prepared spots. Multiple reflections from the layered substrate generate a spectral signature due to interference, detectable on a camera as intensity variations when the illumination wavelength is varied. We scan the equivalent of one period of the spectral oscillations at four discrete spectral positions represented by the different LED wavelengths. Deposition of analyte on the spotted surface shifts the interference pattern which is detected as a change in height of the silicon substrate. We have achieved picometer noise floor for an entire field-of-view. To achieve single-particle detection sensitivity, the field-of-view was reduced to increase the effective interference signature for one adsorbed single pathogen. The time-to-answer for acquiring and processing data is under 10 minutes with a limit of detection of a single 100 nm particle or < 10pg/mm^2 of biomaterial for high and low magnification systems, respectively. Since the sensitivity and response are independent of the position on the sensor surface, it is possible to detect a single particle on the entire sensor surface. Furthermore, the measurements yield a quantifiable signature proportional to the size of the particle allowing for size discrimination. Non-specific capture and detection of single H1N1 virus has been demonstrated using poly-L-lysine as a binding agent. An immunoassay is being developed for specific-capture and detection of single H1N1 virus using traditional antibody probes and glycan probes multiplexed on the same substrate. Preliminary results show sensitivities of the LED-IRIS system are comparable and possibly an improvement on those of the Luminex system. While current work is focused on detection of the H1N1 virus, the LED-IRIS platform may also be used to characterize dielectric nanoparticles to, for example, monitor occupational safety compliance levels. The long-term impact of this work is the future development of a commercial optical immunoassay technology which will address the need for high-throughput disease diagnostics, ultra-sensitive virus detection, and occupational health-related dieletric nanoparticle monitoring. Approved for Public Release: 10-2569. Distribution Unlimited. ©2010 The MITRE Corporation. All rights reserved.