Symposium Organizers
John A. Carlisle Advanced Diamond Technologies, Inc.
Martin Eickhoff Technische Universitaet Muenchen
Jose A. Garrido Technische Universitaet Muenchen
Janos Voeroes University and ETH Zurich
Erika Johnston Genzyme Corporation
D1: Nanobiotechnology
Session Chairs
Monday PM, November 27, 2006
Room 202 (Hynes)
9:30 AM - **D1.1
Bionanoarrays Prepared by Massive Parallel Dip-Pen Nanolithography
Chad Mirkin 1 2 , Khalid Salaita 1 2 , Yuhuang Wang 1 2 , Rafael Vega 1 2 , Joseph Kakkassery 1 2 , Clifton Shen 1 2 , Daniel Maspoch 1 2
1 International Institute for Nanotechnology, Northwestern University, Evanston, Illinois, United States, 2 Department of Chemistry, Northwestern University, Evanston, Illinois, United States
Show AbstractThe emerging field of nanobiotechnology relies on precise patterning of biological molecules on surfaces with nanometer resolution. Examples include the generation of DNA, protein, virus, and cell arrays that have potential biosensing, proteomics, and theranostics applications. There are currently a number of techniques for generating nanoscale features of biological molecules. These include electron-beam lithography, Dip-Pen Nanolithography (DPN), nanografting, nanoimprint lithography, nanopipet deposition, and contact printing. Each of these techniques has a set of capabilities that differentiate it from the other ones, and they all possess strengths and weaknesses with regard to resolution, speed, materials compatibility, complexity, and cost.DPN, a scanning-probe-based lithography in which an AFM tip is used to generate nanoscale biological patterns by directly transferring biomolecules to a surface, offers a number of realized and potential advantages over other nanopatterning techniques. It is substrate general and the patterning is typically performed under ambient conditions, which is critical for biomolecules. However, in its current state of development, the biggest limitation of DPN is its speed, especially when carried out in the context of single pen experiments. In addition, the bionanoarrays generated by DPN thus far are limited to a surface area of 100 μm × 100 μm using conventional single pens. Recently, DPN has evolved from a serial-based single pen experiment to a parallel patterning tool for generating complex nanoscale features over a large area.In this talk, we will discuss the massive parallel writing capabilities of DPN using a 2-D tip-array consisting of 55,000 individual tips (NanoPrint Array™). We will also discuss the strategies that we employed to perfectly align all of the 55,000 tips with the substrate. High-throughput DPN allowed us to fabricate in 20 minutes 88 million 100 nm-size high-resolution features. The 2-D tip array was used in the direct and indirect write approaches to generate nanoscale biological features. In particular, we have generated fibronectin and biological lipids nanoarrays over 1 cm2 substrate areas.
10:00 AM - D1.2
Lab-on-a-Chip Devices with Nanoscale Surface Topography for Neural Electrophysiological Applications.
Ludovico Dell'Acqua-Bellavitis 1 3 , Richard Siegel 2 3
1 Engineering Science, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractThis study is aimed at developing and fabricating novel in vitro electrophysiological devices capable of concurrently enhancing cell-biomaterial interaction and signal discrimination and resolution. The approach combines (i) the design and fabrication of integrated circuit platform (IC) and (ii) the synthesis ex situ of electrically insulated and aligned conducting nanowire arrays within a single device for electrophysiological studies of neuronal cells. The IC platform, which features an array of electrically-insulated electrodes deposited on thermally-grown silicon dioxide, was fabricated at three different scales of resolution to enable recordings of field potentials, action potentials and ionic channel potentials, respectively, at the multicellular, intercellular and intracellular levels (1).A conducting gold-plated copper / anodized alumina composite construct was fabricated as the interface between neuronal cells and the IC platform. The fabrication process was comprised of the following steps: (i) synthesis of anodized alumina templates (2); (ii) conformal copper metallization within the pores of anodized alumina templates; (iii) electropolishing of the excess copper on the anodized alumina templates; (iv) selective alumina etching; and (v) selective electroless gold deposition on the copper nanowires. The composites were then positioned in intimate contact with the previously manufactured multiple electrode array, therefore constituting an interface between an underlying IC platform and neuronal cells.The device was then interfaced with external amplification and data acquisition hardware and software in order to either record bioelectric signals from both single and multiple neural cells or to electrically stimulate them with ultimate nanometric space resolution.This work was supported by Philip Morris USA and the Nanoscale Science and Engineering Initiative of the National Science Foundation under NSF Award No. DMR-0117702.References(1)L.M. Dell’Acqua-Bellavitis, J.D. Ballard, R. Bizios, R.W. Siegel (2005) Synthesis of nanoscale devices for neural electrophysiological imaging, Mater. Res. Soc. Symp. Proc. 872, J18.17.1.(2) G.W. Meng, Y.J. Yung, A.Y. Cao, R. Vajtai, P.M. Ajayan (2005) Controlled fabrication of hierarchically branched nanopores, nanotubes, and nanowires, Proc. Natl. Acad. Sci. USA 102, 7074-7078.
10:15 AM - D1.3
Stack of BioCells Converting ATP to Electrical Power and Possible Applications.
Vishnu Baba Sundaresan 1 , Donald Leo 1 , Andy Sarles 1
1 Mechanical Engineering Department, Virginia Tech, Blacksburg, Virginia, United States
Show Abstract10:30 AM - D1.4
Use of sub-10 nm Diameter Upconversion Nanophosphors as Bio-labels.
Shuang Fang Lim 1 , Robert Riehn 1 , Chih-kuan Tung 1 , David Tank 1 , Robert Austin 1 , William Ryu 2 , Margarita Herrera-Alonso 3 , Robert Prud'homme 3
1 Physics, Princeton University, Princeton, New Jersey, United States, 2 Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States, 3 Chemical Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractWe have synthesized rare-earth doped sub-10 nm diameter upconverting yttrium oxide based nanophosphors by flame spray pyrolysis. We show that upconversion nanophosphors can be imaged by both infrared excitation and electron excitation in a scanning electron microscope. We have investigated the optical properties of 50-200 nm diameter sized nanophosphors, and found a square-dependence of the emitted visible fluorescence on the infrared excitation, and verified that under electron excitation similar narrow band emission spectra can be obtained as is seen with IR upconversion. We have surface functionalized the nanophosphors making them suitable for bio labeling. The viability of the nanoparticles for biological imaging was confirmed by imaging the digestive system of the nematode worm C. elegans, confirming that the upconversion nanophosphors can be identified in a scanning electron microscope at high spatial resolution.
D2: Nanoparticles
Session Chairs
Monday PM, November 27, 2006
Room 202 (Hynes)
11:15 AM - **D2.1
Modular Designed Functional Nanoparticles for Clinical Theranostics.
Dar-Bin Shieh 1 , Cheng-Shen Yeh 2 , Yonhua Tzeng 3 4
1 Institute of Oral Medicine and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan Taiwan, 2 Department of Chemistry and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan Taiwan, 3 Institute of Nanotechnology and Microsystems Engineering and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan Taiwan, 4 Dept. of Electrical & Computer Engineering, Auburn University, Auburn University, Alabama, United States
Show Abstract11:45 AM - D2.2
Gold Nanoparticle Covalent Labeling of Proteins at Specific Sites.
Marie-Eve Aubin-Tam 1 , Kimberly Hamad-Schifferli 2 1
1 Biological Engineering Department, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Mechanical Engineering Department, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSite-specifically labeling of a protein is challenging as the nanoparticle can link in many number of ways on the protein. An ideal labeling approach would be targeted to a specific amino acid and would be independent of physical characteristics of the milieu like pH, salt concentration or temperature. Furthermore, for most applications of gold NP-protein conjugates, it is crucial that labeling does not distort the protein structure, hamper any interactions of the protein with its partners or obstruct its active site. We report covalent labeling of a 1.5nm gold nanoparticle on specific amino acids of the protein Cytochrome c. Multiple labeling sites and nanoparticle surface chemistry are considered to minimize protein denaturation. This study is of great importance for applications in which biomolecules are linked to nanoscale structures, such as imaging, sensing, and microfluidic devices.Our labeling strategy aims to attach the gold nanoparticle at a specific single surface cysteine. The chemistry of labeling relies on the gold-thiol covalent bond. Nanoparticles with negatively, positively charged and neutral ligand are successfully labeled with Cytochrome c. The conjugates are purified by gel electrophoresis or HPLC. The protein secondary structure is studied by circular dichroism. We find that changing the chemical moiety on the end of the ligand can dramatically affect the structure of the Cytochrome c, supporting that nanoparticle ligands play a major role in the protein-nanoparticle interactions.Cytochrome c is mutated in order to present single cysteine residues at various positions on its surface in order to identify how the secondary structure of the labeling site and its surrounding amino acids affect the propensity of the protein structure to be disturbed by the nanoparticle. The protein structural disturbance is rationalized by considering the electrostatic interaction likely to occur between the nanoparticle ligand molecules and the amino acids in the vicinity of the labeled surface cysteine. Structural disturbance of Cytochrome c is known to affect its redox potential. Thus, the protein electrochemistry is characterized by cyclic voltammetry.
12:15 PM - D2.4
Fluorescent Silica Nanoparticles: Probes for Imaging and Sensing in Biology
Andrew Burns 1 , Prabuddha Sengupta 2 , Ethan Chiang 2 , Erik Herz 1 , Barbara Baird 2 , Ulrich Wiesner 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Chemistry and Biochemistry, Cornell University, Ithaca, New York, United States
Show AbstractThe study of the colloidal chemistry of silica has created a versatile toolbox for the design of novel materials on the nanoscale. We have integrated this knowledge of silica sol-gel chemistry with the wide array of fluorescent organic dyes to develop a family of bright and stable, core-shell, fluorescent silica nanoparticles. These novel materials show considerable enhancements in brightness (tens- to hundred-fold compared to single fluorophores) through multiple fluorophore encapsulation and fluorescence enhancement effects, in addition to increased resistance to photobleaching and solvatochromic shifts for encapsulated dyes. These nanoparticles have been further developed as a platform for quantitative ratiometric sensing and imaging of chemical concentrations in biological samples. The co-localizaton of sensor and reference dye molecules in a core-shell architecture is an optimized design for sensing, placing the sensor dyes in the high surface area outer shell, while sequestering the reference dyes deep within the particle, away from environmental perturbations. In order for these particles to become effective tools for biologists, their interactions with cell surfaces must be addressed. Towards that end, we have developed several targeting methods to mediate specific labeling and uptake of particles in various cell lines. In addition, given that theses particles are natively electrostatically stabilized, the question of colloidal stability in biological media must be addressed and we will present our recent findings in the development of highly functional nanoparticles for biology.
12:30 PM - D2.5
Magnetic Nanoparticle-biomolecule Interfaces: Synthesis, Characterization, and Implementation in Bioengineering Applications.
Kimberly Hamad-Schifferli 1 2
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Biological Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract12:45 PM - D2.6
Particle Size Effects in Magnetite Nanoparticle Uptake into Cells
Juan Meng 1 , Patrick Clasen 2 , Tracy Vu 1 , Shuailei Ma 2 , Christopher J. Kiely 2 , Martin P. Harmer 2 , Winston O Soboyejo 1
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractThis paper presents the results of an experimental study of the effects of magnetite nanoparticle size on the uptake of nanoparticles into breast cancer and normal breast cells. The uptake of the nanoparticles is studied using a combination of transmission electron microscope and quantitative image analysis. The particle size effects in receptor-mediated and non-receptor-mediated endocytosis are then considered within a theoretical framework that considers the combined effects of adhesive forces and elastic energy on the entry of nanoparticles into biological cells. The results suggest an optimal nanoparticle size that is consistent with the experimental observations of 20-30nm.
D3: Cell Surface Interactions
Session Chairs
Monday PM, November 27, 2006
Room 202 (Hynes)
2:30 PM - **D3.1
Molecularly Engineered Surfaces for Cell Biology.
George Whitesides 1 , J. Jiang 1 , D. Bruzewicz 1 , A. McGuidon 1 , N. Shen 1 , A. Wong 1 , D. Weibel 1 , J. Kriebel 1 , M. Butte 1
1 The Whitesides Research Group, Harvard University, Cambridge , Massachusetts, United States
Show Abstract3:00 PM - D3.2
Engineering Cellular Behavior via Cell-Surface Interactions with Fibronectin Nanoislands.
John Slater 1 , Wolfgang Frey 1
1 Department of Biomedical Engineering and Center for Nano and Molecular Science and Technology, University of Texas at Austin, Austin, Texas, United States
Show AbstractIntracellular signaling events initiated by cell-surface interactions have proven to be an influential component governing cellular behavior. These interactions are mediated by integrins that aggregate into small clusters to form either focal complexes or focal adhesions. Focal complexes are smaller, typically less than 1 µm2, and less molecularly complex than their mature counterparts. With the recent explosion of nanofabrication techniques much attention has been focused on creating surfaces that allow for the manipulation of these adhesion sites in order to investigate their influence on cellular behavior. Here we present a technique that utilizes nanosphere lithography in combination with a dual chemical functionality that allows for the creation of fibronectin nanoislands against a non-adhesive background. The dual chemical functionalization was tested using both x-ray photoelectron spectroscopy and with cell seeding experiments. The results indicate that fibronectin absorbed exclusively to the nanoislands and that cellular attachment to the passive background was prevented. We investigated the influence of varied island size, spacing, and percent ligand density on cellular proliferation, cell spreading area, cytoskeletal formation, and focal adhesion properties. After 1 day of culture, cells on both nanopatterned and non-patterned controls displayed a homogenous distribution of adhesion sites throughout the cell with a focal adhesion density of approximately 40,000 FA/mm2, while after 3 days a significant difference was observed. Cells on the control surfaces redistributed their adhesions to the cell periphery and the adhesion density decreased to 7,500 FA/mm2 while cells adhering to the nanoislands maintained a homogenous distribution and a high adhesion density, 30,000 FA/mm2. No changes in cellular proliferation or gross cell morphology were seen, yet the nanopatterns induced a significant decrease in cell spreading area, a more diffuse actin cytoskeleton, and increased cellular motility over a 3 day period. These results provide insight into the relationship between adhesion site properties and cellular behavior and lay a foundation for cellular engineering via cell-surface interactions.
3:15 PM - D3.3
Application of Biomolecular Machinery for Nanoscale Device Assembly.
Erik Spoerke 1 , George Bachand 1 , Haiqing Liu 1 , John Nogan 1 , Thomas Swiler 1 , Subhash Shinde 1 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractMicrotubules and motor proteins are key components involved in the active transport and assembly of nanostructures in living organisms. Such biological systems rely on the careful organization of microtubules into complex networks. These networks, then, serve as supramolecular tracks, directing the movement of cargo-laden motor proteins, such as kinesins, which transport and position their cargo throughout a cell. The controlled precision and scalability evident in this natural technology address some of the major challenges limiting nanomaterials assembly today. Our work attempts to utilize these active biological agents as tools for assembling technological nanomaterials into functional device structures. Our approach integrates lithographically-patterned platforms with selective surface functionalization chemistries and specialized interactions between microtubules and motor proteins to assemble functional nanostructures. In this talk, we will discuss the chemical and biological methods used to direct the formation of microtubule network structures and how these structures are used to create functional nanoscale device assemblies. This biomolecular approach to nanomanufacturing has tremendous potential to influence the application of functional nanostructures. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.
4:30 PM - D3.4
Engineering Loading Stations for Cargo Pick-up by Molecular Shuttles.
Christian Brunner 1 , Christian Wahnes 1 , Volker Jacobsen 2 , Vahid Sandoghdar 2 , Viola Vogel 1
1 Biologically-Oriented Materials, Dept. of Materials, ETH Zurich, Zurich Switzerland, 2 Nano-Optics Group, Laboratory of Physical Chemistry, ETH Zurich, Zurich Switzerland
Show AbstractThe controlled step-by-step assembly of molecular building blocks to larger, possibly macroscopic entities with nanometer precision, potentiates the fabrication of new devices such as biosensors. The development of sequential assembly lines on the micro- and nanoscale requires (1) motors to enable active transport, (2) specific pick-up and delivery of cargo, (3) defined pathways for directed transport and (4) sequential assembly at desired locations.Nature provides a manifold toolbox of highly efficient molecular motors. These biomolecular motors exceed the functionality of synthetic motors, have been proven to operate in synthetic environments and can thus be integrated in hybrid devices. In our approach, kinesin motor proteins move microtubule filaments (molecular shuttles) along a surface. The propulsion mechanism is based on active transport, the conversion of chemical energy (ATP hydrolysis) into mechanical motion. Various challenges such as directional control over the microtubule movement or specific binding of cargo to functionalized shuttles have already been successfully addressed. However, until now specific pick-up of cargo was only achieved out of solution using biological linkers such as biotin/streptavidin. An unsolved challenge in the assembly process is the pick-up of cargo from defined areas (loading stations). Spacial control over pick-up is essential to avoid cross-reaction of cargo with other parts of the system.We fabricated loading stations that exhibit reversibly immobilized cargo via different linker chemistries prepared by using a photolithographic lift-off process. In more detail, 40 nm gold(graft-anti-biotin)-colloids were immobilized via two different linker chemistries: cationic biotinylated poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG-biotin) and biotinylated deoxyribonucleic acid (DNA) double-strands. Both approaches feature ease of use and, in the case of the DNA-based design, the binding strength can be adjusted by varying the length of the hybridizing sequence. Single 40 nm gold colloids were directly detected using an interferometric confocal scheme. Cargo pick-up was tested in motility assays, where biotinylated microtubules propelled by kinesin motors bound to the antibody-coated gold nanoparticles and picked them off the surface.Our results show that microtubule shuttles are able to pick up stationary cargo if it is surface-bound via DNA oligonucleotides, but are ineffective in removing cargo from loading zones if PLL-g-PEG-biotin is used as a surface tether.Background:Hess, H., Bachand, G. D. and Vogel, V. Powering Nanodevices with Biomolecular Motors. Chem. Eur. J., 10, 2110–2116, 2004.Jacobsen, V., Stoller, P., Brunner, C., Vogel, V. and Sandoghdar, V. Interferometric optical detection and tracking of very small gold nanoparticles at a water-glass interface. Optics Express, 14(1), 405–414, 2006.
4:45 PM - D3.5
A High-Throughput-Screening Approach for Cell-Surface-Roughness Interaction.
Tobias Kunzler 1 , Tanja Drobek 1 , Nicholas Spencer 1
1 Material Science, Federal Institute of Technology (ETH), Zuerich, ZH, Switzerland
Show AbstractSurface morphology plays an important role in cell growth, proliferation and attachment to the surface [1,2]. It is known that different cells behave differently on smooth surfaces compared to rough ones [3]. However, investigations considering the effect of morphology are often limited to either rough or smooth surfaces and the influence of roughness has only rarely been systematically studied. Roughness gradients can greatly facilitate this kind of investigation. We developed a process that allows for the production of roughness gradient surfaces on a centimeter scale with topographical features in the micrometer and sub-micrometer range.Morphology gradients were fabricated using a two-step roughening and smoothening process. In a first step, a homogeneous roughness was created on aluminium sheets by sand blasting (particles diameter between 300 and 420 micrometer). In a subsequent chemical polishing process, the sheet was immersed into a hot acidic solution and continuously withdrawn by means of a linear motion drive. The polishing solution, depending on the residence time of a specific surface location, preferentially removed features with a small radius of curvature and thus led to the smoothing out of the surface topography.The smoothing out of the surface topography could qualitatively be proven with SEM images at different positions on the gradient. Optical profilometry measurements quantitatively showed that following the gradient axis from rough to smooth the roughness decreases monotonically. Calculations of the standardized integral roughness values showed values of 6.0 micrometer for Ra (arithmetic average) at the rough end and 0.8 micrometer at the smooth end of the gradient. Typically, roughness values (Ra) of surfaces used in cell studies lie between 0.2 micrometer for polished and 3.4 micrometer for blasted surfaces [4]. A roughness gradient produced with our method covers most of the roughness values in-between this range on a single surface.Cell experiments with rat calvaria osteoblasts (RCO) have been carried out on gradients to determine the effect of roughness of various degrees on cell behavior. RCOs showed an increased proliferation rate with increasing roughness. The number of cells was found to be more than two times higher on the rough side of the gradient compared to the smooth side after 7 days. Cells also varied in shape at different positions on the gradient. On the rough part osteoblasts were rather small, whereas on the smooth side individual cells spread over a large area.REFERENCES[1] G. Abrams, et al., Effects of Substratum Topography on Cell Behavior in Biomimetic Materials and Design, Springer, 1998, pp. 91-137. [2] R. Flemming, et al., Biomaterials 20, 1998, pp. 573-588.[3] D. M. Brunette, et al., J Biomech Eng 121, 1999, pp. 49-57.[4] K. Anselme, et al., J Biomed Mater Res 49, 2000, pp. 155-166.
5:00 PM - D3.6
Engineered bio/nano Interfaces via Cell-directed Assembly.
C. Jeffrey Brinker 1 2 , Eric Carnes 2 , Carlee Ashley 2 , Seema Singh 1
1 , Sandia Labs/UNM, Albuquerque, New Mexico, United States, 2 , The University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractBiological systems evolved to perform complex functions like molecular detection, replication, and repair. To develop life-like qualities in synthetic materials, recent research has focused on incorporation of biomolecules, while incorporation of living organisms is less well studied. Furthermore in areas like cell-based sensing little effort has been made to create the nanoscale structure of the extra-cellular matrix (ECM). This is problematic in that cells are inherently sensitive to local nano-to-micro-scale patterns of chemistry and topography. This presentation will describe our recent discovery of the ability of living cells to organize extended nanostructures and nano-objects in a manner that creates a unique, highly biocompatible nano//bio interface, mimicking the ECM. Using amphiphilic phospholipids to direct inorganic self-assembly in the presence of living cells, we find that yeast and bacterial cells intervene, re-directing the assembly process to form a fluid, multi-layered lipid interface at the cell surface that interfaces coherently with an ordered lipid/silica nanostructure. Remarkably this hybrid structure maintains fluidic accessibility and cell viability even after evacuation and electron imaging [1]. Using printing and patterning techniques developed previously by us for inorganic nanostructures [2,3], we can integrate cells into platforms needed for electronic, optical, and spectroscopic interrogation. Using this ‘cell-directed assembly’ approach, we have discovered efficient means to achieve non-native functionalities via localization of foreign transmembrane proteins in the lipid-rich bio/nano interface and spatially patterned cell transformation using plasmid vectors. Overall cell-directed self-assembly represents a new immobilization methodology allowing facile integration of cells into devices with engineered bio/nano interfaces. It should enable the development of (1) surface enhanced Raman spectroscopy nanostructures in which living cells direct the localization of metallic nanocrystals at the cell surface, enabling sensitive monitoring of the bio/nano interface and onset of disease and (2) cellular arrays fabricated with precise control of cell density and spacing allowing the development and interrogation of cell-to-cell communication networks associated with quorum sensing, biofilm formation, and many physiological events in pathogenic bacterial infections.[1] Baca et al. Science, in press; [2] Doshi et al. Science, 2000; [3] Fan et al. Nature, 2000.
5:15 PM - D3.7
Investigation of Spreading and Adhesion of Human Osteosarcoma Cells on Smooth and Microgrooved Polydimethylsilaxone Surfaces.
Yifang Cao 1 , Jianbo Chen 2 , Winston Soboyejo 2
1 Engineering Science Programme and Division of Bioengineering, National University of Singapore, Singapore Singapore, 2 Department of Mechanical and Aerospace Engineering and Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey, United States
Show Abstract5:30 PM - D3.8
Cellular Traction Forces of Adult Human Dermal Fibroblasts in Response to Fibronectin Functional Domains: from Biochemical Signals to Mechanical Responses
Zhi Pan 1 , Kaustabh Ghosh 2 , Yajie Liu 3 , Xiaozheng Shu 5 , Toshio Nakamura 3 , Glenn Prestwich 5 , Xiang-Dong Ren 4 , Richard Clark 2 4 , Miriam Rafailovich 1
1 Materials Science & Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 2 Biomedical Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 3 Mechanical Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 5 Medicinal Chemistry, University of Utah, Salt Lake City, Utah, United States, 4 Dermatology and Medicine, SUNY at Stony Brook, Stony Brook, New York, United States
Show AbstractCells contact the extracellular matrix (ECM) in their exterior environment though specialized focal adhesions that not only work as a bidirectional signal transmitter in response to biochemical stimuli, but also as the micromechanical sensor for the cell. The formation of focal adhesion requires actomyosin-based contractility. Therefore, if cell adhesions also produced different mechanical responses to specific biochemical ligand(s), we will achieve further understanding of focal adhesions by studying the related cellular traction forces.Fibronectin (FN), a multidomain adhesive glycoprotein, works as cell linker in ECM and plays an important role in cytoskeleton-dependent cell growth, migration, differentiation, proliferation, and apoptosis. The central cell-binding domain (CBD), the major heparin-binding domain (HepII) and the variable domain (IIICS) are the major functional domains of FN (FNfds) which can be recognized by distinct receptors on the cell surface and form affinitive bonds. In this study, specific type and density of FNfds were applied in crosslinked hyaluronic acid (HA) hydrogel substrates as the ECM mimic.By using the optical digital image speckle correlation (DISC) technique and finite element method (FEM), the cellular traction forces of adult human dermal fibroblasts (AHDF) and mechanical work induced by the interaction between cell and FNfds were quantitive determined on 2D surface. To this end, the results indicated clearly that not only CBD but also HepII containing IIICS can support strong cell adhesions. Specifically, HepII and IIICS appear to cooperate together to mediate the generation of cellular traction forces, and neither of them is robust enough to lead a comparable result even with a much higher density, although all of these FNfds support the cell adhesion in a dose-dependent manner. Additionally, in order to evaluate how the biochemical signals influence cell behaves, these results were then correlated with auxiliary measurements of both en mass cell migration and single cell migration. The interrelationship between the cellular traction forces and cell migration will be discussed.This work was supported by NSF-MRSEC program (M. R.) and NIH AG10143 (R. A. F. C.).
5:45 PM - D3.9
Effect of m-Calpain Degradation on Cartilage Aggrecan Nanomechanical Properties.
Lin Han 1 , Delphine Dean 2 , Han-Hwa Hung 3 , John Sandy 4 5 , Christine Ortiz 1 7 , Alan Grodzinsky 2 6 7
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Pharmacology and Therapeutics, University of South Florida, Tampa, Florida, United States, 5 Shriners Hospital for Children, University of South Florida, Tampa, Florida, United States, 7 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 6 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractAggrecan, the most abundant proteoglycan in the cartilage extracellular matrix (contour length L~400nm), is known to provide ~50% of the compressive tissue modulus due to intra/intermolecular interactions between its densely packed chondroitin sulfate glycosaminoglycan side chains (L~40nm, molecular separation distance ~2-4nm). A number of enzymes present in vivo are responsible for the degradation of aggrecan by cleaving the core protein backbone at specific sites. For example m-calpain, activated at [Ca2+]~mM (physiological), cleaves sites within the interglobular, chondroitin sulfate 1, and keratan sulfate domains. One of the earliest events in osteoarthritis and post acute injury is the loss of aggrecan from cartilage, possibly due to the upregulation of these enzymes, which leads to irreversible deterioration of the tissue’s biomechanical properties. To understand the degradation mechanisms of cartilage aggrecan and its effect on tissue mechanical integrity, we measured the change of aggrecan compressive nanomechanical properties in phosphate buffered saline (PBS) during m-calpain digestion via atomic force microscopy (AFM). Thiol-functionalized fetal epiphyseal aggrecan was chemically end-attached on microcontact printed planar gold substrates with 10μm hexagons (distance between neighboring aggrecan ~25nm), where the region outside the hexagons was previously functionalized with the neutral self-assembled monolayer, 11-mecaptoundecanol, HS(CH2)11OH (OH-SAM). Gold-coated AFM probe tips (end radii ~50nm) functionalized with the same OH-SAM were used to measure the aggrecan layer height via contact mode AFM and the compressive normal force between the tip and aggrecan via high resolution force spectroscopy in 0.1M PBS. Under applied normal force F~3nN, the aggrecan layer height prior to m-calpain treatment was found to be 22±1nm (~200nm at F~0nN) and the repulsion force between aggrecan and the probe tip was measured to start at a distance of 169±28nm from the underlying substrate. After adding ~200μL of 4.5μM porcine kidney m-calpain in 0.1M PBS ([Ca2+]=7mM) on top of the sample, the normal force was measured after 10, 20, and 30 minutes. The aggrecan layer height was found to decrease homogeneously within the hexagonal areas of the substrate with increasing m-calpain incubation time; the height was measured to be 6±2nm at F~3nN after 30min of the incubation. A marked decrease in the repulsion force was observed with increasing m-calpain incubation time; after 10min the repulsive force started at a distance of 35±4nm, after 20min 24±5nm, and after 30min 22±5nm. The methodology presented here allows for quantifying the kinetics of enzymatic degradation of nanomechanical properties of aggrecan. Ongoing studies are focused on aggrecan nanomechanics modulated by other physiologically relevant proteinases, e.g., the aggrecanase (ADAMTS, a disintegrin and metalloprotease with thrombospondin motifs) and matrix metalloproteinase (MMP) families.
D4: Poster Session
Session Chairs
Tuesday AM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - D4.1
Synthesis of Platinum Nanocages Using Liposomes Containing Photocatalyst Molecules,
Yujiang Song 1 , Robert Garcia 1 2 , Rachel Dorin 1 2 , Haorong Wang 1 2 , Yan Qiu 1 2 , John Shelnutt 1 3
1 Surface and Interface Sciences Department, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Chemistry and Chemical & Engineering Department, The University of New Mexico, Albuquerque, New Mexico, United States, 3 Chemistry Department, University of Georgia, Athens, Georgia, United States
Show AbstractHollow nanospheres are of interest due to their tunable structural features, including shell thickness, interior cavity size, and chemical compositions. In particular, hollow metallic spheres have drawn much attention because of their high specific surface, low density, material economy, cost reduction and in some cases surface permeability compared with solid nanospheres. These unique properties lead to a diverse range of applications. For example, hollow Au nanospheres have been applied for rapid immunoassay and near-infrared thermal therapy of tumours; hollow Pd nanospheres composed of 10 nm particles have shown remarkable catalytic activity and stability in Suzuki coupling reactions; Pd nanoboxes were recently reported to have controllable optical properties arising from the variation of surface plasmon resonance. The synthesis of hollow metallic nanospheres is limited mainly to two approaches. One is to deposit metal onto solid nanospheres of silica, Latex, metal, and other materials, and followed by removal of the templating core typically by replacement reactions or corrosion. The other approach is co-assembly of metallic nanoparticles with organic molecules into hollow nanospheres. A disadvantage of these approaches is that the hollow nanospheres are mainly composed of discrete nanoparticles, making them relatively unstable. Furthermore, these methods encounter the hurdle of making hollow nanospheres larger than 100 nm in diameter with thin 2-3 nm shells. Herein, we report a new method for making hollow metallic nanospheres using templating liposomes containing photocatalyst molecules. We selected platinum to demonstrate this concept in light of its catalytic activity in many applications. This synthetic approach leads to novel porous platinum nanocages with 2-nm shell thickness and diameters up to 200 nm. These cages are assembled from joined dendritic nanosheets instead of individual nanoparticles. Synthetic control over their structure was achieved by simply varying the concentration of platinum complex. The dendritic character of the constituent nanosheets makes the hollow spheres porous, and their empty interiors are interconnected by channels, providing another dimension of porosity potentially suitable for efficient mass-transport.
9:00 PM - D4.10
Controlled Electrostatic-Based Multilayer Adsorption of Nanoparticles for Novel Coatings with Biological Activity
Stoyan Smoukov 1 , Bartosz Grzybowski 1 , Alexander Kalsin 1 , Bartlomiej Kowalczyk 1 , Maciej Paszewski 1 , Kristiana Kandere-Grzybowska 1
1 Chem. & Biol. Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract9:00 PM - D4.11
Nanoparticle Size Effect on Human Dermal Fibroblasts.
Nadine Pernodet 1 , Asya Bakhtina 2 , Jonathan Sokolov 1 , Abraham Ulman 2 , Kalle Levon 2 , Miriam Rafailovich 1
1 Materials Science & Engineering, Stony Brook University, Stony Brook, New York, United States, 2 Chemical and Biological Sciences, Polytechnic University, Brooklyn, New York, United States
Show Abstract9:00 PM - D4.12
Magnetic Field Heating of Fe3O4 Nanoparticles.
Shahriar Khushrushahi 1 , Kimberly Hamad-Schifferli 2
1 Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States, 2 Department of Mechanical and Biological Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - D4.13
A Strong Interaction Between Chemical Functionality and Nanoscale Surface Topography Impacts Fibronectin Conformation and Neuronal Differentiation on Model Sol-gel Silica Substrates.
Sabrina Jedlicka 1 3 , Silas Leavesley 2 3 , Kenneth Little 4 , J. Robinson 2 3 5 , David Nivens 4 , Jenna Rickus 1 2 3
1 Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana, United States, 3 Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States, 2 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States, 4 Department of Food Science, Purdue University, West Lafayette, Indiana, United States, 5 Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana, United States
Show Abstract9:00 PM - D4.14
Electronic Control of Cell Adhesion and Tissue Formation using Electronic Surface Tension Switches.
Magnus Berggren 1 , Kalle Svennersten 2 , Agneta Richter-Dahlfors 2 , Maria Bolin 1 , Nathaniel Robinson 1
1 ITN, Linkoping University, Norrkoping Sweden, 2 MTC, Karolinska Institutet, Solna Sweden
Show Abstract9:00 PM - D4.15
Controlling Cell Growth by Nanoparticles.
Sergiy Zankovych 1 , Joerg Bossert 1 , Liga Berzina-Cimdina 1 , Ines Thiele 1 , Klaus Jandt 1
1 , Friedrich-Schiller-University Jena, Institute of Materials Science and Technology, Jena Germany
Show AbstractParticles with sub-micrometer diameters (nanopowders) provide unique properties that are not available at the macroscopic scale. Nanopowders can be found in daily use in a broad range of applications like cosmetics and toothpastes, inks, food and photo films, as well as in pharmaceutical and drug delivery applications. The new and promising fields of application of nanopowders are the bio- and medical applications. In particular, such properties of nanoparticles as extremely high surface area, enhanced chemical activity of molecules and perhaps proteins and cells at interface and control over microstructure are of interest. As such, nanopowders open a variety of possibilities to integrate special functions in biorelevant structures and coatings.We report the results of using nanopowder to control protein adsorption, cell adhesion and growth. We examine proteins adsorption and cell proliferation on substrates with artificially increased surface roughness compared to smooth titanium surface. We demonstrate controlled cell growth on substrate structured with nanopowders.We produced nanopowders composed of different materials, such as alumina, zirconia and calcium phosphate, by pulsation reactor technology. Titanium surface with artificially increased roughness were prepared by dip-coating glass slides in suspension with nanopowder and subsequent deposition of titanium film. Structured templates for cell proliferation tests were fabricated by means of microcontact printing (muCP) of gold films on glass slides, where hydrophobic and hydrophilic areas are defined, and dip-coating in suspension with nanopowder. Regular structures of different size and spacing were created depending on the structures of preforms and the amount of powder in the slurry. Powders were characterised using XRD, TEM, BET. Structured samples were characterized using light microscopy and partially SEM, AFM. Templates were used for tests with different cells. First results show differences between the samples structured with alumina powder and calcium phosphate powder.
9:00 PM - D4.16
Cell Viability and Adhesion on as Grown Vertically Aligned Carbon Nanotubes.
Evaldo Corat 1 , Anderson Lobo 1 , Erica Antunes 1 , Cristina Soares 2 , Mariana Palma 1 2 , Vladimir Trava-Airoldi 1
1 Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, São Paulo, Brazil, 2 Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil
Show Abstract9:00 PM - D4.17
Glycosylated Polyelectrolyte Multilayer Films: Differential Adhesion of Primary Versus Tumor Cells.
Aurore Schneider 1 , Jean-Claude Voegel 1 , Catherine Picart 1 , Benoit Frisch 2
1 , INSERM U 595, Strasbourg France, 2 , CNRS-ULP UMR 7514, Strasbourg France
Show Abstract9:00 PM - D4.18
Differentiation of Bone Marrow Stem Cells on Inkjet Printed Silk Lines.
Paul Calvert 1 , Skander Limem 1 , David Kaplan 2 , Hyeon Joo Kim 2
1 , umass dartmouth, north dartmouth, Massachusetts, United States, 2 , Tufts University, Medford, Massachusetts, United States
Show AbstractWater based silk solutions were successfully inkjet printed into patterns of parallel lines onto vinyl plastic substrates. Human bone marrow stromal cells (hBMSCs) were seeded on the silk printed patterns and cultured in the presence of 100 ng/ml of bone morphogenic protein (BMP-2). After one week of culture cell growth and attachment showed site specificity on the silk printed lines. Both alkaline phosphatase activity and cell morphology indicated hBMSCs differentiation into osteogenic cells along the silk printed lines. After 4 week of culture, the cellular bridging of adjacent silk printed lines took place for all interline distances lower than 1.25 mm. Therefore, commercial inkjet printing technology can produce complex viable cellular patterns with 111 µm lateral resolution, through the deposition of bioactive materials. The results provide a first step toward cell specific control using 3D inkjet printing techniques using biocompatible gel systems to regulate cell functions. Response of cells to growth on self-assembled ionic polymer layers will also be reported.
9:00 PM - D4.19
Persistent Inhibition of Cell Growth on Silver Implanted Glassy Polymeric Carbon
Robert Zimmerman 1 , Ismet Gurhan 2 , Fayse Ozdal-Kurt 3 , B. Sen 4 , Marcello Rodrigues 5 , Daryush Ila 1
1 Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama, United States, 2 , Ege University Faculty of Engineering, Izmir Turkey, 3 , CBU Faculty of Science, Manisa Turkey, 4 , EU Faculty of Dentistry, Izmir Turkey, 5 , University of São Paulo, Ribeirão Preto, SP, Brazil
Show AbstractWe have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in GPC can completely inhibit cell attachment on implanted areas while leaving adjacent areas vulnerable to strong cell adhesion. After cleaning and sterilization and more than one year in physiologic solution, the silver implanted GPC persists in inhibiting cell attachment.
9:00 PM - D4.2
A FRET Study on Conformational Change of Electrophoretic Nanoparticle-Polymer Conjugates
Sunho Park 1 , Kimberly Hamad-Schifferli 1 2
1 Department of Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Biological Engineering Division, MIT, Cambridge, Massachusetts, United States
Show AbstractIt is suggested in the previous research that Au nanoparticle-DNA conjugates free from surface adsorption usually have smaller hydrodynamic size during gel electrophoresis compared with those of conjugates still retaining some non-specific adsorptions. A possible explanation is that DNA strands tethered to Au nanoparticles via thiol chemistry are somewhat stretched when they migrate in gel running buffer if there exists notable difference in mobilities between the nanoparticles and DNA strands. Although there are numerous studies of DNA stretching by DC electric field with one end of relatively long DNA being bound or by AC electric field for freely migrating randomly coiled DNA, quantitative electrophoretic studies of nanoparticle-polymer conjugates have been limited. To verify the hypothesis on DNA stretching, Forster resonance energy transfer(FRET) between nanoparticle and fluorophore residing at the end of DNA is studied. The conformational change of DNA leads to variation of relative distance between fluorophores(acceptors) and nanoparticles(donors), thus results in change of fluorescence intensity, which is measured while actual voltage difference is applied to running buffer containing the conjugates. Some related theories are adopted to describe the data.
9:00 PM - D4.20
An Enzymatically Switchable Hydrogel Surface for Controlled Cell Adhesion.
Simon Todd 1 , Rein Ulijn 1 , Julie Gough 1
1 Materials Science Centre, University of Manchester, Manchester United Kingdom
Show AbstractThe developed world continues to see dramatic increases in the use of materials that interact with living cells and tissues. Understanding and ultimately controlling these interactions is of importance for a number of existing and emerging technologies, including tissue engineering and biosensing. A new challenge in this area is to engineer materials surfaces that allow for a two-way communication between biology and biomaterial. Here, we demonstrate an example of a hydrogel surface that can be switched between adhesive and non-adhesive when triggered by an enzyme.[1] Our system is based on modified poly(ethylene glycol) acrylamide (PEGA) hydrogel surfaces. PEGA has been shown to have desirable properties for use as thin 3D hydrogel surfaces in biomedical applications. PEGA can be easily micropatterned, contains a high density of functional groups, provides a passive background that resists non-specific biomolecule adsorption, and is highly hydrated mimicking the natural tissue environment. [2] We also demonstrated that these surfaces could be made cell-adhesive by incorporating the well known RGD integrin cell binding sequence into the hydrogel structure (no cell adhesion observed for the RGE control).[2] In this work, PEGA surfaces were modified with enzyme cleavable peptide linkers using a solid phase peptide synthesis (SPPS) approach, directly onto the micropatterned hydrogel. By using a combination of surface analysis (ToF SIMS) and fluorescence microscopy, we demonstrate that by choosing a peptide sequence to match a certain protease, hydrogel surfaces can be made responsive to target enzymes only. We then applied these systems in cell culture and demonstrate that for the first time the possibility of switching cell adhesion ON or OFF in response to an enzyme.References:1 RV Ulijn, J. Mater. Chem. 2006, 16 (23): 2217-2225. 2. M. Zourob, J.E. Gough, R.V. Ulijn. Adv. Mater. 2006, 18: 655-699
9:00 PM - D4.21
High Density Addressable Protein and Cell Patterning via Switchable Superhydrophobic Microarrays
Jau-Ye Shiu 1 , Peilin Chen 1
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Show AbstractThere have been increasing research interests in the development of novel nano or micro-patterning techniques to create arrays of functional biomolecules for miniaturized assays, which could be used in various biomedical applications such as biosensors, proteomic, immunoassays or drug screening. Several techniques have been demonstrated capable of writing or printing biomolecules with very high degree of spatial control including dip-pen lithography, nanopipet, inkjet printing, photolithography, micro contact printing etc. The serial writing techniques provide the individual addressability whereas the parallel printing processes offer easy and fast protein patterning. However, it remains difficult to create complex patterns, such as functional multicomponent protein arrays, in parallel with individual addressability. Here we describe a novel approach to fabricate functional multicomponent protein and cell arrays where the electrowetting effect was employed to convert a water-repellent superhydrophobic surface into a wettable one allowing fast and high density addressable protein and cell deposition on the otherwise protein- and cell-resistant superhydrophobic surface. It has been shown that each element on the switchable superhydrophobic microarray could be addressed individually and different types of functional biomolecules could be selectively deposited on the microarray. To our best knowledge, this is the first demonstration of the application for the switchable superhydrophobic surfaces. Such protein patterning technique offers several advantages over other techniques including parallel protein deposition with individual addressability, possibility for large-scale patterning and easy integration with microfluidic system. The facts that the superhydrophobic surfaces can be fabricated from many hydrophobic materials and the electrowetting works for most dielectric materials allow great flexibility in the selection of the surface materials for protein deposition.
9:00 PM - D4.22
Culture of Mammalian Cells on Single Crystal SiC Substrates.
Camilla Coletti 1 , Mark Jaroszeski 2 , Andrew Hoff 1 , Stephen Saddow 1
1 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 Chemical Engineering, University of South Florida, Tampa, Florida, United States
Show Abstract9:00 PM - D4.23
A Novel Nano Coating Technique to Increase Osteoblast Functions: Ionic Plasma Deposition
Alex Reising 1 , Ariel Cohen 1 , Chang Yao 1 , Dan Storey 2 , Thomas Webster 1
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 , Ionic Fusion, Denver, Colorado, United States
Show AbstractBioactive coatings are in high demand to increase the functions of cells for numerous medical devices. The objective of this in vitro study was to characterize osteoblast (bone-forming cell) and fibroblast (cells that contribute to the formation of soft fibrous tissue) functions on several potential orthopedic implant materials coated using a novel Ionic Plasma Deposition process which creates a surface-engineered nanostructure (with features below 100 nm) by first using a vacuum to remove all contaminants, then guiding charged metallic ions or plasma to the surface of a medical device at ambient temperature. Results show greater functions of osteoblasts on several commonly used polymers for orthopedic applications coated with titanium by this process. In this manner, this study suggests that Ionic Plasma Deposition should be further studied for orthopedic applications.
9:00 PM - D4.24
The Dynamics of Cell Migration on Hyaluronic Acid Hydrogel Surface
Zhi Pan 1 , Kaustabh Ghosh 2 , Xiaozheng Shu 4 , Glenn Prestwich 4 , Richard Clark 2 3 , Miriam Rafailovich 1
1 Materials Science & Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 2 Biomedical Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 4 Medicinal Chemistry, University of Utah, Salt Lake City, Utah, United States, 3 Dermatology and Medicine, SUNY at Stony Brook, Stony Brook, New York, United States
Show Abstract9:00 PM - D4.25
Composite Films of PLLA and PLLA/PEG Copolymer with Dual Surface Properties.
Bokyung Kim 1 , Jisook Lee 1 , Ick Chan Kwon 1 , Hesson Chung 1
1 , Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show Abstract9:00 PM - D4.26
Biocompatible Clay Langmuir Blogett Films
Jaseung Koo 1 , Tadanori Koga 1 , Mark Schlossman 2 , Aleksey Tikhonov 3 , Jonathan Sokolov 1 , Miriam Rafailovich 1
1 Materials Science, State University of New York at Stony Brook, Stony Brook, New York, United States, 2 , University of Illinois at Chicago, Chicago, Illinois, United States, 3 NSLS, BrookHaven National Laboratory, Upton, New York, United States
Show Abstract We have proposed the method for fabrication of biocompatible clay monolayer using Langmuir-Blogett (LB) technique. A sodium clay and surfactant modified clay LB films with a different hydrophobicity have been prepared. Surface pressure-molecular area (π-A) isotherm measurements, atomic force microscopy (AFM), X-ray reflectivity and grazing incident X-ray diffraction (GID) were used to characterize formation of the clay LB monolayers. The adsorption of the plasma protein, fibrinogen, on these two different clay monolayers has been studied first since protein adsorption event occurs well before cells approaches to the surface. The different conformational structures have been formed on the clay surfaces with varying hydrophobicity. On the sodium clay surface, individual fibrinogen molecules appear globular in shape while, on the orgno-clay surface, the trinodular structure is most commonly observed. This different conformational structure is ascribed to the different hydorphobicity of each domain of the fibrinogen. To investigate the cellular interaction with the clay surfaces, we prepared the clay LB monolayer on the poly(dimethylsiloxane) (PDMS) substrate with toxicity and the clay nanocomposites in that polymer gel matrix. The number of fibroblast cells in a reference area and the shape of the cells have been monitored by an optical microscope and a confocal microscope as a function of incubation time. On the bare PDMS surface, the cell is not confluent and count is also low whereas, on the clay surfaces, actin fibrils are clearly visible and cells proliferate normally regardless of the type of the clay, indicating that addition of clay remediate adverse effects of PDMS on cell appearance and growth.
9:00 PM - D4.27
Enhanced Cell Activity and Mechanical Property of Calcium Phosphate Coatings with Preferred Orientation.
Hyunbin Kim 1 , Renato Camata 2 , Kristin Hennessy 3 , Susan Bellis 3 , Sukbin Lee 4 , Gregory Rohrer 4 , Anthony Rollett 4 , Yogesh Vohra 2
1 Materials Science and Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States, 2 Physics, University of Alabama at Birmingham, Birmingham, Alabama, United States, 3 Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama, United States, 4 Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractOwing to the excellent biocompatibility and bioactivity, calcium phosphates offer great opportunity in various biomedical applications to bone repair, augmentation, and substitution, as well as gene therapy. Naturally occurring bioceramics such as calcium phosphates often exhibit preferred orientation resulting from highly specific biological processes. These textures affect the biological and biomechanical performance of hard tissues such as bone and tooth. Texturing has also been observed in synthetic calcium phosphates that are coated onto metallic implants in dentistry and orthopedics to improve implant integration with adjacent bone tissue. Recent studies have shown that the crystallographic texture of calcium phosphate-coated implants may significantly affect osseointegration. This suggests that calcium phosphates with surfaces exhibiting tailored crystallographic texture may enable a new level of control of processes such as cell adhesion, differentiation, and proliferation. In this study, we report how pulsed laser deposition can be used to produce calcium phosphate coatings with controlled crystallographic texture that may be relevant in controlling cell activity and mechanical property. The orientation distribution of crystalline grains in calcium phosphate coatings produced by pulsed laser deposition was investigated using an X-ray pole-figure diffractometer. Increased laser energy density of a KrF excimer laser in the 4–7 J/cm2 range leads to the formation of hydroxyapatite grains with the c-axis preferentially aligned perpendicular to the substrates. This preferred orientation is most pronounced when the plume direction of incidence is normal to the substrate. This crystallographic texture of hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Studies of cell adsorption using human Mesenchymal stem cells reveal that hydroxyapatite coatings with strong texture and random orientation show different cell adsorption behavior, which is consistent with the notion that proteins attach differently on different faces of hydroxyapatite crystals. The surfaces with an oriented distribution of hydroxyapatite grains promote significantly better cell adhesion than the surfaces with random grain distribution. Nanoindentation studies on hydroxyapatite coatings with strong texture and random orientation also show a difference in their mechanical properties. The hardness and Young's modulus of textured coatings are enhanced, compared to the ones of randomly oriented coatings.
9:00 PM - D4.28
Artificially Induced Ca2+ Flux in HCN-2 Neuronal Cells Using an Organic Electronic Ion Pump
Joakim Isaksson 1 , Peter Kjäll 2 , David Nilsson 3 , Nathaniel Robinson 1 , Magnus Berggren 1 , Agneta Richter-Dahlfors 2
1 Dept of Science and Technology, Linkopings Universitet, Norrkoping Sweden, 2 Microbiology and Tumor Biology Center, Karolinska Institutet, Stockholm Sweden, 3 , Acreo AB, Norrkoping Sweden
Show Abstract9:00 PM - D4.29
Characterization and Quantification of the Extracellular Matrix Deposited by Embryonic Hippocampal Neurons and Dorsal Root Ganglion Neurons in a Defined, Serum-free In Vitro Culture System.
Melissa Hirsch-Kuchma 1 , John Rumsey 1 , Megan Murphy 1 , Neelima Bhargava 1 , Mainak Das 1 , Mikhail Klimov 2 , Joseph Bielitzki 1 , James Hickman 1
1 Nanoscience Technology Center, University of Central Florida, Orlando, Florida, United States, 2 Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, Florida, United States
Show AbstractNeurons depend on interactions with the extracellular matrix (ECM) for growth and survival. We have studied the composition of the ECM proteins deposited by embryonic rat hippocampal and dorsal root ganglion (DRG) cultures on two different organosilane substrates, one cytophobic and one cytophilic. Our defined, serum-free culture system allows us to control many of variables in an in vitro model such as cell type, culture environment and surface composition. We have used immunocytochemistry and confocal laser microscopy to observe the deposition and composition of ECM proteins by cells in both cultures over time. Embryonic hippocampal neurons produce laminin and collagen and minimal amounts of fibronectin and vitronectin. These proteins associate closely with the soma and processes. The deposition of laminin, fibronectin, collagen and vitronectin is more extensive in the DRG culture and proximate to non-neuronal cells. Glial cells closely associate with the neurons to provide an ECM matrix for the neurons. We have quantified the amounts of different ECM proteins on the surface using Western blotting and secondary ion mass spectrometry (SIMS) techniques.
9:00 PM - D4.30
Scanning Force Microscopy and Fluorescent Microscopy of Microcontact Printed Antibodies and Antibody Fragments.
Quynh Chu-LaGraff 1 , John LaGraff 2
1 Biology, Union College, Schenectady, New York, United States, 2 Chemistry, Siena College, Loudonville, New York, United States
Show AbstractUnlabeled primary immunoglobulin G (IgG) antibodies and its F(ab’)2 and Fc fragments were attached to oxygen plasma cleaned glass substrates using either microcontact printing (MCP) or physical adsorption during bath application from dilute solutions. Fluorescently labeled secondary IgG’s were then bound to surface immobilized IgG and the relative surface coverage was determined by measuring fluorescent intensity. Results indicated that surface coverage of IgG increased with increasing protein solution concentration for both MCP and bath applied IgG and that a greater concentration of IgG was transferred to a glass substrate using MCP than during physisorption during bath applications. Scanning force microscopy (SFM) showed that patterned MCP IgG monolayers were 5 nm in height indicating that IgG molecules lie flat on the substrate. After incubation with a secondary IgG, the overall line thickness increased to around 15 nm indicating that the secondary IgG was in a more vertical orientation with respect to the substrate. Surface roughnesses of these MCP patterned IgG bilayers as measured by SFM were observed to increase with increasing surface coverage. Physisorption of IgG to both unmodified patterned polydimethylsiloxane (PDMS) stamps and plasma-cleaned glass substrates was modeled by Langmuir adsorption kinetics yielding IgG binding constants of KMCP = 1.7(2) x 107 M-1 and Kbath = 7.8(7) x 105 M-1, respectively. MCP experiments involving primary F(ab’)2 and Fc fragments incubated in fluorescently labeled fragment specific secondary IgG’s were carried out to test for function and orientation of IgG. Finally, possible origins of MCP stamping defects are discussed such as pits, pull-outs, droplets, and reverse protein transfer.
9:00 PM - D4.31
A Surface-Supported Bilayer Platform for Probing Membrane Protein Interactions.
Kalina Hristova 1
1 Materials Science, Johns Hopkins University, Baltimore, Maryland, United States
Show Abstract9:00 PM - D4.33
Engineered Self-Assembly of Cardiomyocytes into 3-Dimensional Muscular Thin Film Bio-composites.
Adam Feinberg 1 , Alex Feigel 2 , Sergey Shevkoplyas 2 , Sean Sheehy 1 , George Whitesides 2 , Kevin Parker 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Show AbstractWe have leveraged the linear motor and self-assembly capabilities of cardiomyocytes to build free-standing, muscular thin film (MTF) bio-composites that represent a new class of contractile hybrid materials. MTFs are formed by patterning extracellular matrix on polydimethylsiloxane (PDMS) thin films to direct the genetically programmed self-assembly of cardiomyocytes into an anisotropic, 2D myocardium. This results in a hierarchical ensemble of actin-myosin motor complexes spatially organized from 10-9 to 10-2 meters and synchronized by the excitation-contraction coupling inherent to cardiac tissue. The integrated PDMS film mechanically constrains the overall MTF shape and provides an elastic, restorative (antagonistic) force during diastole. Independent control of tissue microarchitecture, film shape, film curvature and external electrical pacing are used to control MTF 3D conformation, bending axes, peak systolic force, maximum strain and contraction kinetics. We demonstrate that MTF performance exceeds that of current artificial muscles due to the ability to (i) operate over a wide temporal range of 0.1 to 10 Hz via external electrical pacing, (ii) generate high forces and strains on par with natural muscle and (iii) operate in a biological environment and respond to biochemical signaling molecules. To establish key MTF capabilities, we have fabricated proof-of-concept actuators and devices capable of self-excitation, linear and rotational displacement, external control of tetanus and semi-autonomous movement. Further, we have used MTFs to model the fundamental spatial and temporal symmetry break required for directed mobility in uniped and anguilliform locomotion. In total, we show that MTFs have application as linear motors, soft robotic actuators, sensors, tissue engineering scaffolds and as a tool for studying organismal locomotion and cardiac biomechanics.
9:00 PM - D4.34
Preparation of novel three-dimensional protein-based porous hydrogels
Toshifumi Shiroya 1 , Tatsushi Isojima 1 , Hiroyuki Tanaka 1 , Minako Hanasaki 1 , Hisao Takeuchi 1 , Yasuo Ifuku 2
1 Functional Materials Laboratory , Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama Japan, 2 Research & Development , Mitsubishi Kagaku Iatron, Inc., Yachiyo Japan
Show AbstractWe prepared novel protein-based porous hydrogels on substrates using proteins and reactive polymers. The hydrogel was prepared by depositing a mixture of protein and reactive polymer on substrate followed by reaction between the protein and the reactive polymer with concentrating the mixture during drying process. The novel hydrogels were protein-based gels which consisted of proteins crosslinked by a small amount of reactive polymers. Atomic force microscopy measurement showed that these hydrogels had pores in the sub-micron range. We named these novel protein-based porous hydrogels as “three-dimensional nano-structured protein hydrogels (3-D NPHs)”. We confirmed by using surface plasmon resonance imaging technique that protein ligands immobilized in the 3-D NPHs were active and accessible to target protein molecules in solution efficiently. Also, since a small amount of reactive polymers was used to prepare the 3-D NPHs, nonspecific protein adsorption to the polymer molecules included in the 3-D NPHs was suppressed. Therefore, we could improve sensitivity to detect analyte proteins by using the 3-D NPHs. Furthermore, because of low nonspecific protein adsorption to the 3-D NPHs, the 3-D NPHs could be used to novel carriers for affinity purification of proteins. Synthesis, characterization and some applications of the 3-D NPHs will be presented in detail.
9:00 PM - D4.35
Silicones at the Ophthalmic Interface: Controlling Surface Roughness and (Bio)Chemistry
Michael Brook 1 2 , Heather Sheardown 2 , Lihua Liu 1 , Yang Chen 1 , Diana Morarescu 2
1 Chemistry, McMaster University, Hamilton , Ontario, Canada, 2 Chemical Engineering, McMaster University, Hamilton, Ontario, Canada
Show AbstractSilicone (PDMS) elastomers have excellent biomaterials properties except, in some cases, for their hydrophobicity which can lead to excessive protein adsorption: hydrophilic coatings can reduce the magnitude and change the nature of biofilms that form. The driving force for our research in this area is to control biofilm formation on ophthalmic silicone surfaces by manipulating surface roughness, chemo- and biofunctionality. Silicones, unlike most polymers, undergo (de)polymerization reactions under equilibrating conditions. We describe the use of this technique both to introduce new functionality and to change surface roughness on silicone elastomer surfaces, and also describe the in vitro response to these surfaces by corneal and lens epithelial cells. Standard silicone elastomers, prepared using a 2-part platinum cured system, were cut into small disks. These were exposed to either acid or base, optionally in the presence of a functional silicone. Both acid and base lead to increases in roughness, with more profound changes under basic conditions: the surfaces were less uniform and rougher. SiH functional surfaces could be modified by hydrosilylation with a variety of polymers including NHS-modified PEO [1]. A series of peptides, proteins, and polysaccharides were chemically grafted to the PEO tether simply by immersion of the surface in a buffered solution of the biomolecule. The original roughness of the surface was amplified during this process. The proliferation of corneal and lens cells on these surfaces was more dependent on the chemical nature and roughness of the surface. Thus, lens cells formed multilayers on tethered collagen/silicone surfaces; a confluent layer on the PDMS elastomer, but would not settle on poly(ethylene oxide) modified surfaces. This is a consequence of the surface polarity. Improved cellular adhesion to the surface could be induced by the use of RGDS and related adhesion peptides, or growth factors). The ability to control cellular growth on these functional silicone surfaces will be discussed.1. Chen, H., Brook, M. A., Sheardown, H. D., Chen, Y., Klenkler, B. Bioconj. Chem. 2006, 17, 21-28.
9:00 PM - D4.36
Preferential Immobilization of Biomolecules on Self-Assembled Monolayer Template
Takeo Miyake 1
1 , waseda.univ, Tokyo Japan
Show AbstractSelf-assembled monolayer (SAM) has been studied in the past as a template for preferential immobilization of proteins. The immobilization is commonly carried out as follows; (1) Patterning the SAM on the solid substrate by various lithography tools, and next (2) Immobilizing proteins on the SAM pattern. Recently, electron-beam (EB) lithography enables us to fabricate a sub-10nm pattern on CH3- and CF3-terminated SAM [1]. Because miniaturization of the pattern to single-protein size (sub-10nm) is possible by EB lithography, the SAMs are promising as templates for single-protein deposition. However both the CH3-groups and the CF3-groups induce nonspecific adsorption due to hydrophobic interaction between the SAM surface and the protein, preventing further miniaturization to less than 100 nm [2]. Therefore the terminal groups of SAMs utilized as EB resists should have high repellency to proteins. Here, we suggest preferential immobilization of biomolecule with OH-terminated SAM template using EB lithography. OH terminated SAM can be highly repellent to proteins. Since an OH-terminated silane coupling agent cannot be formed into a SAM due to its high activity, a precursor should initially be terminated with an inactive group during SAM formation and subsequently modified into an OH group.7-octenyltrimethoxysilane (OCS), which is terminated with a vinyl group, is deposited on the silicon dioxide surface by chemical vapor deposition (CVD). After immersion into boran-THF and NaOH, The vinyl groups of the OCS SAM are modified into OH-groups. The OCS SAM is patterned by EB lithography. Next, aminopropyltriethoxysilane (APTES) is deposited on the pattern region. Then the amino groups within the pattern are modified with biotin-(AC5)2-Osu. Finally, the fluorophore-labeled avidin is immobilized on the biotin. The fluorophore-labeled avidin bound to the biotin immobilized on the pattern is observed by fluorescent microscopy. In the presentation, we will report the condition in detail and the fluorescent signal to noise ratio.
9:00 PM - D4.37
Chemical Modification of the Substrate Surface for Uniform Lipid Bilayer Formation
Toshinari Isono 1 , Hanako Tanaka 1 , Toshio Ogino 1
1 , Yokohama National University, Yokohama Japan
Show Abstract Cell surfaces consist of a lipid bilayer and membrane proteins. The research on membrane proteins is important in application to biochips and biosensors. Artificial lipid bilayers are often used as a model system of the cells in in vitro studies of the fundamental properties of the membrane proteins. Lipid bilayers are formed by fusion and expansion of vesicles. In the formation process, hydrophilic and/or hydrophobic interactions between the vesicles and the substrate surface are essential. For the formation of uniform low-defect-density bilayers, the chemical state control plays an important role. We focused on the surface chemical states, in particular hydrophilicity and/or hydrophobicity. We also examined the effect of surface charge by modifying the surfaces with various self-assemble monolayers (SAMs).Lipid bilayers were formed by vesicle fusion method on the pre-oxidized Si surfaces. To examine the effect of the oxide formation process, the surfaces were oxidized chemically or thermally. The as-prepared SiO2 surfaces are hydrophilic. To make the SiO2 surfaces hydrophobic, octadecyltrichlorosilane (OTS) was deposited. To form cationic surfaces, the SiO2 surfaces were modified with 3-aminopropyltriethoxysilane (APTES). To form the anionic surfaces, the SiO2 surfaces were modified with 2-(carbomethoxy)ethyltrichlorosilane (CMETS) and then the CMETS-deposited surfaces were treated with HNO3 for carboxylation. These SAMs were deposited by the dipping method. The lipid bilayers were deposited on the oxidized surfaces and the chemically modified surfaces. The formed bilayer patterns were observed by a fluorescence microscopy in a buffer solution.No lipid bilayer formed on the hydrogen-terminated surface. Lipid bilayer islands, on the other hand, formed on the oxidized surfaces, and the island size is larger on the thermally oxidized surface than the chemically oxidized one.No lipid bilayer formed on the OTS surface whereas lipid bilayers formed on the APTES and the acid-treated CMETS surfaces. The effect of the surface charge, however, was found to be small. This may be because the phospholipid used in the experiments is neutral.The above results show that the hydrophilic surfaces are more suitable for the uniform lipid bilayer formation than the hydrophobic surfaces. The vesicles are hydrophilic and accompanied with the low-mobility water layer on their surfaces. Therefore, the vesicles can approach the hydrophilic substrate surface and expand. On the other hand, the water layer around the vesicles prevents the approach of the vesicles to the hydrophobic surfaces, resulting in no bilayer island.
9:00 PM - D4.38
Modified Self-assembled Monolayers for Biosensing on Waveguide Surfaces
Andrew Dattlebaum 1 , Aaron Anderson 2 , Jennifer Martinez 1 , Jurgen Schmidt 3 , W. Grace 2 , Karen Grace 4 , Basil Swanson 2
1 Center for Integrated Nanotechnologies, Los Alamos National Lab, Los Alamos, New Mexico, United States, 2 Chemistry Division, Los Alamos National Lab, Los Alamos, New Mexico, United States, 3 Bioscience Division, Los Alamos National Lab, Los Alamos, New Mexico, United States, 4 , Los Alamos National Lab, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - D4.39
Self-Assembled Artificial Protein Coatings With Distinct Biofunctionality
Stephen Fischer 1 , Xingyu Liu 2 , Hai-Quan Mao 2 3 , James Harden 4
1 Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 3 Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 4 Physics, University of Ottawa, Ottawa, Ontario, Canada
Show AbstractSubstrates with well-defined structural and biofunctional features are of great value in the biomaterials field. For applications in which cell response must be precisely controlled, the ability of a substrate to present ligands with controlled specificity, density, and distribution is a must. To help address this need, we are using recombinant DNA technology to generate artificial protein-based hydrogel surface coatings with a number of these desirable attributes. Our protein design is based on a modular, tri-block architecture in which the end blocks are leucine zipper peptides designed to associate exclusively into trimeric aggregates and the center block is a disordered and water-soluble polyelectrolyte peptide. Under physiological conditions of pH, temperature, and ionic strength, the proteins self-assemble into homogeneous hydrogels – the center block swells with water and the network is physically crosslinked through leucine zipper association. Utilizing recombinant DNA technology affords us the ability to modify these proteins in a targeted and specific manner. We have exploited this feature and embedded an array of extracellular matrix (ECM)-derived peptide sequences, including integrin and non-integrin binding domains as well as heparin binding sequences, into the center block of the proteins.In this work, we show that these hydrogels can self-assemble into a surface layer on substrates by simple protein adsorption and that these layers can be stabilized in cell culture media for extended periods of time. Additionally, we demonstrate that several of the embedded ECM-derived peptides are bioactive in the surface layer for cell types including human foreskin fibroblasts (HFFs), human umbilical vein endothelial cells (HUVECs), and adult rat neural stem cells (rNSCs). A major benefit of employing this surface coating technology for demanding cell culture applications is that the responses of numerous cell types to the surface layer are quite specific in nature. That is, a layer formed from proteins without an ECM-derived peptide insert is completely bio-inert. This allows for tight control over ligand density on the substrate by simple titration of the bioactive and non-bioactive proteins and for incorporation of multiple ligands serving different functions at predetermined concentrations. To highlight the latter feature, we show an example of a binary surface coating containing fibronectin- and laminin-derived ligands that appears to synergistically affect the adhesion, proliferation and phenotype maintenance of rNSCs.
9:00 PM - D4.4
Room Temperature Synthesis of Semiconductor, Metal, and Ferroelectric Nanoparticles Using Ring-shaped Peptide Assemblies as Nanoreactors.
Nuerxiati Nueraji 1 , Hiroshi Matsui 1
1 Department of Chemistry and Biochemistry, Hunter college and the Graduate Center, the City University of New York, New York, New York, United States
Show AbstractBiological and biomimetic systems have been widely studied in creating various shape and crystalline structure of nanomaterials of metals, semiconductors, ferroelectrics, etc. The synthesis of nanomaterials in controlled shape and crystalline structure is crucial for developing building blocks of nanodevices. With the low energy consumption and more efficient requirement for future devices, novel approach needs to exploit, such as biofunctionality, which regulates nanomaterial structure and shape. Here we report a novel material synthesis technique applying ring-structured biotemplates, assembled from synthetic peptides and inorganic precursors. The self-assembled nano-ring from this bolaamphiphilic peptide provides both biomimetic function and templates roles for new material synthesis. This biomimetic method not only produced monodisperse nanoparticles with controlled crystalline structure but also yields nanocrystals at room temperature, which are not grown at the same condition without the peptide ring templates. Various nanoparticles including BaTiO3, Ga2O3, Al2O3, SiO2, Ni, and Au were synthesized from their corresponding inorganic precursors. Among those materials, tetragonal BaTiO3 and monoclinic Ga2O3 cannot be grown at the room temperature without the peptide templates. The templating technique using the peptide nano-rings has an advantage over the conventional high temperature synthesis since the material synthesis at the ambient condition will reduce the production cost and the size of facilities. Moreover, the nanoscale ring template prevented the crystalline growth from thermal stress in the synthetic process. The biomimetic approach will be applicable as a new route for the novel nanomaterial synthesis.
9:00 PM - D4.40
Targeted Drug Delivery: Effects of Grafted Polyethylene Glycol on Ligand-Receptor Binding Under Flow.
Kelley Burridge 1 2 , Joyce Wong 1 2
1 Biomedical Engineering, Boston University, Boston, Massachusetts, United States, 2 Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts, United States
Show AbstractAlthough a polyethylene glycol (PEG) coating prolongs drug delivery carrier circulation time, steric hindrance from PEG also interferes with specific ligand-receptor interactions necessary for targeted binding. To improve the targeting efficiency of carriers we investigated the effects of PEGylation conditions on particle attachment under shear flow. Image analysis software automatically tracks the movement of receptor-coated beads over supported lipid bilayers containing physiologically-relevant (5 mol%) concentrations of liganded and unliganded PEGylated lipids. Our results demonstrate that the two most important surface composition parameters conferring stable attachment under flow are ligand accessibility and ligand concentration. Ligand accessibility depends on the relative molecular weights (MW) of liganded and unliganded PEGs. Unliganded PEG of MW 5000 (PEG5000) greatly reduces the accessibility of liganded PEG2000. Increasing the tether length from PEG2000 to PEG3350 has no significant effect on velocity before arrest, binding frequency, or arrest duration when used with unliganded PEG2000. A 5-fold drop in ligand concentration results in a 3-fold drop in binding frequency and a 30% drop in the number of terminal arrests. Brownian motion of beads increases the observed binding distance range beyond the maximum extended tether lengths (>85% of binding occurs within 100 nm of surface, >95% within 200 nm). In summary, we find that while ligand accessibility and concentration promote targeted binding under flow, particle dynamics set the binding distance range.
9:00 PM - D4.41
A Dynamical Light Scattering Study of Interactions of Oppositely Charged Proteins in Solution.
Perumal Ramasamy 1 , Gary Halada 1
1 Materials Science and Engineering Department, SUNY - Stony Brook , Stony Brook , New York, United States
Show Abstract9:00 PM - D4.42
Enzymatic Activity of Proteins Covalently Attached to Polymeric Nanoparticles.
Gary Thompson 1 , Brittney Zemp 1 , Erica Andreozzi 1 , Rohan Satishkumar 1 , Alexey Vertegel 1
1 Bioengineering, Clemson University, Clemson, South Carolina, United States
Show AbstractConjugation of functional enzymes to polymeric nanoparticles is a promising way for the design of novel nanodevices and therapeutic systems. In spite of the fact that much work has been done on protein binding to nanoparticles, no systematic study have been performed on how covalent attachment to nanoparticles affects activities and binding efficiencies for various enzymes. The enzymes included in this study were plasminogen, tissue plasminogen activator, uricase, glucose oxidase, phosphorylase kinase, glycogen phosphorylase, acid lipase, trypsin, lysozyme, horseradish peroxidase, and xanthine dehydrogenase. These were covalently attached via ~4kDa PEG tethers to two types of ~20 nm polystyrene latex nanoparticles, those with positively charged aliphatic amine surface groups and those with negatively charged chloromethyl groups. Bisbutyraldehyde-PEG tethers were used with aliphatic amine latex, and PEG tethers with one amine terminus and one carboxyl terminus were used with the chloromethyl latex. After PEGylation, Tween 20 was used to block any remaining surface groups and to prevent protein adsorption onto the nanoparticle surface. Butyraldehyde was reduced with sodium cyanoborohydride at pH 5.0 to bind the primary amino terminals of the enzymes. For chloromethyl latex, water soluble carbodiimide coupling was used to bind enzymes to the carboxyl ends of the PEG tethers. After centrifugations to separate nanoparticles and free protein in liquid supernatant, BCA assays were used to measure unbound and total protein concentrations, and binding efficiency curves were obtained. Enzyme functionality was assessed using activity assays. In general, binding efficiencies were similar among the enzymes, and chloromethyl latex had somewhat higher amounts of bound enzyme. Larger, more complex enzymes lost much or showed no detectable activity when attached to nanoparticles, in comparison to smaller enzymes.
9:00 PM - D4.43
Characterization of Structure of Synthetic Antimicrobial Peptide Anologue and Lipid Bilayer Complex.
Lanfang Li 1 , Gerard Wong 1
1 , Univ. of Illinois at Urbana Champaign, Urbana, Illinois, United States
Show Abstract9:00 PM - D4.44
First-principles Study of Adsorption Energetics of Alkanethiols on GaAs(001).
Oleksandr Voznyy 1 , Jan Dubowski 1
1 Department of Electrical and Computer Engineering, University of Sherbrooke, Sherbrooke, Quebec, Canada
Show AbstractSelf-assembled monolayers (SAMs) of organosulfur compounds on solid surfaces attract a lot of interest both from fundamental perspective and due to their potential applications among which are development of precursors for the growth of II-VI materials, creation of transition layers for ohmic contacts and Schottky diodes, surface passivation, nanolithography, electrochemical applications and biosensing. Theoretical modeling of the semiconductor-thiol interface can provide valuable information about the bonding nature in such material system and, ultimately, it would help to design and optimize a semiconductor-thiol interface addressing specific application. In contrast to alkanethiols on gold which are considered a prototype example of SAMs, theoretical studies of thiols on GaAs appear to be missing in the literature.The calculations have been performed using a density functional theory (DFT) in a periodic supercell approach, based on pseudopotentials and numerical localized atomic orbitals as basis sets, as implemented in the SIESTA code. Molecular dynamics simulations of thiol incoming to the surface with speeds corresponding to temperatures up to 1000 K show the impossibility of thiol chemisorption due to easy hydrogen rotation around S-C bond which complicates the S-H bond cleavage. Thus thiol chemisorption is believed to take place via physisorbed precursor, similar to that on gold. Simulations of physisorption state and thiols close packing have shown that GGA scheme can’t reproduce van der Waals attraction for alkanethiols while LDA reasonably reproduces intermolecular distances and slightly overestimates the binding energy. Physisorption energy is found to be 1.1 eV for 11-carbons chain which is much higher than expected chemisorption activation barrier and depends on the chain length nonlinearly due to the fact that (001) surface is not atomically flat. The geometry and energetics of the chemisorption state were investigated using PBE functional since it was found to reasonably reproduce the properties of bulk and surface GaAs as well as dissociation energies of different thiol molecules. The thiolate adsorption site, tilt angle and its direction are found to be dictated by high directionality of As dangling bond and unhybridized sulfur 3p orbital, and steric repulsion of the first CH2 unit from the surface. Calculated S-As and S-Ga binding energies of 2.1 eV and 2.8 eV respectively are bigger than 1.7 eV for thiols on gold and 2.03 eV for thiols on copper. However the desorption of thiol requires much less energy since the hydrogen which stays on the surface upon S-H bond cleavage participates in recombinative desorption with creation of molecular hydrogen, thiol and/or alkane, in qualitative agreement with available experimental results.
9:00 PM - D4.46
Biomimetic Approach to Drug Design: Poly-L-glutamic Acid Based Polyvalent Inhibitors of Anthrax Toxin.
Amit Joshi 1 , Arundhati Saraph 1 , Vincent Poon 2 , Jeremy Mogridge 2 , Ravi Kane 1
1 Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Pathobiology and Laboratory Medicine, University of Toronto, Toronto, Ontario, Canada
Show Abstract9:00 PM - D4.47
Nitrophenyl Layer Properties on Boron-doped Single Crystalline Diamond Characterized by AFM.
Hiroshi Uetsuka 1 2 , Dongchan Shin 1 2 , Norio Tokuda 1 , Christoph Nebel 1 2
1 Diamond Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 , New Energy and Industrial Technology development Organization (NEDO), Kawasaki Japan
Show AbstractModifications of diamond surfaces by organic molecules via covalent bonds have been gathering great attention because of its biocompatibility, chemical inertness and electrochemical properties. However, almost no direct observation of the modified surface has been reported by scanning probe microscopy. Nitro groups of nitrophenyl can be reduced to obtain amino groups which are used as linker for next attachments such as DNAs and proteins [1]. Therefore, well controlled periodical arranged single molecular layers of linker molecules are needed to develop high quality sensors. In the present study, atomic force microscopy (AFM) has been used to investigate the nitrophenyl attachment to single crystalline diamond.Boron-doped single crystalline diamond films grown homoepitaxially on Ib(100) diamond were used as substrates. Nitrophenyl groups were electrochemically attached to the hydrogen terminated substrates by reduction of 4-nitrobenzene diazonium tetrafluorobarate in dehydrated acetonitrile. For the first time, PicoPlus (Molecular Imaging) electrochemical system was used for AFM observation and surface treatment (scratching) with tapping mode and contact mode, respectively. Typical loading forces during scratching were calculated from force curve measurements for each cantilever. To attach nitrophenyl to diamond, the number of electrochemical cycles has been varied between 1 and 5 (scan rate 100mV/s). In addition, bonding has been applied where -0.2 V (vs. Ag/Ag+) has been applied for different durations (5 to 90 s). The AFM experiments reveal multi-layer formation, with thickness sensitively dependent on the attachment time. In all experiments, multi-layers are deposited which show different bonding forces. Most of the layer thickness can be removed by force typically in the range of 90 to 100 nN, leaving a monolayer of nitrophenyl, which needs removal force in the range of 200 nN. This layer is the covalently bonded nitrophenyl layer to diamond, which is covered by several layers of weakly bonded aryl-molecules. A detailed AFM investigation is presented taking into account removal forces to discuss the properties of the linker molecule layer, like molecule bonding, multi-layer formation, arrangement and molecule periodicity. The forces will be discussed taking into account covalent bonding, polymerization and formation of optimized aryl-layers to manufacture high quality bio-sensors on diamond.[1] D. Shin et al., Electrochem. Commun. 8 (2006) 844.
9:00 PM - D4.48
Fluorescent Microscopy of Adsorbed Fibrinogen on Nanocrystalline Diamond.
Jacob Garguilo 1 , Guilhem Ribeill 1 , John Sakon 1 , Keith Weninger 1 , Robert Nemanich 1
1 Physics, NCSU, Raleigh, North Carolina, United States
Show AbstractNanocrystalline diamond is a promising candidate for biosensor and biological applications due to its chemical inertness and the stability of electro or photochemically attached functional groups. This study focuses on the characterization of nonspecific adsorbed protein to nanocrystalline diamond surfaces through fluorescence microscopy. Fibrinogen protein adsorption, which largely dictates the haemostatic response, was used as a means of determining compatibility for a potential blood-contacting implant. Fluorescent dye-bound fibrinogen molecules were studied at three concentrations (10, 50 and 100 nM) on nanocrystalline diamond films as well as two biologically applicable surfaces (quartz and PEG). It was shown that single molecule fluorescence experiments can be performed on nanocrystalline diamond surfaces using epi-fluorescence techniques, indicating fluorescent quenching is not a significant factor in the measurements. The fibrinogen adsorption results indicate that nanocrystalline diamond minimally adsorbs protein - only slightly more than PEG and significantly less than quartz. These data suggest that the films may possess characteristics favorable as a substrate material for surface immobilized protein experiments and blood contacting devices.
9:00 PM - D4.49
Tailoring the Pyrolytic Graphite Edge `Plane' for Binding of an O2-Reducing Enzyme.
Rachel Heath 1 , Christopher Blanford 1 , Fraser Armstrong 1
1 Inorganic Chemistry, University of Oxford, Oxford United Kingdom
Show Abstract9:00 PM - D4.5
Magnetic Nanoparticle Protein Conjugates: Study of Magnetic Field Heating.
Joshua Alper 1 , Katherine Rahlin 2 , Marie-Eve Aubin-Tam 3 , Kimberly Hamad-Schifferli 1 3
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIt has been shown that the conformation of biological molecules can be controlled by an alternating magnetic field (Hamad-Schifferli, Nature, 2002) providing a nanoparticle is attached. By introducing a conjugated particle/biological molecule to a biological system and placing the system in an alternating magnetic field, the functionality of the bio molecule can be controlled externally. We present here a study to quantify the energy that is transferred from the nanoparticle to a protein upon nanoparticle heating. Bulk heating tests of 1-10nm Fe3O4 nanoparticles are performed where an alternating magnetic field is applied to highly concentrated solutions of the nanoparticles. The overall solution temperature is measured as a function of time, field strength and frequency for determination of the power output per particle. Fe3O4 nanoparticle-protein conjugates are synthesized where the size of the nanoparticle ranges from 1-10nm. Proteins studied include cytochrome c and ferritin. The effects of the alternating magnetic field on the protein structure are observed by circular dichroism, fluorescence and absorbance spectroscopies. These effects are then correlated to the power outputs of the nanoparticles to quantify the energy transfer.
9:00 PM - D4.50
Robust Attachment of Biomolecules to Encoded Metal Nanowires.
James Sioss 1 , Susan Patrick 2 , Gary Clawson 2 , Christine Keating 1
1 , Penn State University, University Park, Pennsylvania, United States, 2 , Hershey Medical Center, Hershey, Pennsylvania, United States
Show Abstract9:00 PM - D4.51
Characterization of Directly Immobilized Probe DNA and Hybridized with Target DNA on Partially Functionalized Diamond Surface.
Jung-Hoon Yang 1 2 3 , Kwang-Soup Song 1 2 3 , Shouma Kuga 1 , Hiroshi Kawarada 1 2 3
1 Nano science and engineering, Waseda university, Tokyo Japan, 2 Nanotechnology Research Center & Institute of Biomedical Engineering, Waseda University, Tokyo Japan, 3 Consolidated Research Institute for Advanced Science and Medical Care, Waseda University, Tokyo Japan
Show Abstract9:00 PM - D4.52
Biointerfacial Reactivity and Assembly of Gold Nanoparticles in the Presence of Amino Acids
Stephanie Lim 1 , Wui Ip 1 , Peter Njoki 1 , Chuan-Jian Zhong 1
1 Chemistry, State Univ. of New York at Binghamton, Binghamton, New York, United States
Show Abstract9:00 PM - D4.53
Matrix Assisted Pulsed Laser Evaporation-Direct Write of Tissue-Engineered Materials
Timothy Patz 1 , Anand Doraiswamy 2 , Roger Narayan 2 , Douglas Chrisey 3
1 , Starr-Edwards, Irvine, California, United States, 2 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 3 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show Abstract9:00 PM - D4.6
Delivery, Biocompatibility and Surface Chemistry of Polyamidoamine-Gold Nanocrystals for Live Cell Imaging.
Victor Lelyveld 1 , Kimberly Hamad-Schifferli 2 1
1 Biological Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractSub-nanometer metallic clusters have enormous potential for use in biological systems. Their unique quantum physical properties and biocompatible size scale could open the door to new imaging and manipulative possibilities. However, for such materials to be viable for use in labeling structures in intact cells, we must employ a surface chemistry at the inorganic-biological interface that is biocompatible, deliverable, and specifically-modifiable to target molecules of interest. In this work, we have examined the cellular uptake and biocompatibility of polyamidoamine-stabilized gold nanocrystals. We show that these nanocrystals can be delivered to live tissue culture cells without modifying their surface chemistry, in a mechanism that likely involves endocytosis. Furthermore, we have developed methods to covalently modify the dendrimer surface chemistry to display biologically-relevant targeting peptides for tracking subcellular localization in live cells.
9:00 PM - D4.7
Encapsulation of Fe3O4 and Au Nanoparticles in Thermosensitive Liposomes: Synthesis and Applications
Andy Wijaya 1 , Kimberly Hamad-Schifferli 2 3
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 3 Biological Engineering Division, MIT, Cambridge, Massachusetts, United States
Show AbstractThe synthesis of spherical thermosensitive liposomes has been well known for quite sometimes. Although a few attempts have successfully utilized this synthesis method to encapsulate nanoparticles, unfortunately these typically produce liposomes that encapsulate a very low yield of nanoparticles, and are largely non-uniform in shape. We refined the reverse-phase evaporation (REV) synthesis method to produce highly uniform spherical liposomes with diameters approximately 200nm, that encapsulate a high yield of nanoparticles. We investigated the applicability of this method to encapsulate a variety of magnetic and metallic nanoparticles such as Fe3O4 and Au. In addition, these liposomes encapsulating nanoparticles have interesting applications for controlled release of a molecule in biological applications. We present a preliminary study of these liposomes for control-release applications.
9:00 PM - D4.8
Charge-Directed Targeting of Antimicrobial Protein-Nanoparticle Conjugates.
Rohan Satishkumar 1 , Gary Thompson 1 , Alexey Vertegel 1
1 Bioengineering, Clemson University, Clemson, South Carolina, United States
Show AbstractIntrinsic properties of nanoparticles can be used to add functionality to their conjugates with biomolecules. Here, we show that nanoparticle charge can be used to enhance delivery of an antimicrobial enzyme, lysozyme, to bacteria.Hen egg lysozyme was covalently attached to two types of polystyrene latex nanoparticles: positively charged, containing aliphatic amine surface groups, and negatively charged, containing sulfate and chloromethyl surface groups. Covalent coupling was achieved by using water soluble carbodiimide chemistry in the case of aliphatic amine latex and direct reaction of protein amine groups with chloromethylated latex. Tween 20 was used to remove physically adsorbed enzyme. The amount of enzyme covalently attached to nanoparticles was quantified using fluorescently labeled lysozyme. In the case of bacterial degradation assay with Micrococcus lysodeikticus, activity of lysozyme attached to positively charged nanoparticles was higher than that of free lysozyme, whereas lysozyme attached to negatively charged nanoparticles showed no detectable activity. At the same time, when assayed using an oligosaccharide substrate, p-Nitrophenyl-penta-N-acetyl-β-chitopentaoside, lysozyme attached to both the positively and negatively charged nanoparticles showed similar activity to that of the free enzyme. Thus, nanoparticle charge is an important factor that can be used to control the properties of protein-nanoparticle conjugates. Bacterial cell walls are negatively charged due to the presence of carboxyl groups in the outer oligosaccharide chains. Lysozyme attached to negatively charged nanoparticles cannot be effectively delivered to its substrate due to Coulombic repulsion, while lysozyme conjugated to positively charged nanoparticles is targeted even more effectively than free lysozyme.
9:00 PM - D4.9
Biocompatible Polymeric Nanoparticles and Films Containing Hydrophobic Quantum Dots.
Jisook Lee 1 , Ick Chan Kwon 1 , Hesson Chung 1
1 Biomedical research center, KIST, Seoul Korea (the Republic of)
Show Abstract
Symposium Organizers
John A. Carlisle Advanced Diamond Technologies, Inc.
Martin Eickhoff Technische Universitaet Muenchen
Jose A. Garrido Technische Universitaet Muenchen
Janos Voeroes University and ETH Zurich
Erika Johnston Genzyme Corporation
D5: Surface Modification I
Session Chairs
Tuesday AM, November 28, 2006
Room 202 (Hynes)
9:30 AM - **D5.1
Charging and Structural Transitions of Cellulose and Collagen Layers.
Uwe Freudenberg 1 , Sven Holger Behrens 2 , Carsten Werner 1
1 Max Bergmann Center of Biomaterials, IPF , Dresden Germany, 2 , BASF AG, Ludwigshafen Germany
Show AbstractTwo fiber forming polymers ubiquitous in nature are collagen and cellulose. The interactions of these polymers and their assemblies with aqueous solutions are important not only for technical processes like tanning, papermaking, textile fabrication and washing, but essential for new applications in the life sciences and beyond. To unravel relations of electrical charging and structural changes in materials based on collagen or cellulose thin films of the plain polymers were developed for analytical studies in aqueous environments (1, 2). Swelling and electrical charging of these thin layers were investigated using electrokinetic measurements (3) and ellipsometry. Furthermore collagen samples were analyzed in detail with respect to conformation and thermal stability by circular dichroism and differential scanning calorimetry, respectively.Both collagen and cellulose strongly respond to changes of the environmental pH. The acid base behavior and the conformation of collagen I was furthermore found to significantly depend on the ionic strength in different electrolyte solutions. In contrast, the type of electrolyte but not the ionic strength influenced swelling and charge formation at cellulose layers.(1)Freudenberg, U., Zschoche, S., Simon, F., Janke, A. Schmidt, K., Behrens, S.-H., Auweter, H., Werner, C. Biomacromolecules 2005, 6, 1628-1634 (2)Salchert, K., Streller, U., Pompe, T., Herold, N., Grimmer, M., Werner,C. In vitro reconstitution of fibrillar collagen type I assemblies at reactive polymer surfaces, Biomacromolecules 2004 5, 1340-1350(3)Werner, C.; Körber, H.; Zimmermann, R.; Dukhin, S.; Jacobasch, H.-J. J. Colloid Interface Sci. 1998, 208, 329-346
10:15 AM - D5.3
Tailoring UV Photochemistry to Manage Polymer Surface Bioactivity
Zhengmao Zhu 1 , Dallas Hoover 2 , Michael Kelley 1 3
1 Applied Science, Coll. of William & Mary, Newport News, Virginia, United States, 2 Animal and Food Science, U. Delaware, Newark, Delaware, United States, 3 , Thomas Jefferson National Accelerator Facility, Newport News, Virginia, United States
Show AbstractThe continuing emergence of antibiotic-resistant, newly-virulent or entirely-new microbial strains is a cause of concern, especially in health care. Antimicrobial surfaces could block transmission by contact, provided they are effective, durable, versatile, affordable and environment-friendly. Our efforts to achieve them focus on surface-bound amine functionality. Computational modeling and measurement of absorption and action spectra points to promising opportunities for deep UV light to initiate surface radical chemistry. Polyamides respond by homogeneous transformation of amides to secondary amines [1,2]. Polyesters may be approached by using the surface radicals as graft sites [3]. XPS and ToF/SIMS provide mechanistic and process insight. Laboratory antimicrobial activity in shake flask testing may be compared to that of a molecular proxy, dibutylamine. We describe the results of a first-phase field test.[1.] J.D.Cohen, C.W.Erkenbrecher Jr., S.L.Haynie, M.J.Kelley, H.Kobsa, A.N.Roe, M.H.Scholla; U.S.Patent 5,428,078; June 27, 1995.[2.] Adrienne E. H. Shearer, James S. Paik, Dallas G. Hoover, Sharon L. Haynie, Michael J. Kelley; Biotechnol. Bioeng 67 (2000) 141-146.[3.] Zhengmao Zhu, Michael J. Kelley; Appl.Surf.Sci.252 (2005) 303-310.
10:45 AM - D5.5
Poly(2-methyl-2-oxazoline): A Novel Nonfouling Polymer.
Rupert Konradi 1 , Bidhari Pidhatika 1 , Marcus Textor 1
1 Dept. of Materials, LSST, ETH Zurich, Zurich Switzerland
Show AbstractSeveral hydrophilic polymers including poly(acryl amide), poly(hydroxyethyl methacrylate), poly(2-methacryloyloxyethyl phosphorylcholine) and polysaccharides have been used to impart anti-bioadhesive properties to (bio)materials surfaces.[1-4] However, in quantitative studies of protein adsorption, none of them has proven to be as successful as poly(ethylene glycol) (PEG). Accordingly, PEG is the by far most intensively studied polymer to equip surfaces with an antibiofouling coating.[1, 5]We are striving to better understand the molecular structural motifs required for protein-repellent polymers having properties that allow for the construction of protein-resistant surface adlayers that quantitatively equal those of PEG-based coatings. In the quest for such polymers we are investigating poly(2-methyl-2-oxazoline) (PMOXA). This polymer is uncharged, hydrophilic and has a backbone structure similar to that of PEG with a heteroatom (nitrogen) separated by an ethylene unit. Furthermore, since PMOXA essentially comprises of peptide bonds and not of ether linkages in the repetition unit we expect that PMOXA will allow to overcome the problems associated with the autoxidation of PEG such as the formation of hydroperoxides and oxidative degradation. The living character of the cationic ring-opening polymerization of oxazolines allows to readily prepare end-functionalized PMOXA-chains.[6] We have grafted carboxy-functional PMOXA to poly(L-lysine) to obtain graft-copolymers (PLL-g-PMOXA) with a structure very similar to that of the respective PEG analog (PLL-g-PEG). PLL-g-PEG sponateously adsorbs onto oppositely charged metal oxide surfaces and renders them highly protein-resistant.[7] The very similar architecture of the two copolymers for the first time allows us to carry out a systematic and detailed comparison of a nonfouling polymer to the ‘benchmark’ PEG. We use highly sensitive in situ techniques (optical waveguide lightmode spectroscopy OWLS and quarz crystal microbalance QCM) to study the adsorption of the copolymers and their interaction with full human serum as a function of the graft-copolymer architecture. A comparison of OWLS with QCM data allows us to estimate and compare the amount of hydration of the two polymers. We find that PLL-g-PMOXA prevents protein adhesion to the same extent as PLL-g-PEG and has a similar degree of hydration.[1]Kingshott, P.; Griesser, H. J. Curr. Op. Solid State Mater. Sci. 1999, 4, 403[2]McArthur, S. L.; McLean, K. M.; Kingshott, P.; St John, H. A. W.; Chatelier, R. C.; Griesser, H. J. Coll. Surf. B 2000, 17, 37[3]Kulik, E.; Ikada, Y. J. Biomed. Mater. Res. 1996, 30, 295[4]Feng, W.; Brash, J. L.; Zhu, S. Biomaterials 2006, 27, 847[5]Krsko, P.; Libera, M. Mater. Today 2005, 8, 36[6]Kobayashi, S.; Uyama, H. J. Polym. Sci. A 2001, 40, 192[7]Pasche, S.; De Paul, S. M.; Voeroes, J.; Spencer, N. D.; Textor, M. Langmuir 2003, 19, 9216
D6: Surface Modification II
Session Chairs
Tuesday PM, November 28, 2006
Room 202 (Hynes)
11:30 AM - **D6.1
From Non-specific to Specific to Biospecific Surface Modifications: A Precision Control of the Biointerface
Buddy Ratner 1
1 UWEB, University of Washington, Seattle, Washington, United States
Show AbstractSurface modification as a strategy for biomaterials design dates back at least to the early 1960's. Through most of this history, surface modifications were non-specific, often a distribution of functional groups induced by plasmas, corona discharge or chemical oxidation. More recently we have acheived the ability to create surfaces with accurate functionality though controlled organic plasma deposition and through self-assembly. Though these are accurately defined surfaces, they are still alien to biology. In this talk, the path from non-specific surfaces to specific surfaces to biospecific surfaces will be traced. Then, non-specific strategies to "prime the interface" will be combined with specific ideas to create highly biofunctional surfaces. Plasma treatments to create non-fouling surfaces and surfaces for specific bioimmobilization will be discussed. The pros and cons of direct immobilization of biomolecules to such surfaces will be considered. Finally, a new strategy in which a template biomolecule is immobilized and used to specifically delivery a biomolecule signal will be presented. Surface analysis methods such as electron spectroscopy for chemical analysis (ESCA) and static secondary ion mass spectrometry (SIMS) will be used extensively to monitor progress in the creation of these multilayer surfaces-immobilized structures.
12:00 PM - D6.2
The Role of Geometry and Surface Chemistry on the Stability of Supported Lipid Bilayers
Morgan Mager 1 , Nicholas Melosh 1
1 Materials Science, Stanford University, Stanford, California, United States
Show AbstractAssembly of lipid bilayers onto solid substrates has been critically important in the study of ion channels, lipid mechanics and many other aspects of cell membrane behavior. Early work focused on so called black lipid membranes that were painted onto apertures, usually in a Teflon sheet. More recently, experiments have been done involving suspended bilayers over micromachined apertures through silicon dioxide, silicon nitride, polyimide and other materials common to the semiconductor industry. Although these techniques have greatly advanced knowledge in the field, they all suffer from a chronic frailty. To date, researches have been unable to stabilize laterally supported bilayers for as long as free vesicles in solution. We present a systematic study of the role of substrate geometry and surface chemistry on the lifetime of these structures. Through the use of nanofabrication and surface functionalization, we can actively and independently control many of the factors affecting bilayer stability. The information thus gained will help guide the future development of drug delivery and biosensor systems built around biologically active thin membranes.
12:15 PM - D6.3
Atomic Layer Deposition on Biological Macromolecules: Metal Oxide Coating of Tobacco Mosaic Virus, Ferritin and DNA
Mato Knez 1 , Anan Kadri 2 , Christina Wege 2 , Ulrich Gösele 1 , Holger Jeske 2 , Kornelius Nielsch 1
1 , Max Planck Institute of Microstructure Physics, Halle Germany, 2 , University of Stuttgart, Stuttgart Germany
Show AbstractDecoration of nanoparticles with metals and semiconductors, in particular perfectly defined structures like biomolecules, gathered high attention in recent years. In most cases the natural environment for biomolecules is water. Therefore most of the approaches are performed in aqueous environment. However, some of those molecules can also be treated in a dry environment. In this work we show the application of atomic layer deposition (ALD) to biological macromolecules which are frequently used as nanoscaled templates. Our target molecules are the tobacco mosaic virus (TMV), Ferritin and DNA. In this way metal oxide nanotubes can be fabricated inside biological nanotubes (tubular viruses) as well as thin metal oxide films with embedded biological nanospheres (ferritin). The results show the potential of ALD for the decoration of biological macromolecules. On the one hand, as can be seen from the decoration experiments of TMV narrow pores and channels with less than 4 nm in diameter can be accessed by the precursors and nanotubes can be fabricated, on the other hand the metal oxide deposition of the ferritin molecules shows that ALD can easily be expanded to the fabrication of thin films of interconnected biomolecules and other temperature-sensitive nanoparticles. The chemical or physical properties of the biomolecules can be altered with the metal oxide coating. Detailed information about this work are published in Nano Letters 6, 1172 (2006).Three of the authors (M. Knez, U. Gösele and K. Nielsch) appreciate the financial support by the German Ministry of Science and Education, BMBF, via research contract FKZ 03N8701.
12:30 PM - D6.4
Photochemical Micro-pattern Substitution of Functional Groups for Protein Attachment Control.
Masataka Murahara 1 , Yuji Sato 1
1 Entropia Laser Initiative, Tokyo Institute of Technology, Meguro, Tokyo, Japan
Show AbstractHydrophilic and hydrophobic groups were selectively incorporated on the PMMA (polymethyl methacrylate) surface using Xe2 excimer lamp and ArF excimer laser; which allows controlling protein attachment. In our previous studies, both hydrophilic and hydrophobic groups were incorporated on the plastic surface by ultraviolet photon-induced photochemical reactions. As for fluorocarbon, PTFE (polytetrafluoroethylene) surface was modified into hydrophilic using H2O as a reaction solution. In this study, a PMMA surface with hydrophilic and hydrophobic micro-domains has been created by photochemical reactions in order to render it controllability of protein attachment. PMMA was first irradiated with an Xe2 excimer lamp in the presence of PFPE (perfluoropolyether) liquid layer to incorporate CF3 groups, and second, the PMMA surface was irradiated by an ArF excimer laser through a dot patterned reticle in the presence of water to incorporate OH groups. As a result, hydrophilic and hydrophobic micro-domains were alternately created on the sample surface. The contact angle of physiological salt solution on the sample surface was measured. While the contact angle on the untreated PMMA was 83 degrees, the contact angle on the hydrophobic sample increased to 99 degrees. On the sample surface with hydrophilic and hydrophobic micro-domains, the density of functional groups incorporated and the fibrin attachment by the size of functional groups were evaluated. The modified sample was soaked in 0.1% aqueous fibrin solution for 48 hours at 37°C and rinsed with water to measure the absorption coefficient (1650 cm-1) of the fibrin adsorbed by Fourier-transform infrared (ATR-FT-IR) spectroscopy. On the untreated PMMA, the absorption coefficient of amide band was 0.004 (arbitrary unit); on the modified sample with hydrophilic and hydrophobic micro-domains in the ratio of 1 to 3, 1 to 1, or 3 to 1, the absorption coefficient varied. With increase in hydrophilic proportion, both water contact angle and absorption coefficient of fibrin decreased. It was found that fibrin attachment depends on the ratio of the hydrophilic and hydrophobic groups. When the surface was modified to be hydrophilic and its contact angle became 44 degrees, the absorption coefficient of fibrin increased to 0.0055. In contrast, the absorption coefficient of the amide band remarkably decreased with increasing water contact angle and reduced to 0.003 when the angle reached 99 degrees. Furthermore, it was confirmed that the absorption coefficient decreased as the size of OH groups was narrowed from 250 to 20 μm. The fibrin attachment on the sample surface with micro-domains structure consisting of hydrophilic and hydrophobic groups at 20-μm intervals was reduced to 0.0002, which is one-twentieth of that on the untreated sample. The results suggest that with this new technique, protein attachment can be controlled.
12:45 PM - D6.5
Strong Resistance of Zwitterionic-Based Materials and Coatings for Biomedical and Engineering Applications.
Shaoyi Jiang 1 , Zheng Zhang 1 , Shengfu Chen 1
1 , U. of Washington, Seattle, Washington, United States
Show AbstractThis talk will cover two topics – (a) recent advances in the fundamental understanding of molecular-level nonfouling mechanism, (b) design of new nonfouling materials beyond PEG to resist nonspecific protein adsorption and bacterial adhesion/biofilm formation. Two main classes of nonfouling materials (i.e., PEG and zwitterionic-based polymers) will be compared. PEG and zwitterionic chains bind to water molecules via hydrogen bonding and ionic solvation, respectively. It is shown that hydration water is the key to surface resistance to nonspecific protein adsorption. PEG and zwitterionic-based materials effectively resist nonspecific protein adsorption when their surface densities are well controlled. Zwitterionic-based materials will be highlighted since they not only highly resist nonspecific protein adsorption (adsorbed proteins <0.3 ng/cm2), but also exhibit superior performance to inhibit bacterial adhesion/biofilm formation. For these studies, zwitterionic polymers are grafted either from a surface via the atom transfer radical polymerization (ATRP) method or to a surface via the physical adsorption of block copolymers containing zwitterionic and hydrophobic moieties. To improve the mechanical properties of a nonfouling material, interpenetrating polymer networks (IPNs) are prepared by the modification of a segmented polyurethane (SPU) with zwitterionic-based polymers.
D7: Functional Carbon Surfaces I
Session Chairs
Tuesday PM, November 28, 2006
Room 202 (Hynes)
2:30 PM - **D7.1
From Diamonds to Soot: Carbon as a Versatile Platform for Biomaterials Integration
Robert Hamers 1
1 Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractCarbon is a material with an amazing range of properties, ranging from the crystalline to amorphous, with electronic properties ranging from wide-bandgap semiconductor to metallic, and in bulk and nanostructured forms. The intrinsic chemical stability of carbon makes all these forms attractive platforms for biomaterials integration. The chemical functionalization of carbon-based materials can be used as a starting point for linking biomolecules to the surfaces, resulting in interfaces exhibiting extremely high stability and excellent selectivity. Most recent efforts have focused on photochemical functionalization using UV-initiated reactions between carbon surfaces and organic alkenes. This method is also attractive because using simple masking methods, photochemical functionalization can be used to directly photopattern the spatial distribution of binding sites on the surface on a few-micron length scale, while electrochemical methods can be used to functionalize specific surface regions down to sub-micron length scales. Although diamond provides many excellent properties, the high deposition and processing temperatures limit the ability to integrate it with many temperature-sensitive systems and materials. Recently we have found that amorphous carbon coatings can be provide similar chemical stability, facilitating the integration of ultra-stable bio-surface chemistry with temperature-sensitive materials such as piezoelectrics and microelectromechanical systems (MEMS). Thin films of amorphous carbon, covalently functionalized with DNA, exhibit chemical stability similar to that reported previously for diamond, as demonstrated by the ability to be repeatedly hybridized and denatured more than 25 times with no detectable change. We demonstrate the use of amorphous carbon as a protective coating for electromechanical resonator, leading to an resonator that, in initial experiments, is capable of detecting DNA hybridization in real time with a sensitivity of <3% of a monolayer, with excellent reversibility. In this talk I will discuss the successes and challenges of working with carbon-based materials for biomaterials integration.
3:00 PM - D7.2
Surface Wettability of Nanostructured Carbon Materials- From Superhydrophobicity to Superhydrophilicity
Xingcheng Xiao 1 , Brian Sheldon 1 , Janet Rankin 1 , Aihui Yan 1 , Robert Hurt 1 , Sirinrath Sirivisoot 1 , Thomas Webster 1 , Erkan Konca 1 , Orlando Auciello 2 , John Carlisle 2
1 Engineering Division, Brown University, Providence, Rhode Island, United States, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractNanostructured Carbon materials exhibit interesting physical, chemical, mechanical, tribological, and transport properties that are dictated by the many different bonding configurations available to carbon, which in turn gives rise to various nanoscale carbon forms, such as carbon nanotubes, nanofibers, nanowalls, nano-onions and nanocrystalline diamond coatings. Many of them have potential applications in biomedical devices, such as the hermetic coatings for bioimplants, platform materials for biosensors and drug delivery, and supercapacitors for energy storage. In these applications, the surface chemistry and morphology play a critical role in the material properties. A thorough understanding of the wetting behavior and how to control their hydrophobicity is of practical interest to the above mentioned applications. In this study, we will symmetrically compare the wetting behavior of three types of nanostructured carbon materials including carbon nanotubes, carbon nanowalls and nanocrystalline diamond coatings. By modifying the surface morphology (roughness, mimicking the lotus effect), and functionalizing the carbon surface through plasma treatment and wet chemistry, we were able to tailor the surface wetting behavior from superhydrophilic (~ 5 degrees) to superhydrophobic (~ 170 degrees). The synergic effect of surface morphology combining surface chemistry (varying surface energy) on the wetting behavior of carbon surfaces will be discussed. One example will be given to illustrate how the hydrophobicity influences cellular functions (including fibroblast and osteoblast) important for variouos biomedical implant applications on nanocrystalline diamond surfaces. The work at Argonne was supported by the US Department of Energy, BES-Materials Sciences, under Contract W-13-109-ENG-38
3:15 PM - D7.3
Engineered Carbon Surfaces for Enzymatic Bio-fuel Cells.
Christopher Blanford 1 , Rachel Heath 1 , Fraser Armstrong 1
1 , University of Oxford, Oxford United Kingdom
Show AbstractCarbon electrodes, in particular the pyrolytic graphite edge (PGE) ‘plane’, are known to adsorb a wide variety of redox-active proteins [1]. The numerous carbon-oxygen functional groups generated by abrasion with materials such as alumina or sandpaper are thought to contribute to surface stabilization through non-covalent and electrostatic interactions. We have investigated carbon electrode surfaces with a variety of analytical techniques including SEM, nitrogen adsorption, and fluorescence microscopy. The nature of the surface, on a microscopic level, is complex. A PGE surface, as conventionally polished for protein electrochemistry, shows numerous trenches and surface areas that are two to four orders of magnitude higher than the geometric surface area (i.e., the area one would measure with a ruler) [2].Most of this additional surface may be unproductive for enzyme adsorption, however, because the newly exposed surface arises primarily from basal planes which have a very low electron transfer rate, and because most of the trench-like pores that are exposed are too narrow for enzymes to enter.We are improving exposed surfaces of both pyrolytic graphite and novel, engineered forms of carbon through rational surface modification to make them more compatible with the enzyme, to ensure they are oriented for fast electron transfer and to improve the strength of the enzyme–surface interaction.[1] Hirst, J.; Armstrong, F.A. Anal. Chem., 1998, 70, 5062–5071.[2] Blanford, C.F.; Armstrong, F.A. J. Solid State Electr., in press.
3:30 PM - D7.4
Diamond Surfaces: A Novel Platform for Biosensors.
Jose Garrido 1 , Andreas Haertl 1 , Simon Lud 1 , Martin Stutzmann 1
1 Walter Schottky Institut, Technische Universitat Munchen, Garching Germany
Show AbstractDiamond exhibits several special properties, e.g. chemical stability, large electrochemical potential window, and excellent biocompatibility, which make it particularly suitable for biofunctionalization and biosensing. However, interfacing diamond surfaces with organic molecules and bio molecules is still a major challenge before the potential of diamond can be fully exploited in the field of biosensors. In addition, very little is known about the interface between diamond surfaces and aqueous electrolytes. In this contribution, we survey our recent work on the electrochemical characterization of modified C-H and C-O diamond surfaces in contact with aqueous electrolytes. Surface charging processes have been investigated as a function of electrolyte pH, ionic strength, and applied potential. Our results imply the presence of a negative surface potential resulting from a negatively charged diamond/electrolyte interface. The effect of screening and/or specific adsorption of electrolyte ions will be discussed.We will additionally present our work on the functionalization of diamond surfaces with bio/organic molecules for the development of diamond-based biochemical sensors. Different routes will be reported for the functionalization of diamond surfaces, depending on the surface termination and the type of diamond films. We will show how different proteins and enzymes can be immobilized on activated diamond surfaces and still maintain their enzymatic activity.
D8: Functional Carbon Surfaces II
Session Chairs
Orlando Auciello
Jose Garrido
Tuesday PM, November 28, 2006
Room 202 (Hynes)
4:30 PM - **D8.1
DLC Coatings in Medical Applications
Roland Hauert 1
1 Nanoscale Materials Science, EMPA, Dübendorf Switzerland
Show AbstractDLC has outstanding tribological properties and is, additionally, tolerated well by the body. Due to this advantageous combination of properties, research and development efforts have been made towards the use of DLC coatings in biomedical applications. It has been demonstrated that DLC coatings do not trigger any adverse effects on attached cells and that DLC can be considered to be biocompatible by in-vivo and also many in-vitro experiments. DLC surfaces also have an excellent haemocompatibility and DLC coated cardiovascular implants such as artificial heart valves, blood pumps and stents are already commercially available. The different studies presented demonstrate that DLC has the ability to reduce wear, more or less independently of the lubricant used, in load bearing implants when sliding against metals or against DLC. However, it seems that when DLC slides against UHMWPE in the presence of body fluids, the good tribological properties that DLC shows in air could not be obtained. The in-vitro experiments of DLC sliding against UHMWPE apparently showed different results, due to variations in experimental setups (ball-on-disk, hip or knee simulator, surface roughness) and especially the different liquids used as lubricants. In some medical applications such as guidewires, urinary tract catheters and orthodontic archwires, the in-vitro and in-vivo experiments on DLC coated parts showed an improved tribological performance. When implanting a DLC coated material, it has to be considered that the reaction layer at the DLC/substrate interface has to have a high chemical durability under in-vivo conditions to guarantee lifetime adhesion.
5:00 PM - D8.2
Antibacterial Silver-containing DLC and ta-C coatings: A Comparative Study.
Jose Endrino 1 2 , Matthew Allen 3 , Ramon Escobar Galindo 2 , Jose Albella 2 , Andre Anders 1
1 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 , Instituto de Ciencias de Materiales de Madrid, Madrid Spain, 3 , SUNY Upstate Medical University, Syracuse, New York, United States
Show AbstractHydrogenated diamond-like carbon (DLC) and (hydrogen-free) tetrahedral amorphous carbon (ta-C) coatings are known to be biocompatible and chemically inert. For these reasons, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into hydrogenated DLC coatings, obtaining DLC:Ag, synthesized by plasma based ion implantation using methane (CH4) plasma, while simultaneously depositing silver from a pulsed cathodic arc source. In addition, we have grown tetrahedral amorphous carbon – silver composite coatings, ta-C:Ag, using a dual-cathode pulsed cathodic-arc source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). For both DLC:Ag and ta-C:Ag coatings, the pulse frequency of the silver cathodic arc was adjusted in order to obtain samples with approximately equal silver content. The deposited films were characterized by X-ray diffraction and Raman spectroscopy. The bactericidal efficacy against cytotoxicity was evaluated for both DLC:Ag and and ta-C:Ag samples deposited on 24 well tissue culture plates.
5:15 PM - D8.3
Study of Ultrananocrystalline Diamond Films as Implantable Biomedical Devices: Assessment of their Biocompatibility to Cell Attachment and Growth
Bing Shi 1 , Qiaoling Jin 2 , Liaohai Chen 2 , Orlando Auciello 1 3
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Biosciences Division, Argonne National Laboratory, Argonne, Illinois, United States, 3 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract5:30 PM - D8.4
Large-Scale Carbon Nanotube Patterns for Directed Growth of Mesenchymal Stem Cells
Sung Young Park 1 , Kyu-Back Lee 2 , Yongdoo Park 2 , Seunghun Hong 1
1 Physics and NANO Systems Institute, Seoul National University, Seoul Korea (the Republic of), 2 Dept. of Biomedical Engineering, College of Medicine, Korea University, Seoul Korea (the Republic of)
Show AbstractMesenchymal stem cells (MSC) have been drawing a large attention because of their amazing capability of self-renewal and differentiations into various tissue lineages including osteoblasts, adipocytes, etc. A key issue in MSC-based biomedical applications is controlling their morphology and differentiation. Herein, we report a method to pattern carbon nanotubes (CNTs) over a large surface area for the directed-growth of MSCs. Significantly, we found that MSCs preferentially adhere to CNT patterns, and they even reform their shapes to fit in the pattern shapes. Furthermore, the long-term growth shows that CNT patterns do not have a harmful effect on the growth of MSCs in terms of cell growth morphology implying that CNT-based structures can be a good platform for the controlled growth of MSCs. As a proof-of–concept experiment, we fabricated the high-density array of CNT junctions and demonstrated the long-term growth of MSCs on the junctions. This result clearly shows that CNT-based surface structures have enormous potentials as a platform for basic research and biomedical applications using stem cells.
5:45 PM - D8.5
Mesoporous Carbide-derived Carbons with Porosity Tuned for Efficient Adsorption of Cytokines.
Gleb Yushin 1 , Elizabeth Hoffman 1 , Michel Barsoum 1 , Yury Gogotsi 1 , Carol Howell 2 , Susan Sandeman 2 , Gary Phillips 2 , Andrew Lloyd 2 , Sergey Mikhalovsky 2
1 Materials Science and Engineering, A.J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania, United States, 2 School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, Moulsecoomb, United Kingdom
Show Abstract
Symposium Organizers
John A. Carlisle Advanced Diamond Technologies, Inc.
Martin Eickhoff Technische Universitaet Muenchen
Jose A. Garrido Technische Universitaet Muenchen
Janos Voeroes University and ETH Zurich
Erika Johnston Genzyme Corporation
D9: Advances in Tissue Engineering
Session Chairs
Erika Johnston
Anne Meyer
Wednesday AM, November 29, 2006
Room 202 (Hynes)
9:30 AM - **D9.1
Membrane Solutions Enabling Channel Protein-based Sensing.
Noah Malmstadt 1 , Tae-Joon Jeon 1 , Jacob Schmidt 1
1 Bioengineering, UCLA, Los Angeles, California, United States
Show AbstractMembrane channel proteins play crucial roles in governing the transport of material and energy across every cellular membrane. Accordingly, they are the subjects of interest for science and medicine as well as major targets of drug discovery efforts. Recent work has also shown their potential as highly rapid and sensitive single molecule sensors. However, the membranes conventionally used to measure the electrical transport through these proteins can be problematic to form and are extremely fragile, limiting the range and scope of channel protein-based sensing as a technology. We have developed two new technologies which address these shortcomings: in situ encapsulation of lipid membranes in hydrogels and automated microfluidic formation. The hydrogel encapsulated membranes are created by conventionally forming a freestanding lipid bilayer membrane in the presence of a hydrogel precursor solution. This solution is then polymerized by a brief exposure to UV radiation. We show that these encapsulated membranes are more robust with respect vibration and pressure than their unencapsulated counterparts as a result of the intimate contact between the hydrogel and the membrane. Furthermore, creating membranes from cross-linkable lipids can conjugate the membrane directly to the hydrogel matrix, further strengthening the membrane and resulting in extended membrane lifetimes (>11 days). We show the maintained functionality of these membranes through the incorporation and measurement of single channel proteins in the membranes. The automated microfluidic formation apparatus enables the automated creation and manipulation of lipid membranes through a novel membrane formation process in a microfluidic channel. The microfluidic channels are molded in PDMS, and the solvent absorptive properties of this elastomer are used to mediate solvent extraction from a droplet of lipid-containing organic solvent. The lipid does not partition into the PDMS and is left behind, eventually forming a lipid bilayer membrane, into which we have also incorporated and measured single channel proteins. This process, and the incorporation and measurement of channel proteins in these membranes, is an entirely computer controlled process. This new method of membrane formation lends itself very readily to further miniaturization and in an array format. We will show the formation and measurement of these membranes and the proteins contained therein, as well as the development of an array-based device for automated high-throughput measurements of channel proteins. This has potential applications for drug discovery and screening as well as small molecule sensing.
10:00 AM - D9.2
Development of Multifunctional Photocurable Degradable Elastomers
Christiaan Nijst 1 , Jeffrey Karp 1 , Joost Bruggeman 1 , Lino Ferreira 1 , Andreas Zumbuehl 1 , Christopher Bettinger 1 , Robert Langer 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThere is considerable need and interest to develop tough biodegradable elastomers, which exhibit mechanical properties similar to that of soft tissue. We recently created a tough degradable elastomer, poly(glycerol sebacate) (PGS) which degrades via surface erosion, exhibits in vitro and in vivo biocompatibility, consists of inexpensive FDA approved building blocks (within certain products) and features functionalizable groups throughout the polymer matrix [1]. However, harsh conditions (>80°C, <5 Pa) and long reaction times (typically >24h) are required for its curing and thus limit the ability to polymerize directly in a tissue or to incorporate cells, drugs or growth factors that are temperature sensitive. Herein we demonstrate the ability to rapidly form complex structures from acrylated poly(glycerol sebacate) (PGSA) and poly(ethelene glycol) di-acrylate (PEG-DA) under ambient conditions. The mechanical and degradation properties and cell interaction of this new photocurable elastomer can be precisely controlled by varying the co-polymer ratios. 1 H-NMR and FTIR confirms acrylation of PGS polymer matrix, tensile tests showed control of Young’s modulus between 0.05 to 1.38 MPa, ultimate strength from 0.06 to 0.47 MPa and elongation at break between 42 and 189% strain. Copolymerization of the acrylated-PGS and PEG-DA results in a two fold increase in the Young’s modulus and ultimate strength, while maintaining its elongation at break. The acrylated PGS was used to manufacture nano/ microparticles, very thin walled tubes (0.20 mm wall thickness), micropatterned surfaces and porous scaffolds. The development of multifunctional photocurable degradable elastomers with precisely controlled material properties is an important step towards multiple medical applications.1Y. Wang, G. A. Ameer, B. J. Sheppard and R. Langer (2002). "A tough biodegradable elastomer." Nat Biotechnol 20(6): 602-6.2J. Yang, A. R. Webb and G. A. Ameer (2004). "Novel Citric-Acid Based Biodegradable elastomers for Tissue Engineering." Adv. Mater. 16(6): 511-516.
10:15 AM - D9.3
DNA Hydrogels
Soong Ho Um 1 , Nokyoung Park 1 , Dan Luo 1
1 Biological and Environmental Engineering, Cornell University, Ithaca, New York, United States
Show AbstractA hydrogel has been developed into a promising scaffold for cell encapsulation or drug delivery useful in various biorelated research areas. DNA, with its outstanding specificity and flexibility and intrinsic biocompatibility, has been utilized as a new building block in the construction of this new three dimensional material-a DNA based hydrogel. Here, we report the synthesis, properties and applications of a DNA based hydrogel system. The DNA hydrogels are entirely constructed from branched DNA building blocks such as X-shaped DNA (X-DNA), Y-shaped DNA (Y-DNA), and T-shaped DNA (T-DNA) through an enzyme-catalyzed reaction. These DNA hydrogels can be easily patterned into different sizes with millimeter or micrometer scale and different shapes including cylindrical, rectangular, cross, star, and even the "CORNELL" logo.By adjusting the initial concentrations and original shapes of the different building blocks, the external and internal morphology and chemical/physical properties of the DNA hydrogel were easily tuned: The X-DNA based hydrogel (X-DNA gel) showed both the most swelling degree and mechanical strength as well as the higher resistance to chemical and biological degradation. Inspired by these distinctive features of the DNA hydrogels, we have developed them into a drug delivery system, an artificial extracellular matrix, and even a cell-free protein producing template.
10:30 AM - D9.4
Synthetic ECM Differentially Modulates the Growth of Stem Cells and Preosteoblasts.
Susan Hsiong 1 2 , Paolo Carampin 1 , Hyun-Joon Kong 1 , David Mooney 1
1 DEAS, Harvard University, Cambridge, Massachusetts, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractIt is well known that the presentation of RGD (arginine-glycine-aspartic acid) peptide sequences, common cell attachment sites present in many extracellular matrices, and the elastic modulus of the substrate presenting these peptides regulate the phenotype of differentiated cells. However, it is unclear how stem cells are regulated by the substrate cues. This study examined how nanoscale RGD ligand organization and substrate stiffness regulates stem cell (D1 cell line; clonally derived from mouse bone marrow) and murine preosteoblast (MC3T3-E1) proliferation using RGD modified alginate hydrogels as a model system. To control the of RGD ligand presentation in our system, RGD modified alginate polymer chains were mixed in various ratios with unmodified polymer chains. The number of RGD ligands per island (2 – 40) as well as the spacing between RGD islands (36 – 121 nm) was varied while maintaining constant overall bulk density of the peptide (6.25 or 12.5 mg RGD/g alginate). The elastic modulus of the alginate substrate (20 – 110 kPa) was controlled by the extent of ionic cross-linking. Although both MC3T3 preosteoblast and D1 stem cell growth rates were enhanced at lower RGD island spacing, the preosteoblasts were twice as responsive to differences in RGD island spacing as the stem cells. Furthermore, increasing substrate stiffness (at a constant RGD presentation) promoted preosteoblast proliferation, whereas it minimally influenced stem cell proliferation. However, when D1 cells were pre-differentiated toward the osteoblast phenotype, the cells subsequently responded to RGD island spacing and gel stiffness in a similar manner as the osteoblasts. These results demonstrate that the cell response to nanoscale organization of RGD ligands and substrate stiffness is dependent on the stage of cell commitment or differentiation, and these findings can aid in the design of biomaterials for cell-based therapies.
10:45 AM - D9.5
Biochemical Surface Modifications of Collagen-GAG Membranes Direct Keratinocyte Function.
Katie Bush 1 2 , Brett Downing 1 2 , Ernesto Soto 3 , W. McGimpsey 3 , Mehmet Toner 4 5 6 , George Pins 1
1 Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts, United States, 2 Graduate School of Biomedical Sciences, University of Massachusetts, Worcester, Massachusetts, United States, 3 Chemistry & Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, United States, 4 Center for Engineering in Medicine/Surgical Services, Massachusetts General Hospital, Boston, Massachusetts, United States, 5 , Shriners Burns Hospital, Boston, Massachusetts, United States, 6 , Harvard Medical School, Boston, Massachusetts, United States
Show AbstractBioengineered skin substitutes offer an advanced wound therapy to patients suffering from severe burns and chronic ulcers. Despite favorable results with these analogs, there is still a need to improve the rate at which autologous keratinocytes attach, populate, and epithelialize the surface of the biomaterial scaffold, as well as to improve the integration of the analog with the surrounding environment. Optimizing current design strategies requires an understanding of the underlying mechanisms by which three-dimensional microarchitecture and biochemical composition of tissue scaffolds can modulate keratinocyte function and enhance the rate of epidermal regeneration. We developed methods to create collagen-glycosaminoglycan (GAG) membranes or basal lamina analogs with precise topographical features that provide interfaces to facilitate the formation of robust epidermal layers on the surfaces of dermal analogs. In the present study, we explore methodologies to further enhance the functionality of these membranes by modifying the surface biochemistry in order to provide cell-signaling cues to direct keratinocyte functions. Specifically, we used a multi-scale approach to tailor the surfaces of the collagen-GAG membranes with biochemistries that are found at the dermal-epidermal junction. A high throughput screening device was developed by our laboratory to establish a quantitative link between keratinocyte attachment and extracellular matrix proteins coupled to collagen-GAG membranes at the cellular level. Using this model system we found that keratinocyte attachment is enhanced proportionally with the number of active fibronectin binding sites on the membrane surfaces. To further analyze keratinocyte binding interactions with fibronectin at the sub-cellular level, we developed a series of self-assembled monolayers that control protein confirmation and spatial location. Preliminary results indicate that keratinocyte morphology and attachment can be modulated by these surfaces. Our future studies will further analyze keratinocyte proliferation, differentiation, and protein deposition as a function of biochemical composition using these two separate model systems. Ultimately, the results of these studies will be used to identify parameters to enhance the surface biochemistry of microtextured collagen membranes that will improve the performance of bioengineered skin substitutes.
11:30 AM - **D9.6
Matrix Manipulation of Growth Factor Signaling to Enhance Regenerative Cell Behaviors.
Linda Griffith 1
1 Professor of Biological Engineering and Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract12:00 PM - D9.7
Preparation of Hydroxyapatite Sheet with Various Shapes and its Application to Programmable Tissue Engineering Scaffold.
Hiroaki Nishikawa 1 2 3 , Ryouta Hatanaka 1 2 , Masanobu Kusunoki 1 2 3 , Shigeki Hontsu 1 2 3
1 , B.O.S.T., Kinki Univ., Kinokawa, Wakayama, Japan, 2 , CREST-JST, Tokyo Japan, 3 , Wakayama Pref. C.R.E.A.T.E. of the JST, Wakayama Japan
Show Abstract12:15 PM - D9.8
Synthesis of a Novel Electrically Conducting, Biocompatible, Biodegradable Polymer for Biomedical Applications.
Nathalie Guimard 1 , Jonathan Sessler 1 , Christine Schmidt 2
1 Chemistry, University of Texas at Austin, Austin, Texas, United States, 2 Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractUpon the discovery of the first conducting polymer in 1976, the replacement of metal-based semiconductors in many applications with conducting polymers was inevitable. Perhaps more surprisingly these materials showed promise in many biomedical applications. The finding that electrical fields and charges modulate shape, size, and proliferation of a number of cell types including nerve and bone, has prompted biomedical engineers to focus on the development of conducting polymer scaffolds for tissue regeneration and neural probes. A number of polymers have been studied for these applications, including polypyrrole (PPy), polythiophene, and polyaniline. One serious limitation to the use of conducting polymers in biological systems is their inability to degrade. Therefore, it has been proposed to design and synthesize a biocompatible, biodegradable, semiconducting polymer, which could broaden the scope of applications for conducting polymers. For instance, these unique polymers could potentially be implemented in temporary tissue and neural scaffolds, drug delivery, short-term electrodes, and tethers between nanotubes.Therefore, the goal of this investigation is to synthesize a polymer that is degradable, while maintaining conductivity. Initially, the incorporation of pyrrole oligomers into a biodegradable polymer was attempted; however, to overcome difficulties associated with the instability of these oligopyrroles, a novel polymer design has been proposed which incorporates thiophene oligomers. Oligothiophenes (OTs) are apt to be more conductive than oligopyrroles due to a smaller band gap between the valence and conductance bands. Additionally, OTs share many of the advantageous properties of oligopyrroles, including cell compatibility, but are more stable. The proposed novel co-polymer consists of quaterthiophene oligomers tethered together by aliphatic ester linkages, which would potentially render the co-polymer conductive by means of inter and intra chain oligo overlap and degradable via cleavage of the ester bond by esterases in the body. The synthesis of the novel copolymer, poly-dialcohol dimethyl quaterthiophene-co-adipic acid (PAMQAA) has been completed successfully and corroborated by NMR and MALDI. Initial characterization indicates PAMQAA has the following properties: Mw = 11,240-64,080 Da, PI = 1.2-1.4, and degradation temperature = ~160°C. Currently PAMQAA is being characterized to assess its Tg, Tm, conductivity, degradability, and biocompatability. Polymer modifications could allow further optimization of properties, such as the rate of degradation and conductivity, to target better the application of interest.
12:30 PM - D9.9
Three-dimensional Control of Biospecificity via Two-photon Engineered Polymer Scaffolds
Prakriti Tayalia 1 , Tommaso Baldacchini 1 , Cleber Mendonca 1 3 , David Mooney 1 , Eric Mazur 1 2
1 Division of Engineering & Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil, 2 Department of Physics, Harvard University, Cambridge, Massachusetts, United States
Show AbstractIn tissue engineering, control of ligand-receptor-mediated interaction between cell and material is an underlying principle for designing biomaterials. Microfabrication techniques such as soft lithography have enabled researchers to study cell behavior extensively in two dimensions (2D) by controlling the spatial distribution of ligands on a micrometer and sub-micrometer scale. However, lack of an appropriate three-dimensional (3D) microfabrication technique with micrometer resolution has prevented from presenting cell adhesion ligands in an organized fashion in 3D. Thus, fabricating such a spatially selective 3D matrix that mimics the extracellular environment more than a 2D flat substrate is important to do a systematic study of various cell phenomena like cell spreading, adhesion, migration and proliferation.We fabricate three-dimensional polymer scaffolds by two-photon absorption (2PA) polymerization in an acrylic based resin caused by a tightly focused femtosecond laser beam. Upon simultaneous absorption of two photons by the photoinitiator, the resin undergoes a phase change from liquid to solid. Since this non-linear absorption is confined to the focal volume, three-dimensional microstructures can be fabricated by scanning the laser beam in the resin with a desired pattern.The resin used for 2PA polymerization consists of two triacrylate monomers and an acyl phosphine oxide photoinitiator. The latter absorbs two photons in the infrared and efficiently induces free radical polymerization process at the focal point. We use host-guest chemistry to functionalize resin with peptides, whose sequence can be varied to have specific interaction with cells. The triacrylate monomer is blended with a polypeptide containing an amino acid sequence of arginine-glycine-aspartate, which is known to promote cell adhesion. Microstructures with and without peptide are then made by 2PA polymerization. The adhesion of NIH-3T3 fibroblast cells on peptide treated and untreated structures, is investigated for spatial selectivity in three-dimensions using confocal microscopy.The use of two-photon absorption polymerization to fabricate peptide-functionalized microstructures opens the doors to new opportunities for investigation of cell migration in three dimensions.
12:45 PM - D9.10
Novel Microfabrication Methods and Materials for Producing 3D Physically and Chemically Structured Polymeric Tissue Engineering Scaffolds
Benita Comeau 1 , Clifford Henderson 1
1 School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe overall goal of this work is to develop new methods and materials for the fabrication of hierarchically structured, 3D tissue scaffolds. Conventional scaffolds commonly lack substantial strength, and there is difficulty in controlling porosity, pore distribution, and pore interconnectivity. Additionally, the chemical nature of these scaffolds is typically homogenous; as there is no mechanism for creating additional chemical functionality, distinct from the bulk chemistry, in a specified geometry on the scaffold. The ability to chemically modify selected regions is one way to direct cell growth in deliberate patterns. The aim of this work is to address these issues through the application of stereolithography (SL) to the fabrication of hierarchically structured tissue engineering scaffolds. One prevalent tissue engineering approach is to create a 3D scaffold, seed it with the appropriate cells and signaling cues, allow the cells to grow and differentiate, and finally implant this engineered tissue into a patient. The scaffold must support many functions such as providing mechanical support and structure, facilitating nutrient and waste transport, and supplying physical and chemical cues to the growing cells. One focus of our work is to adapt SL to produce a method that allows for the direct fabrication of physically complex and chemically structured scaffolds using a single process. The goal of this work is to develop mixtures of biocompatible monomers and photoinitiators that can be used in conjunction with SL tools to create 3D polymeric scaffolds. Furthermore, beyond the use of SL to control the physical structure of a polymer object or scaffold, this work is directed at developing strategies for using SL methods to also control the local chemical composition of the polymer scaffold surface. To that end, biocompatible monomers containing hydroxyl groups that are reactively capped with a “protecting” group (e.g. t-butoxycarbonyl group) that can be selectively removed in desired areas using exposure to light in the SL tool. This de-protection chemistry is analogous to the strategy employed for making the “chemically amplified photoresists” (CARs) that are used in microlithography processes for semiconductor fabrication. Addition of a photoacid generator (PAG) to a protected monomer material permits local control of the polymer surface chemistry using a photoinitiated catalytic deprotection process that changes the local hydrophilicity of the polymer. This presentation provides an update of the work including demonstration of the ability to direct cell growth on the photopolymerized scaffolds, cell growth studies on the engineered materials, and discussion of the impact of plating conditions on cell patterning performance in such systems. Resin compositions are prepared and evaluated for biocompatibility, degradation rate, and capability for use in an SL apparatus.
D10: Bone and Biomineral Interfaces
Session Chairs
Erika Johnston
Jacob Schmidt
Wednesday PM, November 29, 2006
Room 202 (Hynes)
2:30 PM - **D10.1
Aspects of Biosurface Friction and Lubrication
Anne Meyer 1
1 Industry/University Center for Biosurfaces, University at Buffalo, Buffalo, New York, United States
Show AbstractIt would be a strange world, indeed, if all biological surfaces exhibited minimal coefficients of friction. Yet, reliable approaches for long-term reduction of friction are needed for many clinical applications. For instance, Sjogren’s Syndrome patients suffer from both chronic “dry mouth” and “dry eye” conditions. Another example: friction and wear characteristics of load-bearing joint surfaces, as well as the orthopedic implants that replace diseased joints, are paramount to mobility and overall health. Numerous published reports of clinical observations and in-vitro studies of “particle disease” resulting from material wear provide another testament to the need for advanced materials and improved understanding of the tribological aspects of biological surfaces and materials used for their restoration. Several decades ago, a direct correlation between critical surface tension (CST) and coefficient of friction of dry, synthetic materials was demonstrated. Can this correlation be applied to materials underwater, biological tissues, and/or biological lubricants? Comprehensive contact angle measurements made in our laboratories demonstrate that interfacial properties of healthy, load-bearing low-friction tissues (e.g. articular cartilage) differ from surfaces of non-load-bearing tissues that are minimally adhesive (e.g. cornea, oral mucosa). CSTs of such non-load-bearing tissues are in a bioabhesive zone defined as the low- to mid-20’s mN/m, in agreement with the correlation between low CST and low coefficient of friction. On the other hand, the CST of healthy articular cartilage is in the high-20’s to low 30’s mN/m; medium CST, but still of low coefficient of friction. The performance of low-load, low-friction tissues often is attributed to retention of water at interfaces, and much effort has been expended to ensure hydration of the surfaces of some implant materials. High-load metallic and ceramic couples, like their articular cartilage counterparts, must remain free of cellular encroachment and adhesion in the body. Reduced bioadhesion could be explained by mechanical disruption of cells and tissues, lubrication by highly hydroxylated fluids, and/or remodeling of proteinaceous conditioning films in the mechanical joint to present a less adhesive, lower friction interface. Regarding the potential for dynamic remodeling of proteinaceous films, our early in-vitro studies of the effects of fluid shear on conditioning film formation indicated that seawater and saliva conditioning films formed during high shear flow over medium- to high-energy materials had lower CSTs than conditioning films formed under moderate shear conditions. More recent experiments demonstrated a similar phenomenon when protein solutions were sheared between metal substrata in a friction device. Work in progress will determine whether these changes result from different film compositions, proteinaceous breakdown, and/or tribochemical interactions with the contacting substrata.
3:00 PM - D10.2
Hydroxyapatite-peptide Based Composite Hydrogels for Bone Regeneration.
Hassna Ramay 1 2 , Darrin Pochan 1 2 , Joel Schneider 3
1 Materials Science and Engineering, University of Delaware, Newark, Delaware, United States, 2 Delaware Biotechnology Institute, University of Delaware, Newark, Delaware, United States, 3 Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States
Show Abstract3:15 PM - D10.3
Polymer/Ceramic Nanocomposite Tissue Engineering Scaffolds for More Effective Orthopedic Applications.
Huinan Liu 1 , Thomas Webster 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractThe life time of current metallic orthopedic implants is only 10-15 years, which indicates that several painful and expensive revision surgeries are required for younger patients who receive bone fixation devices. Therefore, better bone substitutes are exceedingly in high demand considering that an estimated 1.5 million individuals in the United States annually suffer a bone fracture caused by some form of bone disease and/or bone injury. The common reasons for the failure of current bone substitutes are: (i) lack of osseointegration (that is, insufficient juxtaposed bone growth on implant surfaces) and (ii) stress shielding caused by mismatched mechanical properties between implanted materials and natural bone tissue which leads to tissue necrosis around implants and clinical failure. One approach to solve current problems associated with today’s implants is to integrate nanotechnology to closely mimic natural bone in terms of its chemistry, nanostructure and associated properties.Polymer/ceramic nanocomposites simulate bone much closer in terms of its nanostructure and associated properties thus offer a promising opportunity for bone regeneration in a natural way. Previous studies demonstrated improved osteoblast (bone-forming cell) adhesion and long-term functions (such as alkaline phosphatase activity and calcium-containing mineral deposition) on the nanometer scale surface roughness provided by well-dispersed titania nanoparticles in poly-lactic-co-glycolic acid (PLGA). For example, the composites with the closest surface roughness to natural bone at the nano-scale promoted bone cell adhesion and calcium deposition by osteoblasts the most. The current studies are focusing on further mimicking bone by building three-dimensional structures from polymer/ceramic nanocomposites using novel aerosol based 3D printing technique, one type of rapid prototyping technique, because, similarly, natural bone assembles its three-dimensional hierarchical architecture from nanostructured building blocks. Using this technique, bone fracture data acquired by computed tomography (CT) can be transferred into CAD models and used to direct the fabrication of versatile bone substitutes. Osteoblast adhesion tests were conducted on the 3D PLGA/titania nanocomposite scaffolds created by this technique and the results demonstrated that these 3D scaffolds further promoted osteoblast infiltration into porous structures compared to previous nanostructured surfaces. In conclusion, so far, results of these studies have evaluated a promising new orthopedic nanocomposite and a means of fabricating a macro structure from such nanomaterials that can mimic properties of natural bone, thus, providing a new material and approach for more effective orthopedic applications.
3:30 PM - D10.4
Bone Formation Mediated by Growth Factors Embedded in a Polyelectrolyte Multilayer Film.
Erell Le guen 1 , Andree Dierich 2 , Pierre Schaaf 3 , Jean-Claude Voegel 1 , Nadia Jessel 1
1 UMR 595, Biomaterials, INSERM, Strasbourg France, 2 IGBMC, ICS, CNRS/ULP, Strasbourg France, 3 Institut Charles Sadron, CNRS/ULP, Strasbourg France
Show AbstractIn recent years, considerable effort has been devoted to the design and controlled fabrication of structured materials with functional properties. The layer by layer buildup of polyelectrolyte multilayer films (PEM films) from oppositely charged polyelectrolytes1 offers new opportunities for the preparation of functionalized biomaterial coatings. This technique allows the preparation of supramolecular nano-architectures exhibiting specific properties in terms of control of cell activation and may also play a role in the development of local drug delivery systems. Peptides, proteins or DNA, chemically bound to polyelectrolytes, adsorbed or embedded in PEM films, have been shown to retain their biological activities(2-7). Recently, tissue engineering has merged with stem cell technology with interest to develop new sources of transplantable material for injury or disease treatment. Eminently interesting, are bone and joint injuries disorders because of the low self-regenerating capacity of the matrix secreting cells. We present here for the first time that embedded BMP-2 and TGFβ1 in a multilayered polyelectrolyte film can drive embryonic stem cells to the cartilage or bone differentiation depending on supplementary co-factors. We selected a model system made from layer by layer poly-L-glutamic acid (PLGA) and poly-L-lysine succinylated (PLLs) films into which BMP-2 and TGFβ1 have been embedded. Our results demonstrate clearly that we are able to induce osteogenesis in embryonic stem cells mediated by growth factors embedded in a polyelectrolyte multilayer film.References1. Decher, G. Fuzzy nanoassemblies: Toward layered polymeric multicomposites. Science 277, 1232-1237 (1997)2. Jessel, N. et al. Bioactive coatings based on a polyelectrolyte multilayer architecture functionalized by embedded proteins. Adv. Mater. 15, 692-695 (2003)3. Jessel, N. et al. Build-up of polypeptide multilayer coatings with anti-inflammatory properties based on the embedding of piroxicam-cyclodextrin complexes. Adv. Funct. Mater. 14, 174-182 (2004)4. Jessel, N. et al. Pyridylamino-beta-cyclodextrin as a molecular chaperone for lipopolysaccharide embedded in a multilayered polyelectrolyte architecture. Adv. Funct. Mater. 14, 963-969 (2004)5. Jessel, N. et al. Control of monocyte morphology on and response to model surfaces for implants equipped with anti-inflammatory agents. Adv. Mater. 16, 1507-1511 (2004)6. Jessel, N. et al. Short-time tuning of the biological activity of functionalized polyelectrolyte. Adv. Funct. Mater. 15, 648-654 (2005)7. Jessel, N. et al. Multiple and time scheduled in situ DNA delivery mediated by β-cyclodextrin embedded in a polyelectrolyte multilayer. Proc. Natl. Acad. Sci (USA). 103, 8618-8621 (2006)
4:15 PM - **D10.5
Interface Tissue Engineering for Soft and Hard Tissue Integration.
Helen Lu 1 , J. Spalazzi 1 , K. Moffat 1 , I. Wang 1
1 Biomedical Engineering, Columbia University, New York, New York, United States
Show Abstract4:45 PM - D10.6
Carbon Nanotube-Reinforced Hydroxyapatite Nanocomposites.
Ashley White 1 , Osa Emohare 2 , Roger Brooks 2 , Neil Rushton 2 , Ian Kinloch 1 , Serena Best 1
1 Dept. of Materials Science & Metallurgy, University of Cambridge, Cambridge United Kingdom, 2 Orthopaedic Research Unit, University of Cambridge, Cambridge United Kingdom
Show AbstractHydroxyapatite (HA) is a biologically active ceramic that is used in surgery to replace and mimic bone. While HA promotes bone growth along its surface, its mechanical properties are not sufficient for load-bearing medical devices [1]. To address this issue, current devices combine HA with other materials, such as polyethylene and yttrium-doped zirconia. However, significant amounts of these secondary materials must be used, and they are either bioinert or significantly less biologically active than HA, thus lowering the overall biological compatibility of the composite material. An ideal filler material would reinforce the HA at loadings sufficiently small not to significantly reduce the overall bioactivity of the composite. Carbon nanotubes (CNTs), as one of the strongest and stiffest materials available [2-4], have the potential to accomplish this aim. Furthermore, recent work suggests that the nanotubes themselves possess some bioactivity [5-7]. In this study, HA was synthesised by the wet chemical method using Ca(OH)2 and H3PO4. Multiwalled CNTs were produced by chemical vapour deposition of ferrocene and toluene. Composite materials were made both by mechanically mixing the two materials and by in-situ formation of HA in the presence of CNTs. Given that the ability of a filler to reinforce the matrix depends strongly on the interface between the two phases, we have functionalised the nanotubes to improve their adhesion to the HA. For both methods, the resultant HA/CNT powders were pressed into pellets and sintered to produce the final specimens. The sintering parameters were optimised for maximum sintering of the HA, without burning out the nanotubes or removing the hydroxyl groups of the HA.We have studied the effect of nanotube concentration, nanotube surface chemistry, composite preparation methods, and sintering conditions on the microstructure, mechanical properties, and bioactivity of the final composites. The raw materials, composite microstructure, and HA/CNT interface were investigated using SEM, TEM, XRD, FTIR, TGA, DSC, and BET surface area. The mechanical properties of the composites were evaluated by three-point bending and compression tests, while the bioactivity was analysed using cell adhesion, proliferation, and differentiation. [1] Hench, J. Amer. Ceram. Soc., 74 (1991).[2] Yu, et al., Science, 287 (2000).[3] Wong, et al., Science, 277 (1997).[4] Falvo, et al., Nature, 389 (1997).[5] George, et al., J. of Exp. Nanoscience, 1 (2006).[6] Zanello, et al., Nano Letters, 6 (2006).[7] Price, et al., Biomaterials, 24 (2003).
5:00 PM - D10.7
Laser Direct Writing of Bioceramics for Tissue Engineering
Lance Harris 1 , Anand Doraiswamy 2 , Roger Narayan 2 , S. Qadri 1 , R. Modi 1 , Douglas Chrisey 1 3
1 , United States Naval Research Laboratory, Washington, District of Columbia, United States, 2 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 3 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Washington, New York, United States
Show AbstractWe have developed a novel approach for layer-by-layer growth of tissue engineered materials using a direct writing process known as matrix assisted pulsed laser evaporation- direct write. The material to be transferred is solvated and evenly coated onto an optically transparent quartz disk, which is referred to as a “ribbon”. When low energy laser light is applied to the ribbon, the solute material is driven forward onto a receiving substrate. The resolution of the transferred pattern is controlled by the distance between the ribbon/substrate, the fluence, the spot-size, and the movement of the stage. Laser-based processing provides several advantages over solvent-based direct writing techniques, including (1) enhanced cell-substrate adhesion, (2) deposition can be performed under ambient conditions, (3) deposition of mesoscopic voxels can be performed at rapid deposition rates, and (4) matrix processing allows the amount of transferred material to be quantitatively determined. We have investigated co-deposition of bioceramics, osteoblast-like cells cells, and extracellular matrix in mesoscopic patterns using matrix assisted pulsed laser evaporation- direct write. X-ray diffraction pattern of MAPLE DW-transferred hydroxyapatite reveals the (200), (111), (002), (102), (210), (211), (112), (300), (202), (310), (222), (320), (213), (004), and (304) peaks of crystalline hydroxyapatite. The growth rates of MAPLE DW-transferred osteoblast-like cells in MG63-hydroxyapatite composites, MAPLE DW-transferred osteoblast-like cells, and cultured cells were statistically identical at time intervals up to 96 hours. Our findings on depositing mesoscopic patterns of cells, ceramics, and extracellular matrix composites that possess controlled microstructures will allow the development of novel dental and orthopaedic tissue substitutes.
5:15 PM - D10.8
Patterning Inorganic Films by Templating Colloids of an Amorphous Mineral Precursor
Yi-Yeoun Kim 1 , Laurie Gower 1
1 Materials Science & Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractAn understanding of the mechanisms involved in biomineralization may provide new processing strategies for regulating crystal growth using organic additives and templates. Recent reports have shown that many biominerals may follow a synthetic route that involves an amorphous mineral precursor. Our laboratory has developed an in vitro model system for examining the role of organic templates in modulating crystal growth of calcific minerals (calcium carbonates, phosphates, and oxalates), with emphasis on the growth of crystals from an amorphous precursor. In particular, we have found that polyanionic additives that mimic the acidic proteins found in biominerals can stabilize an amorphous mineral that is initially so highly hydrated that it is in a liquid-like state. This has significant consequences in terms of molding and shaping crystals into non-equilibrium morphologies. Using microcontact printing of self-assembled monolayers (SAMs), we show that colloids of this polymer-induced liquid-precursor (PILP) phase can be selectively adsorbed onto SAM templates to produce thin calcium carbonate films of controlled location and morphology. In addition, continuous mineral films with regions templated for differential film thickness can be created using SAMs of tailored surface chemistry. These patterning techniques can also be performed at the air-water interface of phase-segregated Langmuir monolayers, generating free-standing mineral films of controlled porosity. The organic-inorganic interactions within this system are relatively ‘non-specific’ (i.e., not based on molecular recognition), suggesting that this system may be a powerful tool for regulating a variety of aqueous-based inorganic systems.
5:30 PM - D10.9
Effect of Substrate Surface Modification on Biomineralization of Osteoblasts.
Yizhi Meng 1 , Xiaolan Ba 2 , Seo-Young Kwak 3 , Elaine DiMasi 3 , Jiji Gu 4 , Milan Kahanda 5 , Vladimir Zaitsev 2 , Shouren Ge 2 , Nadine Pernodet 2 , Miriam Rafailovich 2 , Yi-Xian Qin 1
1 Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States, 2 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 3 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York, United States, 4 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 , Ward Melville High School, East Setauket, New York, United States
Show Abstract5:45 PM - D10.10
Nano to Micro Scale Porous Silicon as a Cell Interface for Bone Tissue Engineering.
Wei Sun 1 , Tzong-Jen Sheu 2 , Edward Puzas 2 1 , Philippe Fauchet 3 1
1 Biomedical Engineering, University of Rochester, Rochester, New York, United States, 2 Orthopaedics, University of Rochester, Rochester, New York, United States, 3 Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States
Show Abstract
Symposium Organizers
John A. Carlisle Advanced Diamond Technologies, Inc.
Martin Eickhoff Technische Universitaet Muenchen
Jose A. Garrido Technische Universitaet Muenchen
Janos Voeroes University and ETH Zurich
Erika Johnston Genzyme Corporation
D11: Molecular Bioelectronics
Session Chairs
Thursday AM, November 30, 2006
Room 202 (Hynes)
9:30 AM - **D11.1
Electric Field Induced Attachment of Proteins Monitored by Surface Plasmon Resonance
David McKenzie 1 , Richard Morrow 1 , Marcela Bilek 1
1 School of Physics, University of Sydney, Sydney, New South Wales, Australia
Show AbstractProtein molecules in solution have charged regions on their surfaces that may impart a net charge to the molecule and/or a net dipole moment. The charges depend on the solution conditions, especially the pH. An externally applied electric field can interact with these charges and dipole moments under conditions in which the field penetrates the solution to a sufficient depth. The penetration depth depends on the ionic concentrations, the frequency of the field and the current passing through the solution. In this paper, we explore the conditions under which interactions are possible between an externally applied field and proteins in solution. We describe the design and operation of a surface plasmon resonance apparatus which enables the observation of attachment to a surface while an electric field is applied. We report on the results of the investigation for an enzyme, soybean peroxidase and show that manipulation of the protein is possible and can be monitored. The protein behaves in a manner determined by its charge in solution. The technique of electric field manipulation has potential applications to biosensors and array technologies. The use of an electric field may facilitate an increase in the density of immobilized protein while optimizing its orientation and hence its functional activity.
10:00 AM - D11.2
Reconstitution of Protein for Bioelectronic Applications
Jae-Woo Kim 1 , Sang Choi 2 , Peter Lillehei 2 , Sang-Hyon Chu 1 , Glen King 2
1 , National Institute of Aerospace, Hampton, Virginia, United States, 2 , NASA LaRC, Hampton, Virginia, United States
Show AbstractThe immobilization of biomolecules on electrode surfaces is of great importance and interest in biosensor and bioelectronic applications. To develop electrodes for bioelectronic applications, system miniaturization and compact integration are equally important. Various inorganic molecules appear to be good candidates for power generation and energy storage materials. If they can be easily incorporated into biological molecules via bioinorganic chemistry techniques, a fundamental building block for a power unit can be formed on such a small scale while ensuring biocompatibility. The ferritin used in this work is a natural iron storage protein that presents a high degree of structural similarity across a wide range of biological species. The ferritin protein is composed of 24 organic subunits that build a segmented hollow protein shell with an outer diameter of 12.5 nm and an inner diameter of 7.5 nm. The assembled structure of ferritin is remarkably stable and robust, and able to withstand biologically extremes of temperature (up to 70 oC) and pH (2.0 ~ 10.0). The ferritin protein has hydrophobic and hydrophilic molecular channels through the protein shell, which enables the removal of the inorganic phase in vitro by reductive dissolution.As one of the applications of bioinorganic molecules, the bionanobattery concept is based on the ferritin protein’s ability to store energy. By a reconstitution process of site-specific biomineralization within the protein cage, ferritins are loaded with different core materials such as Co, Mn, Ni, Pt, etc. Each of the core materials has a different redox potential and can be fabricated into densely packed 2-D arrays. The bionanobattery consists of two ferritin half-cell units with a different redox potential between them. Biofuel cells as another application area are an excellent strategy provided that sufficient power is available without having to enlarge the system significantly. The biofuel cells, functioning as an energy conversion device, are based on the reconstituted ferritin combined with other biomolecules to generate power. In this work, an electrochemically-controlled, site-specific biomineralization was demonstrated through the immobilization of biomolecules on a substrate to position the biologically-derived nanoparticles in an array. The electrode surface was modified for strong and stable adhesion of the ferritin molecules and to reconstitute the core material with another metal. We used the electrochemical biomineralization technique for direct reconstitution of immobilized ferritins on a gold electrode. We also characterized the electrochemical behaviors of reconstituted ferritin electrodes for bioelectronics applications such as bionanobattery and biofuel cells.
10:15 AM - D11.3
Optically Induced Changes in the Electrical Propertiesof the Protein – Porphyrin Complexes.
Maxim Nikiforov 1 , Bohdana Discher 2 , Dawn Bonnell 1
1 MSE, University of Pennsylvania, Philadlephia, Pennsylvania, United States, 2 Dept of Biochemistry&Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract10:30 AM - D11.4
Dynamic Control of Biomolecular Activity Using Nanoscale Electrical Interfaces
Ian Wong 1 , Nicholas Melosh 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractThe structure and function of biological macromolecules depend sensitively on the local electrostatic conditions, which can be artificially regulated at molecular scales through the use of nanoscale electrodes. This approach allows for the manipulation of proteins in microfluidic systems through a variety of electrokinetic phenomena, such as ionic double layers, linear and non-linear electrophoresis. These represent novel mechanisms that may be used to interface artificial electronic architectures with a wide variety of biological systems, including many molecular species that are not redox-active. One such model system is the cytoskeletal polymer F-actin, which can be simultaneously polymerized and aligned through these effects. Under non-physiological low ionic salt conditions, this protein remains in an inactive, monomeric state. The application of a low-frequency AC voltage alternately concentrates divalent cations and negatively charged G-actin monomers at the electrode surface, promoting highly localized polymerization. Moreover, the superposition of a high-frequency AC voltage allows for the trapping and alignment of single actin filaments through dielectrophoresis. The high aspect ratio and dimensions of these filaments are similar to inorganic nanowires, and this system may be relevant for the self-organization of hybrid synthetic-biological nanostructures. A second system of interest is redox-active, containing two coupled enzymes - horseradish peroxidase (HRP) and glucose oxidase (GOx). The associated chemical reactions can be perturbed both spatially and temporally using electrokinetics and the activity can then be characterized using fluorescence measurements. This simple biomimetic control motif may yield insight into the design of field-programmable biochemical logic circuits or step-by-step molecular synthesis. Furthermore, these electronic mechanisms may be relevant for the development of interfaces to perturb and quantitatively analyze actual biochemical networks.
D12: Bioelectronics and Biomedical Tools
Session Chairs
Thursday PM, November 30, 2006
Room 202 (Hynes)
11:15 AM - **D12.1
Micro-structured Platinum Electrodes for a Retinal Prosthesis.
Brian Mech 1 , Robert Greenberg 1 , David Zhou 1
1 , Second Sight Medical Products, Sylmar, California, United States
Show AbstractVisual retinal prostheses, aimed at partially restoring vision to patients suffering from advanced forms of outer retinal degenerative diseases, are currently under development by several groups around the world. Such implants, in general, rely on by-passing the defunct photo-receptors and electrically stimulating remaining viable retinal ganglion and/or bi-polar cells in order to produce ‘phosphene vision’ in the visual cortex. Second Sight Medical Products Inc. has sponsored a clinical trial at the University of Southern California’s Doheny Retina Institute for its first generation 16- electrode retinal implant. The device was implanted in 6 patients chronically (24 – 52 months ongoing). Some results of this trial relative to patient performance will be presented. It is generally accepted that the fidelity of artificial vision will improve with increasing electrode count and so many development efforts are aimed at increasing the number of electrodes for a retinal prosthesis. This introduces several technical challenges, including materials limits imposed by the charge transfer capabilities of implantable electrode materials. As the size of these electrodes is reduced to accommodate greater electrode numbers, the charge density that the material must deliver increases. Above material specific safe charge density limits a number of reactions, including water electrolysis and electrode dissolution which are damaging to living tissue, may occur. Second Sight has developed a new process for forming a robust thin film platinum electrode with an electrochemical surface area that is at least five times larger than that of normal thin film platinum, enabling higher charge densities per unit of geometric surface area. The results of acute and chronic tests of this material in-vitro and in-vivo will be presented. The data supports the use of this ‘platinum gray’ for smaller electrodes, such as those that are part of the second generation Second Sight implant (50-100 electrodes) about to begin clinical trials.
11:45 AM - D12.2
Optical Micro-resonator Probes for Cortical Recording.
Jiayi Zhang 1 , Yoon-Kyu Song 2 , John Donoghue 3 , Arto Nurmikko 2 1
1 Physics Department, Brown University, Providence, Rhode Island, United States, 2 Division of Engineering, Brown University, Providence, Rhode Island, United States, 3 Neuroscience Department, Brown University, Providence, Rhode Island, United States
Show AbstractIn vivo cortical recordings have been extensively performed in different areas of neuroscience and biomedical engineering including neuronal network mapping, nervous system disease diagnosis, and brain-computer interface. Silicon based multi-channel microelectrode arrays are commonly utilized as cortical implants to record local neural activity. While optical imaging techniques as a class of neuroscience tools are well established, the need for fluorescent labeling makes these approaches unlikely for long term chronic implant applications. Here we present all-optical cortical implant microarray technology, for enabling large bandwidth, real-time, in vivo multichannel recording of many neurons simultaneously whereby neural electrical potentials are converted directly into modulated optical signals at each microprobe by photonic waveguide microresonator designs. In our approach, the resonators incorporate electro-optical polymer thin films which convert the local electric fields into index of refraction changes, which work in the telecommunication wavelength range. As a first step, an array of three micro-resonator structures is fabricated on a SOI (Silicon-on-Insulator) substrate using e-beam lithography and RIE (reactive-ion etching) techniques. Each resonator is composed of two parallel silicon ridge waveguides and a silicon microring waveguide in between. RIE stops at the silicon dioxide layer such that the refractive index contrast between the waveguides and the environment is around 2 at 1.55 micron wavelength. Each resonator structure is then fabricated into blade shaped optical probe arrays through silicon wet etching. For optical measurement, light from a tunable external cavity laser is coupled to the input waveguide through optical fiber and the output waveguide is coupled to an optical spectrum analyzer. Preliminary results show our ability in fabricating such optical micro-resonator arrays, as well as the optical modulation measurement of electrical signals with incorporation of electro-optic polymer at 1kHz, which is within the electrophysiological frequency range. Ultimately, the optical neural microprobe array technology will provide possibility for novel large bandwidth cortical recordings, by integration with state-of-art telecommunication capabilities, such as dense wavelength division multiplexing.
12:00 PM - D12.3
An Electronically Controlled Release Platform for Studying Cell Behavior
Elizabeth Hager-Barnard 1 , Jules VanDersarl 1 , Erhan Yenilmez 1 , Nicholas Melosh 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractElectronically controlled inorganic platforms which can dynamicallyinteract with biological species are an evolving and powerful means withwhich to probe the temporal and spatial dependency of cell behavior. Oneof the key challenges to creating these systems is translating betweenelectrical signals and specific biological stimuli, which are often in theform of small molecular messengers. In order to solve these issues, wehave designed a new platform that utilizes reversible electrochemistry torelease femtoliters of signaling agents or other biochemically activespecies to cells. On each chip there is a cross-array of electrodes, sothat each reservoir can be individually addressed. To manufacture ourdevices, we deposit an electrode pattern on a silicon wafer and thendeposit a photoresist. By etching with an ion beam and then a XeF2system, we create nanoreservoirs in the silicon. By using a solution ofgold chloride ions and applying a succession of microsecond electricpulses, we are able to reversibly seal these reservoirs. This designallows the use of different reagents in different reservoirs and alsoenables both temporal and spatial resolution. The biocompatibility of theplatform and the influence of signal release on cell behavior will bepresented.
12:15 PM - D12.4
Imaging Electromechanical Coupling of a Protein Membrane in Solution with an Electrically Biased Tip.
Brian Rodriguez 1 , Stephen Jesse 1 , Sergei Kalinin 1 , Sophia Hohlbauch 2 , Irene Revenko 2 , Roger Proksch 2
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , Asylum Research, Santa Barbara, California, United States
Show AbstractElectromechanical coupling, the mechanical response to an applied electric field, is common in inorganic materials and universal in biosystems. Piezoresponse Force Microscopy (PFM) has emerged as the primary tool for imaging ferroelectric materials in ambient, and has recently been extended to piezoelectric biosystems, including calcified tissues. These results have allowed the internal structure of materials such as dentin and enamel to be mapped with resolution below 10 nm. To extend this technique to living biosystems, we have adapted PFM for imaging in a liquid environment. Resolution on the order of 3 nm, approaching the theoretical domain wall width, as compared to a resolution of ~30 nm in ambient, is reported on model ferroelectric ceramics. Screening by mobile ions in liquid localizes the ac-field to the tip-surface junction, thus, choice of imaging medium allows control of double layer and electrostatic interactions. We report imaging of the electromechancial coupling of the purple membrane, bacteriorhodopsin, in buffer solution, and applications of PFM and liquid PFM to biosystems are discussed.Research sponsored by Asylum Research and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U. S. Department of Energy under Contract No. DE-AC05-00OR22725.
12:30 PM - D12.5
Inkjet Printing of Biocompatible Adhesives: Surgical Adhesives, Wound Closures and Anti-fouling in Medical Devices
Anand Doraiswamy 1 , Peter Mente 1 , Roger Narayan 1
1 Joint Dept. of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractSynthetic adhesives have largely displaced natural adhesives in the automotive, aerospace, biomedical, electronic, and marine equipment industries over the past century. However, rising concerns over the environmental and health effects of solvents, monomers, and additives used in synthetic adhesives have led the adhesives community to seek natural alternatives. Marine mussel adhesive protein is a formaldehyde-free natural adhesive that demonstrates excellent adhesion to several classes of materials including pure metals, metal oxides, polymers, and glasses. We have demonstrated the thin film deposition of various biological adhesives including naturally derived mussel adhesive proteins using piezoelectric inkjet technology. A MEMS based piezoelectric actuator was controlled to jet uniform fluid flow of the adhesive solution through the ink jet nozzles. Using an Enduratec tensile test system, we have studied the strength of adhesion of these biological adhesives in porcine skin. Ink jet deposition of naturally derived biological adhesives may overcome several problems associated with conventional tissue bonding materials, and greatly improve wound repair in next generation eye repair, fracture fixation, organ fixation, wound closure, tissue engineering, and drug delivery devices.
D13: Nanopatterning
Session Chairs
Thursday PM, November 30, 2006
Room 202 (Hynes)
2:30 PM - **D13.1
Integration of Biomolecules with Inorganic Framework Materials: Novel Approaches to Protein-Based Nanoscale Devices
Millicent Firestone 1 2 , Brian Reiss 1 2 , Orlando Auciello 1 2 , Leonidas E. Ocola 2 , Deborah Hanson 3
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 3 Biosciences Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractInnovative approaches are needed for the design and fabrication of functional nanoscale materials and devices. Biological molecules such as proteins, which are optimized by nature, possess the requisite size and functionality to permit their use as the basis for nanoscale device components. Significant materials challenges exist, however, for the successful integration of these molecules with conventional inorganic components. In this presentation, two strategies for the fabrication of bio-based materials will be described. In the first, a phage-identified peptide is selectively coupled to a pervoskite ferroelectric (PZT) to yield a nanoscale biomolecular valve actuated by changes in the polarization / charge state of the PZT. In the second, a synthetic approach is described for the asymmetric surface coupling and orienting of a bacterial photosynthetic reaction center protein, a membrane protein that undergoes efficient light induced charge separation, and its “hardwiring” onto a patterned electrode to form the basis of a photobioelectronic device.
3:00 PM - D13.2
Surface Patterning Proteins and Protein-conjugated Nanoparticles in Immobilized or Lipid-membrane-supported Arrays: Using Engineered Cell-surface Contacts to Model Complex Cell-cell Interactions.
Darrell Irvine 1 , Junsang Doh 2
1 Mat. Sci. & Eng./Biological Eng., MIT, Cambridge, Massachusetts, United States, 2 Chemical Eng., MIT, Cambridge, Massachusetts, United States
Show Abstract3:15 PM - D13.3
Directed Self-assembly of Virus Particles at Chemical Templates.
James DeYoreo 1 , Sung-Wook Chung 1 , Chin Cheung 1 , Selim Elhadj 1 , Anju Chatterji 2 , Tianwei Lin 2 , John Johnson 2 , Chung-Yi Chiang 3 , Angela Belcher 3 , Andrew Presley 4 , Matthew Francis 4
1 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , The Scripps Research Institute, La Jolla, California, United States, 3 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 , University of California at Berkeley, Berkeley, California, United States
Show Abstract3:30 PM - D13.4
S-layers as Templates in the Formation of Two-dimensional Nanoscale Patterns.
Dietmar Pum 1 , Uwe Sleytr 1
1 Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences, Vienna Austria
Show AbstractOne of the most challenging research areas is currently found at the interface between biology and physics. In particular, the technological utilization of self-assembly systems wherein molecules spontaneously associate under equilibrium conditions into reproducible supramolecular aggregates has grown into a scientific and engineering discipline that crosses the boundaries of several established fields.Two-dimensional bacterial surface layer proteins (S-layer proteins), isolated from prokaryotic organisms (bacteria and archaea), have the intrinsic tendency to self-assembly into two-dimensional arrays in suspension, at solid supports (e.g. silicon wafers), at the air-water interface, at floating lipid monolayers and at vesicles (liposomes and nanocapsules) [1]. This presentation is focussing on the reassembly of native and genetically functionalized S-layer proteins on solid supports and, in particular, on their use as templates for the precisely controlled assembly of biological molecules and metallic or semiconducting nanoparticles into extended arrays. The incorporation of highly specific functional domains in S-layer proteins by genetic approaches opened a new horizon for the tuning of the structural and functional properties of these two-dimensional protein lattices. A broad range of S-layer fusion proteins with different functionalities has already been developed. For example, genetically engineered S-layer streptavidin fusion proteins were capable to bind biotinylated ferritin molecules (12nm diameter) into large scale ordered arrays. This concept of a biointerface engineered with nanometer precision is of a more general nature since it allows the direct interfacing of (bio)molecules and nanoparticles to a broad range of surfaces, such as silicon, gold, ITO, glass or polymers. S-layers are currently used in the development of new affinity matrices, diagnostics, vaccines, biocompatible surfaces, microcarriers, and specific biomineralisation strategies on surfaces.[1] Sára, M., Pum, D., Schuster, B., Sleytr, U.B. 2005. S-Layers as Patterning Elements for Application in Nanobiotechnology. J. Nanosci. Nanotechnol., 5:1939–1953 .
3:45 PM - D13.5
Protein Orientation and Conformation Controlled by Charged Self-Assembled Monolayers on Nano-patterned Au Discs and Holes.
Qiuming Yu 1 2 , Dong Qin 1 2 , Greg Golden 1 2
1 Center for Nanotechnology, University of Washington, Seattle, Washington, United States, 2 Department of Bioengineering, University of Washignton, Seattle, Washington, United States
Show AbstractControl of the orientation and conformation of proteins immobilized on surfaces is critical to retain protein functionality for the applications of biosensors and implanted medical devices. Due to the charge distribution in a protein, the orientation and conformation of proteins on a surface can be controlled by the polarity of electrostatic charges on a surface. Surface enhanced Raman scattering (SERS) spectroscopy is a powerful method in studying the protein structure by immobilizing proteins on nano-patterned noble metal surfaces. The polarity of electrostatic charge is controlled by forming self-assembled monolayers of alkane thiols with positively (-NH2) and negatively (-COOH) charged terminal groups, respectively, on surfaces with nano-patterned Au discs or holes fabricated by electron beam lithography. Cytochrome c is known to have strong dipole moment and is used as a model protein system. Optimized enhancement of Raman scattering is obtained by varying the dimension of nano-discs and nano-holes and the grating of nano-patterns. The topographic difference in nano-discs and nano-holes shows different effects on the enhancement of Raman scattering, i.e., smaller discs for strong enhancement while larger holes for strong enhancement. The vibration modes related to the protein secondary structures are also enhanced in different ways on nano-discs and nano-holes, which provides comprehension study in protein orientation and conformation on charged surfaces. The correlation between protein orientation and conformation to the polarity of electrostatic charges on surfaces will be presented and the effects on their bio-functionality will be discussed.
D14: Nanobioelectronics
Session Chairs
Thursday PM, November 30, 2006
Room 202 (Hynes)
4:30 PM - **D14.1
DNA, Proteins, and Neurons Coupled to Electronic Devices.
Andreas Offenhausser 1
1 , Forschungszentrum Juelich, Juelich Germany
Show Abstract5:00 PM - D14.2
Selective Biofunctionalization of Silicon Nanowires on SiO2 Surfaces
Ansoon Kim 1 , Chil Seong Ah 1 , Han Young Yu 1 , In Bok Baek 1 , Jong-Heon Yang 1 , Chang-Geun Ahn 1 , Seong Jae Lee 1
1 IT Convergence & Components Lab., Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of)
Show AbstractWe have achieved the covalent functionalization of silicon nanowires, which were fabricated on SiO2 surface, toward immobilization of biomolecules such as proteins, DNAs, and cancer markers. An UV-initiated modification of silicon surface with alkene was used to modify silicon nanowires to aldehyde-terminated surface without the reaction with underlying SiO2 substrate for the covalent immobilization of the biomaterials. The surface aldehyde forms a covalent link to the amine incorporated into the DNA, which was proved by subsequent hybridization with complementary DNA-linked Au nanoparticle (13 nm). Likewise, the aldehyde functionality works on proteins by binding to random amine sites on the proteins. These attachment strategies show the minimization of nonspecific binding both to the incorrect sequences of DNA oligonucleotides and to the underlying SiO2 substrate. This selective photochemical hydrosilation provides a strategy to with which to design and produce Si nanowire biosensor with high sensitivity and selectivity.
5:15 PM - D14.3
3-D Conformal Electrode Arrays for Interfacing with Topologically Complex Neural Surfaces.
Karlene Maskaly 1 , John George 1 , Craig Chavez 1 , James Maxwell 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractThe DOE Artificial Retina Project is a large collaborative effort, including national laboratories and universities, with the goal of creating a device that restores sight in patients where blindness is attributed to the loss of photoreceptor function. The planned device consists of several components, including a prosthetic electrode array that sits on the retina and transmits electrical impulses to residual neurons. Among the many challenges that arise in fabricating such a device is how to create a sufficiently dense electrode array (~20-25 electrodes per mm) that has ample conductivity to stimulate the retinal neurons while also providing a bio-compatible, conformal surface that can interface with the complex topology of the retina. Such a device will also prove useful for recording activity from many neurons simultaneously. We will present recent progress towards the creation of such arrays through the use of laser chemical vapor deposition (LCVD). Dense three-dimensional conformal microprobe arrays have been created through the laser-catalyzed growth of high-aspect-ratio carbon and platinum microfibers on individually addressable planar electrode array substrates. The profile of the tips in these microfiber arrays maps out a topologically complex surface that can be designed to correspond to the specific topologies of individual retinas. Array recording and stimulation results on an amphibian retina will be presented.
5:30 PM - D14.4
Designing and Implementing High Density Nanowire Arrays for Detection, Stimulation, and Inhibition of Neuronal Signals
Brian Timko 1 , Fernando Patolsky 1 , Guihua Yu 1 , Ying Fang 1 , Andrew Greytak 2 , Charles Lieber 1 3
1 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States
Show AbstractWe report two-way electrical communication between integrated arrays of biocompatible nanowires and the individual axons, dendrites and soma of live mammalian neurons, where each nanoscale junction can be used for spatially-resolved, highly-sensitive detection, stimulation and/or inhibition of neuronal signal propagation. Arrays of nanowires operated as field effect transistors enable simultaneous measurement of the rate, amplitude and shape of signals propagating along individual axons and dendrites. Our highly configurable nanowire devices can also be used as analog hyperpolarizing inputs to axons, making possible controlled studies of partial to complete inhibition of signal propagation. Additionally, we have demonstrated the assembly of integrated n- and p-type structures allowing for the generation of bipolar signals that could mimic the inhibitory and excitatory signals used in neural networks. Nanowire/axon junction arrays were integrated and tested at a level of at least fifty ‘artificial synapses’ per neuron. The flexible assembly of arrays of these structures could prove useful for fundamental neurophysiological studies, real-time cellular interaction with chemical signals, and the creation of hybrid neuron/nanowire networks.
5:45 PM - D14.5
Study of Polymeric Microneedle Arrays for Drug Delivery.
Aleksandr Ovsianikov 1 , Roger Narayan 2 , Anand Doraiswamy 2 , Peter Mente 2 , Prasad Mageswaran 2 , Boris Chichkov 1
1 Nanotechnology Department, Laser Zentrum Hannover e.V., Hannover Germany, 2 Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractD15: Poster Session
Session Chairs
Friday AM, December 01, 2006
Exhibition Hall D (Hynes)
9:00 PM - D15.10
Nonfouling and Responsive Zwitterionic Hydrogels with Immobilized Proteins and Improved Mechanical Strength.
Shaoyi Jiang 1 , Zheng Zhang 1 , Shengfu Chen 1
1 , U. of Washington, Seattle, Washington, United States
Show Abstract[Poly(SBMA)] and poly(caboxybetaine) methacrylate [poly(CBMA)] have been synthesized and evaluated for their applications as tissue engineering scaffolds. Their cytotoxticity and endotoxicity are tested and their resistance to nonspecific protein adsorption are compared with those of poly(HEMA) hydrogels. In vitro results show that both hydrogels inhibit cell adhesion. Using the EDC/NHS chemistry, fibronectin is covalently bound to poly(CBMA) hydrogels. In vitro experiments show that the protein-immobilized poly(CBMA) facilitates endothelial cell adhesion and still resists nonspecific protein adsorption. In vivo implants of poly(SBMA) are also evaluated and compared for their vascularity and foreign body reaction. Both hydrogels are responsive to changes in ionic strength and pH value. Based on their responsive properties, the mechanical properties of the hydrogels are improved by a novel swelling-penetrating method.
9:00 PM - D15.11
Molecular Origins of the Protein-Resistant Properties of Methyl 1-(3-Mercaptopropyl) Penta(Ethylene Oxide) Self-Assembled Monolayers.
Jae Hyeok Choi 1 , Hailemariam Negussie 2 , Sarah Ng 3 , David Vanderah 4 , Ortiz Christine 3
1 Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States, 3 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Biochemical Sciences Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractSelf-assembled monolayers (SAMs) of methyl 1-(3-mercaptopropyl) penta(ethylene oxide), HS(CH2)3O (CH2CH2O)5CH3 (C3EO5) have been shown to exhibit resistance to protein adsorption at 60 ~ 80 % surface coverage, where a more disordered and mobile molecular packing is known to exist. In order to gain a fundamental understanding of the molecular origins of the protein resistant properties of C3EO5 SAMs, the technique of chemically specific high resolution force spectroscopy was employed to quantify the nanoscale intersurface forces in 25 mM tris (hydroxymethyl) aminomethane buffer as a function of ionic strength (IS = 0.01M, 0.1M and 1M) using gold-coated nanosized probe tips of varying surface chemistry, i.e. via functionalization with SAMs (HS-(CH2)11-CH3, HS-(CH2)11-OH, HS-(CH2)10-CO2H, and C3EO5). C3EO5 SAMs were prepared on planar gold substrates and nanosized gold-coated probe tips via incubation in 0.5 mM C3EO5 95% ethanol solution with varying different chemisorption incubation times that ranged between 5 seconds and 3 days.). Contact angle measurements using deionized water showed the temporal evolution of the SAM formation; after 5 seconds the initially hydrophobic gold surface (79.7 ± 4.0°) becomes more hydrophilic (57.0 ± 0.5°) and then reaches equilibrium to a more hydophobic state for chemisorption incubation times greater than 3 hrs (65.64 ± 2.3°). For the C3EO5 5 second chemisorption incubation time (planar substrate), all types of functionalized probe tips exhibited a net repulsive intersurface interaction on both approach and retract with a range of ~ 15 nm (IS = 0.01M), except for the C3EO5 vs. C3EO5 combination which exhibited a small adhesion on retract (maximum adhesive forces, Fadhesion < 0.4 nN). The magnitude and range of the net repulsion decreased for the 24 hour and 3 day C3EO5 chemisorption incubation times for all probe tips (compared to the 5 second incubation time), except the C3EO5 vs. C3EO5 which exhibited similar intersurface interactions. For almost all nanomechanical experiments, the repulsive force on approach decreased and Fadhesion increased with increasing IS. Since the maximum height of the C3EO5 is ~ 2.3 nm (as calculated for the molecule in an all 7/2 helical conformation), our results show that the molecular coverage, and likely the molecular mobility, affect the hydrated near-surface environment (water and ions). The repulsive interaction could have two possible origins; templated water layers or electrostatic double layer repulsion due to an effective charge from adsorbed anions. This near-surface repulsive interaction may play a role in protein resistance, as well as short range molecular mobility. For the C3EO5 vs. C3EO5 experiments, nanoscale adhesion may be due to the propensity for short oligo(ethylene oxide) chains to establish, on Au, close interchain contact (in this case intercalate) and adopt the ordered 7/2 helical conformation with the concurrent expulsion of water.
9:00 PM - D15.12
Finite Element Analysis of Microjoint Bond Degradation in Cerebrospinal Fluid.
Jesse Law 1 , Ahsan Mian 1
1 Mechanical and Industrial Engineering, Montana State University, Bozeman, Montana, United States
Show AbstractFor application in active biomedical implants, materials with established biocompatibility are required for the encapsulation of sensors and circuitry. Encapsulated elements are typically reactive in a biological environment and must be isolated. Such isolation requires that the element be enclosed in a biocompatible material and then the material hermetically bonded and sealed. Transmission laser bonding is a method that is applicable when one of the materials is transparent and the other is opaque to a given laser frequency. The overlapped materials are bonded by local heating of the interface between the transparent and opaque material. Advantages of transmission laser bonding are the ability to form continuous and precise microscale bonds, and obviating the need for biologically toxic glues or solders which are common in traditional bonding methods. In this study, transmission type laser bonds between 180 µm Polyimide film and 50 µm Titanium foil are investigated. Bonds of width 200 µm were created and tested for strength (N/mm) in tension using a microtester. Bonded samples were exposed to artificial cerebrospinal fluid (CSF), for two, four, and twelve weeks. Bond strength was observed to decline with increased exposure time up to four weeks. The hypothesized mechanism of bond degradation is absorption of CSF in Polyimide in the near-bond region. Due to CTE (coefficient of thermal expansion) and CHE (coefficient of hygroscopic expansion) mismatch between materials at the bond interface, high gradient stresses are induced in the bond region that potentially degrade the strength and integrity of the bond. To substantiate the above, a finite element model was developed to simulate the behavior of the bond upon introduction to a neural environment. The model requires the diffusion properties of 180 µm Polyimide Imidex™ to accurately simulate the coupled diffusion/stress analysis. Hence, the diffusivity of CSF in polyimide was measured in a separate experiment. A 2D plane-strain model was developed in ABAQUS/CAE and was used to predict the transient and final stress distribution in the bond region. Two modeling methods, namely, a coupled pore fluid flow/stress analysis and a coupled heat transfer/stress analysis were independently employed. Variations in the induced peak stress values with CSF exposure time from the two analysis methods were compared to the experimental bond strength results, and suggestions are made for accurate modeling of such bonds. Verification of the coupled diffusion / stress model allows faster design and characterization of bonded joints for neural implants.
9:00 PM - D15.13
Fabrication of Nano-patterned Surfaces for Bio-sensing Devices by Colloidal Lithography.
Andrea Valsesia 1 , Pascal Colpo 1 , Patricia Lisboa 1 , Frederic Bretagnol 1 , Giacomo Ceccone 1 , Francois Rossi 1
1 , EC-JRC-IHCP, Ispra, Varese, Italy
Show AbstractThe nano-fabrication and nanotechnology is hardly driving the development of new generation of biosensing devices. Together with the necessity of the reduction of the device typical size, nano-structured surfaces provides a considerable enhancement in the specificity and in the sensitivity of the detection.Many works are performed worldwide to develop advanced platforms with controlled surface chemistry and morphology at the nano-scale. The objective is to be able to immobilize the biomolecules in an active and controlled state, allowing the biological reaction to occur. Among the different nanopatterning techniques nano-sphere lithography is a very flexible technique to produce nano-structured and chemically nano-patterned surfaces. Moreover this technique presents the advantage to be inexpensive and enable to produce nano-topography over large area surfaces. In this work, we present the fabrication strategy and the surface characterization of different types of nano-structures. In particular Poly Acrylic acid (carboxylic functional) nano-domes in anti-fouling matrix have been fabricated by combining colloidal lithography and Plasma Enhanced Chemical Vapor Deposition and carboxylic terminated nano-spots in an anti-fouling matrix have been produced by combining nano-sphere lithography and Self Assembled Molecular Monolayers on gold. We show that these chemical nano-patterns are able to immobilize proteins selectively in the carboxylic functional nano-domains, leaving the anti-fouling matrix clear. Moreover Enzyme-Linked Immunosorbent Assay experiments were set-up showing that nano-patterned surface constrains the immobilization of the antibodies in a biological reactive configuration, thus significantly improving the device performances as compared to more conventional non-patterned surfaces.
9:00 PM - D15.14
Site-Specific Patterning of Biomaterials on PECVD Generated Surfaces
Jeffrey Zabinski 1 , Joseph Slocik 1 , Eric Beckel 1 , Hao Jiang 1 , Jesse Enlow 1 , Timothy Bunning 1 , Rajesh Naik 1
1 , Air Force Research Lab, Wright-Patterson AFB, Ohio, United States
Show AbstractPlasma enhanced chemical vapor deposition (PECVD) shows great promise for generating micropatterned surfaces. Using PECVD, high fidelity micropatterned surfaces for biomolecular coupling can be generated using a variety of monomers. PECVD offers a stable and sterile surface, the ability to use various substrates and geometries, and large surface area patterning. Site specific patterning on single and multifunctional surfaces displaying thiols and amines were created on an individual substrate. On this platform, the controlled patterning of quantum dots, green fluorescent protein, and enzymes is possible by targeting different surface chemistries. In some cases, the immobilization of enzymes in patterned regions added stability and activity to the enzyme as compared to immobilization in non-patterned areas. Furthermore, protein surfaces can be used with variable surface patterns to create a template for patterned cell growth and an increased range of biomolecular coupling. Extending these approaches, multifunctional chemical or biological sensors can be created with tunable properties on a generalized, durable platform.
9:00 PM - D15.15
Photolithographic Process, Based on High Contrast Acrylate Photoresist, for Multi –Protein Patterning.
Margarita Chatzichristidi 1 , Panagiota Petrou 2 , Antonios Douvas 1 , Constantinos Diakoumakos 1 , Ioannis Raptis 1 , Konstantinos Misiakos 1 , Sotiris Kakabakos 2 , Panagiotis Argitis 1
1 Inst. of Microelectronics, NCSR "Demokritos", Athens Greece, 2 Inst. of Radioisotopes & Radiodiagnostic Products, NCSR "Demokritos", Athens Greece
Show Abstract9:00 PM - D15.17
Far-Field Arrangement of Proteins in a Zero-mode Waveguide for Single Molecule Imaging
Takashi Tanii 1 , Hironori Sonobe 1 , Rena Akahori 1 , Takeo Miyake 1 , Taro Ueno 2 , Takashi Funatsu 2 , Naonobu Shimamoto 1 , Iwao Ohdomari 1
1 School of Sci. & Eng., Waseda University, Tokyo Japan, 2 Graduate School of Parmaceutical Sciences, The University of Tokyo, Tokyo Japan
Show Abstract The single molecule imaging method developed by Funatsu et al. in 1995 enables us to observe single biomolecules in real time [1]. The total internal reflective illumination confines the excitation laser light within the water/glass interface as an evanescent wave exposing the behavior of proteins immobilized near the interface. This enables us also to image the protein-protein interaction [2]. However, this method is limited in the observation of proteins with a dissociation constant of less than 50 nM. In order to overcome this limitation, and to observe weak protein-protein interaction, a novel single molecule imaging method using a zero-mode waveguide has been proposed by Levene et al. in 2003 [3]. In this method, a nanohole array is fabricated in a thin metal film deposited on a glass slide, and functional proteins of interest are immobilized in the nanoholes one by one. Because the evanescent wave generated within each nanohole can be controlled according to the nanohole diameter, the background noise, which is in proportion to the number of fluorophore labeled molecules within the evanescent wave, can be reduced. Nevertheless, the intensity of the detected fluorescent signals is roughly 1/7 times weaker than that of the conventional method. In particular, the intensity drastically decreases when GroELs are immobilized not directly on the glass surface but arranged inside nanoholes via cushion molecules. In this paper, we propose two different arrangements of proteins using the modified zero-mode waveguides that can enhance the fluorescent intensity from the proteins. One is the arrangement of a protein at the bottom of a concave nanohole, and the other is the arrangement of a protein on the top of a convex nanohole. The key in enhancing the fluorescent signals is that the proteins of interest are arranged in far-field, while other proteins causing noises are optically shielded by the evanescent field. The feasibility of this method is discussed from the view point of signal to noise ratio using chaperonin GroEL and GroES as the example.[1] T. Funatsu et al., Nature, 374, 555, (1995).[2] T. Ueno et al., Molecular Cell, 14, 423, (2004).[3] M. J. Levene et al., Science, 299, 682, (2003).
9:00 PM - D15.18
Local Electron Beam Induced Reduction and Crystallization in Electrochemically Deposited Amorphous TiO2 Films
Philippe Kern 1 , Johann Michler 1
1 , EMPA, Thun Switzerland
Show AbstractBased on a peroxo-precursor method using TiCl4 and H2O2 in CH3OH/H2O environment, we have recently succeeded in electrodeposition of uniform Ti-peroxohydrate films on conductive substrates. Morphological, chemical, structural and nano-mechanical properties of the thermally crystallized TiO2 films have been reported [1]. In comparison to crystalline TiO2, thermally densified amorphous TiO2 (a-TiO2) thin films show a remarkably high sensitivity towards electron beam (e-beam) irradiation at moderate energies under SEM conditions (20 keV) [2]. Previously reported work on e-beam irradiation effects has exclusively focussed on crystalline TiO2 and mostly under TEM conditions [3]. E-beam exposure of a-TiO2 leads to immediate electron stimulated desorption of oxygen through a radiolysis effect, resulting in a well-defined volume loss limited to the irradiated area. We found that the sensitivity towards O desorption is decreasing with higher annealing temperatures and thus, lower oxygen content in the film.Well-defined irradiation conditions on the μm-scale were achieved with an electron probe micro-analyzer. Working with a probe current of 5 μA, reduction to mostly Ti2O3 was observed at a current density of 0.8 A/cm2, whereas 5 A/cm2 resulted in local crystallization to anatase already within 1 s of irradiation and to the monoxide TiO after 60 s of irradiation. At 5 μA and 126 A/cm2, reduction to the metallic state occurred. Chemical, structural and topographical effects were followed by AFM, Micro-Raman, WDX and Auger. An estimation of the temperature rise in the beam centre as well as in-situ temperature measurements of the global substrate temperature during exposure shows that crystallization occurred below 150 °C, compared to 450 °C needed for atmospheric crystallization. The local reduction and crystallization phenomena strongly influence the electrical resistance of the couple steel/TiO2, as measured with AFM using a conductive tip. Rather unexpected, we found a higher resistance at low density irradiated spots compared to the surrounding film. A strong resistance drop is observed with the occurrence of anatase, steadily decreasing with ongoing crystallization with prolonged irradiation. A further rapid drop to almost metallic behaviour coincides with the observation of TiO. The steel/TiO2 interface at locally crystallized spots is shown to behave as a Schottky barrier. The high e-beam sensitivity of the present a-TiO2 films is shown to be attractive for precise topographical patterning with e-beam lithography. The possibility of local modification of topography, oxidation state, phase, and hence, for controlling electrical, optical, (photo)catalytic etc. properties on a local scale in an amorphous matrix opens interesting applications also in the biomedical field.[1] P. Kern et al., Thin Solid Films 2006, 494, 279. [2] P. Kern et al., accepted for publication in Appl. Phys. Lett. 2006.[3] M. R. McCartney et al., Vacuum 1991, 42 (4), 301.
9:00 PM - D15.19
Control of Enzymatic Activities by Fe3O4 Nanoparticles
Hui Zhou 1 , Marie-Eve Aubin-Tam 2 , Kimberly Hamad-Schifferli 3 2
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractEnzymatic activities were controlled by external magnetic field through nanosized antenna. Ribonuclease A (RNase A) is a relative small enzyme that cleave single-stranded RNA, and was conjugated to magnetite nanoparticles (NPs) by electrostatic interaction. The diameters of Fe3O4 NPs are less than 10nm. External radio frequency magnetic field was applied, and the enzymatic activities of RNase A changed. It was clearly observed that we could control the activities of RNase A on degrading RNA by using an external magnetic field. Variety of surfactant ligands and different sizes of NPs were adopted, and the effects of NP size and ligand were reported.
9:00 PM - D15.2
Dental Prostheses with Anti-Fungus Surface Layer Based on Segmented Polyurethane.
Erkesh Batyrbekov 1 , Rinat Iskakov 1 , Bulat Zhubanov 1
1 , Institute of Chemical Sciences, Almaty Kazakhstan
Show Abstract9:00 PM - D15.20
Increased Osteoblast Adhesion on Nanograined Hydroxyapatite/Calcium Titanate and Tricalcium Phosphate/Calcium Titanate Composites
Huinan Liu 1 , Celaletdin Ergun 2 , John Halloran 3 , Thomas Webster 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States, 2 Mechanical Engineering Department, Istanbul Technical University, Istanbul Turkey, 3 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractDepending on the coating method utilized and subsequent heat treatments (such as through the use of plasma-spray deposition), inter-diffusion of atomic species across titanium (Ti) and hydroxyapatite (HA) coatings may result. These events may lead to structural and compositional changes that consequently cause unanticipated HA phase transformations which may clearly influence the performance of an orthopedic implant. Thus, the objective of the present in vitro study was to compare the cytocompatibility properties of chemistries that may form at the Ti/HA interface, specifically HA, tricalcium phosphate (TCP), HA doped with Ti, and those containing calcium titanate (CaTiO3). In doing so, results of this study showed that osteoblast adhesion increased with greater CaTiO3 substitutions in either HA or TCP. Specifically, osteoblast adhesion on HA and TCP composites with CaTiO3 was almost 4.5 times higher than over pure HA. Material characterization studies revealed that enhanced osteoblast adhesion on these compacts may be due to increasing shrinkage in the unit lattice parameters and decreasing grain size. Although all CaTiO3 composites exhibited excellent osteoblast adhesion results, Ca9HPO4(PO4)5OH phase formation in TCP/CaTiO3 increased osteoblast adhesion the most; due to these reasons, these materials should be further studied for orthopedic applications.
9:00 PM - D15.21
Patterned Polymer Brushes for Directed Ionic and Molecular Transport
Rachel Evans 1 2 3 , Huilin Tu 1 2 3 , Paul Braun 1 2 3
1 Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States, 2 , Fredrick Seitz Materials Research Laboratory, Urbana, Illinois, United States, 3 , Beckman Institute for Advanced Science and Technology, Urbana, Illinois, United States
Show AbstractTwo-dimensionally patterned poly(oligo ethylene glycol acrylate) polymer brushes have been fabricated and studied for their efficacy of directing the transport of organic fluorescent molecules and ions. The polymer brushes were patterned by microcontact printing of a silane initiator and then grown via surface initiated atom transfer radical polymerization. These polymer brushes were used to transport various fluorophores and biologically relevant ions such as calcium; the transport was studied using both laser scanning confocal microscopy and fluorescence microscopy. Three types of experiments were designed to study the transport of fluorophores in polymer brushes: the first method was conventional fluorescence recovery after photobleaching; the second was to directly observe the diffusion of uncaged fluorophores which were switched and released from their original caged form upon UV exposure; the third was to monitor the fluorescence intensity of fluorophores which were controllably introduced into water-swollen, patterned polymer brushes via microfluidic channels as a function of time and therefore distance away from the source channel. Transport of calcium ions in patterned polymer brushes was studied as a model system for our ionic transport concept. Calcium ions were released from their cages in a defined region by photolyzing the ion-chelating molecules which were spin coated homogeneously into the patterned polymer brushes, and the ion transport through the pattered polymer brush was tracked by probing the fluorescence of calcium indicating fluorophores which were also evenly distributed within the polymer brushes. One potential application for these patterned polymer brushes lies in cell communication where, for example, two cells in contact with either end of a polymer brush pathway may send and receive chemical signals as ions or molecules are transported along the pathway.
9:00 PM - D15.22
Reusable, Reversibly Sealable Parylene-C Membranes for Cell and Protein Patterning.
Bimalraj Rajalingam 1 2 , Dylan Wright 3 , Jeffrey Karp 3 , Selvapraba Selvarasah 4 , Yibo Ling 2 5 , Judy Yeh 6 , Robert Langer 2 3 6 , Mehmet Dokmeci 4 , Ali Khademhosseini 2 1
1 Department of Medicine, Brigham and Women's Hospital,Harvard Medical School, Boston, Massachusetts, United States, 2 Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Electrical and Computer Engineering Department,Center for High Rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States, 5 Department of Electrical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 6 Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - D15.23
Micro and Nano-structured Bioactive Interfaces using Piezoelectric Ink Jet Technology
Anand Doraiswamy 1 , Jan Sumerel 2 , Cerasela Dinu 3 , Joe Howard 3 , Douglas Chrisey 4 , Roger Narayan 1
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 2 , Dimatix Inc., Santa Clara, California, United States, 3 , Max Planck Institute of Molecular Cell Biology and Genetics, Dresden Germany, 4 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractPiezoelectric inkjet deposition is a powerful non-contact, non-destructive process for developing high-throughput biological microarrays. We have demonstrated the microfabrication of nano-structured streptavidin proteins using piezoelectric inkjet technology as a rapid prototyping process. A MEMS based actuator was controlled to jet uniform fluid flow of the protein solution through the ink jet nozzles. Using CAD/CAM generated patterns, we have studied the process under various deposition conditions to develop a processing technique to produce spatially patterned streptavidin protein microarrays. Fluorescein-labeled biotin was used to image and verify the functionality of the streptavidin microarrays via a ligand-recognition reaction. Moreover, competing with unlabeled biotin furthers the determination of specificity and the requisite kinetic data mirrors expected kinetics suggesting that the protein retained its biological activity during the printing process. Jetting parameters and ink composition will be discussed. Potential uses for these spatially patterned arrays in the biomedical arena include bio-sensors, selective cell-culturing, tissue engineering and surface tethered three-dimensional bio-interfaces.
9:00 PM - D15.24
Micropatterned Parylene Stencils for Generation of Dynamic and Static Patterned Cellular Co-cultures.
Dylan Wright 1 , Bimalraj Rajalingam 2 3 , Selvapraba Selvarasah 4 , Yibo Ling 3 5 , Mehmet Dokmeci 4 , Ali Khademhosseini 2 3
1 Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States, 2 Department of Medicine, Brigham and Women's Hospital,Harvard Medical School , Boston, Massachusetts, United States, 3 Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Electrical and Computer Engineering Department,Center for High Rate Nanomanufacturing, Northeastern University , Boston, Massachusetts, United States, 5 Department of Electrical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States
Show Abstract9:00 PM - D15.25
Modeling Block Copolymer Interactions with Biomimetic Membranes
Shashishekar Adiga 1 , Peter Zapol 1 , Millicent Firestone 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractAssociation of amphiphilic di- and triblock copolymers with biomimetic membranes results in versatile novel materials with enormous potential in many areas of bionanotechnology. The molecular architecture and concentration of block copolymers along with environmental variables such as temperature and pH provide means to tune these structures for desired applications and also allow for designing signal-responsive materials. Understanding interaction between block copolymers and lipid bilayers is crucial for applications in nanomedicine. MD simulations based on coarse grained models are used to explore the effect of molecular architecture and concentration on the phase behavior of these materials. In particular, the dependence of copolymer-membrane association on block lengths is explored. The results are compared with small angle X-ray scattering data.This work is supported by the U.S. Department of Energy, BES-Materials Sciences, under Contract W-31-109-ENG-38.
9:00 PM - D15.26
Agarose Microfluidics Devices for Diagnostics and Tissue Engineering.
Yibo Ling 1 2 , Jamie Rubin 3 , Jeffrey Karp 3 , Ali Khademhosseini 1 4
1 Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Electrical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States, 3 Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States, 4 Department of Medicine, Brigham and Women's Hospital,Harvard Medical School , Boston, Massachusetts, United States
Show AbstractMicrofluidics has been a subject of intensive research during the past decade because they can be used to miniaturize experiments, and to perform high-throughput assays easily and inexpensively and in a more physiologically relevant manner. Microfluidic channels fabricated from hydrogels offer a potentially powerful method of generating in vitro systems for drug discovery and tissue engineering. Here, we report the construction of a microfluidics device from agarose, a biocompatible hydrogel. Agarose microfluidic channels were molded from microfabricated silicon wafers that were patterned with SU-8 photoresist. Channels of various sizes and shapes could be fabricated ranging from a few micrometers to millimeter length scales. We determined the optimum conditions for bonding agarose microgels to obtain sealed channels and demonstrate that microchannels remain stable for at least 1 day. The diffusive properties of polypeptides and small molecule solutes within the agarose gel were analyzed using quantified analysis of fluorescently labeled proteins (BSA and IgG) that were flowed through the channels. In addition, we demonstrate that NIH-3T3 cells, hepatocytes and embryonic stem cells could be encapsulated and maintained their viability within the agarose microfluidics devices. Cells were evenly distributed throughout the hydrogel and grew in spherical aggregates. We envision that cell-laden microfluidic hydrogels that were developed here could be useful in various tissue engineering and diagnostic applications.
9:00 PM - D15.27
Atomic Structure and Bonding of Water Overlayer on Cu(110): the Borderline for Intact and Dissociative Adsorption.
Jun Ren 1 , Sheng Meng 2
1 Department of Physics, Sichuan Normal University, Chengdu China, 2 Physics Department, Harvard University, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - D15.28
Preparation and Characterization of a Superparamagnetic Polymer Nanocomposite
Nicole Brenner 1 2 , Rebecca Isseroff 2 , Richard Gambino 1 , Shian Liang 1 , D. Sunil 3 , Mayu Si 1 , Lourdes Collazo 1 , Nadine Pernodet 1 , Miriam Rafailovich 1
1 Materials Science & Engineering, Stony Brook University, Stony Brook, New York, United States, 2 , Lawrence High School, Cedarhurst, New York, United States, 3 , Queens college, Queens, New York, United States
Show AbstractFe(CO)5 decomposition produced ferro- and superparamagnetic polymer nanocomposites. Fe(CO)5 and Cloisite 20A clay were combined in a closed vial for 12 hours, then opened to air for 2 hours. Mossbauer analysis indicated formation of Fe2O3 on clay; mass analysis indicated 12% Fe in clay. A Brabender mixed Fe2O3/clays with PMMA and EVA at ratios by mass of 9:4:36 and 1:1:4 respectively (Fe(CO)5:clay:polymer). TEM displayed Fe2O3 nanoparticles, 3.3 +0.8 nm in diameter adsorbed on exfoliated clay platelet surfaces in polymer matrices. VSM data indicated superparamagnetism with moments of 510.3 emu/g(Fe2O3) (PMMA) and 8.46 emu/g(Fe2O3) (EVA). DMA showed 37% decreased dynamic modulus (EVA) and 11% (PMMA) due to Fe2O3. TGA indicated PMMA stability to 400oC (9.3% mass residual) and EVA to 435 degrees Celsius (11% mass residual). Cell adhesion tests showed Fe2O3/clay enhanced proliferation, promising applications in bone implants. Confocal images showed alignment and increased growth of osteoblasts with addition of Fe2O3/clay to polymers with the presence of exterior magnetic fields.
9:00 PM - D15.29
Label-free Biological Microarray Imaging Using Spectral Reflectivity Information.
Emre Ozkumur 1 , Julia Rentz Dupuis 1 , David Bergstein 1 , Rostem Irani 2 , Michael Ruane 1 , Bennett Goldberg 3 , Selim Unlu 1
1 Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States, 2 Center for Advanced Genomic Technology, Boston University, Boston, Massachusetts, United States, 3 Physics, Boston University, Boston, Massachusetts, United States
Show Abstract9:00 PM - D15.3
Biomineralization Induced by Self-assembled Proteins and Extracellular Protein Matrix of Osteoblasts.
Xiaolan Ba 1 , Yi-zhi Meng 2 , Seo Young Kwak 3 , Elaine DiMasi 3 , Shou-ren Ge 1 , Vladimir Zaitsev 1 , Yi-xian Qin 2 , Nadine Pernodet 1 , Miriam Rafailovich 1
1 Materials Science and Engineering, SUNY-Stony Brook, Stony Brook, New York, United States, 2 Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States, 3 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractThe biological formation of mineralized tissues such as bones is a complex multi-step process leading from a precursor soft tissue, formed by extracellular matrix proteins to a mineralized tissue. The objective of this study is to understand how the biomineralization process can be guided by self-assembled proteins vs. protein networks produced by cells in vitro. To this end, we first measure the mechanical and crystalline properties of fibronectin and elastin networks mineralized in a supersaturated calcium carbonate solution and a meta-stable calcium phosphate solution using atomic force microscopy (AFM), optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and secondary ion mass spectrometry (SIMS). We then use the same techniques to mineralize and characterize the protein networks that are formed by osteoblast-like MC3T3-E1 cells. Preliminary data have shown that the mineralization in these systems is templated by the network of proteins. This work is supported by the NSF, MRSEC, DOE and NIH.
9:00 PM - D15.31
Quantum Chemical Study of TiO2/Dopamine-DNA Triads.
Peter Zapol 1 2 , Manuel Vega-Arroyo 2 , Larry Curtiss 1 2 , Tijana Rajh 2
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Chemistry Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractRecently, hybrid nanocomposites were developed consisting of anatase nanoparticles with a dopamine linker that was attached via the amine group to a specific single-stranded oligonucleotide having a carboxyl group at the 5’-end. The advantage of using enediol ligands such as dopamine to interface DNA with TiO2 nanoparticles is their ability for tight coupling to the surface. Photoinduced charge separation in triads of DNA covalently linked to an anatase nanoparticle via a dopamine bridge was studied by ab initio calculations of the oxidation potentials of carboxyl-DNA trimers and the TiO2/dopamine complex. Conjugation of dopamine to the TiO2 surface results in a lower oxidation potential of the complex relative to the surface and in localization of photogenerated holes on dopamine, while photogenerated electrons are excited into the conduction band of TiO2. Linking dopamine to the DNA trimers at the 5’ end of the oligonucleotide may lead to further hole migration to the DNA. Calculations show that for several different sequences hole migration is favorable in double stranded DNA and unfavorable in single stranded DNA. This extended charge separation was shown to follow from the redox properties of DNA sequence rather than from the modification of DNA’s electron donating properties by the dopamine linker, which explains experimental observations.This work is supported by the U.S. Department of Energy, Basic Energy Sciences, under Contract W-31-109-ENG-38.
9:00 PM - D15.32
Detection of the Enzyme Glucose Oxidase Immobilized on Si-based Surfaces
Sebania Libertino 1 , Manuela Fichera 1 , Patrick Fiorenza 1 , Corrado Bongiorno 1 , Antonino Scandurra 2
1 Catania, CNR - IMM, Catania Italy, 2 SUPERLAB, Consorzio Catania Ricerche, Catania Italy
Show Abstract9:00 PM - D15.33
Detection of Respiratory Viruses with Plastic High Throughput Screening Devices
Zhengshan Zhao 2 , Gerardo Diaz-Quijada 1 , Regis Peytavi 2 , Éric LeBlanc 2 , Johanne Frenette 2 , Guy Boivin 2 , Jim Zoval 3 , Marc Madou 3 , Michel Dumoulin 1 , Teodor Veres 1 , Michel Bergeron 2
2 Centre de recherche en infectiologie, Université Laval, Sainte Foy, Quebec, Canada, 1 Industrial Materials Institute, National Research Council, Boucherville, Quebec, Canada, 3 Department of Mechanical and Aerospace Engineering, University of California, Irvine, California, United States
Show AbstractMicroarrays have become one of the most convenient tools for high throughput screening and they have catalyzed major advances in genomics and proteomics. Other important applications can be found in medical diagnostics, detection of biothreats, drug discovery, etc. Integration of microarrays with microfluidic devices can be highly advantageous in terms of portability, shorter analysis time and lower consumption of expensive biological analytes. Since fabrication of microfluidic devices using traditional materials such as glass is rather expensive, there is a high interest in employing polymeric materials as a low cost alternative that is suitable for mass production. We present proof-of-concept DNA arrays on a plastic platform for the detection of four important respiratory pathogens: Influenza A virus, respiratory syncytial virus, human enterovirus, and human metapneumovirus.This was accomplished by amplifying the genetic material from the viruses and simultaneously labeling the amplicons with a fluorescent dye (Cy3) via a highly sensitive multiplexed Room Temperature Polymerase Chain Reaction (RT-PCR). The resultant RT-PCR product was hybridized, without further purification, with an array of specific oligonucleotide probes (20mers) that had been covalently bound to a plastic substrate. Results indicate a high signal to background ratio that is comparable to commercially available microarray glass slides. In addition, 5 minutes hybridization on this plastic substrate has been demonstrated using a centrifugal microfluidic platform, paving the way towards a rapid medical diagnostic device for point-of-care use that is based on a low-cost portable Micro-Total-Analysis-System (micro-TAS).
9:00 PM - D15.34
DNA-Mediated Assembly and Disassembly of Micron-Sized Particles
Chris Tison 1 , Valeria Milam 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe controlled assembly of micron to nano-sized colloids via hybridization between complementary strands of DNA has generated great interest in the past decade; however, disassembly of these aggregates is currently achieved using temperature and salt concentration changes. By carefully designing primary targets to weakly but fully hybridize to surface-coupled probe strands, we have developed a system which can be reversed by the addition of longer, competitive secondary targets with greater affinity for the probe sequence. Using flow cytometry we have determined conditions for displacing a hybridized primary target sequence. The efficiency of this competitive displacement is based upon both the length of the primary target hybridizing segment, the competitive target hybridizing segment, and the time allowed for both hybridizations to occur. Using fluorescence and confocal microscopy, we have observed DNA-linked particles disperse upon the addition of soluble, competitive oligonucleotides. To the best of our knowledge, this study is the first to examine using DNA to both assemble and disassemble colloidal particles at a fixed temperature. It is proposed that these controlled assembly and disassembly systems will play an important role in drug delivery technologies, DNA-detection techniques, and continue advances being made on nano-scale control of material surfaces by specific biological functionality.
9:00 PM - D15.35
Efficiency of Gold DNA Conjugates for Antisense Gene Silencing.
Katherine Brown 1 , Kimberly Hamad-Schifferli 1
1 Biological Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - D15.36
Multiscale Modeling of DNA Translocation through a Nanopore.
Maria Fyta 1 , Simone Melchionna 2 , Efthimios Kaxiras 1 , Sauro Succi 3
1 Department of Physics and Division of Engineering and Applied Sciences, Harvard Univeristy, Cambridge, Massachusetts, United States, 2 INFM-SOFT, Department of Physics, Universita di Roma 'La Sapienza', Rome Italy, 3 Istituto Applicazioni Calcolo, CNR, Rome Italy
Show Abstract9:00 PM - D15.37
Titania Nanoscrolls for Drug Delivery.
Harsha Kulkarni 1 , Yue Wu 1 2
1 Curriculum in Applied and Material Science, University Of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Department Of Physics and Astronomy, University Of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show Abstract9:00 PM - D15.38
Polyelectrolyte assemblies as multicompartment films for embedding drugs
Philippe Lavalle 1 , Juan Mendez Garza 1 , Erell Le Guen 1 , Nadia Jessel 1 , Pierre Schaaf 2 , Jean-Claude Voegel 1
1 Biomaterials, INSERM, Strasbourg France, 2 Institut Charles Sadron, CNRS, Strasbourg France
Show Abstract9:00 PM - D15.39
The Design of Potent Liposome-Based Inhibitors of Anthrax Toxin.
Prakash Rai 1 , Chakradhar Padala 1 , Vincent Poon 2 , Arundhati Saraph 1 , Saleem Basha 1 , Sandesh Kate 1 , Kevin Tao 2 , Jeremy Mogridge 2 , Ravi Kane 1
1 , Rensselaer Polytechnic Institute, Troy, New York, United States, 2 , University of Toronto, Toronto, Ontario, Canada
Show AbstractSeveral biological processes involve the recognition of a specific pattern of binding sites on a target surface. Theoreticians have predicted that endowing synthetic biomimetic structures with statistical pattern matching capabilities may impact the development of sensors and separation processes. We demonstrated for the first time that statistical pattern matching significantly enhances the potency of a polyvalent therapeutic – an anthrax toxin inhibitor. We functionalized liposomes with an inhibitory peptide at different densities and observed a sharp increase in potency when the average separation between adjacent peptides matched the average separation between peptide-binding sites on the toxin. Pattern-matched polyvalent liposomes neutralized anthrax toxin in vitro, at concentrations four orders of magnitude lower than the corresponding monovalent peptide. We have also studied the influence of membrane fluidity and heterogeneity on inhibitor potency, and have designed inhibitors that neutralize anthrax toxin in vivo. Statistical pattern matching represents a facile strategy to enhance the potency of therapeutics targeting toxins or pathogens.
9:00 PM - D15.4
Developing Biosensors for Monitoring Orthopedic Tissue Growth
Sirinrath Sirivisoot 1 , Chang Yao 1 , Xingcheng Xiao 1 , Brian Sheldon 1 , Thomas Webster 1
1 Engineering, Brown University, Providence, Rhode Island, United States
Show Abstract9:00 PM - D15.41
Formation of DMPC Bilayers on Polyelectrolyte Multilayers Studied by Neutron Reflectometry
Rumen Krastev 1 , Christophe Delajon 1 , Narayan Mishra 1 , Helmuth Möhwald 1
1 Interfaces, Max-Planck Institute of Colloids and Interfaces, Potsdam Germany
Show Abstract9:00 PM - D15.42
On-dependent s-SNOM on Porphyrin Monolayers.
Maxim Nikiforov 1 , Susanne Schneider 2 , Ulrich Zerweck 2 , Christian Loppacher 2 , Stefan Grafstroem 2 , Tae-Hong Park 3 , Michael Therien 3 , Lukas Eng 3 , Dawn Bonnell 1
1 MSE, University of Pennsylvania, Philadlephia, Pennsylvania, United States, 2 , Institute of applied photophysics, Dresden, D-01062, Germany, 3 Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - D15.5
In vitro Evaluation of Macrophage Activity on Nanophase Ceramics.
Peishan Liu-Snyder 1 , Thomas Webster 1
1 , Brown University, Providence, Rhode Island, United States
Show Abstract9:00 PM - D15.6
Evaluation of Biological Responses of UMR-106 Cells to Porous PHBV Matrix Coated with Collagen.
Hui Liu 1 , John Stubbs 2 , Dharmaraj Raghavan 1
1 Chemistry, Howard University , Washington, DC, District of Columbia, United States, 2 Microbiology, College of Medicine, Howard University, Washington, District of Columbia, United States
Show Abstract9:00 PM - D15.7
The Growth of CdS Films under Aqueous Conditions using a Biomimetic Approach.
Sang Soo Jee 1 , Yi-yeoun Kim 2 , Laurie Gower 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States, 2 , Specialty Minerals Inc., Bethlehem, Pennsylvania, United States
Show Abstract9:00 PM - D15.8
Development of Novel Nano-structured Tissue Engineering Scaffold Materials through Self-assembly for Bed-side Orthopedic Applications.
Lijie Zhang 1 , Hicham Fenniri 2 , Thomas Webster 1
1 Divisions of Engineering and Orthopedics, Brown University, Providence, Rhode Island, United States, 2 National Institute for Nanotechnology and Department of Chemistry, National Research Council and the University of Alberta, Edmonton, Alberta, Canada
Show Abstract9:00 PM - D15.9
Dual-Syringe Reactive Electrospinning of Cross-linked Hyaluronic Acid Hydrogel Nanofibers for Tissue Engineering Applications
Yuan Ji 1 , Kaustabh Ghosh 2 , Bingquan Li 1 , Jonathan Sokolov 1 , Richard Clark 2 , Miriam Rafailovich 1
1 Materials Science and Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 2 Department of Biomedical Engineering, SUNY at Stony Brook, Stony Brook, New York, United States
Show AbstractWe described a facile fabrication of cross-linked hyaluronic acid (HA) hydrogel nanofibers via a reactive electrospinning method. Thiolated HA derivative, 3,3'-dithiobis(propanoic dihydrazide)-modified HA (HA-DTPH), and Poly (ethylene glycol)-diacrylate (PEGDA) were selected as the cross-linking system. The cross-linking reaction occurred simultaneously during the electrospinning process using a dual-syringe mixing technique. Poly(ethylene oxide) (PEO) was added into the spinning solution as a viscosity modifier to facilitate the fiber formation and was selectively removed with water after the electrospinning process. The nanofibrous structure of the as-prepared HA scaffold was well preserved after hydration with an average fiber diameter of 110 nm. Cell morphology study on fibronectin (FN)-adsorbed HA nanofibrous scaffolds shows that the NIH 3T3 fibroblasts migrated into the scaffold via the nanofibrous network, demonstrating elaborate three-dimensional (3D) dendritic morphologies within the scaffold, which reflected the dimensions of the electrospun HA nanofibers. These results suggest potential applications of electrospun HA nanofibrous scaffolds as ideal soft tissue scaffold materials for wound healing and tissue regeneration. Supported by NSF-MRSEC