Tuan Vo-Dinh Duke University
Chang Liu Northwestern University
Anis Zribi United Technologies Corporation Fire and Security
Yiping Zhao The University of Georgia
II1: Sensors for Biomedical Applications
Tuesday PM, December 02, 2008
Room 301 (Hynes)
9:30 AM - **II1.1
Surface-Enhanced Raman Nanoparticle Sensors Based on Bioconjugated Nanocrystals and Long-Range Plasmonic Coupling.
Ximei Qian 1 , Shuming Nie 1 Show Abstract
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
10:00 AM - II1.2
Specific Pathogen Recognition on Single-Step Modified Carbohydrate Nanodevice.
HeaYeon Lee 1 , JeongHyun Seo 2 , HyungJoon Cha 2 , BongKuk Lee 1 , Tomoji Kawai 1 Show Abstract
1 Institute for Scientific and Industrial Research(ISIR-SANKEN), Osaka University , Osaka Japan, 2 Department of Chemical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Carbohydrates play critical roles in chemistry, biology, materials science, and related fields. Carbohydrate-protein interactions have been used to elucidate fundamental biochemical processes and identity new pharmaceutical substances in biological systems. Generally, interaction between ganglioside GM1 and Vibrio cholera toxin proteins is regarded as a good model for carbohydrate-protein interaction. Pentameric B subunits of Vibrio cholera toxin are well known to interact individually with pentasaccharide of ganglioside GM1. Monomeric A subunit may interact with the membrane surface through pentameric B subunit and enhance the avidity of the whole interaction. Until now, various kinds of analytical methods have been attempted to reveal the structural and relative interaction relationships for ganglioside GM1-B subunits. However, understanding of quantitative analysis or single molecular level was not settled down util. now. Here, we present a directly immobilization of carbohydrate with orientation and a high specific pathogenic detection through carbohydrate-protein interactions by amperometric analytical, surface plasmon resonance, atomic force microscopy. In addition, we describe surface characterization of single oligosaccharide assemblies for single level interaction force detection by AFM which was a major driving force in nanotechnology research. For the development of biomimetic carbohydrate nanodevices, simple immobilized method of carbohydrate is a prerequisite to verify carbohydrate-protein interaction. We successfully immobilized monosaccharide (glucose) and lactose (disaccharide), and GM1 pentasaccharide by introduction thiol-group to reducing sugar. The our proposed modification method has several advantages including direct and rapid one-step immobilization onto a gold surface and exposure of functional carbohydrate moieties through oriented modification by coupling thiol group to the terminal reducing sugar of the carbohydrate. This novel immobilization method of carbohydrate and high specific assay of carbohydrate-protein should prove useful for diverse biomimetic carbohydrate sensor/devices studies for preventive medicine and diagnosis.
10:15 AM - II1.3
Peptide Beacons: A Versatile Optical Platform for Detecting Polypeptide-Macromolecular Interactions.
Kevin Cash 1 , Kenneth Oh 2 , Arica Lubin 2 , Kevin Plaxco 2 3 Show Abstract
1 Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California, United States, 2 Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, United States, 3 Program in BioMolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, California, United States
Many methods, including molecular beacons, exist for the detection of nucleic acids resulting from the specific, predictable nature of complementary hybridization. Methods for the detection of proteins are more limited, as most proteins do not have a specific interaction with target biomolecules that results in a large conformational change analogous to that which occurs in a molecular beacon upon hybridization. We have overcome this problem and designed a number of sensing architectures based the binding-induced folding of polypeptides.Our sensors, which we have termed peptide beacons (PBs), harness the observation that short peptide sequences are almost always dynamic and structureless when in free solution, but rigidify upon binding to a macromolecular target. To date, three PB architectures have been developed which allow protein-polypeptide and nucleotide-polypeptide binding events to be observed using a benchtop fluorimeter. Two of our architectures, excimer PBs and chimeric PBs are engineered such that terminal fluorescence reporters are held in close proximity in the unbound PB. The two reporters are segregated when the polypeptide adopts its target-bound structure. A third system, dynamic PBs, utilizes the change from a flexible, highly dynamic unbound state to a rigid bound polypeptide as is signal transduction mechanism and thus obviates the need for additional engineering to enforce structure in the unbound state. All three PB architectures show nanomolar detection limits, sufficient for many applications. Additionally the dynamic PB system is able to detect target in contaminant-ridden medium such as blood serum, allowing real world detection applications.
10:30 AM - **II1.4
Nanorod Array Substrates for High Sensitivity Photonic Sensing of Biopathogens.
Richard Dluhy 1 , Jeremy Driskell 3 , Yiping Zhao 2 , Ralph Tripp 3 Show Abstract
1 Department of Chemistry, University of Georgia, Athens, Georgia, United States, 3 Department of Infectious Disease, University of Georgia, Athens, Georgia, United States, 2 Department of Physics, University of Georgia, Athens, Georgia, United States
Development of diagnostic methods for rapid and sensitive identification of viruses and other biomedical pathogens is essential for the advancement of therapeutic and intervention strategies necessary to protect public health. Current diagnostic methods for viruses in particular, e.g. isolation, PCR, antigen detection and serology, are time-consuming, cumbersome, or lack sensitivity. We have investigated the use of aligned Ag nanorod arrays, prepared by oblique angle vapor deposition (OAD), as surface-enhanced Raman scattering (SERS) substrates for the identification and classification of viral pathogens. The OAD method of substrate preparation facilitates the selection of nanorod size, shape, density, alignment, orientation, and composition, while the procedure is reproducible and relatively simple to implement. The current talk will address aspects of the fundamental nanostructural design of metallic nanorod arrays and their influence on SERS enhancement, as well as the development of a spectroscopic assay for virus detection based on these unique nanostructured SERS probes. We will also present results of multivariate statistical analyses on the SERS spectra of different pathogenic species that indicate that it is possible to identify, differentiate and classify viruses and other biomolecules based on their intrinsic SERS spectra, even down to the individual strain level.
11:30 AM - II1.5
Peptide-Nanowire Hybrid Materials for Selective Sensing ofSmall Molecules.
Michael McAlpine 1 2 , Heather Agnew 2 , Rosemary Rohde 2 , Mario Blanco 2 , Habib Ahmad 2 , Andreea Stuparu 2 , William Goddard 2 , James Heath 2 Show Abstract
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 , California Institute of Technology, Pasadena, California, United States
The development of a miniaturized sensing platform for the selective detection of chemical odorants could stimulate exciting scientific and technological opportunities. Biomimicking smart materials which integrate chemical recognition moieties with sensitive transducers could provide a general system for highly specific smell sensors. Oligopeptides are robust substrates for the selective recognition of a variety of chemical and biological species. Likewise, semiconducting nanowires are extremely sensitive gas sensors. Here we explore a bio-inspired approach to mimicking olfaction by linking peptides to silicon nanowire sensors for the selective detection of small molecules. The silica surface of the nanowires is passivated with peptides using amide coupling chemistry. The peptide/nanowire sensors can be designed, through the peptide sequence, to exhibit orthogonal responses to acetic acid and ammonia vapors, and can detect traces of these gases from "chemically camouflaged" mixtures. Through both theory and experiment, we find that this sensing selectivity arises from both acid/base reactivity and from molecular structure. These results provide a model platform for what can be achieved in terms of selective and sensitive "electronic noses," and suggest application as implantable breath sensors for molecular disease indicators.
11:45 AM - II1.6
Fabrication of HAp/ZnO Bilayer for Protein Sensitive Field Effect Transistor.
Hiroaki Nishikawa 1 2 , Masanobu Kusunoki 1 2 , Shigeki Hontsu 1 2 Show Abstract
1 , School of Biology-Oriented Science and Technology, Kinki University, Kinokawa Japan, 2 , Wakayama Industry Promotion Foundation, Wakayama Japan
Hydroxyapatite (HAp) surface has excellent adsorption ability with high efficiency for functional biomolecules such as protein, DNA and so on. Thus HAp is a good candidate for a receptor material of high-sensitive biosensor. Toward the realization of the novel biosensor with the high-sensitive HAp receptor, we have noted dielectric and insulating properties of HAp, the relative dielectric constant εr = 5.7 at 1 MHz and the break down electric field of more than 104 V/cm for 1 μm thick HAp film . These properties are useful as gate insulator of field effect transistor (FET). The FET proposed in this study consists of bilayer of HAp and semiconducting ZnO thin films. Adsorption of charged protein can induce polarization of the HAp gate layer and will control current flowing in the ZnO channel layer under the HAp. The HAp and the ZnO thin films were deposited by the pulsed laser deposition technique on Al2O3(0001) single crystal. The substrate temperature during deposition was 600 °C ~ 750 °C with O2 + H2O partial pressure of 1.3 × 10-4 mbar ~ 1.3 × 10-1 mbar. H2O atmosphere is essential for high quality HAp thin film. Under these conditions,  oriented ZnO thin film was prepared even in the atmosphere including H2O gas. The HAp/ZnO bilayer was also deposited on the Al2O3(0001) while the HAp was polycrystalline. The carrier density in the ZnO channel layer can be drastically controlled by partial pressure of O2 + H2O during the ZnO deposition because origin of the semiconducting property of the ZnO is the oxygen vacancies. The carrier density of the ZnO layer was evaluated by the Hall measurement. The FET behavior of the bilayer structure and the effect of the carrier density of the ZnO layer are reported for the adsorption of protein such as bovine serum albumin on the HAp gate layer. Acknowledgement. This work was supported in part by a grant from the Wakayama Prefecture Collaboration of Regional Entities for the Advancement of Technological Excellence of the Japan Science and Technology Agency (JST).  Hontsu et.al., Thin Solid Films 295, 214 (1994).
12:00 PM - **II1.7
Finding the Needle: Challenges, Strategies, and Opportunities.
Jerry Lee 1 Show Abstract
1 Office of the Director, National Cancer Institute, Bethesa, Maryland, United States
12:30 PM - II1.8
Field Effect-Based Biosensing Device for Cell-Functional Analysis.
Toshiya Sakata 1 , Yuji Miyahara 2 1 Show Abstract
1 Department of Materials Engineering, The University of Tokyo, Tokyo Japan, 2 , National Institute for Materials Science, Tsukuba Japan
12:45 PM - II1.9
Peptide Nanotubes as Building Blocks for Nanobiosensors: Label-free Electrical Detection of Viruses on the Nanotubes.
Roberto de la Rica 1 , Ernest Mendoza 2 , Hiroshi Matsui 1 Show Abstract
1 Chemistry and Biochemistry, City University of New York-Hunter College, New York, New York, United States, 2 Nanobiosensors and Molecular Nanobiophysics Group, Research Center on Nanoscience and Nanotechnology(CIN2)CSIC-ICN, Barcelona, Barcelona, Spain
II2: Synthesis and Characterization of Bio-inspired Materials
Tuesday PM, December 02, 2008
Room 301 (Hynes)
2:30 PM - **II2.1
Fish Locomotion: Inspiration for Biomaterials and Biosensors.
George Lauder 1 Show Abstract
1 Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, United States
3:00 PM - II2.2
Bioinspired Materials Based on Molecular Recognition: The Fine Characterization of the H-Bond Transcription by Advanced Solid State NMR.
Christian Bonhomme 1 , Florence Babonneau 1 , Michel Wong Chi Man 2 , Guilhem Arrachart 2 , Carole Carcel 2 , Joel Moreau 2 , Hubert Wadepohl 3 Show Abstract
1 , universite P et M Curie, Paris France, 2 ENSCM, Institut Charles Gerhardt, Montpellier France, 3 , Heidelberg university, Heidelberg Germany
The structural characterization of biological/inorganic interfaces is one of the most fascinating spectroscopic challenges in the frame of bio-inspired materials. Recent developments in high resolution solid state NMR offers new perspectives in terms of chemical bonding and spatial connectivities between the organic and inorganic components of a given material. 1H nuclei are a key structural probe, as protons are present at all interfaces and "tailor" them by establishing complex hydrogen bonded networks. We will present the latest 1H NMR experiments, including 1D (single quantum -SQ-, ultra fast MAS at very high fied) and 2D (double quantum, DQ) experiments, illuminating the structural features of ureidopyrimidinone silica based materials [1-2]. The DQ experiments allow establishing unambiguous connectivities between pairs of protons, allowing the precise description of H-bonded networks in the crystalline precursors, as well as in the corresponding structured materials. The 1H high resolution solid state NMR approach has been extended to the study of bio-inspired materials, involving SiO2 pillars and adenine/thymine complementary bases . The transcription of the H-bond network from the precursors to the final materials has been unambiguously demonstrated.Solid state NMR offers original approaches, based on the various interactions involved, such as the heteronuclear dipolar coupling (involving unlike spins) and J-coupling (establishing chemical bond connectivities). These new opportunities will be illustrated by the study of silicophosphate gels, which are excellent candidates for biocompatible materials. New NMR techniques have been implemented for that purpose, including original MAS-J-techniques . The study of substituted HAP materials will be also presented, including new insights obtained by 1H/13C/31P triple resonance dipolar-mediated experiments . J. J. E. Moreau, M. Wong Chi Man et al. Angew. Chem., 43, 203, 2004. G. Arrachart, C. Bonhomme et al., J. Mater. Chem., 18, 392, 2008. (a) C. Coelho, C. Bonhomme et al. J. Sol-Gel Sc. Technol., 40, 181, 2006. (b) C. Lejeune, C. Bonhomme et al. Solid State NMR, 27, 242, 2005. (c) C. Coelho, C. Bonhomme et al. J. Magn. Reson., 179, 114, 2006.  (a) E. Fujii, A. Osaka, S. Hayakawa, F. Babonneau, C. Bonhomme et al. Acta Biomaterialia, 2, 69, 2006. (b) S. Hayakawa, A. Osaka, F. Babonneau, C. Bonhomme et al. Key Engin. Mater., 309, 503, 2006. (c) S. Hayakawa, A. Osaka, F. Babonneau, C. Bonhomme et al. J. Am. Ceram. Soc, 90, 565, 2007.
3:15 PM - II2.3
Monitoring Biomimetic Nanomaterials Formation in Dps Protein Cages at the Molecular Level using Non-covalent Mass Spectrometry.
Sebyung Kang 1 3 , Janice Lucon 1 3 , Mark Young 2 3 , Trevor Douglas 1 3 Show Abstract
1 Chemistry and Biochemistry, Montana State University, Bozeman, Montana, United States, 3 Center for BioInspired Nanomaterials, Montana State University, Bozeman, Montana, United States, 2 Plant Sciences, Montana State University, Bozeman, Montana, United States
We have investigated biomimetic nanomaterials synthetic processes in the Dps protein cages from Listeria innocua using non-covalent mass spectrometry. The LiDps is a member of the ferritin superfamily and composed of 12 identical 18 kDa subunits with an outer diameter of 9 nm and an inner cavity diameter of 4 nm. The LiDps produces an iron oxide core similar to that of typical ferritins in situ and has been used for mineralizing metal oxides, such as iron and cobalt oxides, and cadmium sulfide. Biomimetic nanomaterials syntheses utilizing protein cages, including ferritins, viruses, and heat shock proteins, provide a high degree of control over the particle morphology, composition, and polymorph selection under relatively mild synthetic conditions. Although protein cages have been widely used as powerful templates for nanomaterials syntheses, the processes of metal ion accumulation and core formation coupled to the protein cage are still poorly elucidated. This is mainly due to the lack of appropriate analytical tools that detect multiple transient state species simultaneously with sufficient resolution and accuracy. Here, we have independently monitored metal ion (Fe2+, Au3+, and Pt2+) binding and subsequent formation of LiDps protein stabilized nanoclusters (Fe(O)OH, Au0, and Pt0), upon oxidation or reduction, using non-covalent mass spectrometry. Mass measurements of cluster intermediates during the mineralization reaction have allowed us to follow these nanomaterial synthetic processes at the molecular level. Better understanding of the biomimetic mineralization processes may lead to more controlled material synthesis under the mild conditions.
4:00 PM - **II2.4
Stimulus Responsive Allosteric Biopolymer Actuators Triggered by Ligand Binding.
Ashutosh Chilkoti 1 Show Abstract
1 Dept of Biomedical Engineering, Duke University, Durham, North Carolina, United States
4:30 PM - II2.5
Uptake and Transmission of Carbon Nanoparticles in Food Crop Species.
Sijie Lin 1 , Jason Reppert 1 , Qian Hu 1 , Michelle Reid 1 , Tatsiana Ratnikova 1 , Apparao Rao 1 , Hong Luo 1 , Pu Chun Ke 1 Show Abstract
1 Physics and Astronomy, Clemson University, Clemson , South Carolina, United States
With the mass production of nanomaterials in research laboratories and on the consumer market it has become crucial to understand the fate of nanomaterials from cradle to grave. Despite the tremendous advances in nanotechnology research, little is known about the fate of nanomaterials discharged into the environment. Due to their mutual interactions, carbon-based nanomaterials readily aggregate and are not considered as potential contaminants in water sources and crop fields3. However, natural organic matter (NOM), the heterogeneous substances abundant in all river sources and agricultural soils, has recently been found effective in suspending multiwalled carbon nanotubes (MWNTs). Here we show that fullerene C70 and MWNTs dispersed by NOM can be taken up by rice plants, a major crop species in the food chain. We further show the temporal and spatial distributions of C70 uptake in the plants and demonstrate the robust generational transmission of C70 through the plant seeds. This study suggests the potential impact of discharged nanomaterials on ecological plant systems.
4:45 PM - II2.6
Control of Intermolecular Quadruplex DNA Folding by Cationic Comb-type Copolymer.
Rui Moriyama 1 , Naohiko Shimada 1 , Arihiro Kano 1 , Atsushi Maruyama 1 2 Show Abstract
1 1Institute of Materials Chemistry and Engineering, Kyushu University, Fukuoka Japan, 2 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama Japan
The (TGnT)4 quadruplexes are formed by four parallel strands bound together by n layers of G-quartets including n-1 monovalent cations bound between the G-quartets in the central cavity. Because their structures are stable strand assembles with well-characterized structures, there are applied as building blocks of molecular networks. However, since the association and/or dissociation rates of their structures are extremely slow, their applications to smart nanodevices whose functions can be switched in response to external stimuli are difficult. The association mechanism of tetramolecular quadruplex involves the nucleation-zipping model. To promote the association of tetramolecular quadruplex, we focus on the properties of cationic comb-type copolymers, poly(L-lysine)-graft-dextran (PLL-g-Dex) consisting of a PLL backbone and abundant grafts of Dex. PLL-g-Dex forms totally soluble interpolyelectrolyte complexes (IPEC) in which DNA condensation is suppressed. We have previously reported that PLL-g-Dex accelerates the strand-exchange reaction between a double-stranded DNA and its complementary single-stranded DNA probably by promoting nucleation step, the rate-determining step, of the reaction. In this study, the effect of the copolymer on the intermolecular quadruplex folding was investigated by using circular dichroism spectrometer. As described mentioned, TG4T quadruplex formation is a slow process. Only a trace amount (< 1%) of the quadruplex formed with two hours incubation at 15 μM TG4T at 4oC. In the presence of PLL-g-Dex, however, a substantial amount of quadruplex was formed under the same conditions, demonstrating significant accelerating activity of PLL-g-Dex on the quadruplex association. PLL-g-Dex was demonstrated to accelerate the association of quadruplex by 1000-folds. We also estimated the effect of the copolymer on the dissociation rate of the quadruplex. While the half-dissociation time, τ1/2, of (TG4T)4 was 1.7×102 sec in the absence of PLL-g-Dex at 15 μM 60oC, it decreased to 1.1 × 10 sec by PLL-g-Dex addition. This result showed that PLL-g-Dex accelerates the dissociation of quadruplex by 15-folds. These results indicated that PLL-g-Dex accelerated both the association and dissociation of tetramolecular quadruplex. We believe that combination of Gn quadruplex and PLL-g-Dex would open novel strategy for designing DNA nanodevices whose functions can be switched in response to external stimuli.
5:00 PM - II2.7
Microcontact Printing of Carbon and Metal Surfaces Using Spontaneous Reaction With Aryldiazonium Salts.
Joshua Lehr 1 2 , David Garrett 1 2 , Matthew Paulik 1 2 , Paula Brooksby 1 2 , Alison Downard 1 2 Show Abstract
1 Department of Chemistry, University of Canterbury, Christchurch, Canterbury, New Zealand, 2 , MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington New Zealand
5:15 PM - II2.8
Monolayer Based Sample Target Substrates for MALDI-TOF Mass Spectrometry.
Nicole Herzer 1 , Stephanie Hoeppener 1 , Ulrich Schubert 1 2 Show Abstract
1 Lab. of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology, Eindhoven Netherlands, 2 Lab. of Organic and Macromolecular Chemistry, Friedrich-Schiller-University Jena, Jena Germany
II3: Poster Session: Bio-mimic Materials and Applications
Wednesday AM, December 03, 2008
Exhibition Hall D (Hynes)
9:00 PM - II3.1
Ordered Inorganic/Polymer Hybrids Formed by Using Liquid-Crystalline Matrices.
Tatsuya Nishimura 1 , Takahiro Ito 1 , Yuya Oaki 1 , Satoshi Kajiyama 1 , Takashi Kato 1 Show Abstract
1 , The University of Tokyo, Tokyo Japan
Living organisms produce a variety of inorganic/organic composites such as teeth, bone, and seashells. A variety of minerals such as calcium carbonate, hydroxyapatite, silicate, and iron oxides are employed as biominerals. These biominerals are formed through self-organization processes by using organic macromolecules interacting with inorganic substances. Biomineralization has recently received much attention from materials scientists because these biominerals form hierarchical structures exhibiting significant properties under mild conditions. Previously, we succeeded in the preparation of calcium carbonate thin films on the polymer matrix[1,2]. The process was inspired by biomineralization. The combination of solid polymer matrix such as chitin with poly(acrylic acid) is essential for the formation of the calcium carbonate thin films. We also reported on the formation of macroscopically oriented polymer/calcium carbonate hybrids on liquid-crystalline chitin derivatives. The oriented chitin matrix has unidirectionally aligned functional groups. Such alignments serve as ordered templates for the calcium carbonate crystallization. In the present study, we have examined the effect of the ordered structure of an insoluble chitin matrix on the functional inorganic crystal growth to develop the unidirectionally aligned inorganic /polymer hybrid material. One of our targets of the functional inorganic crystals is strontium carbonate. In the presence of poly(acrylic acid), unidirectionally oriented strontium carbonate thin film crystals are grown on the ordered chitin matrix. The matrix also serves as an ordered template for the strontium carbonate thin film crystallization and the cooperation of the matrix and the soluble polymers induces unidirectional oriented thin film crystal growth.1) Kato, T.; Sugawara, A.; Hosoda, N. Adv. Mater. 2002, 14, 869.2) Sugawara, A.; Oichi, A.; Suzuki, H.; Shigesato, Y.; Kogure, T.; Kato, T. J Polym. Sci. A, 2006, 44, 5153. 3) Nishimura, T.; Ito, T.; Yamamoto, Y.; Yoshio, M.; Kato, T. Angew. Chem., Int. Ed. 2008, 47, 2800.
9:00 PM - II3.2
New Bionanocomposites Based On Gold Nanoparticles And Alginate.
Vincent Jaouen 1 , Nathalie Steunou 1 , Jacques Livage 1 , Thibaud Coradin 1 Show Abstract
1 Chimie de la Matière Condensée de Paris, UPMC, Univ Paris 06, Collège de France, Paris France
9:00 PM - II3.3
Reversibility and Irreversibility in Specific Binding Reaction of Antigen and Antibody Dependent on Ionic Strengths of Reaction Solutions.
Chil Seong Ah 1 , Ansoon Kim 1 , Chan Woo Park 1 , Chang-geun Ahn 1 , Jeong-Heon Yang 1 , In Bok Baek 1 , Taeyoub Kim 1 , Gun Yong Sung 1 Show Abstract
1 , Electronics and Telecommunications Research Institute (ETRI), Daejeon Korea (the Republic of)
The degree of specific reversible and irreversible binding reaction of antigen and antibody is greatly affected by ionic strengths of used reaction solutions. About PSA and anti-PSA specific binding, in case specific binding reaction happens in PSA solutions of low ionic strengths, the washing with a buffer solution of low ionic strengths results in PSAs removal from anti-PSA binding almost 100 %. In contrary, in case specific binding reaction happens in PSA solutions of high ionic strengths, the washing with a low ionic strength buffer solution does not remove the PSA from anti-PSA binding at all and the PSA exists in the condition of PSA-anti-PSA binding almost 100%. These could be demonstrated by the SEM analysis of the Au nanoparticles (NPs) coverage and fluorescence analysis from sandwich-type polyclonal anti-PSA Au NPs conjugates immunoassay and ELISA protein detection method.In addition, reversibility and irreversibility of antigen-antibody binding reaction dependent on ionic strengths of reaction solutions was confirmed in PSA detection experiments which use the Si FET biosensor. After inducing PSA-anti PSA specific binding reactions in PSA solutions of low ionic strengths, the remained PSA solution unbinded with anti PSA was completely removed and the saturation current was measured in a pure buffer solution of low ionic strengths. The level of saturation current measured in a pure buffer solution of low ionic strengths before and after PSA-anti PSA specific binding reactions was same, meaning antigen-antibody binding reaction is reversible in reaction solutions of low ionic strengths. In contrary, after inducing PSA-anti PSA specific binding reactions in PSA solutions of high ionic strengths, the remained PSA solution unbinded with anti PSA was completely removed and the saturation current was measured in a pure buffer solution of low ionic strengths. The level of saturation current measured in a pure buffer solution of low ionic strengths before and aftere PSA-anti PSA specific binding reactions was not same (increased or decreased), meaning antigen-antibody binding reaction is irreversible in solutions of high ionic strengths.
9:00 PM - II3.4
Electronic Application of Stochastic Resonance by Utilizing Nonlinear Property of Vanadium Oxide: Toward Creation of Bio-mimetic Devices.
Teruo Kanki 1 , Yasushi Hotta 1 , Naoki Asakawa 1 , Hidekazu Tanaka 1 , Tomoji Kawai 1 Show Abstract
1 , ISIR, Osaka University, Osaka Japan
The realization of bio-mimetically functional applications with highly flexible and robust responses against abrupt environmental changes will offer more stable and human-friendly infrastructures. Stochastic resonance (SR) is a key principal to obtain such a bio-mimetic system. Various biological systems harness SR to detect weak signal within noisy circumstances  and/or to enhance organic activities by noise , that is, moderate level of noise in a nonlinear system can enhance the information throughput. We believe that a stochastic information-propagation driven by noise creates flexibility and robustness, likely working a different principle from present silicon technology. Our research purpose is to construct new functional devices based on the principle of SR in terms of material developments. Vanadium oxides are well-known materials showing huge nonlinear response of transport properties, which expect construction of basic SR devices with high efficiency. The components of SR devices consist of threshold parts and noise generators. In this research, basic properties of vanadium oxides as SR components were investigated. Vanadium oxide thin films were fabricated on Al2O3 (0001) substrates by a pulsed laser deposition technique. As a result, the comparator property having a threshold at 8V was obtained in the thin films with several hundreds micrometer size, showing pulse trains like nerve activity when the signal amplitude was beyond the threshold. For the noise generator, the phase-instability between monoclinic with high resistivity and triclinic with low resistivity cause electronic oscillation which can be used as noise generator. Thus the two components that are indispensable for SR devices are provided from a vanadium oxide. This advantage will facilitate the creation of novel bio-mimic devices with high efficiency and with multi-functions. David F. Russell, Lon A. Wilkens and Frank Moss: Nature 402, 291(1999). A. Priplata, J. Niemi, M. Salen, J. Harry, L. A. Lipsitz and J. J. Collins: Phys. Rev. Lett. 89, 238101 (2002).
9:00 PM - II3.5
Bio-Inspired Magnetite Nanocrystals Studied on a Self-Assembled Organic Template: Avoiding Bulk-Synthesis Artefacts.
Tanya Prozorov 1 , Surya K. Mallapragada 1 2 , Pierre Palo 3 , Lijun Wang 3 , Marit Nilsen-Hamilton 1 3 Show Abstract
1 Materials Chemistry and Biomolecular Materials, Ames Laboratory, Ames, Iowa, United States, 2 Chemical and Biological Engineering, Iowa State University, Ames, Iowa, United States, 3 Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, United States
Tuan Vo-Dinh Duke University
Chang Liu Northwestern University
Anis Zribi United Technologies Corporation Fire and Security
Yiping Zhao The University of Georgia
II4: Applications of Bio-inspired Materials
Tuan Vo Dinh
Wednesday AM, December 03, 2008
Room 301 (Hynes)
9:30 AM - **II4.1
Bottom-up Assembly of phi29 DNA Packaging Motor Components for Nanotechnology and Nanomedicine.
Peixuan Guo 1 , Songchuan Guo 1 , Dan Shu 1 , Yi Shu 1 , Jing Liu 1 Show Abstract
1 Dept of Biomedical Engineering, University of Cincinnati, Cincinnai, Ohio, United States
Bacterial virus phi29 DNA packaging motor is geared by the ATP-binding pRNA that binds to the connector containing a 3.6-nm central channel as a path for DNA. A mimetic DNA-packaging motor has been constructed. The 3D structures of pRNAs have been probed by photoaffinity crosslinking, chemical modification interference, compensatory modification, cryo-AFM, and 3D computer modeling. The active motor was stalled and restarted to observe DNA motion in real time. A single fluorophore dual imaging system was constructed to count the number of fluorescent-pRNA directly within the motor by photobleaching. The unique feature of pRNA in its two interlocking loops makes it a promising tool for bottom-up assembly in nanomachine fabrication, pathogen detection, and gene delivery. Chimerical pRNA/aptamer, pRNA/ribozyme, pRNA/siRNA and pRNA/ligand complexes were successfully constructed for detection, targeting, gene/drug delivery, and the diagnosis/treatment of diseases. The chimerical RNAs were further assembled into nanoparticles. Larger RNA complexes can be constructed from the following three building blocks: (a) Monomer with intramolecularly self-complementary left and right loops. (b) Monomer with noncomplementary left and right loops for intermolecular interaction. Both building blocks can be self-assembled into monomers, dimers and trimers. (c) Monomer with intermolecularly self-complementary left and right loops and palindromic 3’ ends that can form into RNA twins, tetramers, and arrays. Additionally, we have designed the pRNA assembled from a two-piece module with full DNA packaging activity. The 117-nt pRNA is dissected with one RNA oligo encompassing both the procapsid binding domain and the R loop and the other RNA oligo containing only the L loop. The two pieces of oligos are clamped together via a 6-nt duplex. The polyvalent pRNA can deliver up to six kinds of therapeutics to specific cells, as demonstrated in breast cancer, leukemia, lung cancer, and prostate cancer cell lines. Incubation of the synthetic RNA nanoparticles containing receptor-binding aptamers or folates resulted in cell binding and transportation of the chimeric pRNA/siRNA, pRNA/ribozyme, or drugs into cells, subsequently modulating programmed cell death. The delivery efficiency was confirmed in animal trials. RNA 3-D design, circular permutation, folding energy alteration, and nucleotide modification were applied to generate stable RNA nanoparticles with low toxicity and to make the chimeric RNA complexes processed into siRNA by Dicer after delivery. Using such protein-free nanoparticles as therapeutic reagents would allow repeated treatment of chronic diseases.
10:00 AM - II4.2
Functionalization of Silicon Nanowires with Myosin Protein Motors for Bio-inspired Nanomechanical Applications.
Kyung-Eun Byun 1 , Kwang Heo 1 , Han-Nah Jeong 2 , Heon-Jin Choi 2 , Seunghun Hong 1 Show Abstract
1 Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 2 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of)
Protein motors such as actomyosin have been drawing an attention as a key component for bio-inspired nanomechanical applications such as protein motor-based nanoscale engines. For such applications, it is crucial to combine protein motors with inorganic nanostructure components such as nanowires. However, it has been extremely difficult, if not impossible, to functionalize nanowires with biological motors due to various issues such as nanowire dispersion and biocompatibility. Herein, we present a method to functionalize silicon nanowires (Si NWs) with myosin protein motors, where myosin was assembled onto the 3-aminopropyltriethoxysilane (APTES) treated Si NWs. Significantly, we, for the first time, successfully demonstrated the motility experiments of actin filaments on the myosin-functionalized Si NWs. This result should be a major breakthrough in the area of bio-inspired nanomechanics research and should pave the way toward advanced nanomechanical systems such as biomotor-based engine structures.
10:15 AM - II4.3
Harvesting Electrical Energy from Living Human Cells.
Miho Sakai 1 , Andreas Vonderheit 1 , Andreas Stemmer 1 Show Abstract
1 Nanotechnology Group, ETH Zurich, Zurich Switzerland
It would be an attractive option to power implantable medical devices such as sensors, hearing aids or pace makers with electrical current harvested directly from the human body, rather than batteries that need to be replaced periodically. Glucose is an abundant energy source and its conversion into electrical energy has been demonstrated in bacterial  and enzyme-based  fuel cells. However, for an implantable device, the former lacks biocompatibility while the latter suffers from the short lifetime of the enzyme catalyst.Here we present first results obtained with a novel bio fuel cell utilizing trans-membrane electron transport of human macrophages. When foreign substances invade the body, macrophages differentiated from monocytes are activated to initiate phagocytosis. In this process, macrophages produce reactive oxygen species via electron transport through a membrane-bound protein complex, the NADPH oxidase (nicotinamide adenine dinucleotide phosphate-oxidase) .In our two-compartment fuel cell set-up, macrophages are seeded onto a gold electrode (anode) to collect electrons transferred to the cell exterior by the NADPH oxidase. A series of inhibitory experiments shows that the current produced correlates with the activity of NADPH oxidase. With non-optimized electrode surface and in the absence of mediators the extracted power is 250 nW per 106cells.B. Logan et al., Environ. Sci. Technol. 40 (2006) 5181E. Katz, A. Shipway, I. Willner, Handbook of Fuel Cells 1, Wiley (2003) (Chapter 21).A. Cross, A. Segal, Biochim. Biophys. Acta 1657 (2004) 1
10:30 AM - **II4.4
Chemo-hydrodynamic Signal Detection in Marine Navigation Tasks: Sharks, Lobsters and Machines.
Jelle Atema 1 Show Abstract
1 Biology Department, Boston University Marine Program, Boston, Massachusetts, United States
11:30 AM - II4.5
Single-Carbon-Atomic-Resolution Detection of Odorant Molecules using Human Olfactory Receptor-based Bioelectronic Nose.
Tae Hyun Kim 1 , Sang Hun Lee 2 , Tai Hyun Park 2 , Seunghun Hong 1 Show Abstract
1 Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 2 School of Chemical and Biological Engineering, Institute of Bioengineering, Seoul National University, Seoul Korea (the Republic of)
Portable nano-sensor systems for the rapid detection of specific odorants are crucial for anti-bioterrorism, disease diagnostics, and food safety. Since the first report of ‘electronic nose’, there have been many efforts to develop artificial olfactory sensors based on the arrays of semiconductor devices. However, the capability of the electronic nose is still, in many ways, inferior to that of the human olfactory system in terms of selectivity. Herein, we report the detection of odorant molecules with single carbon atomic resolution using the human olfactory receptor-based ‘bioelectronic nose’. In this device, lipid membranes containing human olfactory receptor 2AG1 (hOR2AG1) were coated on single-walled carbon nanotube (swCNT) - field effect transistors (FET) surfaces, and the deformation of the hOR2AG1 protein due to the binding of specific odorant molecules was detected via the swCNT-FET. We demonstrated the detection of specific odorant molecules with single-carbon-atomic resolution and femto-molar sensitivity in real time. Furthermore, this is the first demonstration of monitoring the operation of G-protein-coupled receptors (GPCR) in cell membrane with swCNT-FET sensors, and it should open various new applications in drug and fragrance development because the olfactory receptor proteins are the largest family of GPCR which is the most ubiquitous class of drug targets- up to 50% of current drugs are targeted at GPCR.
11:45 AM - II4.6
Electrochemically Synthesized Magnetostrictive Nanowire Arrays and Heterostructures for Acoustic Sensing.
Patrick McGary 1 2 , Bethanie J Stadler 1 3 , Patrick Downey 4 , Alison Flatau 4 Show Abstract
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 Physics and Engineering, Bob Jones University, Greenville, South Carolina, United States, 3 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 4 Aerospace Engineering, University of Maryland, College Park, Maryland, United States
Biological cilia in humans and animals serve many functions, including sensing of acoustic and sensory signals and actuation for mobility of small species or of bodily fluids in larger species. This work seeks to fabricate nanowire arrays as artificial cilia. Arrays of tiny sensors at nanoscale dimensions have theoretical advantages to macro sensors and sensor arrays including higher spatial resolution, miniscule size, and higher ultimate strength for each sensing element. Theoretical investigations showed that a magnetic/non-magnetic heterostructure would enable nanowires with improved sensitivity over single element nanowires. Here, nanowire structures included a soft magnetostrictive sensing segment (such as Ni or Fe1–xGax [also called Galfenol]), a permanent magnetic segment to provide an integrated magnetic bias, and a long and stiff non-magnetic end segment to increase the viscous drag force of the fluid on the nanowire. Galfenol is a new magnetostrictive material that has moderate magnetostriction but excellent mechanical properties. The fabrication of these into nanoscopic form is a recent advance. These nanowire structures were grown into nanoporous anodic aluminum oxide (AAO) templates using a robust two-step anodization process. When anodized at the proper conditions (temperature, electrolyte, and voltage) the templates were highly-ordered nanopores with small diameters (10-100 nm), center-to-center distances (25-250 nm), and long lengths (0.1-100 µm). Metal contacts were deposited onto one side of the templates, and non-magnetic, magnetic, and magnetostrictive materials were sequentially electrodeposited into the nanopores. Controlling the non-magnetic segment lengths enabled control of the nanowire resonant frequency. By using graded nanowire lengths across the array, frequency pre-filtering for subsequent signal processing could be performed. The non-magnetic segments were mechanically polished to obtain graded lengths. Magnetic states of Galfenol nanowires freed from the array were analyzed using magnetic force microscopy and Lorentz microscopy. It was found that shape anisotropy was a dominant factor in controlling the rotation of the magnetization. This factor must be addressed in design employing this material. The mechanical properties of the nanowires were tested using a nanomanipulator inside a scanning electron microscope. The Young’s modulus was 50-58 GPa and the ultimate strength was 1150 MPa. By coupling the magnetic flux from the nanowire array into a 1-dimensional array of tiny magnetoresistive sensors, mechanical deformation sensing performance was characterized. The process for producing complete magnetic heterostructured nanowires for biomimetic cilia has been achieved. P. D. McGary, L. Tan, J. Zou, Bethanie J. H. Stadler, P. R. Downey, and A. B. Flatau, J. Appl. Phys. 99, 08B310 (2006).
12:00 PM - II4.7
Cell Compaction Induced by Fullerene Translocation.
Emppu Salonen 2 , Sijie Lin 1 , Michelle Reid 1 , Apparao Rao 1 , Ilpo Vattulainen 2 , Pu Chun Ke 1 Show Abstract
2 Laboratory of Physics , Helsinki University of Technology , Helsinki Finland, 1 Physics and Astronomy, Clemson University, Clemson , South Carolina, United States
Fullerenes possess unique structural, mechanical, and electronic properties that are exploited in broad applications. Due to their mutual van der Waals interaction, fullerenes readily accumulate and their aggregates have been found to facilitate electron transfer across cell membranes, a phenomenon which may impact photosynthesis and cancer medicine. Here we show how the interaction of fullerene with natural phenolic acid induces cell contraction. Our atomistic simulations reveal that the self-assembly of C70-gallic acid favors aggregation. Confocal fluorescence microscopy shows that C70-gallic acid complexes translocate across the membranes of HT-29 colon cancer cells and enter nuclear membranes. Confocal imaging further reveals the real-time uptake of C70-gallic acid and the consequent contraction of the cell membranes. This contraction is attributed to the mechanical pressure induced by fullerene aggregation on membrane surfaces, a new physical mechanism for deciphering nanotoxicity in biological and ecological systems.
12:15 PM - II4.8
Biomolecular Activity Switch Actuated By Ultrafast Pulsed Laser Irradiation Of Gold Nanorods.
Joshua Alper 1 , Monica Crespo 2 , Kevin Jones 3 , Andrei Tokmakoff 3 , Kimberly Hamad-Schifferli 1 3 Show Abstract
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
II5: Bio-inspired Sensors
Wednesday PM, December 03, 2008
Room 301 (Hynes)
2:30 PM - **II5.1
Selective Vapor Sensing using Bio-inspired Hierarchical Photonic Structures.
Radislav Potyrailo 1 , Cheryl Surman 1 , Katharine Dovidenko 1 Show Abstract
1 , GE Global Research Center, Niskayuna, New York, United States
3:00 PM - II5.2
Arrays of Cross-Reactive Sensors based on Nanomaterials: From Synthesis to Applications.
Peng Gang 1 , Ossama Assad 1 , Hossam Haick 1 Show Abstract
1 Chemical Engineering, Technion-Israel Institute of Technology, Haifa Israel
Arrays of broadly cross-reactive vapor sensors provide a man-made implementation of an olfactory system, in which an analyte elicits a response from many receptors and each receptor responds to a variety of analytes. Pattern recognition methods are then used to detect analytes based on the collective response of the sensor array.With the use of this architecture, we found that arrays sensors made from composites of inorganic nanomaterials (silicon nanowires and single wall carbon nanotubes) and organic monolayers can robustly classify, identify, and quantify a diverse collection of organic volatile biomarkers of disease states (e.g., lung cancer and renal failure), even though no individual sensor responds selectively to a particular biomarker. The discrimination ability of the developed arrays of sensors was found to depend critically on the (chemical, physical, and electrical) properties of the interface between the inorganic material and capping monolayer, and, furthermore, on the deformation of the capping monolayer in the presence of biomarkers. The “smelling” mechanism and the ability of the developed arrays to detect diseases will be presented and discussed.
3:15 PM - II5.3
Selective Target Recognition and Chromic Response Transduction in a Polymeric Sensor.
Justyn Jaworski 4 3 , Keisuke Yokoyama 3 , Chris Zueger 1 , Arun Majumdar 3 1 , Seung-Wuk Lee 4 2 Show Abstract
4 Bioengineering, UC Berkeley / UCSF, Berkeley, California, United States, 3 Materials Sciences Division, LBNL, Berkeley, California, United States, 1 Mechanical Engineering, UC Berkeley , Berkeley, California, United States, 2 Physical Biosciences Division, LBNL, Berkeley, California, United States
Widespread use of chemical sensors has yet to be realized in part due to their lack of selectivity. Herein, we undertake the issue of selective target recognition and transduction through a modular sensor approach in which selectivity elements are directly coupled to chromic response elements. Thus far, we have achieved selective target binding through the use of peptide based recognition motifs. We developed such novel recognition elements via the evolutionary process of phage display. Specifically, we have created peptides with high selectivity for the explosive TNT (trinitrotoluene) as well as the decomposition product DNT (dinitrotoluene). In addition, we have demonstrated that naturally occurring cell surface receptor motifs may also be used as functioning selectivity elements. Utilizing a facile synthesis method, these selective recognition elements are conjugated to colorimetric response elements. The response elements, amphiphilic polydiacetylene molecules, will self-assemble in solution to form vesicles structures. Exposure of the vesicles to UV light results in cross-linking to form a planar conjugated system possessing a visibly blue color response. Breaks in the planarity of the conjugated polydiacetylene, such as those resulting from bond rotation due to target binding with surface coated selective recognition elements, will induce a noticeable color change to red. We have shown that the length as well as the surface density of recognition elements is important in tuning the response of the system. Control of the surface composition is of particular interest, as it can dramatically affect the chromic response in addition to the initial color produced by the vesicle; therefore, a tradeoff exists between surface density and efficacy of the sensor. In order to maintain a sufficiently high initial blue color, it is necessary to have a low surface density of recognition elements. However, a low surface density of receptors can cause a reduction in the perceived chromic response upon target exposure. For instance, vesicles coated with TNT selective element have a favorable surface receptor density range of 4% - 10%. We have investigated the efficacy of this modular sensing platform for a wide range of targets from small molecules (TNT) to large cellular targets (human fibroblasts). We believe the advantages of selective detection and transduction achieved from this approach may be utilized in furthering the capabilities of current sensing systems, as the ability to selectively detect a given target provides an exciting tool for the chemical sensing industry.
4:00 PM - **II5.4
Development of Novel Biologically-inspired Directional Microphones.
Ron Miles 1 Show Abstract
1 Mechanical Engineering, SUNY-Binghamton, Binghamton, New York, United States
4:30 PM - II5.5
Minute Signaling Recognition for Smart Bio-Device Systems.
HeaYeon Lee 1 , BongKuk Lee 1 , PilNam Kim 2 , KahpYang Suh 2 , Tomoji Kawai 1 Show Abstract
1 Institute for Scientific and Industrial Research(ISIR-SANKEN),, Osaka University , Osaka Japan, 2 School of Mechanical and Aerospace Engineering, Seoul National University, Seoul Korea (the Republic of)
Recently, state-of-the-art tools for smart biosensor-chip systems were discussed. One of the critical issues in the development of biological-nanosystem is how differentiated signal-to-noise ratio per very small amount of signal. A new paradigm of nanomedicine combining miniaturization and integration has been exploited in fields such as artificial organ construction and biosensor chips. Developing biocompatible integrated nanosystem requires the fabrication of appropriately designed nanomatrix for high sensitivity homogenous assays. Until now, we achieved high specific recognition of DNA molecule on nanowell array system integrated top-down and bottom-up technology. We obtained a 150-orders–of-magnitude enhancement in sensitivity. This nanometric system could be applied to numerous other integrated digital biosensors. In this present, we describe a demonstration of switching action of precious molecule recognition without nonspecific binding while maintaining the bioactivity on ultra-limited nanostructured space. Lipid membranes vesicles are a biomimetic platform for various application of ligand-receptor interactions, cellular attack or signal transduction. It turned out the well-oriented nanowell geometry of a gently-sloped vertical wall was optimal for selective docking of single liposomes without capillary resistances. With this nanowell electrode, the electrochemical responses were significantly enhanced for the binding event of streptavidin to the biotinylated functional lipid vesicles and the electron transfer was efficiently blocked by the captured liposome. The nanosized geometry of a gently-sloped vertical wall was optimal for selective docking of single liposomes without capillary resistances. With this nanostructure, the electrochemical responses were significantly enhanced for the binding event of streptavidin to the biotinylated functional vesicles (about 220 times increase in signal amplification as compared to bare electrode) and the electron transfer was efficiently blocked by the captured liposome. Also, a simple sandwich format was used for the detection of a specific target of obesity molecules with a small amount using the nanowell electrode. A substantial decrease in peak current density was found with the addition of leptin without nonspecific binding or false positives. It is envisioned that the miniaturized integrated nanowell array-chip system has excellent advantages over conventional instrumental systems for analysis of biomaterials such as compactness, economical, rapid, and multiplex capability. Furthermore, the nanowell array-chip system should be compatible with a variety of nanodevices that aim at high throughput analysis.
4:45 PM - II5.6
Effects of Probe Length, Geometry and Redox-tag Placement on the Performance of the Electrochemical E-DNA Sensor.
Arica Lubin 1 , Brook Vander Stoep Hunt 1 , Kevin Plaxco 1 Show Abstract
1 Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, United States
We have previously described a reagentless, electrochemical DNA sensor (termed E-DNA) that is comprised of an electrode-immobilized stem-loop oligonucleotide1,2. The DNA probe, immobilized on a gold surface via thiol self-assembly, is tagged with a redox reporter at its 3’ terminus which readily transfers electrons to the gold electrode in the absence of complementary target oligonucleotides. In the presence of target, the oligonucleotide target hybridizes to the loop, lifting the reporter tag away from the surface and inhibiting electron transfer. In an effort to elucidate the sensing mechanism of the E-DNA sensor and to determine which sensor construct is optimal for such a surface-immobilized oligonucleotide sensor, we have characterized E-DNA sensors built using linear and stem-loop probe geometries of various lengths. We have also varied the location of our reporter element (Methylene Blue) on the probe to determine how the location of the redox tag affects signaling. The results from these six E-DNA constructs indicate a distinction in sensor behavior not only between the linear and stem-loop designs, but also in the location of the reporter tag. Our results indicate that for example, a shorter linear E-DNA probe sequence gives greater signal gain upon target detection versus a probe that is twice as long, and that moving the Methylene Blue redox label from the 3’-terminal to the center of the E-DNA sequence, in both the linear and stem-loop constructs, greatly improves the sensor’s behavior with the internally-labeled linear probe performing the best (ie: increased signal gain and faster equilibration times). The sensors are all easily regenerated (with a water rinse), respond to nanomolar target concentrations and can be employed in contaminant-rich samples such as serum. The results of this comparative study will help guide future designs and applications of the E-DNA sensor. References:1. Fan, C.; Plaxco, K. W.; Heeger, A. J. Electrochemical interrogation of conformational changes as a reagentless method for the sequence-specific detection of DNA. Proc. Natl.Acad. Sci 2003, 100, 9134-9137.2. Lubin, A.A., Lai, R.Y., Baker, B.R., Heeger, A.J. and Plaxco, K.W. The sequence-specific, electronic detection of oligonucleotides in blood, soil and foodstuffs with the reagentless, reusable E-DNA sensor. Anal. Chem., 2006, 78, 5671-5677.
5:00 PM - II5.7
Optimizing Electrochemical Aptamer-Based Sensors.
Ryan White 1 , Noelle Phares 1 , Arica Lubin 1 , Yi Xiao 1 , Kevin Plaxco 1 Show Abstract
1 Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, United States
Electrochemical aptamer-based (E-AB) sensors, which are comprised of an electrode modified with surface immobilized, redox-tagged DNA aptamers, have emerged as a promising new biosensor platform. In order to further improve this technology, we have systematically studied the effects of probe (aptamer) packing, the AC frequency used to interrogate the sensor, and the nature of the self-assembled monolayer (SAM) used to passivate the electrode on the performance of two representative E-AB sensors, directed against the small molecule cocaine and the protein thrombin. We find that controlling the concentration of aptamer employed during sensor fabrication allows us to control the probe density on the electrode surface for both sensor architectures (1.2 x 10^11 molecules/cm^2 – 4.4 x 10^12 molecules/cm^2 for the cocaine sensor; 5.7 x 10^11 – 1.3 x 10^13 molecules/cm^2 for the thrombin sensor). Over this range the gain of the cocaine sensor increases from 60% to 200%, with the maximum gain observed near the lowest packing densities. Alternatively, the thrombin sensor signal suppression ranges from 16% to 42% exhibiting better signal at higher probe densities. However, with higher packing density, the thrombin sensor equilibration time is slower. We also find that E-AB signal gain is sensitive to the nature of the alkanethiol self-assembled monolayer (SAM) employed to passivate the interrogating electrode. Specifically, while shorter alkanethiol SAMs lead to higher absolute sensor currents, reducing the length of the SAM from the original 6-carbon alkane to a 2-carbon alkane reduces the observed cocaine sensor signal gain 10-fold. By changing simple fabrication parameters we can readily change the sensing capabilities of an E-AB sensor.
5:15 PM - II5.8
Reusable, Electrochemical DNA Sensor Based on a Target Induced-Resolution of an Electrode-Bound DNA Pseudoknot.
Kevin Cash 1 , Yi Xiao 2 3 , Xiaogang Qu 4 , Kevin Plaxco 3 5 , Alan Heeger 2 Show Abstract
1 Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California, United States, 2 Department of Physics and Institute for Polymers and Organic Solids, University of California Santa Barbara, Santa Barbara, California, United States, 3 Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, United States, 4 Division of Biological Inorganic Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China, 5 Program in BioMolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, California, United States
The ability to rapidly and accurately detect specific nucleic acid sequences in complex clinical samples could greatly improve disease diagnostics in both the clinical and research setting. Electrochemical DNA (E-DNA) sensors are single step, reusable, reagentless and stable enough to perform when challenged with complex media, and are thus capable of meeting the demanding needs of this application. However, the current generation of E-DNA sensors indicate the presence of target DNA with a decrease in measured signal, ultimately limiting the achievable signal gain and increasing the risk of false positivesThus motivated, we present an E-DNA sensor based on an electrode-bound DNA pseudoknot that embodies “signal-on” sensing and increased mismatch detection capabilities. The pseudoknot consists of two stem-loop structures (see figure) such that, in the absence of target, a redox tag is held away from the electrode surface, minimizing electron transfer. Upon target binding, the pseudoknot structure is disrupted, liberating a single stranded DNA region allowing the redox tag to collide with the electrode surface and transfer electrons, thus leading to an increased signal.The new sensor architecture is sensitive, with a detection limit in the low nM, and specific enough to discriminate between a perfectly matched DNA target and multiple-mismatch targets (point mutations). For example, a 68% or 2% signal increase is observed for a one- or three-mismatch target respectively (compared to a 100% signal increase with a perfectly matched target). Finally, the sensor is selective and stable enough to function in 50% blood serum without performance loss, and is readily regenerated with a simple water rinse.Xiao, Y.; Qu, X.; Plaxco, K. W.; Heeger, A. J. (2007) J. Am. Chem. Soc.; 129(39); 11896-11897.
5:30 PM - II5.9
Surface Patterning of a Bi-enzymatic System for the Detection of L-glutamate.
Danielle Rand 1 , Dries Braeken 1 , Josine Loo 1 , Guillaume Mernier 1 , Gustaaf Borghs 1 , Carmen Bartic 1 Show Abstract
1 , IMEC, Leuven Belgium