Symposium Organizers
Magnus Berggren Linkoping University
David C. Martin University of Delaware
George Malliaras Ecole Nationale Superieure des Mines de St. Etienne
TimothyM. Swager Massachusetts Institute of Technology
MM2: Organic Transistors for Biosensors and Regulation II
Session Chairs
Zhenan Bao
Magnus Berggren
George Malliaras
Luisa Torsi
Tuesday PM, April 26, 2011
Salons 14-15 (Marriott)
2:30 PM - **MM2.1
Organic Transistor Based Sensors for Flexible Electronic Skin
Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe field of organic electronics holds tremendous potential for applications that benefit from the use of organic materials, (e.g. very low cost, flexible and amendable to large-area processing techniques or roll-to-roll printing). Specifically, the design and development of sensors that take advantage of these benefits can lead to manufacturing of cheap electronic units for electronic skin as well as medicinal, food storage, and environmental monitoring applications. The ability to couple the sensory electrical output with on-chip signal processing can overcome the need for bulky, expensive equipment typically required for most optical detection methods. In order to attain commercial viability, chemical sensors based on organic electronics must continue to address the remaining issues in repeatability, reproducibility, stability, and selectivity. In this talk, I will present recent progress in materials and fabrication of chemical, biological and pressure sensors.
3:00 PM - MM2.2
Reduced Graphene Oxide Field-effect Transistor for Detection of Cancer Biomarker.
Duckjin Kim 1 , Il Yung Sohn 1 , Do Il Kim 1 , Ok Ja Yoon 1 , Cheol-Woong Yang 1 , Nae-Eung Lee 1 , Joon-Shik Park 2
1 School of Advanced Materials Science & Engineering, Sungkyunkwan Univ., Suwon, Gyeonggi-do, Korea (the Republic of), 2 Environmental Sensor and Device Research Center, Korea Electronics Technology Institute (KETI), Seongnam-si, Gyeonggi-do, Korea (the Republic of)
Show AbstractLabel-free electrical detection of biomarkers using nanosensors such as one-dimensional (1-D) Si nanowires and carbon nanotubes can possibly provide the point-of-care diagnostics for early diagnosis of cancer that requires high sensitivity, high specificity, low limit of detection, large dynamic range, multiplexing diagnosis and real-time detection. However, low-cost, scalable, and highly reliable fabrications of such ultra-sensitive nanosensors based on one-dimensional semiconductors are still limited due to constraints of nanofabrication. Graphene has attracted an enormous amount of interest due to excellent electrical, chemical and mechanical properties with atomic thickness. Especially, the reduced graphene oxide (rGO) has advantage to facile control of the surface functional group for biomolecule immobilization as well as solution processability. Despite of importance to the disease diagnosis, there are a few reports to demonstrate the graphene- and rGO-FET for biological sensors. Here we describe scalable and facile fabrication of rGO-FET with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/α1-antichymotrypsin (PSA-ACT) complex, in which the ultrathin rGO sensing channel was simply formed by a uniform self-assembly of two-dimensional rGO nanosheets on aminated pattern generated by inkjet printing. Sensing characteristics of rGO-FET immunosensor showed the highly precise, reliable, and linear shift in the Dirac point with the analyte concentration of PSA-ACT complex and extremely low detection limit as low as 1 fg/ml. We further analyzed the charge doping mechanism, which is the change in the charge carrier in the rGO channel varying by the concentration of biomolecules. Amenability of solution-based scalable fabrication and extremely high performance may enable rGO-FET device as a versatile multiplexed diagnostic biosensor for disease biomarkers.
3:15 PM - **MM2.3
Foldable, Ultraflexible, Stretchable Organic Integrated Circuits for Robotics and Medical Sensor Applications.
Takao Someya 1 , Tsuyoshi Sekitani 1
1 Department of Electric and Electronic Engineering, The University of Tokyo, Tokyo Japan
Show AbstractWe have successfully manufactured organic thin-film transistors and complementary inverter circuits that are functional without degradation while being sharply folded into a radius of 100 μm. Such flexibility and bending stability is enabled by a 12.5 µm thick plastic substrate, a 500 nm thick planarization coating, and a hybrid encapsulation stack that places the transistors in the neutral strain position. As a potential application for tightly bent organic circuits, we demonstrate a catheter with a sheet of transistors and sensors wrapped around it that enables the spatially resolved measurement of physical or chemical properties inside long, narrow tubes. Furthermore, recent progress of stretchable organic integrated circuits using elastic conductors will be presented from the context of robotic skin applications.
4:15 PM - **MM2.4
A Hybrid Bioorganic Interface For Neuronal Photoactivation.
Diego Ghezzi 1 , Maria Rosa Antognazza 2 , Marco Dal Maschio 1 , Erica Lanzarini 2 3 , Fabio Benfenati 1 , Guglielmo Lanzani 2 3
1 Istituto Italiano di Tecnologia, Department of Neurosciences and Brain Technologies, Genova Italy, 2 , Center for Nanoscience and Technology of IIT@POLIMI, Milano Italy, 3 Politecnico di Milano, Physics Department, Milano Italy
Show AbstractA key issue in the realization of retinal prosthetic devices is reliable transduction of the information carried by light into specific patterns of electrical activity in the networks involved in visual information processing. Soft organic materials can be used to couple artificial sensors with neuronal tissues. Here, we interface a network of primary neurons with an organic blend. We show that primary neurons can be successfully grown onto the polymer layer, without affecting the optoelectronic properties of the active material or the biological functionality of the neuronal network. Moreover, action potentials can be triggered in a temporally reliable and spatially selective manner with short pulses of visible light. Our results may lead to new neuronal communication and photo-manipulation techniques, thus paving the way to the development of artificial retinas and other neuro-prosthetic interfaces based on organic photo-detectors.References: [1] D. Ghezzi, M. R. Antognazza, M. Dal Maschio, E. Lanzarini, F. Benfenati, G. Lanzani Nature Commun. DOI 10.1038/ncomms1164.
4:45 PM - MM2.5
Electrolyte-gated Organic Thin-film Transistors for Sensing Applications.
Felix Buth 1 , Deepu Kumar 1 , Martin Stutzmann 1 , Jose Garrido 1
1 Walter Schottky Institut, Technische Universität München, Garching Germany
Show AbstractOrganic thin films can potentially be used in low-cost, disposable devices for chemical or bio-sensing. However, operating the device in an aqueous environment raises difficulties when it comes to operational voltages or stability. One approach to reduce the gate voltage is increasing the capacitance of the gate dielectric. Several different materials, including high-k dielectrics, ultra-thin cross-linked polymers, and electrolytes have been tested for this purpose. In particular, electrolyte gates offer extraordinarily large capacitances, up to several µF at low frequencies. The high capacitance which is the result of an electrical double layer formation at the electrolyte – semiconductor interface makes low-voltage operation possible, without high production costs. In this contribution we investigate the behavior of polycrystalline α-sexithiophene (α6T) thin-film transistors with an aqueous electrolyte gate. Electrochemical impedance spectroscopy and cyclic voltammetry measurements indicate a nearly perfectly polarizable interface with negligible parasitic Faradaic currents. For gate voltages below 1 V, a conductive channel is induced at the α6T/electrolyte interface via an electrical field effect. The transistor is stable for several hours and sensitive to changes in the pH or the ionic strength of the solution. These changes are due to a shift in the threshold voltage of the transistor, and not to alterations of the mobility. The response of the transistors to the salt concentration of the electrolyte is interpreted in terms a screening effect. In case of the pH sensitivity the shift, in the range of 10 mV/pH, is caused by a change in the surface charge of the thin film. In summary, our work confirms the potential of electrolyte-gated organic thin-film transistors for chemo- or bio- sensing applications.
5:00 PM - MM2.6
Organic Field Effect Transitor Platform as Chemical and Biological Sensors in Marine Environments.
Olasupo Johnson 1 , Anatoliy Sokolov 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractMarine chemical sensor technology advancements have led to better food safety, increased understanding of marine eco-systems, and improvement in national defense. Organic thin film transitors (OTFTs) are potential candidates for cheap chemical and biological sensors in aquatic systems owing to the combination of cheap manufacturing processes (i.e. printing) and a variety of robust materials available through chemical synthesis. For OTFTs to be commercially viable it is essential that sensors be reasonable sensitivity and selectivity to the chemical and biological analyte being monitored with reproducible sensor responses. The stability of the sensor in the media is an important parameter for multi-use sensors or long term monitoring set ups. We report that low voltage OTFTs with water stable organic semiconductors exhibit stable operation in seawater. These devices were used to detect very low concentrations of chemical and biological analytes with repeatable sensor responses in seawater. Sensor selectivity for relevant biological and chemical analytes was incorporated into the OTFT architecture by functionalizing the surface of the semiconductor with receptor molecules.
Symposium Organizers
Magnus Berggren Linkoping University
David C. Martin University of Delaware
George Malliaras Ecole Nationale Superieure des Mines de St. Etienne
TimothyM. Swager Massachusetts Institute of Technology
MM5: Fluorescent Organic Probes
Session Chairs
Wednesday PM, April 27, 2011
Salons 14-15 (Marriott)
2:30 PM - **MM5.1
Protein, Bacteria, and Mammalian Cell Sensing Using Particle-polymer/Biopolymer Complexes.
Uwe Bunz 2 , Vincent Rotello 1
2 , University of Heidelberg, Heidelberg Germany, 1 , University of Massachusetts, Amherst, Massachusetts, United States
Show AbstractMost biomolecular recognition processes in biology occur via specific interactions. Sensory processes such as taste and smell, however, use “differential” binding where the receptors bind to their analytes by different binding characteristics that are selective rather then specific. The tunability and supramolecular nature of our current nanoparticles makes them excellent candidates for this sensor strategy. In these sensors the polymer fluorescence is quenched by gold nanoparticles: proteins disrupt the nanoparticle-polymer interaction, producing distinct fluorescence response patterns. In our initial studies, sensor arrays containing non-covalent gold nanoparticle-fluorescent polymer assemblies have been used to identify and quantify protein targets at nanomolar concentrations in buffer and serum, differentiate between species and even different strains of bacteria, and detect and identify cancer cells. Ongoing efforts to enhance sensitivity, sense in biofluids, and extend our cell surface diagnostic capabilities will be discussed.
3:00 PM - MM5.2
Simultaneous Separation and Detection Using Magnetic-bead Hybridized Polydiacetylene Core-shells for Direct Sensing Agents in Bulk Liquid-phases.
Hak Jin Kim 1 , Gil Sun Lee 1 , Dong June Ahn 1
1 Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractRecently, organic-inorganic hybridized materials are major focus of research efforts due to their prominence of multiple functions and signal amplification. In this study, we fabricated the PDA/Fe3O4 hybridized beads which were composed of Fe3O4 magnetic particle core and polydiacetylene (PDA) shell. The hybridized beads undergo polymerization upon irradiation with 254 nm UV light, and they are capable of detecting desired target materials by fluorescent change. In magnetic separation process, the hybridized beads have advantage of signal enhancement because target materials are concentrated by the magnetic field. We demonstrate selective detection of alpha-cyclodextrin and anthrax lethal factor DNA by using the proposed hybridized core-shell beads. The advantage of this system is to detect and separate target molecules at the same time. The hybridized beads can be applied to direct and efficient bio/chemical sensor agents in bulk liquid-phases.
3:15 PM - MM5.3
Disposable Organic Fluorescence Biosensor for Water Pollution Monitoring.
Florent Lefevre 1 , Ricardo Izquierdo 1 , Philippe Juneau 1 , Luping Yu 2
1 , Universite du Quebec a Montreal, Montreal, Quebec, Canada, 2 , The University of Chicago, Chicago, Illinois, United States
Show AbstractWe report the first disposable fluorescence biosensor based on algae, with an organic light emitting diode (OLED) and an organic photodetector (OPD) miniaturized into a microfluidic chip. A DPVBi OLED was used as the excitation source, while a PTB3/PCBM blend OPD was use as the organic photodetector. The fluorescence biosensor is integrated in a microfluidic chip made from polymeric material (poly)dimethylsiloxane (PDMS), which is transparent, biocompatible and can easily be processed by conventional lithography. The complete detector is designed to detect Chlamydomonas reinhardtii green algae fluorescence in the microfluidic chamber. Algal chlorophyll fluorescence is a physiological parameter routinely used to measure the photochemical efficiency of PSII. This measurement is a reliable and non-invasive method to determine the activity of pollutants like herbicides and metals. The algal chlorophyll fluorescence is directly or indirectly related to the pollutant concentration, allows us to obtain a sensitive and reliable biosensor. The blue OLED shows high performance in terms of luminescence (more than 10.000 Cd/m2), and is able to apply dozens of pulses of 350 µmol s-1 m-2 in order to excite the algae. The DPVBi OLED has been chosen to get an emission pick lower than 500nm, corresponding to the first absorption pick of chlorophyll The near-infrared solution process OPD has a broadband photo response from 600 to 700nm, entirely recovering the algal fluorescence emission. Its responsivity at 685nm, which is the maximum pick of the algal fluorescence emission, is of 0,58A/W while it has a dark current density lower than 1nA/cm2. The use of organic devices compatible with microfluidic architectures enables the development of a complete autonomous and portable device. OLED and OPD technology, combined with microfluidic technology could be one viable solution to the urgent need to get a real portable and efficient fluorescent biosensor for continuous water monitoring.
4:00 PM - **MM5.4
Multimodal Tools for Molecular Imaging, Diagnostics and Therapeutics.
Peter Nilsson 1
1 , Linkoping University, Linkoping Sweden
Show AbstractLuminescent conjugated polymers (LCPs) are frequently utilized for optical biosensors. The detection schemes of these sensors are employing the light harvesting properties or the conformation sensitive optical properties of the conjugated polymers. The conformation sensitive optical properties of LCPs provide the ability to study the biochemical activity of biological events on the basis of a structure-function relation rather than being limited to studies of molecular abundance (concentration based assay). Here a novel class of chemically defined luminescent conjugated oligothiophenes (LCOs) that can be utilized for real time in vivo imaging of biological events is reported. The use of LCOs for spectral separation of pathological entities associated with protein aggregation diseases, such as Alzheimer’s disease, and for identifying specific cell types, including neural stem cells, are illustrated. Overall, these probes will offer practical research tools for studying a wide range of diseases and facilitate the study of the molecular mechanism underlying these disorders.
4:30 PM - MM5.5
Photonic Crystal Enhanced Fluorescence Using a Quartz Substrate to Reduce Limits of Detection.
Anusha Pokhriyal 1 , Meng Lu 4 , Vikram Chaudhery 2 , Cheng-Sheng Haung 2 , Stephen Schulz 4 , Brian Cunningham 2 3
1 Dept. of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 , SRU Biosystems, Woburn, Massachusetts, United States, 2 Dept. of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Dept. of Bioengineeering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractPhotonic Crystal Enhanced Fluorescence (PCEF) is a powerful technique for reducing the detection limits of surface-based biochemical microarray assays used in the detection of DNA for quantification of gene expression and in the detection of proteins for measuring the presence of cancer biomarkers in serum. A Photonic Crystal (PC) surface fabricated upon a low auotfluorescence quartz substrate using nanoimprint lithography has been demonstrated to substantially increase the signal-to-noise ratio (SNR) for detection of surface-adsorbed fluorophore-tagged biomolecules in comparison to previously demonstrated polymer-based PCs. Design of PC surfaces that behave as highly efficient optical resonators results in enhanced excitation of fluorophores from the resulting high energy density electromagnetic fields. However during resonance coupling, any autofluorescence from the substrate is also enhanced, thus necessitating the use of quartz-based PCs. Previously, the use of quartz surfaces for PCEF applications has been limited by the requirement of producing surface structures with subwavelength dimensions over surface areas large enough to encompass entire DNA microarrays or protein microarrays. These are usually performed on substrates as large as standard microscope slides which are not appropriate for e-beam lithography or DUV lithography. In order to address this issue, a “step-and-flash” nanoimprint lithography (NIL) tool was employed to fabricate subwavelength grating structures over entire 1x3 in2 quartz slides. In this paper we describe the design, fabrication, and characterization of a quartz-based PCEF substrate produced using NIL. The demonstrated PCEF surface supports a transverse magnetic(TM) resonant mode at a wavelength of λ=632.8nm and an incident angle of θ=11°, which amplifies the electric field magnitude experienced by surface-bound fluorophores excited by a HeNe laser. Meanwhile, another TM mode at a wavelength of λ=690nm and incident angle of θ=0° efficiently directs the fluorescent emission towards the detection optics. An enhancement factor as high as 7500× was achieved for the detection of LD700 dye spin-coated upon the PC, compared to detecting the same material on an unpatterned surface. In order to demonstrate the sensitivity enhancement in the context of a multispot microarray assay, a detection experiment using a dye-labeled protein was performed. The detection of spotted Alexa647 labeled polypeptide on the PC resulted in a 330× improvement in SNR. Using dose-response characterization of deposited fluorophore-tagged protein spots, the PCEF surface demonstrated a 140× lower limit of detection compared to detection of the same protein on a conventional glass substrate.
4:45 PM - MM5.6
Conjugated Oligothiophenes as Fluorescent Probes for the Elucidation of Protein Aggregation in vitro and in vivo.
Rozalyn Simon 1 , Karin Magnusson 1 , Leif Johansson 1 , Andreas Aslund 1 , Christina Sigurdson 2 , Peter Nilsson 1
1 Dept. of Chemistry, Linköping University, Linköping Sweden, 2 Dept. of Pathology, University of California, San Diego, La Jolla, California, United States
Show AbstractConjugated polymers (CPs) represent a useful and interesting class of materials well known for their abilities as signal transducers in the form of colorimetric and fluorometric reporting. Specifically, their ability to produce a conformation-dependant spectral signature reflective of changes in their local environment which makes them an indispensible tool in the toolbox of fluorescent reporters. Fluorescence measurements inherently provide a number of parameters for observing changes within a system (e.g., changes in intensity, wavelength, energy transfer, and emission lifetime), thus the coupling of such measurements with the unique fluorescence reporting capabilities of CPs has been successful in elucidating a number of biological systems and continues to develop as a means for "seeing the unseen”. We have previously demonstrated the use of both polydisperse and monodisperse conjugated oligothiophenes for the purpose of amyloid detection both in vitro and in vivo. In this presentation we will discuss evaluation of a small group of these substituted oligothiophenes and their utilization as molecular probes for studying protein structure and conformation in biological systems. We will also discuss their potential use in gaining new insights to variety of biological questions concerning protein aggregation, and more specifically, prion templating and infectivity.
5:00 PM - MM5.7
Differentiation of Escherichia Coli by Polycationic Dendritic Phenylene-ethynylene Fluorophores.
Gamolwan Tumcharern 1 , Radeemada Mungkarndee 2 , Raweewan Thiramanas 1 , Nakorn Niamnont 3 , Mongkol Sukwattanasinitt 3
1 , National Nanotechnology Center, National Science and Technology Development Agency, Pathumthani Thailand, 2 Program in Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok Thailand, 3 Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok Thailand
Show AbstractDiarrhea disease is a worldwide health problem in developing countries. Wide diversities of bacteria; such as, Salmonella typhi, Vibrio cholerae, and Escherichia coli, have been found to be major pathogens for a food poisoning. Among the principal pathogenic bacteria, Escherichia coli commonly causes diarrhea disease to not only local people but also visiting travelers in tropical climate zone. Escherichia coli can be classified into various sub-groups depending on their unique characteristics. The strain differences are often detected at a molecular level by polymerase chain reaction technique.In this contribution, we proposed a chemical sensor array based on polycationic dendritic phenylene-ethynylene fluorophores to discriminate enterotoxigenic Escherichia coli (ETEC) from a harmless strain. Fluorescent emission signals of fluorophores in the presence of two strains of Escherichia coli were statistically analyzed by cluster analysis based on principal component methods. The accuracy of the differentiation between harmful and harmless Escherichia coli were determined by leave-one-out cross validation. This simple and convenient method for identification of the strain of Escherichia coli will benefit for food export and medical diagnosis.
Symposium Organizers
Magnus Berggren Linkoping University
David C. Martin University of Delaware
George Malliaras Ecole Nationale Superieure des Mines de St. Etienne
TimothyM. Swager Massachusetts Institute of Technology
MM6: Organic Photonic Devices and Electrodes for Biosensors and Regulation
Session Chairs
Thursday AM, April 28, 2011
Salons 14-15 (Marriott)
9:30 AM - **MM6.1
Recent Advances and Challenges in Photoluminescent OLED-Based (Bio)Sensors.
Ruth Shinar 1 2
1 Microelectronics Research Center, Iowa State University, Ames, Iowa, United States, 2 Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractWe will describe the development, advantages, challenges, and potential of a compact photoluminescence-based sensing platform for (bio)chemical analytes. In this platform, the excitation source is an array of OLED pixels that is structurally integrated with a sensing component; advanced integration includes additionally an inorganic or organic thin film-based photodetector. The performance of the OLED-based sensing platform in monitoring single analytes and, simultaneously, multiple analytes in mixtures will be shown. Challenges associated with the use of cw and pulsed OLEDs as the excitation source and approaches to alleviate such challenges using different OLED materials and structures, including microcavity and UV OLEDs as well as OLEDs integrated with microlens arrays, will also be discussed.
10:00 AM - MM6.2
Modeling of the Electromechanical Properties of Stretchable Electrodes for Bio-application.
Wenzhe Cao 1 , Patrick Goerrn 1 , Sigurd Wagner 1
1 , Princeton University, Princeton, New Jersey, United States
Show AbstractStretchable electronics is an emergent class of electronics that can retain electrical functionality under mechanical deformation. This special feature of stretchable electronics shows great potential for bio-related applications due to its compatibility with the soft nature of living tissues. We have developed stretchable microelectrode arrays (SMEAs) for traumatic brain injury research. SMEAs are configured as metal film electrodes, patterned on elastomeric substrates polydimethyl siloxane (PDMS) and coated with an elastomeric electrical insulator. The stretchable electrodes can retain electrical conductance under strain. We anticipate other applications of similar elastically stretchable devices in biomedicine, conformable electronic surfaces, and comfortable electronic textiles.The electrodes are fabricated with the following process sequence: 1) preparation by spin-coating on glass substrates of 0.3 mm thick membranes of polydimethyl siloxane; 2) electron-beam evaporation of the 2 nm titanium adhesion layer and of 75 nm of gold conductor; 3) patterning of the metal stack by photolithography, followed by wet etch of the Au. We have measured the resistance of 2mm long and 50 μm wide electrodes both under uni-axial strain and radial strain. Thin gold film electrodes on PDMS substrates can be reversibly stretched up to 80% uni-axially and 15% radially without losing their electrical conductance. The resistance increases from its initial value by factors of 12 times for uni-axial 80% strain, and 20 for 15% radial strain.The stretchability originates in built-in micron-scale cracks in the evaporated gold film, which widen and lengthen reversibly. Under uni-axial strain the microcracks become wider and longer perpendicular to the stretching direction, while they are compressed along the stretching direction. Under radial strain, however, the cracks widen and lengthen in all directions, with the effect that they divide the film into small islands, which reduces the effective cross section for electric conduction. This reduction is much more pronounced than under uni-axial stretching.We introduce a finite element resistance model for the percolating gold network that quantitatively explains the dependence of electrical resistance on mechanical strain. This model indicates that under uni-axial strain of less than 30% and radial strain of less than 10%, the conducting metal film barely stretches, and that the strain is taken up by the opening of the micro-cracks. Results of the finite element simulation correlate well with experimental data. We will describe sample preparation and evaluation, our model and the computational approach, and its results.
10:15 AM - MM6.3
Organic Electronic Artificial Neurons.
Daniel Simon 1 2 , Gustav Burstroem 1 , Magnus Berggren 2 , Agneta Richter-Dahlfors 1
1 Swedish Medical Nanoscience Center, Karolinska Institutet, Stockholm Sweden, 2 Dept. of Science and Technology, Linköping University, Norrköping Sweden
Show AbstractSignaling in the nervous system, in both healthy and diseased states, is based on chemical and electrical signals relayed via neurons. From a functional perspective, these specialized cells can be thought of as chemical-to-electrical-to-chemical transducers: biochemical input triggers the electrical action potential which conveys the signal to distant parts of the cell, which in turn triggers chemical output in the form of synaptic release of neurotransmitters. In this manner, the chemical signaling performed by neurons is highly selective in both its inputs and outputs. While a broad array of technologies ranging from electrical simulation to nanofluidics have been developed for treatment of neurological disorders, most efforts fall short of this simultaneous selectivity of both the triggering input and the chemical target. We have previously demonstrated electrical-to-chemical signal transduction, analogous to neural transduction, exploiting electrophoretic transport in organic electronic ion pumps (OEIPs). The OEIP exemplifies a new breed of delivery technology, exhibiting precise, selective release of neurotransmitters and other small molecules diffusively, without fluid flow. Extending the capabilities of the OEIP to include biochemical input completes the neural analogy. The resulting organic electronic artificial neuron (OEAN) utilizes biosensing technologies for detection of neurotransmitters to achieve self-regulated delivery of biochemicals. In this presentation, we demonstrate how OEANs can transduce the sensed concentration of the neurotransmitters into precise chemical delivery of secondary substances. We also demonstrate efficacy in vitro in the modulation of cellular Ca2+ fluxes in human neuroblastoma cells via neurotransmitter-regulated delivery of acetylcholine. These results illustrate how the OEAN, analogous to biological neurons, is capable of transducing chemical input into precise, localized, and non-disruptive chemical output at some potentially distant point. We will discuss the future of artificial neuron technology, both in future in vitro studies, and in in vivo settings, where it can enable new therapies based on supplementing, augmenting, or even restoring neural signaling pathways.
10:30 AM - MM6.4
Phosphorescent Organic Light-emitting Devices to Sense Contact Stresses.
Xian-an Cao 1 , Yiqiang Zhang 1
1 CSEE, West Viginia University, Morgantown, West Virginia, United States
Show AbstractWe studied the responses of the electrical and optical characteristics of organic light-emitting devices (OLEDs) with green fluorescent and phosphorescent dyes doped in a polymer matrix to compressive stresses. The phosphorescent OLED converted stresses as low as 6.8 kPa into measurable and reversible changes in both current density and electroluminescence (EL) intensity. The current showed a nearly linear characteristic response with sensitivity up to 205 μA kPa-1, whereas EL decreased by over three orders of magnitude at 107 kPa. In contrast, the stress-induced modulations in current and light intensity in the fluorescent OLED were much smaller and saturated at stresses above 26 kPa. The discrepancy has been attributed to stress-enhanced back exciton energy transfer between guest and host molecules, which quenches the EL of the phosphorescent OLED, but has a minimal impact on the performance of the fluorescent OLED. It is expected that similar phosphorescent OLEDs built on large curved surfaces may directly image stress distributions at a high resolution and sense touch on a par with a human finger.
11:15 AM - MM6.5
Conducting Polymer Nanotubes for Glucose Biosensing Application.
Mohammad Reza Abidian 1
1 Bioengineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractDevelopment of glucose biosensors is an intensely investigated research area due to the importance of these biosensors in treatment of diabetes mellitus. To date, the most common aperometric glucose biosensors use the specific recognition of glucose by the enzyme glucose oxidase (GOx). Achieving high sensitivity and longevity in these biosensors has, however, remained a challenge. Conducting polymers have attracted considerable attention in the fields of biosensors due to their suitable matrix for immobilization and entrapment of enzymes and their unique mechanism for direct electron transfer. Among different conducting polymers, poly(3,4-ehthylenedioxythiophene) (PEDOT) has been reported to exhibit superior chemical stability and high conductivity. We have developed a novel method for fabrication of PEDOT nanotube-based glucose biosensor on the surface of platinum microelectrodes. GOx was immobilized into the PEDOT nanotubes during the fabrication process. We have demonstrated that glucose could be detected at a low potential of 400mV versus Ag/AgCl instead of detection of hydrogen peroxide as a by-product at 700mV. The lower voltage applied in this approach may increase the activity and stability of the enzyme. Preliminary results of this work have shown the higher sensitivity (5.7μA.cm-2.mM-1) and lower limit of detection (3μM) in comparison with control PEDOT film (2.1μA.cm-2.mM-1, and 8μM respectively). We will investigate the long–term activity and stability of the enzyme for PEDOT nanotube-based glucose biosensors. We believe this study paves the way for design and development of sensitive and selective neurochemical biosensors, aiming toward long-term in vivo measurements of neurochemicals.
11:30 AM - MM6.6
Amyloid Reactions Using Organic Electronics.
Erik Gabrielsson 1 , Klas Tybrandt 1 , Astrid Armgarth 1 , Per Hammarstroem 2 , K. Peter Nilsson 2 , Magnus Berggren 1
1 Department of Science and Technology, Linköping University, Norrköping Sweden, 2 Department of Physics, Chemistry and Biology, Linköping University , Linköping Sweden
Show AbstractAmyloid fibrils are abnormal protein deposits commonly associated with diseases such as Alzheimer’s and Parkinson’s disease. Amyloid fibrils consist of repeated cross β-sheet structure, resulting in defined structures typically 5-13 nm wide and several micrometers long. In vitro amyloid formation can be induced under appropriate conditions, such as high protein concentration, low pH, or other denaturing conditions. However, current methods for producing amyloid fibrils in vitro offer no spatial control.We have recently developed a method that offers spatial control of the assembly of amyloid fibrils and amyloid-like structures.[1] This method uses an organic electronic ion pump (OEIP) to deliver distinct cations to a peptide solution to create a micro environment where amyloid aggregation is promoted. As a proof of principle, we have used the OEIP to create amyloid-like aggregates of polyglutamic acid by delivery of either H+ or Na+. The aggregates where localized to within 100 µm from the outlet of the OEIP, and their morphologies and kinetics were dependent on the ion and rate of delivery. We also incorporated fluorescent and conducting molecules into the aggregates.We have also used the OEIP to produce fibrils composed of the Aβ peptide, which is associated with Alzheimer’s disease. Again, the morphology and distance to the outlet of the formed fibrils were found to be dependent on the ion species delivered and the rate of pumping.This new method for spatially creating amyloid aggregates show promise for use in biological studies of amyloid assembly and its dependence on the promoting or inhibiting conditions in a micro environment. It has also potential to be used as a method for creating novel nanomaterials for bioelectronics.[1]E. O. Gabrielsson, K. Tybrandt, P. Hammarström, M. Berggren and K. P. R. Nilsson, Small, 2010, 6, 2153-2161.
11:45 AM - MM6.7
Nanosecond Response Organic Photodiodes: From Device Physics towards Biosensor Applications.
Sebastian Valouch 1 , Siegfried Kettlitz 1 , Nico Christ 1 , Simon Zuefle 1 , Celal Oeguen 1 , Uli Lemmer 1
1 Light Technology Institute (LTI), Karlsruhe Institute of Technology (KIT), Karlsruhe Germany
Show AbstractPhotodiodes fabricated from organic semiconductors have the potential to provide cost effective optical detection and easy integration in biological sensing applications. In most biosensing applications, the speed of detection is of utmost importance, among the most demanding applications being flow cytometry and fluorescence lifetime measurements, where response times in the nanoseconds are required. Polymer photodiodes based on a blend system consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and the fullerene derivative (6,6)-phenyl C-butyric acid methyl ester (PCBM) with response times on the order of 10 ns have been demonstrated and successfully employed for optical interconnects showing the feasibility of high-speed applications for these devices. We have studied the underlying device physics and investigated the influence of parameters such as temperature and bias voltage using a numerical simulation software combining a self-consistent drift-diffusion model in conjunction with an optical model based on the transfer matrix method. An optimized matched impedance architecture allows measurements beyond 1 GHz with minimum distortion, while at the same time allowing to probe the favourable sandwich device structure. Using this method organic photodiodes based on P3HT:PCBM achieving bandwidths well into the MHz range have been successfully demonstrated. Transient photocurrent measurements utilizing this matched impedance device architecture excited by 1.6 ns long laser pulses show very good correlation between simulated and measured results. Rise times faster than 1.5 ns are realized even for modest bias voltages of -2 V. To avoid the degradation of the devices by humidity and oxygen we have developed an encapsulation technique to integrate high-speed organic photodiodes onto standard printed circuit boards (PCBs). This technique uses stencil printing and capillary underfill, both methods widely used in the industry. Thus we are able to build stable high-speed organic photodiodes with response times in the 10 ns range. By studying the device physics of high-speed organic detectors and investigating ways to integrate them onto printed circuit boards we pave the way for the application of this technology in particle based microfluidic chips and other high-speed biosensing applications.
12:00 PM - MM6.8
Addressable Matrices of Electro-active Surfaces for Spatially Controlled Adhesion of Proteins and Cells.
Maria Bolin 1 , Karl Svennersten 2 , Edwin Jager 1 , Agneta Richter-Dahlfors 2 , Magnus Berggren 1
1 Department of Science and Technology, Institute of Technology, Linköping University, Norrköping Sweden, 2 Department of Neuroscience, Karolinska Institutet, Stockholm Sweden
Show AbstractHere, we report a matrix addressable electroactive surface based on a conducting polymer to gain dynamic control over the spatial distribution of cell adhesion and proliferation, in vitro. Switchable devices were manufactured using thin film processing and microfabrication techniques to create desired patterns of poly-(3, 4-ethylenedioxytiophene) (PEDOT) on flexible plastic foils. Micro-patterning was achieved at the scale of individual cells, to enable active regulation of cell populations and their extracellular environment at high spatial resolution. Our electrode matrix system opens up for fundamental studies of cell growth behavior and complex manipulation of the growth characteristics in a highly parallel manner. When the structures are electrically biased, PEDOT changes its electrochemical state which results in a reversible control of the surface properties of the material. This surface modulation dictates changes in the conformation and/or orientation, rather than concentrations, of surface proteins, thus regulating cell adhesion. Our findings promise for a future e-dish technology to regulate the fate of cell cultures.
12:15 PM - MM6.9
Cantilevered PEDOT Filaments for Measuring Sub-cellular Forces.
Govind Paneru 1 , Prem Thapa 1 , Sean McBride 1 , Bruce Law 1 , Bret Flanders 1
1 Physics, Kansas State University, Manhattan, Kansas, United States
Show AbstractA migratory cell establishes multiple contacts to the substrate on which it crawls. These contacts are called focal adhesions. The cytoskeleton transmits forces to the substrate at these points, leading to the translational motion of the cell. Measurements with sufficient spatial resolution to resolve the time dependent forces exerted at the single-or-few focal adhesion level are needed to quantitatively understand organism-level processes like migration. The present study reports on the on-chip fabrication of flexible filaments composed of the conducting polymer poly 3,4-ethylenedioxy-thiophene (PEDOT). These structures provide an innovative way to measure the time dependent forces exerted at single-or-few focal adhesion sites on migratory cells. Employing an approach termed directed electrochemical nanowire assembly,[1] PEDOT filaments were grown from gold electrodes that were lithographically deposited on a glass slide. One end of the filament was rigidly attached to the gold electrode while the other was free. Hence, the filament was modeled as a cantilevered rod for which lateral deflection of its free end across distance Δx induced a restoring force of magnitude kΔx; the corresponding spring constant k is 3EI/L3 where E is Young’s modulus, I the second moment of inertia, and L the filament length. This study employed atomic force microscopy to directly measure the force constant of these filaments. As a specific example, a 9 μm long, 400 nm diameter filament exhibited a spring constant of 160 nN/μm, in good agreement with 165 nN/μm, the prediction of the cantilevered rod model (using the Young’s modulus of bulk PEDOT). After filament growth and calibration, D. discoideum cells were cultured on the glass slide. During their random migration, one occasionally adhered to the free end of the PEDOT cantilever. These structures were sufficiently flexible to deflect visibly under ~100 nN cellular forces. Additionally, their ~400 nm diameters were fine enough that the cell-filament contact areas were only ~0.5 μm2, limiting the number of focal adhesions involved in the contact to the single-or-few focal adhesion level; confocal fluorescence imaging of phalloidin stained cells substantiated this determination. Optical microscopy-based observation of the time dependent deflection of a PEDOT cantilever in response to an attached cell permitted measurement of the time dependent forces exerted at the cell-filament contact site. Results on the statistics governing the lifetimes of these contacts and the forces exerted at these contacts will be interpreted in the context of cellular migration. The potential for delivering and detecting electrical signals at these contact sites via the conducting filaments will be discussed. 1.Thapa, P.S., B.J. Ackerson, D.R. Grischkowsky, and B.N. Flanders, "Directional growth of metallic and polymeric nanowires," Nanotechnology, 2009 20: p. 235307.
12:30 PM - MM6.10
Mechanical Stresses at the Implant-brain Tissue Interface in Rodents.
Arati Sridharan 1 , Jit Muthuswamy 1
1 Biological & Health Systems Engineering, Arizona State University, Tempe, Arizona, United States
Show AbstractMost cortical neural prostheses require insertion of microscale implants of various sizes and dimension into the brain. However, these implants induce a chronic tissue response at the implant site, leading to significant changes in the neural tissue-material interface due to inflammation and foreign body reaction. These processes eventually lead to isolation of the implant from the neurons causing failure. It is hypothesized that mechanical stresses on the brain tissue caused by the presence of the rigid implant and the relative micromotion between the brain tissue and the stationary implant exacerbate the above tissue responses making the tissue-implant interface non-functional in the long-term. The aim of this study is to quantitatively assess the mechanical stresses on the brain tissue in the immediate vicinity of the implant (a) during the initial implantation process and (b) after 6 weeks of implantation. Using microprobes of different materials and dimensions, dynamic forces on the electrode inserted real-time in live brains were measured using a sensitive load cell in Sprague-Dawley rat brains. Preliminary data suggests the mechanical stresses on the brain tissue are dependent on 1) insertion speed, 2) microelectrode material and geometry, 3) brain viscoelastic properties. Preliminary in vivo studies (n=2 animals) suggests brain micromotion due to respiration and vascular pulsatility induces continuous, chronic shear forces on the microelectrode. Insertion of microelectrodes shows an increasing, pulsatile shear force exerted on the interface according to penetration depth and electrode diameter. Dynamic peak-to-peak changes of 0.57 ± 0.026 KPa at 1mm depth and 1.69 ± 0.1 KPa at 2mm depth are reported for stainless steel microneedles. Decreasing microelectrode diameter from 200 μm to 100 μm (0.30 ± 21 KPa ) yields ~45% drop in micromotion induced shear forces suggesting smaller microelectrodes impose lower forces at the interface. The constitutive properties of the brain at different times after implantation are then estimated using finite element modeling techniques. Results of this chronic study will be useful in designing appropriate strategies to counter or minimize the tissue reaction around the implant site and potentially enhance the reliability of prosthetic implants in the brain.
12:45 PM - MM6.11
Sensitive Biomolecular Detection Using LSPR Peak Wavelength-shifts.
Longhua Guo 1 , Kim Tae-IL 2 , Donghwan Kim 1
1 Chemical and Biomedical Engineering, Nanyang Technological University, Singapore Singapore, 2 Department of periodontology, Seoul National University, Seoul Korea (the Republic of)
Show AbstractRecent progress on plasmonic biosensors has enabled LSPR-shift assay with single nanoparticles. Single-nanoparticle plasmonic sensors are particularly attractive because of small sample volume required, better signal-to-noise resolution, and lower limits of detection. However, variations in the corresponding LSPR-shifts to surrounding refractive index change among structurally different particles have not fully studied. Hence, we discuss the LSPR scattering peak wavelength distribution of individual gold nanoparticles, the effect of this variation to the sensitivity of LSPR-based sensors, and methods to minimize the variations in the LSPR responses among different particles, thus improving sensitivity of single plasmonic sensors. First, an optical detection platform that allows the simultaneous measurement of high-resolution LSPR wavelength-shift and identification of individual nanoparticles with their corresponding spectra in 2D nanoarrays was developed. Second, an experimentally determined equation to minimize particle-to-particle variation of the LSPR response from nanoparticles with potentially inhomogeneous structural geometry was developed. Finally, by combining 1) and 2), we demonstrate a biomolecular assay based on LSPR wavelength-shift on a nanoarray that employed individual nanoparticles as sensing units. This promising plasmonic biomolecular assay on the nanoarray should find application in parallel screening of nucleic acid and protein profiles and will compete with current microarrays.