Shachar Richter Tel Aviv University
David Waldeck University of Pittsburgh
David Lederman West Virginia University
Jason Davis University of Oxford
HH1: DNA Bioelectronics
Tuesday PM, November 29, 2011
Room 204 (Hynes)
9:15 AM - **HH1.1
Electrochemistry in Nanopore/Electrode Structures - From Pore Fabrication to DNA Sequencing-by-Tunneling.
Tim Albrecht 1 Show Abstract
1 Department of Chemistry, Imperial College London, London United Kingdom
Solid-state nanopores have recently attracted much interest as ultrafast and robust DNA fragment sizing and sequencing devices. Other, perhaps equally attractive applications include the detection of proteins, RNA, protein/protein and protein/DNA interactions [1, 2]. These sensors combine the features of true single-molecule sensing with the prospects of working in rather concentrated solutions, for example under physiological conditions. One of the challenges in nanopore sensing is however rooted in the lack of spatial resolution and specificity of the pore, and the poor control over the translocation speed. For example, with a view on DNA sequencing, even thin solid-state membranes of, say 30 nm in thickness, are still contain many DNA bases at the same time and any detected signal is a convolution from many bases.Integrating electrode structures with the nanopore is one way to overcome (some of) these issues and also offers new routes to nanopore device fabrication, including small metallic nanopores [3, 4]. We have fabricated a range of different electrode structures, including ‘large’ membrane electrode devices, ‘small’ micro-electrode/nanopore architectures, and multi-electrode/nanopore devices (e.g. tunnelling junctions aligned with the nanopore) . I will present a selection of these nanopore/electrode structures, their electrochemical characterization (current flow in the cell, pore conductance), and how they can be used for single-molecule biosensing applications . Detection of single molecules can be based on electric current, optical spectroscopy or a combination of both, offering a unique set of tools for biomolecular sensing.  C. Dekker, “Solid-state nanopores”, Nature Nanotechnol. 2007, 2, 209-215. Z. Siwy, S. Howorka, “Nanopore analytics: sensing of single molecules”, Chem. Soc. Rev. 2009, 38, 2360-2384. M. Ayub et al., “Nanopore/electrode structures for single-molecule biosensing”, Electrochim. Acta 2010, 55, 8237-8243. M. Ayub et al., “Fabrication of sub-20 nm Solid-State Nanopores for Single-Molecule Biosensing”, J. Phys.: Cond. Matt. 2010, 22, 454128. A.P. Ivanov et al., "DNA tunneling detector embedded in a nanopore", Nano Lett. 2011, 11, 279-285.
9:45 AM - HH1.2
Fundamentals of Electron Transport through DNA.
Jason Slinker 1 2 , Natalie Muren 2 , Sara Renfrew 2 , Chris Wohlgamuth 1 , Marc McWilliams 1 , Jacqueline Barton 2 Show Abstract
1 Department of Physics, The University of Texas at Dallas, Richardson, Texas, United States, 2 Chemistry and Chemical Engineering, The California Institute of Technology, Pasadena, California, United States
We report recent results concerning the length and temperature dependence of DNA charge transport as measured electrochemically through DNA monolayers. We have observed charge transport through 100 base pairs of DNA, a distance spanning 34 nm. Charge transport through well-matched DNA was measured to be over a factor of 2 greater than through DNA containing a single base pair mismatch, strongly indicating transport through the base pair pi-stack as well as the delicacy of the transport process. Estimation of electron transport kinetics implied rapid transport through the DNA. These monolayers were shown to be biologically active by the restriction activity of the enzyme Rsa1. Temperature dependence of DNA charge transport was also investigated through 17mer and 34mer DNA monolayers, revealing activation behavior and implying transport occurs via temperature-assisted conformational gating. In total, these results strongly indicate DNA can serve as a molecular wire with important implications for biology and biological sensing.
10:00 AM - HH1.3
Electrical Detection of DNA-Binding Enzymes at DNA Bridging a Single Walled Carbon Nanotube Gap.
Alon Gorodetsky 1 , Hanfei Wang 1 , David Ordinario 1 , Natalie Muren 2 , Jacqueline Barton 2 , Colin Nuckolls 1 Show Abstract
1 Deprtment of Chemistry, Columbia University, New York, New York, United States, 2 Department of Chemistry, California Institute of Technology, New York, New York, United States
We have developed a strategy for wiring single molecules into carbon nanotube field effect transistors (CNT-FETs) via robust electrical contacts. This CNT-FET platform has enabled us to definitively elucidate the electrical properties of single DNA duplexes, and our measurements indicate that the effective resistance of B-form DNA is comparable to that of highly oriented pyrolytic graphite. In addition, while the conductivity of DNA bears little sequence or length dependence, it is exquisitely sensitive to perturbations of the base pair stack; the inclusion of even a single base pair mismatch within the duplex dramatically attenuates charge transport. We have further utilized such integrated devices, wherein a single DNA duplex serves as both a recognition and signal transduction element, as a platform for the electrical detection of methyltransferases at the single molecular level. Indeed, we are able to electrically detect sequence-specific DNA binding by the methyltransferase M. SssI, where methylation of the device-integrated DNA alters the affinity of the enzyme for the device. Our fully electrical methodology holds great promise for the general, single-molecular, real-time detection of the activity of DNA-binding enzymes.
10:15 AM - HH1.4
Charge Transport in Single DNA Duplexes: Statistical Analysis of Conductance, I-V Characteristics and Transition Voltage Spectroscopy.
Limin Xiang 1 , Shaoyin Guo 1 , Josh Hihath 1 , Nongjian Tao 1 Show Abstract
1 Center for Bioelectronics and Biosensors, The Biodesign Institute at Arizona State University, Tempe, Arizona, United States
Although much is known about the biological significance of DNA as a genetic code, and the utility of DNA as a scaffolding for the fabrication of nanostructures, the task of understanding the charge transport properties of DNA is still incomplete. Recent work has demonstrated that direct conductance measurements of short DNA duplexes in a solution environment are capable of yielding reproducible results, and provide insights into the conduction mechanisms in DNA and the roles of G:C and A:T basepairs. In this talk we will discuss the expansion of these tools to rapidly perform I-V characteristics and Transition Voltage Spectroscopy (TVS) on individual DNA molecules. The ability to rapidly obtain thousands of these curves allows us to perform statistical analyses of the high-bias conductance behavior and to determine the alignment between the molecular energy levels and the Fermi levels of the electrodes. We will also discuss the utility of these methods for measuring biologically relevant modifications to DNA such as the methylation of cytosine bases within the stack, with the aim of measuring the modification of a single base within the sequence.
HH2: Biomaterials and Applications
Tuesday PM, November 29, 2011
Room 204 (Hynes)
11:00 AM - **HH2.1
Nanostructured Biofilms for High Performance Electronic Biosensors.
Changming Li 1 Show Abstract
1 Bioengineering, Nanyang Technological University, Singapore Singapore
Nanostructured biofilms for high performance electronic biosensorsChang Ming Li*School of Chemical and Biomedical Engineering and Center for Advanced Bionanosystems, Nanyang Technological University, 70 Nanyang Drive, Singapore 637457Nanostructured multifunctional biofilms can significantly enhance the bioelectronics performance. In particular, smart biofilms can be used to fabricate high performance electronic biosensors.A smart multifunctional biofilm with a layered graphene-artificial peroxidase-extracellular matrix protein nanostructure to compose different elements, allowing good cell growth for in situ selective and quantitative H2O2 detection has been demonstrated for the first time, in which graphene can provide dimensionally compatible interface for growth of human cells and excellent electrical conductivity for electrical detection, while incorporating artificial peroxidase and extracellular matrix protein to achieve good selectivity and enhanced cell adhesion/growth capability, respectively. Additionally, the layered nanostructure could allow assembling more active components to tailor the interface properties.Ischemia is inadequate blood supply (circulation) to a local area due to blockage of the blood vessels and is a symptom of heart diseases, transient ischemic attacks, cerebrovascular accidents and brain tissue death. Its important indicator is the increased H2O2 molecules released from ischemic tissues. To overcome shortcomings of the ex-situ approaches, in-situ detecting H2O2 molecules to diagnose ischemia through enhanced protein direct electron transfer on a unique horseradish peroxidase-Au nanoparticles-polyaniline nanowires biofilm is demonstrated and discovers the extracellular H2O2 molecule released per ischemic cell is 2.7-times of that of a normal cell.Nanocomposites have attracted great research and development interests. Lactate oxidase (LOD) in presence of lactate is used to initiate the polymerization of pyrrole monomer with and without carbon nanotube (CNT) to produce 2- or 3-component nanocomposite biofilm. In this case, an interesting self-assembly of the nanoparticles is observed. When CNTs are introduced into the reaction system, they function as the seeds for the polymerization and a CNT-networked nanocomposite film is formed. The application of the nanocomposite film for the lactase biosensor and the effects of components of the nanocomposite on both sensing and electronic properties are also studied, demonstrating their novelty and superior properties. In a brief, engineering various nanostructured biofilm can be used to sensitively and specifically detect various target biomolecules. The superior performance is related to the unique properties and functions of biofilms.
11:30 AM - HH2.2
DNA Block Copolymer Doing It All: From Selection to Self-Assembly of Semiconducting Carbon Nanotubes.
Lifei Zheng 1 , Minseok Kwak 1 , Andreas Herrmann 1 Show Abstract
1 , Zernike Institute for Advanced materials University of Groningen, Groningen Netherlands
This talk will focus on the utilization of DNA block copolymers (DBCs) combined with one of the most promising nanomaterials, single-walled carbon nanotube (SWNT), for eventual incorporation into practical technologies. So far the use of SWNTs is limited by difficulties in solubilizing and isolating individual species and precisely manipulating the structures while preserving their exceptional properties. Here we present a potentially scalable solution to these obstacles using DBCs consisting of a single-stranded DNA block covalently connected to a hydrophobic conjugated polymer segment. This combination of materials enables each to contribute its full potential – self-recognition and selective dispersion, respectively – to the utilization of SWNTs. It is demonstrated that one such hybrid is capable of the whole gamut of solution-based SWNT technologies, from selective dispersion to non-destructive functionalization to high-yield device fabrication such as field effect transistors. These powerful applications are mediated by simple programmed DNA self-assembly, opening the door to broader multidisciplinary materials research in the field of carbon nanotubes.  M. Kwak, J. Gao, M. A. Loi, A. Herrmann, Angew. Chem. Int. Ed. 2011, 123, 3264
11:45 AM - HH2.3
Cholesterol Biosensor Based on Nanodiamond-Polypyrrole Conducting Nanocomposite Membrane.
Pedro Villalba 1 5 , Punya Basnayaka 3 , Mikhail Ladanov 2 , Beverly Liriano 3 , Manoj Ram 2 , Subhra Mohapatra 4 , Ashok Kumar 2 3 Show Abstract
1 Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, Florida, United States, 5 College of Medicine, Universidad del Norte, Barranquilla Colombia, 3 Department of Mechanical Engineering, University of South Florida, Tampa, Florida, United States, 2 Nanotechnology Research & Education Center, University of South Florida, Tampa, Florida, United States, 4 Department of Molecular Medicine, University of South Florida, Tampa, Florida, United States
Nanomaterial composites have been considered as very promising candidates for the construction of high sensitive chemical and biological sensors. Indeed, combination of the enhanced properties of single materials might overcome the limitations of using them solely; holding the special properties of functionalization with wide range of chemical groups, therefore sensitive and specific sensor could be designed. Recently, we have developed nanodiamond (ND)-polypyrrole (PPy) composite using in-situ oxidative polymerization and electrochemical polymerization techniques. ND possess a unique combination of properties i.e., mechanical stability, high corrosion resistance, chemical inertness and biocompatibility which makes it highly suitable for applications in medicine and biosensors. Meanwhile, PPy is a widely used conducting polymer for bioapplications due to its electrical properties, high biocompatibility, and the ease of functionalization with a number of active biological compounds. Also, PPy displays an electroactive behavior under neutral pH solution that makes it very suitable for biosensing application. In this study, we are proposing an integrated solution for the detection and quantification of cholesterol, to offer advantages of higher sensitivity, easy to use, ease of signal processing with better sensor-signal integrity and smaller in size. Under this investigation ND-PPy nanocomposite were deposited on Indium tin oxide (ITO) films, and later choline oxidase (Chx) enzyme was conjugated into the surface using self-assembly technique or physical absorption. ND-PPy/Chx structure was used as a working electrode in three electrode system with Ag/AgCl as a reference and Platinum mesh as a counter electrode. The thickness of ND-PPy film was tailored using cyclic voltammetry procedure. The ND-PPy films deposited on ITO before and after enzyme immobilization were characterized by using Raman spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), FTIR and electrochemical techniques. The cholesterol oxidase immobilized enzymes on ND-PPy structures lead to the production of H2O2 and 4-Cholesten-3-One. Finally, H2O2 was separated into water and electrons which could be amperometrically sensed. The calibration curve of cholesterol concentration has been studied using the novel electrode ND-PPy films for different known concentration of the analyte under steady state and dynamic conditions. Additionally, freshly prepared electrode was also tested against long-term stored biosensor. Finally, the cell culture toxicity testing methods was applied to develop ND-PPy cholesterol biosensor. The toxic effect of a multi-component was spatially visualized with mammalian cell monolayers.
12:00 PM - HH2.4
Gallium Nitride is a Promising Material for Biolectronic Applications.
Albena Ivanisevic 1 Show Abstract
1 , NCSU, Raleigh, North Carolina, United States
Recently the interest in growing different types of gallium nitride (GaN) materials has increased. Such materials are thought to be essential for the fabrication of improved transistor- and light-emitting-based devices. Like other nitride materials, GaN can crystallize in the wurtzide structure. What is particularly interesting about the 0001 surface is the fact that it has three complete bonds to nitrogen atoms of the underlying atomic plane and an additional bond that is “dangling” (also referred to as “unbound”). The presence of this “dangling” bond is expected to make the gallium atoms Lewis acidic and this property has been modeled in the literature. One can significantly change the electronic properties of GaN upon adsorption of different chemical species, which comes as a result of this material’s high spontaneous polarization and piezoelectric constants. Despite the fact that GaN based field effect transistors have shown promise as chemical sensors, they generally have low chemical selectivity. The talk will focus on a novel method of binding biomolecules to the GaN surface with olefin metathesis chemistry, using this chemistry to functionalize GaN with receptors that will specifically bind biological analytes, and designing an electronic GaN biosensor that will monitor concentrations of biomolecules in biological samples. Studies that assess the biocompatibility and toxicity of this material will also be presented. Overall, our results demonstrate that GaN is a robust interface for biolectronic applications.
12:15 PM - HH2.5
Nanostructured Materials from Globular Protein-Polymer Conjugate Self-Assembly.
Bradley Olsen 1 , Carla Thomas 1 , Christopher Lam 1 , Liza Xu 1 Show Abstract
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Protein-based materials show a great deal of potential as catalysts, sensors, and optoelectronics, where the unique efficiency, selectivity, or activity of enzymes can be captured to improve the performance of these devices. However, careful control over the structure and orientation of the protein in three dimensions is required to improve transport through the devices, increase the density of active sites, and optimize the stability of the protein. We demonstrate self-assembly of globular protein-polymer conjugates into nanostructured phases as an elegant and simple method for structural control in bioelectronics. These conjugates may be conceptualized as diblock copolymers, where the first block is the globular protein and the second block is the synthetic polymer. In order to fundamentally investigate self-assembly in these complex block copolymer systems, a mutant of the red fluorescent protein mCherry was expressed in E. coli and site-specifically conjugated to a low polydispersity poly(N-isopropyl acrylamide) (PNIPAM) block using thiol-maleimide coupling to form a well-defined model globular protein-polymer diblock copolymer. Functional protein materials are obtained by solvent evaporation in order to access different pathways toward self-assembly using polymer-selective, non-selective, and protein-selective solvents. Similarly, solvent annealing using these different conditions is exploited as a means to both improve ordering and explore the thermodynamic stability of the as-cast nanostructures. Small angle X-ray scattering and transmission electron microscopy are used to explore the dependence of nanostructure formation on processing conditions and the molecular weight of the PNIPAM block, allowing the phase diagram of these materials to be explored. Wide angle X-ray scattering demonstrates that diblock copolymer self-assembly results in a noncrystalline structure within the protein nanodomains. Circular dichroism, UV/Vis spectroscopy, and Fourier transform infra-red (FTIR) spectroscopy show that a large fraction of the protein remains in its folded and active state after conjugation. The effect of coil fraction and hydrogen bonding additives on maintaining protein activity within nanostructured phases is also explored, demonstrating methods for fabricating structures with both a high protein density and a high fraction of active protein.
12:30 PM - HH2.6
A Novel Urea Conductometric Biosensor Based on Zeolite Immobilized Urease.
Salih Kaan Kirdeciler 1 , Esin Soy 1 , Seckin Oeztuerk 1 3 , Ivan Kucherenko 2 , Oleksandr Soldatkin 2 , Sergei Dzyadevych 2 4 , Burcu Akata 1 3 Show Abstract
1 Micro & Nanotechnology Department, Middle East Tachnical University, Ankara Turkey, 3 Central Laboratory, Middle East Technical University, Ankara Turkey, 2 Laboratory of Biomolecular Electronics, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv Ukraine, 4 d Institute of High Technologies, Taras Shevchenko Kyiv National University, Kyiv Ukraine
A new approach was developed for urea determination where a thin film of silicalite and zeolite Beta deposited onto gold electrodes of a conductometric biosensor was used to immobilize the enzyme. Biosensor responses, operational and storage stabilities were compared with results obtained from the standard membrane methods for the same measurements. For this purpose, different surface modification techniques, which are simply named as Zeolite Membrane Transducers (ZMTs) and Zeolite Coated Transducers (ZCTs) were compared with Standard Membrane Transducers (SMTs). Silicalite and zeolite Beta with Si/Al ratios 40, 50 and 60 were used to modify the conductometric electrodes and to study the biosensor responses as a function of changing zeolitic parameters. During the measurements using ZCT electrodes, there was no need for any cross-linker to immobilize urease, which allowed the direct evaluation of the effect of changing Si/Al ratio for the same type of zeolite on the biosensor responses for the first time. It was seen that silicalite and zeolite Beta added electrodes in all cases lead to increased responses with respect to SMTs. The responses obtained from ZCTs were always higher than ZMTs as well. The responses obtained from zeolite Beta modified ZMTs and ZCTs increased as a function of increasing Si/Al ratio, which might be due to the increased hydrophobicity and/or the acid strength of the medium. This new aproach can be applicable to all kinds of electrochemical biosensors since it`s easy to produce this transducers, it has good storage and working stability and it enhances signals.
Tuesday PM, November 29, 2011
Room 204 (Hynes)
2:30 PM - **HH3.1
Are Proteins Biomolecular Wires?
David Cahen 1 Show Abstract
1 Materials and Interfaces, Weizmann INstitute of Science, Rehovoth Israel
Depositing protein monolayers on ultra-flat surfaces of Si and metals, we can build test structures to measure solid-state electron transport (ETp) across non-modified 'dry' proteins, sandwiched between two solid electrodes. Hitherto we studied the light-induced proton pumping protein, Bacteriorhodopsin (bR), the redox metalloprotein (ET), Azurin (Az), and Bovine Serum Albumin (BSA). Clear differences between these proteins, where for bR and Az we can show that they preserve their structure in the solid state measurement configuration, were observed, with small length decay constants for all three proteins, suggesting incoherent transport as dominant mechanism. Putting our data in perspective by comparing them to all known protein ETp data in the literature, we conclude that, in general, proteins behave more akin to molecular wires than to insulators. An important part of these studies was modification of the proteins by, e.g., removing or disconnecting the retinal in bR and removing or replacing the Cu redox centre in Az. The current-voltage (I-V) characteristics, achieved with these solid state junctions, which were highly reproducible, esp. with Si substrates, enabled us to further investigate the dominant ETp mechanism of the protein-based junctions, using the temperature dependence of the I-V characteristics over a wide temperature range (10-400K). Such measurements are not really feasible with the more3 common wet electrochemical studies of ET across protein monolayers..Remarkably, notwithstanding the above-noted conclusion of incoherent transport, Az shows 10-360K temperature-independent ETp, until its denaturation temperature. Removal of the Cu or its exchange by Zn, changes this behavior to Arrhenius-like, thermally activated ETp. The Arrhenius- like behavior was observed for bR and BSA as well, with different types of averaged activation energies. Below ~ 200K we find temperature independent ETp (with low currents) for all proteins and their variants. Sharp, irreversible decreases of conductivity were observed near the proteins’ denaturation temperatures, showing the sensitivity of our measurements to conformational changes as well.Work of L. Sepunaru, N. Amdursky, W. Li, I. Ron, Y. Jin; collaboration with M. Sheves, I. Pecht, all from the Weizmann Inst.;support from the Minerva foundation.
3:00 PM - HH3.2
Conductance States of Iron Porphyrin Molecules under Electrochemical Potential Control.
Kim Lewis 1 , Jiwang Mao 1 , Guoguang Qian 1 Show Abstract
1 Physics, Applied Physics, & Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States
The dependence of molecular conductance on redox states may be able to explain the electron transport behavior in single molecule junctions. We studied the conductance of Fe (III) 5,15-di [4-(s-acetylthio) phenyl]10,20-diphenyl porphyrin (i.e. Fe porphyrin) by scanning tunneling microscopy (STM). We used an STM tip to apply a bias voltage between the STM tip and a gold (Au) substrate covered by a self-assembled monolayer of Fe porphyrin. By repeatedly forming a molecular break junction  between the Au substrate and Au STM tip, we measured conductance of a single Fe porphyrin molecule at different tip-substrate bias. Previously, it has been shown that by using STM in solution the tunneling current can be controlled through redox molecules, like Fe porphyrin, that are positioned parallel to the substrate. In this work, we investigate a different configuration, that is, a single porphyrin molecule with two opposite ends attached to metallic contacts (i.e., a Au STM tip and Au substrate) to investigate the conductance of Fe porphyrin and its redox states. To study the influence of the redox state on the conductance of Fe porphyrin molecules, the redox state is located by performing cyclic voltammetry in 0.1mM NaClO4 solution. The Fe porphyrin monolayer on the Au substrate served as the working electrode and platinum wire as the counter electrode. The redox state of the Fe porphyrin molecule is found to be at -0.5 V (vs. Ag wire). Conductance measurements were carried out in solution using STM while controlling the potential of the Au substrate by applying a fix bias between the Ag reference electrode and the Au substrate. Electrochemically etched gold STM tips  was coated with Apiezon wax to minimize the faraday current to less than 5 pA. We found that conductance of Fe porphyrin molecules varies with different substrate potentials. Conductance histograms with no potential control were built under tip-substrate bias at 0.5 V and 1.4 V. Based on previous experiments with porphyrin molecules with a metallic atom, we expected to see a bias voltage dependence on the conductance states of the molecules.  However, Fe porphyrin did not show any bias voltage dependence. The conductance histograms did reveal two conductance states of the molecule or single conductance states. References:  Xu, B. and N. J. Tao (2003). "Measurement of Single-Molecule Resistance by Repeated Formation of Molecular Junctions." Science 301: 1221-1223.  Tao, N. J. (1996). "Probing potential-tuned resonant tunneling through redox molecules with scanning tunneling microscopy." Physical Review Letters 76(21): 4066-4069.  Qian, G., S. Saha, K. M. Lewis. (2010). "Note: A simple, convenient, and reliable method to prepare gold scanning tunneling microscope tips." Review of Scientific Instruments 81: 016110.  Qian, G., S. Saha, K. M. Lewis. (2010). "Two-state conductance in single Zn porphyrin molecular junctions." Applied Physics Letters 96(24).
3:15 PM - HH3.3
Design and Characterization of Peptides and Artificial Proteins for Bioelectronics.
Nurit Ashkenasy 1 Show Abstract
1 Materials Engineering, Ben gurion University, Beer Sheva Israel
In recent years there is a great interest in the integration of proteins within electronic devices. Since proteins did not evolve to perform such tasks, the targeted design of proteins for these specific applications is of great importance. I will present two examples for the design and characterization of such proteins, aiming at demonstrating the great potential of the use of specifically designed proteins as components of electronic devices. Moreover, I will show that such systems can be used as simple platforms for understanding the role of different charge transfer mechanisms in proteins. In the first example, the design and characterization of β-sheet like self-assembled cyclic peptide nanotubes, which can potentially be used as protein based molecular wires, will be demonstrated. Taking advantage of a novel layer by layer deposition approach we have developed, the nanotubes’ charge transfer properties have been studied as function of the nanotube length using conductive-atomic force microscopy. These studies have reveal a very efficient charge transfer through this supramolecular protein, with an attenuation factor of 0.1 Å-1. Detailed analysis of the current-voltage relations provide evidence that effective charge transfer can occur through hydrogen bonds in proteins, and that hoping may be a dominant charge transfer mechanism even for very short distances. Charge transfer at protein - inorganic interfaces, which is important for future hybrid device applications, will be presented in the second example for GaAs - peptide hybrids. For the construction of the interface, layers of genetically engineered peptides that bind to GaAs (100) have been formed, and charge transfer has been characterized in a contactless manner using surface photovoltage spectroscopy. I will show that despite the non-covalent character of the interactions in this system, significant charge transfer may occur. In particular, I will show that redox active natural amino-acids, such as tyrosine and tryptophan, play a significant role in the charge transfer. The influence of the location of the active amino acids within the peptide sequence on the strength of the interactions will be discussed and correlated with the structure of the peptide.
3:30 PM - HH3.4
Direct Probe of Protein/Electrode Interface Properties for Bio-Circuit Device Design.
Kendra Kathan-Galipeau 1 , Xi Chen 1 , Sanjini Nanayakkara 1 , Paul O'Brien 2 , Maxim Nikiforov 1 , Bohdana Discher 2 , Dawn Bonnell 1 Show Abstract
1 Materials Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, United States
A novel approach to energy harvesting and biosensing devices would exploit optoelectronic processes found in natural proteins. However, in order to design these bio-circuit based devices the proteins need to be attached to electrodes and the optoelectronic properties in non-liquid (ambient) environments must be understood at a fundamental level. Here we report the simultaneous detection of electron transport and the effect of optical absorption on dielectric polarizability at peptide-electrode interfaces. This characterization requires a peptide design strategy to control protein/electrode interface interactions, allow peptide patterning on an electrode, and induce opto-electronic properties. In addition a new method to probe electronic, dielectric, and optical properties at the single molecular layer level is demonstrated. The combination enables a quantitative characterization of protein properties on conducting electrodes. In one case a comparison of the change in polarization volume between the ground state and excited state in a single molecular layer is made in a manner that allows spatial mapping relevant to ultimate device design. The implications to bioelectronic circuits will be discussed.
4:15 PM - **HH3.5
Superefficient Electron Transfer through 310-Helical Peptides.
Flavio Maran 1 Show Abstract
1 Chemistry, University of Padova, Padova Italy
Electron transfer (ET) reactions are of fundamental importance in a variety of areas of chemistry and biology. Our current understanding of the rate and mechanisms of long-range ETs between an electron donor and an electron acceptor relies on careful experimental and theoretical studies of DNA, proteins, and peptides. Since peptides are key elements of long-range ETs in proteins and can play a considerable role in biosensing, one fundamental question is: among possible peptide bridges, which are likely to provide particularly efficient ET bridge systems? We synthesized a series of thiolated oligopeptides of α-aminoisobutyric acid and used them to prepare self-assembled monolayers (SAMs) on Au electrodes. These peptides form 310-helices and were devised to possess from zero to eight C=O...H-N intramolecular hydrogen bonds. The peptide-SAM electrodes were used to determine the standard heterogeneous rate constant for the reduction of Ru(NH3)6Cl3 in 0.5 M KCl aqueous solution. The results show that as the peptide length increases the ET rate initially decreases but then, for sufficiently long peptides, displays a remarkably shallow dependence on distance. The possible ET mechanisms are discussed.
4:45 PM - **HH3.6
Charge Transfer through Peptide Nucleic Acids.
Catalina Achim 1 , David Waldeck 2 , David Beratan 3 Show Abstract
1 Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Chemistry, Duke University, Raleigh, North Carolina, United States
The charge transfer properties of DNA have been the subject of intense research in the last two decades because of their relevance in biological and medical research and in nanotechnology. We are studying the charge transfer properties of a synthetic analogue of DNA, peptide nucleic acid (PNA). Instead of the sugar diphosphate backbone of DNA, PNA has a pseudopeptide backbone that is typically neutral and achiral but it has the same nucleobases as DNA and, thus, has similar molecular recognition properties to DNA. This presentation will describe studies of charge transfer through non-modified PNAs as a function of sequence and length. Given the relative ease of making synthetic changes in PNA, we have also studied charge transfer through PNAs in which the backbone or the nucleobases have been modified to allow us to address the effect of nucleic acid flexibility on charge transfer. These studies provide insight in the mechanism by which charge transfer occurs in PNA.
5:15 PM - HH3.7
Electron Transport across Bacteriorhodopsin: New Insights from Temperature-Dependent Current-Voltage Characteristics.
Lior Sepunaru 1 2 , Izhar Ron 1 2 , Noga Friedman 2 , Mudi Sheves 2 , David Cahen 1 Show Abstract
1 materials and interfaces, weizmann institute of science, Rehovot Israel, 2 Organic Chemistry, Weizmann institute of Science, Rehovot Israel
Electron transfer (ET) through proteins is a fundamental process in biology, which was and is studied intensively in solution. Solid state electron transport across proteins, sandwiched between two solid electrodes is a molecular electronics approach to study ET. Most solid state ET (which we will call electron transport, ETp) studies to date were conducted with one or just a few molecules in the junction or electrochemically. By designing configurations that allow using experimental methods of solid state electronics, we were able to extract in a reproducible way ETp data between 10 and 400 K on a number of proteins, including the membrane protein from the archaea H. Salinarium, that functions as a light-driven proton pump, bacteriorhodopsin, bR. Our results indicate a transition around 200K from a, (low) temperature-independent regime to a (higher) temperature activated transport. We can also see in the temperature dependence a steps that occurs at the temperature at which a the protein is known to undergo a conformational change. If we use a high enough relative humidity we can reach the bR denaturation temperature, which nicely shows up in the ETp as an irreversible decrease (above that temperature).Further investigation of the protein with its prosthetic group (Retinal chromophore) disattached from its natural location or completely extracted, sheds light on the role of the retinal as an electron transport facilitator.We are now involved in improving our understanding about possible pathways for ETp in this and other proteins. By synthesizing homo-oligo peptides of selected amino acids, with different lengths of the peptides (3-7 amino acids), and using them as samples in solid state transport studies, we are learning to map the efficiency and mechanism of each amino acid for ETp, which will help interpreting the ETp data on actual proteins.
5:30 PM - HH3.8
Charge-Controlled Assembling of Bacteriorhodopsin and Semiconductor Quantum Dots for FRET-Based Nanophotonic Applications.
Nicolas Bouchonville 1 , Michael Molinari 1 , Alyona Sukhanova 2 , Michel Troyon 1 , Igor Nabiev 2 Show Abstract
1 physics, université de reims champagne ardenne (URCA), Reims France, 2 biochemistry, URCA, Reims France
The Fluorescence Resonance Energy Transfer (FRET) between quantum dots (QDs) and photochromic protein bacteriorhodopsin (bR) within its natural purple membrane (PM) is explored to monitor their assembling . The FRET efficiency was tuned by surface charge of QDs and by variation of degree of spectral overlap between QD photoluminescence and bR absorption . The impact of the surface charge and of the diameters of QDs on optical and structural characteristics of QD-PM complexes is investigated via nanoengineering of water-soluble CdSe/ZnS QDs with desired surface charge and thickness of organic shell followed by their assembling with the PM monitored through observation of FRET from QD to PM. Developed QD-PM films were characterized with AFM in order to correlate degree of QDs ordering on the surface of PM with efficiency of FRET between them. Atomic Force Microscopy (AFM) imaging revealed correlation between the surface charge of QDs and degree of their ordering on the surface of PM. The most FRET-efficient QD-PM complexes have the highest level of QDs ordering and their assembling design may be further optimized to engineer a nano-bio hybrid materials with advanced optical and photovoltaic properties for all-optical switching applications.Rakovich A., Sukhanova A., Bouchonville N., Lukashev E., Oleinikov V., Artemyev M., Gaponik N., Molinari M., Troyon M., Rakovich Y.P., Donegan J.F., Nabiev I., Nanoletters 10, 2640 (2010)N. Bouchonville, M. Molinari, A. Sukhanova, M. Artemyev, M. Troyon, I. Nabiev, Applied Physics Letters, 98, 013703 (2011)
HH4: Poster Session
Wednesday AM, November 30, 2011
Exhibition Hall C (Hynes)
9:00 PM - HH4.10
Interfacing Cells with Polysaccharide Protonic Transistors for Senor Applications.
Yingxin Deng 1 , Chao Zhong 1 , Adnan Kapetanovic 1 , Marco Rolandi 1 Show Abstract
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States
Current state-of-the-art devices aimed at interfacing with cells are mainly based on silicon field effect transistors, which modulate and monitor electronic current. However, biological systems mainly use ionic and protonic signals to communicate and exchange information. We have developed a polysaccharide (maleic chitosan) based protonic transistor with protons as majority charge carriers. The flow of protonic current within maleic chitosan, similar to the modulation of electronic current in a typical semiconductor field effect transistor, can be turned on or off by an electrostatic potential applied to a gate electrode. These devices composed of non-toxic maleic chitosan have potential for interfacing with cells. Current efforts are geared towards optimizing cell proliferation onto devices and assessing device performance in physiological conditions. New materials are being investigated that include cross-linked maleic chitosan, chitin/chitosan nanofibers, and novel chitin derivatives with proton conducting groups.
9:00 PM - HH4.11
Highly Sensitive Plastic Based FET Biosensors.
Hyeongyun Yoo 1 , Sangyoung Lee 1 , Taejung Park 2 , Keonjae Lee 1 Show Abstract
1 Department of Material Science and Engineering, Korea Advanced Institute of Science and Technology(KAIST), Daejeon Korea (the Republic of), 2 Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology(KAIST), Daejeon Korea (the Republic of)
Point of care testing (POCT) are being studied with great interest for disease diagnosis such as complete blood count, routine chemistry test, glucose concentration, cancer, DNA and viruses. Essential elements of biosensor that suitable for POCT are portable, simple, highly sensitivity, rapid and real time detection. Considerable researches for biosensor such as surface Plasmon resonance (SPR), enzyme-linked immunosorbent assay (ELISA), micro-cantilevers, surface-enhanced spectroscopies, and optical devices have been performed signicantly over last decades. Each of these methods, however, has yet demonstrated the combination of POCT features such as label free, highly sensitivity, simple, quick and real-time detection of biomolecules. Field effect transistor (FET) type biosensors offer opportunities to develop suitable for POCT by overcoming the deficiencies of above mentioned approaches. Regardless of these merits, FET type biosensors have limit of applications because they are fabricated on non biocompatible, brittle and expensive substrates (e.g. Silicon or SOI wafers). The fabrication of FET type biosensors on flexible substrates has attracted considerable attention due to its potential use in applications such as portable, wearable and implantable biosensors. However, a critical disadvantage of the FET type biosensor on plastic substrates resides in the fact that a high temperature process during the growth of gate dielectric or doping process, which is essential for ensuring high quality, is impossible mainly due to the limitation of plastic substrates.To prepare the high performance flexible devices that incorporate a high temperature process, a microstructured semiconductor (μs-Sc) technology is developed by UIUC research group in 2004. This μs-Sc technology enables to transfer single crystal semiconductor materials onto flexible substrates by carving out from the bulk wafer utilizing the standard microfabrication and soft lithographic printing approach. Herein, we report an approach that highly sensitive FET biosensors utilizing single crystal us-Si transistors and silica binding protein (SBP) immobilization were fabricated on plastic substrates combined with microfluidic technologies for detecting bioreceptor molecule of avian influenza (AI) antigen. From the results, we demonstrate plastic based FET biosensors suitable for POCT and substrate-free bio-compatible applications.
9:00 PM - HH4.13
Oscillatory Dynamics of Flexoelectric Membranes in Viscoelastic Media.
Milad Abou Dakka 1 , Alejandro Rey 1 , Emilio Herrera 1 Show Abstract
1 Chemical Engineering, McGill University, Montreal, Quebec, Canada
This work presents a simple model consisting of a second order linear differential equation describing a thermodynamic phase system (Viscoelastic liquid/Solid-elastic membrane/Viscoelastic liquid) in terms of: the evolution of the membrane curvature, a macroscopic force (electrical field), rheological and surface properties in the system. The model requires eight material parameters, four for the viscoelastic liquid, three for the elastic-membrane (bending and torsion) and the last one is the amplitude of the macroscopic field (electrical field). In non-dimensional form, the model can be described through three dimensional groups associated to the inertial, bulk-viscous and elastic mechanisms. The model is analyzed for an externally imposed oscillating electric field; the storage and loss moduli, power and average power are calculated as a function of the viscoelastic properties. The key findings are: (i) the non-dimensional model contains several particular cases depending on the value of the materials properties, (ii) due to the linear nature of the model, particular cases are easily studied through dimensional numbers, (iii) all equations in this work are analytical and can be extended to other linear models.
9:00 PM - HH4.14
Sialic Acid Sensitive Field Effect Transistor as a Means of Facile and Quantitative Cytology.
Akira Matsumoto 1 , Kazunori Kataoka 2 , Yuji Miyahara 1 Show Abstract
1 Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo Japan, 2 Department of Materials Science and Engineering, The University of Tokyo, Tokyo Japan
Alternations of SA contents on cell surface glycan chains have been implicated in numerous normal and pathological processes including developments, differentiations and tumor metastasis.1,2 A technique to conveniently monitor cell surface SA is therefore relevant to a facile way of cytology. Ordinarily, cell surface SA density is assessed via multiple enzymatic and labeling procedures, which involve severely invasive, in many cases lethal procedures. Besides, SA residues must be either enzymatically or acid-catalytically cleaved from the glycan chains and then disintegrated into the free forms that can finally be subjected to the quantification. Such methods are very unlikely to prevail as standards for clinical practice. This work describes a label free, potentiometric method to detect cell surface sialic acid (SA) using phenylboronic acid (PBA) compound integrated into the form of self-assembled monolayer (SAM) on a field effect transistor (FET) extended gold gate electrode. Owing to specific binding between undisassociated PBA and SA at pH 7.4, carboxyl anions of SA were exclusively detectable among other glycan chain constituent monosaccharides as the change in threshold voltage (VT) of the PBA-modified FET. The technique was applied to analyses of altered SA expressions on rabbit erythrocyte and metastatic murine melanoma cells as models for diabetes and metastasis, respectively. Comparative SA expression analyses for each healthy and diseased model revealed that these diseases could be feasibly diagnosed simply by placing the known-count cell suspensions onto the device without any labeling and enzymatic procedures.
9:00 PM - HH4.15
Bio-Composite Based Devices Using Protein Matrices.
Netta Hendler 1 2 , Elad Mentovich 1 2 , Bogdan Belgorodsky 1 , Ludmila Fadeev 1 , Michael Gozin 1 , Shachar Richter 1 2 Show Abstract
1 Chemistry, Tel-Aviv university, Tel-Aviv Israel, 2 The Center for Nanoscience and Nanotechnology, Tel-Aviv university, Tel-Aviv Israel
In the nanometric world, the inter mix between different types of materials can give novel kinds of composites that results in new and exciting properties. In this context, one of the major challenges and tasks is the incorporation of hydrophilic and hydrophobic phases within the same matrix. In this work, we show that some hydrophilic proteins can serve as appropriate host matrix for the formation of bio-composites by efficiently up-taking of hydrophobic structures. By using the Mucin protein, specifically, bovine submaxillary mucin, as a matrix material and fluorescence dyes molecules as fillers, we have constructed nano-composites materials that can serve as thin films for bio- organic light emitting devices. For white emitting applications we show that this method is more than efficient since the host matrix successfully separates the Red, Green and Blue colors, thus preventing unwanted non-radiative interactions.In addition, the mucin matrix can also function as a chemically active matrix. This matrix was used to synthesize nanoparticles without any help of external reducing agent. The resulting nanoparticles show remarkable chirality in the visible range.
9:00 PM - HH4.16
Mechanisms of Activity Loss in Enzymatically Catalyzed Biological Fuel Cells.
Kulveer Singh 1 , Christopher Blanford 1 Show Abstract
1 School of Materials, University of Manchester, Manchester United Kingdom
Enzymes are being considered as actual or inspirational catalysts for some low-temperature fuel cell applications. Using an electrochemical quartz crystal microbalance with dissipation analysis (E-QCM-D), we followed the changes in electrocatalytic activity of several metalloproteins in the broad class of dioxygen-reducing enzymes known as the blue multicopper oxidases, or BMCOs. The enzymes were attached both covalently and non-covalently to organothiol-modified gold-coated quartz sensor surfaces.Freshly adsorbed BMCOs appear to form bilayers. Cycling the electrochemical potential (as for a cyclic voltammogram) causes the mass of the adsorbed enzyme molecules to decrease rapidly to about 50% of the initial mass, after which point the adsorbed mass remains stable for several hours. The accompanying loss in electrocatalytic activity is consistently smaller than the mass loss, however, consistent with a loosely adsorbed second layer that is in relatively poor electronic contact with the electrode.Enzymes held at a constant reducing electrochemical potential (as for chronoamperometry) produce a stable mass response that persists for at least eight hours. During these measurements the catalytic current density decreases steadily, typically to about 30–60% of its starting value. The concurrent decrease in energy dissipation from the sensor, indicative of a increase in adlayer rigidity, suggests that long-term activity loss is due to changes in protein conformation rather than enzyme desorption (colloquially known as “film loss”).
9:00 PM - HH4.17
Electrical Conduction Along Porphyrin Wires in Solution Using the SC-EHT and Green's Function Method.
Clarence Matthai 1 , Gareth Jones 1 , Martin Elliott 1 Show Abstract
1 Physics and Astronomy, Cardiff University, Cardiff United Kingdom
In recent years, first-principle electronic structure calculations have been carried out to investigate such diverse phenomena as charge transport in molecular wires, optical properties of quantum structures and in photonics. However, at this time the prohibitive computational cost does not allow for such calculations to be easily carried out on nano-scale device structures comprising thousands of atoms. In addition, there are issues relating to the applicability of these approaches to describing the excitations that ought to be involved in charge transport.Semi-empirical methods have the advantage of requiring fewer computational resources, and because some of the parameters are fitted to experimental data, they can provide a better description of physical properties if applied in the right domain. The SC-EHT approach has proved very effective in describing the band alignment at semiconductor interfaces, and optical properties of partially covered surfaces, as well as being employed in studying the electronic states of large molecules.We have developed SC-EHT code that may be applied to study charge transport through molecular wires. This code allows for an external bias to be applied across the molecular wire and also takes into account the ensuing charge redistribution within the wire. We study the transmission of a porphyrin wire attached via thiol linkers to gold electrodes, compare our results with those obtained from density functional theory and show that the far less resource intensive semi-empirical method can give results in qualitative agreement to the more demanding ab-initio calculation. We have applied the SC-EHT code to study the influence of the thiol position on the Au on the conduction. In addition, we also report on the results of some preliminary investigations studying the influence of water on the conduction pathways.
9:00 PM - HH4.18
Electron Transport through Proteins: Comparing Nano- to Acro-Scale.
Wenjie Li 1 , Lior Sepunaru 1 , Sidney Cohen 1 , Israel Pecht 1 , Mordechai Sheves 1 , David Cahen 1 Show Abstract
1 , Weizmann Institute of Science, Rehovot, 0, Israel
Electron transport through Azurin (Az) and apo-Az (Cu-depleted Az) on Au was investigated by conducting probe atomic force microscopy (CP-AFM). Current-voltage (I-V) curve characteristics were measured on the proteins, which were self-assembled as monolayers on the Au substrate. The I-V data were analyzed and compared to those obtained with macro-scale contacts (5.1011 vs. 102 nm2 area) with a macro-scale Au pad as the top electrode prepared by lift-off, float on (LOFO ). We find that the data scale quite well, a correspondence only rarely observed, and in contrast to what was deduced from earlier literature reports. We then performed temperature dependent I-V measurements of electron transport through Az and apo-Az, under dry nitrogen in the range of ~250 - 380K. We found that that current flow through Pt / Az / Au junctions was temperature independent, while for Apo-Az thermally activated behavior was observed, in agreement with our earlier macro-scale results. The influence of AFM tip pressure as well as the I-V-T behavior of Az derivatives will be discussed. Our temperature dependence measurements are of particular importance because so many of the solid state transport measurements on proteins are done using CP-AFM, but only at room temperature.3 Thus, our results add an important dimension to such transport measurements, which enhance our ability to explore electron transport mechanisms through proteins. 1. I. Ron, L. Sepunaro, S. Itzhakov, N. Friedman, I. Pecht, M. Sheves, D. Cahen J. Am. Chem. Soc. 132, 4131–4140 (2010) 2. A.Vilan, D. Cahen Adv. Funct. Mater. 12, 795-807 (2002) 3. I. Ron, I. Pecht, M. Sheves, D. Cahen Acc. Chem. Res. 43, 945 (2010) 4. L. Sepunaru, I. Pecht, M. Sheves, D. Cahen J. Am. Chem. Soc., 133, 2421 -2423 (2011)
9:00 PM - HH4.2
AC Impedance Spectroscopic Analysis of Biofunctionalized Vertically-Aligned Silica Nanospring Surface for Biosensor Applications.
Yukta Timalsina 1 , Joshua Branen 1 , David McIlroy 1 Show Abstract
1 Physics, University of Idaho, Moscow, Idaho, United States
In this study, alternating current impedance spectroscopic analysis of the biofunctionalization process of a vertically-aligned (silica) nanosprings (VANS) surface is presented. The VANS surface is functionalized with a biotinylated immunoglobulin G (B-IgG) layer formed by physisorption of B-IgG from the solution phase. Bovine serum albumin passivation of the B-IgG layer reduces additional surface adsorption by blocking the potential sites of weak bond formation via electrostatic and hydrophobic interactions. As avidin acts as a receptor of biotinylated compounds, avidin conjugated glucose oxidase (Av-GOx) binds to the B-IgG layer via biotin. This avidin-biotin bond is a stable bond with high association affinity (Ka = 1015 M-1) that withstands wide variations in chemistry and pH. An IgG layer without biotin shows no binding to the Av-GOx, indicating that bonding is through the avidin-biotin interaction. Finally, fluoroscein iso-thiocyanate (FITC) labeled biotinylated bovine serum albumin (B-BSA) added to the Av-GOx surface is used to fluorescently label Av-GOx for fluorescent measurements that allow for the correlation of surface binding with impedance measurements. Modeling of impedance spectra measured after the addition of each biological solution indicates that the bimolecular layers behave as insulating layers. The impedance spectra for the VANS-based sensor are compared to simple parallel capacitor sensors, sans VANS, and serve as controls. VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls below 10 kHz Changes in the magnitudes of the components of the VANS equivalent circuit indicate that the addition of biological layers changes the effective dielectric response of the VANS via the impediment of ionic motion and biomolecule polarization.
9:00 PM - HH4.21
DNA Architectures in Non-Aqueous Environments.
Amethist Finch 1 , Christina Jacob 1 , Thomas Proctor 1 , James Sumner 1 Show Abstract
1 , US Army Research Laboratory, Adelphi, Maryland, United States
A methodology that allows for the coupling of biology and electronic materials is presented, where double stranded DNA will ultimately serve as a template for electronic material growth. Self-assembled DNA structures allow for an assortment of patterns on the nanometer size scale that is difficult to achieve using conventional patterning and fabrication techniques. DNA self assembly under non-aqueous conditions has yet to be presented in literature, and is necessary if unwanted oxidation of certain electronic substrates is to be avoided. Solubilization of the DNA in non-aqueous solvents is achieved by replacing charge stabilizing salts with the surfactant cetyl trimethyl ammonium chloride (CTAC). Herein, the procedures for the creation of self-assembled DNA nanostructures in aqueous and non-aqueous media are described, and these structures are subsequently deposited (drop cast, spin cast, and physically adsorbed) onto freshly cleaved mica or silicon wafers. The DNA architectures are characterized either in solution (circular dichroism spectroscopy (CD)) or on the surface (ellipsometry and AFM). These studies illustrate the retention of DNA hierarchical structure under both conditions and this data will be presented by observing the structures using AFM imaging and CD spectroscopic studies.
9:00 PM - HH4.22
Biological Capillaries May Behave as Memristors.
Gorm Johnsen 1 2 , Carsten Luetken 2 , Orjan Martinsen 2 3 , Sverre Grimnes 3 2 Show Abstract
1 Department of Physics, Institute for Energy Technology, NO-2027 Kjeller Norway, 2 Department of Physics, University of Oslo, NO-0316 Oslo Norway, 3 Department of Clinical and Biomedical Engineering, Oslo University Hospital, Rikshospitalet, N-0424 Oslo Norway
We show, by using a general model, that ionic flow in small scale capillaries, subject to a periodically alternating electric field, may act as memristive systems. Memristive systems are generalizations of the memristor concept predicted on theoretical grounds by Chua in 1971, but was not shown much interest until recently (2008). The memristor is an elementary circuit component, complementing resistors, capacitors and inductors and acts as a resistor with some memory of its physical history. We show that the memristor as well as the more general memristive systems are promising in modeling human sweat duct conductivity in particular and suggest that this description also holds for other similar small scale ionic capillary systems where the liquid volume is influenced by the flow of electric charge through it (electro-osmosis). Such ionic transport is a prerequisite for living cells as well as for many other biological systems. The memristive effects of such capillary systems increase rapidly as the systems grow smaller and are therefore interesting also for nano systems, potentially also of solid state nature. As the memristor cannot be represented by any combination of passive resistive, capacitive or inductive elements, it is promising in giving a more correct description of the underlying physics of certain biological phenomena, many that are yet not fully understood.
9:00 PM - HH4.24
Fine Control of Lipid Bilayer Self-Spreading by Using Electric Field Applied to Nanogap.
Yoshiaki Kashimura 1 , Kazuaki Furukawa 1 , Keiichi Torimitsu 1 Show Abstract
1 , NTT Basic Research Laboratories, Atsugi Japan
Self-spreading is a characteristic feature of a supported lipid bilayer (SLB) that derives from the spontaneous growth of an SLB at a solid-liquid interface . We have investigated the effect of nanogap structure on a self-spreading SLB . Very recently, we reported for the first time that self-spreading could be controlled electrostatically by the temporal ON/OFF switching of an electric field applied between nanogap electrodes . However, dynamic control of the self-spreading, namely a detailed analysis of the relationship between the electric field and the spreading velocity, remains a challenging issue. In this study, we attempt the fine control of SLB self-spreading in terms of electric field strength and the Brownian motion of a lipid molecule. A pair of nanogap electrodes was fabricated on a SiO2 surface. A microchannel was fabricated on this nanogap structure. A lipid mixture (L-α-PC : L-α-PG = 7:3) containing 1 mol% Texas Red-DHPE was used for the self-spreading. A self-spreading SLB was observed with a confocal laser scanning microscope. All the experiments were performed in a buffer solution that included NaCl. A DC voltage was applied between the nanogap electrodes during the observation. The effects of an electric field on a self-spreading SLB can be divided into two types depending on the relationship between the nanogap width (d) and the width of the electric double layer (D), which is controlled by the ionic concentration . When d >> D, there was no significant change in the self-spreading because the electric field was shielded by counterions outside the electric double layers. In contrast, when d ≈ D, the electric field was effectively applied over the nanogap as a result of the overlap of two electric double layers, which led to the electrostatic trapping of the SLB. From a molecule level viewpoint, this resulted from the competition between the electrostatic force and the Brownian motion within the SLB. We investigated the dependence of the electric field strength on the self-spreading at a constant ionic concentration. When the electric field was larger than 104 V/cm, the SLB remained trapped. Below 104 V/cm, the spreading velocity increased with a reduction in the electric field strength. For every experiment, the threshold electric field strengths for the trapping/detrapping of the SLBs were almost the same (~104 V/cm). Considering the fact that the trapping energy is comparable to the Brownian energy at the threshold, we can fine-tune both the spreading velocity and the trapping/detrapping of an SLB. J. Rädler et al., Langmuir, 11 (1995) 4539. Y. Kashimura et al., Jpn. J. Appl. Phys., 47 (2008) 3248. Y. Kashimura et al., J. Am. Chem. Soc., 133 (2011) 6118.
9:00 PM - HH4.25
Nano-Chelation of Transition and Heavy Metal Ions by Peptide Nanorings.
Akio Yano 1 , Yasuhiro Suzuki 1 , Kyozaburo Takeda 1 Show Abstract
1 Electrical Engineering and Bioscience, Waseda University, Tokyo Japan
Peptide nanoring (PNR) is a cyclic peptide whose internal diameter and surface properties can be controlled artificially by adjusting the number and kind of component amino acids. Recently, the atomistic structures of a guest ion X and a host PNR chelating system (X/PNR) have been studied computationally, and three clathrate forms of Volcano, Saturn and Waffle are theoretically predicted in accordance with the ratio between the ion radius and PNR pore. Here, we extend our computational study of the X/PNR system, where the guest cation is supposed to be a transition metal (Fe2+) or a heavy metal (Hg2+). The understanding of the chelation of Fe2+ and Hg2+ ions by PNRs would lead to the elucidation of physiological functions and toxification mechanisms in organisms.We have carried out the first-principle DFT molecular orbital calculation by employing Gaussian09 program (B3LYP/6-31G**, LANL2DZ(Hg)). The geometrical optimization has been achieved by using the vibrational frequency analysis.Our calculation demonstrates that the chelation is caused basically by the host-guest electrostatic interaction but the characteristic orbital mixing is induced between the host PNR and guest cation; Fe2+/6PNR causes the d-σ and d-π mixings whereas Hg2+/6PNR does the s-σ mixing. However, the resulting CT from PNR to Fe2+ is less than that to Hg2+ (82%) due to the strong localization of the guest Fe2+ d orbital. We have further examined the ground state of these clathrate compounds with varying a spin multiplicity. The ground state of Fe2+/6PNR is a spin quintet having a Saturn structure, and the change in the spin multiplicity does not vary this form. The ground state of Hg2+/6PNR is a spin singlet providing Saturn form. The higher spin states, however, cause a Volcano form, because the higher spin states request the electron excitation into 6p orbital which lifts Hg2+ cation upwards.
9:00 PM - HH4.27
Cryptosporidium Parvum Oocysts Sensing Based on CVD Grown Graphene.
Jen It Wong 1 , Xiaochen Dong 2 , Su Xiu Ng 3 , Hui Ying Yang 1 Show Abstract
1 Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore Singapore, 2 School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore Singapore, 3 School of Chemical and Life Sciences, Singapore Polytechnic, Singapore Singapore
Cryptosporidium parvum is an ubiquitous intestinal parasitic protozoan that causes gastroenteritis in man and lower animal. It presents a serious threat to human health because of its ubiquitous distribution in water and their oocysts are resistant to harsh environment conditions. Standard procedures such as EPA method 1622 and 1623 were utilized to process the contaiminated water. Conventionally, cryptosporidium oocysts were detected by immunofluorescent microscopy. In this work, we demonstrated the use of large-size chemical vapor deposition (CVD) grown graphene films configure as field-effect transistor for sensing of cryptosporidium parvum oocysts (cp. oocysts) by monitoring the changes in electrical current. The presence of cp. oocysts were detected by the conductance change of the graphene transistor since they are binded specifically to the antibody reagent functionalized onto the graphene film. This study indicated that graphene is a potential candidate for the detection of the cp. oocysts and it is worth exploring the real-time bioelectronic sensing of cp. oocysts.
9:00 PM - HH4.28
DNA Detection Using a Solution-Processed InGaZnO Thin-Film Transistor.
Si Joon Kim 1 , Joohye Jung 1 , Doo Hyun Yoon 1 , Byeonghoon Kim 2 , Sung Ha Park 2 , Hyun Jae Kim 1 Show Abstract
1 , Yonsei University, Seoul Korea (the Republic of), 2 , Sungkyunkwan University, Suwon Korea (the Republic of)
A solution-processed InGaZnO (IGZO) thin-film transistor (TFT) was used for DNA detec-tion for the first time. Also, we adopt artificially designed periodic DNA lattice named DX structure in order to carry out the relation between DNA shape and source/drain current density. To prepare the IGZO TFT, the bottom-gate and top-contact structure was used. A MoW and SiNx were deposited by sputtering and plasma-enhanced chemical vapor deposition as a gate electrode and a gate insulator, respectively. A 0.5 M IGZO solution was spin-coated and annealed at 450oC for 2 h on a hot plate as a channel. Mo metal was sputter-deposited through a shadow mask as source and drain electrodes. The IGZO TFT exhibited a saturation mobility (µsat) of 0.25 cm2/Vs and a threshold voltage (Vth) of -2.24 V. To realize the detecting ability of the IGZO TFT, DNA solution was dropped by pipetting onto the exposed IGZO channel and air-drying for 30 min. Since then, the significantly decreased µsat (0.02 cm2/Vs) and the dramatically shifted Vth (7.09 V) were occurred. It could be explained that the DNA caused conductivity decrease of the near IGZO surface and electron trappings at the interface between IGZO and DNA. The porous IGZO film formed using a solution process is more effective method for detecting DNA.
9:00 PM - HH4.29
Efficient Detection of Uric Acid Using SAM-SnO2 Thin Film Matrix.
Kashima Arora 1 , Monika Tomar 2 , Vinay Gupta 1 Show Abstract
1 Department of physics and Astrophysics, University of Delhi, Delhi, Delhi, India, 2 Department of Physics, Miranda House, University of Delhi, Delhi, Delhi, India
Biosensors including uric acid are becoming increasingly important due to their applications in biological and chemical analyses, clinical detection, and environmental monitoring. A number of diseases and pathological disorders are related to the variation of uric acid concentration in body fluids (e.g. serum and urine), such as gout, arthritis, kidney disease, cardiovascular disease and neurological diseases. Amongst numerous reports on uric acid biosensors, technique of enzyme immobilization holds the key in influencing the sensing aspects of the biosensor and thus, has attracted the attention of researchers worldwide. Literature indicates immobilization of uricase on the surface of metal oxides (ZnO, RuO2, TiO2) as the preferred method for uric acid detection, wherein researchers utilized various methods including physical adsorption and cross linkage but exhibits limited sensitivity. SnO2 is a known wide band gap semiconducting metal oxide [3.9eV], exhibits interesting properties including high catalytic efficiency, chemical stability etc. and is widely used for sensor applications.In the present study SnO2 films were grown on Pt/Ti coated glass slides by RF sputtering technique under an optimized gas composition of 30% oxygen and 70% argon in the reactive (Ar+O2) gas mixture using a metallic tin (Sn) target at deposition pressure of 14 mTorr. The structural and optical properties of SnO2 films were studied using Atomic force microscopy (AFM), X-ray Diffraction (XRD) and UV-Visible spectrophotometry. A well defined interference fringe pattern was observed indicating the growth of good quality SnO2 thin films free from any type of inhomogenities. Uricase was covalently immobilized onto Self Assembled Monolayer (SAM) of 3-Aminopropyl triethoxy silane (APTES) deposited on SnO2 film using EDS/NHS chemistry. The covalently immobilized uricase-modified APTES SnO2 bioelectrode was used for the efficient detection of uric acid. Cyclic Voltammetry (CV) studies indicate the presence of an oxidation peak at 0.4 V in the spectra and the oxidation current was found to increase linearly with an increase in uric acid concentration over the range 0.1 to 5mM, indicating the successful detection of uric acid in physiological range having high sensitivity of 0.46 mA/mM. The low value of Michaelis-Menten constant (0.19mM) indicates an enhanced affinity of the immobilized enzyme towards its substrate. The stability of electrode was approximately 24 weeks when stored at 4oC and the electrode can be reused approximately 20 times. The prepared bio-electrode exhibits the potential to be used as an amperometric biosensor thus offering scope for commercialization for health care applications.
9:00 PM - HH4.3
Biogenic Amine Sensors Based on Monolayer Thin Film Transistors.
Roy Vellaisamy 1 , Zong-Xiang Xu 1 Show Abstract
1 Physics and Materials Science, City University of Hong kong, Hong Kong Hong Kong
Thin film transistors (TFTs) based sensors are getting more popular due to its high sensitivity, selectivity and simple device fabrication process . TFTs based sensors have great potential for a wide variety of applications, especially for gas sensors [2, 3]. In addition, polymer based TFTs can be printed in large areas. In this context, poly-thiophenes has been widely studied in the last decade. By controlling the fabrication condition and modification of the substrate, the resulted ultrathin monolayer poly-thiophene film can be used as a biosensor. Selective and sensitive detection of biogenic amine is observed in these polymer based TFTs. In this presentation, we discuss high performance biogenic amine sensor based on ultrathin poly-thiophene films fabricated by solution process on a flexible substrate.1. A. M. Andringa, M. J. Spijkman, E. C. P. Smits, et. al,. Organic Electronics. 2010, 11, 895.2. J. W. Jeong, Y. D. Lee, Y. M. Kim, Y. W. Park, et. al., Sensors and Actuator B: Chemical. 2010, 146, 40.3. A. Caboni, E. Orgiu, M. Barbaro, Member, IEEE, A. Bonfiglio. IEEE Sensors Journal. 2009, 9, 1963.
9:00 PM - HH4.30
Streptavidin-Coated Quantum Dot Arrays with Direct Nanoimprinting for DNA Sensor.
Yongsuk Oh 1 , Kyung Heon Lee 2 , Seung Hwan Ko 3 , Hyung Jin Sung 4 Show Abstract
1 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 3 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 4 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
For analyzing complex biological events, biomolecule microarrays like DNA, protein have been used with printing process. However, nano - size materials needed for a more sensitive and quantitative tool. Among these materials, quantum dot (QD) is very suitable material for sensing and identifying biological events. Also, it has great potentials due to long-lasting emission property, photostability and size-tunable property. With this reason, QDs have been greatly used in biological imaging, bio sensor with printing technology. In this study, direct nanoimprinting process is used to make bioconjugated QD arrays. Here, QDs were synthesized by that of Peng et al. CdO, oleic acid and non-coordinating solvent, ODE were mixed in a 100mL three-neck flask under Ar atmosphere. The mixture was heated to 50°C with magnetic stirring. As backfilled with Ar, it was reheated to 270 °C. Selenium solution was swiftly injected into this hot solution. After 5mins, 1-dodecanethiol (DDT) and Zinc precursor were added to reaction solution for core-shell structure that is enhanced quantum yield and stability. After cleaning process, precipitated QDs was mixed with streptavidin solution. And then, streptavidin-coated QDs were redispersed in PBS. PDMS mold was fabricated with mixture of silicon elastomer kit and curing agent at 65 °C over 5 hours. Stacked glasses and cover glass were used for horizontality of the PDMS mold. The PDMS mold was carefully released from silcon master. The biomolecule coated QD arrays on the substrate were cooled down to room temperature to keep their patterns. At this point, the solvent properties like viscosity and surface tension as well as reducing residues were quietly considered for good results. Also, concentration of QD solution was manipulated of QDs for patterning the monolayer that can be measured by AFM and confocal microscope. The emitted QD arrays by fluorescent microscope will be quenched by sensing biotin-conjugated DNA. These results indicate that bioconjugated QD arrays allow detection of DNA for biomolecular analysis. In addition, it will be integrated with a fluorescent QD-based device in a micro-chip system.
9:00 PM - HH4.32
Nanometric Ion Sensing Using near-Field Ratiometric Fluorescence Sensing.
Ella Wajnryt 1 , Aaron Lewis 1 , Patricia Hamra 2 , Chaya Lewis 2 Show Abstract
1 Applied Physics, Hebrew University of Jerusalem, Jerusalem Israel, 2 , Nanonics Imaging Ltd., Jerusalem Israel
A nanometric measurement of ionic concentrations at distances extending from nanometers to microns from a charged surface immersed in solution is described. AFM and NSOM techniques are combined using NSOM’s nanometric light confinement abilities for optical pH sensing. AFM allowed for knowledge/control of the distance between the optical pH-meter and investigated surface. A ratiometric method of fluorescence sensing was used. A pH sensing fluorescent dye, i.e. fluorescein was complexed to a non-pH sensing dye, rhodamine through a dextran molecule and thus the concentration of dye molecules were equivalent in each nanometric solution volume element. The results profile the nanometric variation in pH as a function of distance from such a charged surface. The approach has great potential to generally and accurately monitor nanometrically charge distribution in solutions and in close proximity to surfaces. The measurements provide important experimental underpinnings to long established solution structure theories, eg. those of Debye-Huckel and Gouy-Chapman.
9:00 PM - HH4.34
Solid State Electron Transport through Electron Transfer Proteins: Cytochrome C and Azurin.
Nadav Amdursky 1 , Lior Sepunaru 1 , Israel Pecht 1 , Mordechai Sheves 1 , David Cahen 1 Show Abstract
1 , Weizmann Institute of Science, Rehovot Israel
Cytochrome C (CytC) and azurin (Az) are rather small proteins (MW of ~12 kDa and ~14 kDa for CytC and Az, respectively), and they both contain a prosthetic group (heme and copper for CytC and Az, respectively). However, the most notable property of these two proteins is that both of them behave as natural electron carrier proteins. As a result, numerous studies have been conducted to explore this unique function. The vast majority of these studies have been made in solution, to imitate the natural surroundings of the proteins. In recent years, some solid state experiments have been done to explore the electron transport (ETp) mechanism of these proteins, mainly by the use of scanning probe microscopy, which is limited by its small measurement area.Here we report on results with an alternative technique, for macroscopic solid state measurements of the proteins’ ETp mechanism as a function of temperature, in the range of 10-400K. This technique is based on forming a monolayer of the desired protein between two electrodes. In this manner we obtain the ETp activation energy, from data over a wide range of temperatures, which cannot be done in solution. We can now compare ETp between these two natural electron carriers at room temperature and as a function of temperature, and will discuss how changing the protein affects the ETp and its mechanism. In this context, we show the role of the peptide amide bonds in ETp, by following the effect of deuterating these amide bonds, and the importance of the prosthetic group, by comparison to the apo-form of the proteins.
9:00 PM - HH4.35
Investigation of Characteristics of Urea and Butyrylcholine Chloride Biosensors Based on Ion-Selective Field-Effect Transistors Modified by the Incorporation of Heat-Treated Zeolite Beta Crystals.
Esin Soy 1 , Valentyna Arkhypova 2 , Sergei Dzyadevych 2 , Juliusz Warzywoda 3 , Albert Sacco 3 , Burcu Akata 1 Show Abstract
1 , Middle East Technical University, Ankara Turkey, 2 , Institute of Molecular Biology and Genetics, The National Academy of Sciences of Ukraine, Kiev Ukraine, 3 , Department of Chemical Engineering, Texas Tech University, Lubbock, Texas, United States
The sensitivities of urea and butyrylcholine chloride (BuChl) biosensors, prepared by the incorporation of zeolite Beta crystals with varying Brønsted acidity into the membranes deposited on the surface of pH sensitive field effect transistors (pH-FETs), have been studied and compared. In order to study exclusively the effect of zeolite acidity, highly crystalline pure zeolite Beta sample with the Si/Al ratio of 17 was synthesized and subjected to different heat treatment protocols. In this way, the amount of acidic OH groups (Brønsted acid sites) was controllably altered, as determined by Fourier transform infrared (FTIR) spectroscopy, without changing other zeolitic properties such as crystal size, morphology, Si/Al ratio , and the amount of non-/weakly acidic terminal silanol groups. Upon the incorporation of zeolite Beta, the biosensors’ sensitivity towards urea and BuChl increased up to 2 and 3 times, respectively. Operational stability and the feasibility of using the biosensors for inhibition analysis were also investigated. However, thus far an ISFET study, which can potentially give the best indication on whether the obtained biosensor data is affected by the changing nature of the modified electrode, related to any of the acid sites observed by FTIR spectroscopy, has not been published. According to the current results, Brønsted acid sites can be hypothesized to be responsible for the obtained ISFET activities. Since the amount of terminal silanols was not affected by the heat treatment protocols used in this study, no conclusion can be made regarding the effect of these non-/weakly acidic OH groups on the ISFET activities. The current results show that the interactions between the enzymes and the Brønsted acid sites of zeolite support can affect the actual biosensor performances in such a way that the attained responses can be controllably altered. This makes zeolites even stronger candidates for use as electrode modifiers, and for their potential integration into biosensors.
9:00 PM - HH4.36
Nonlinearity in Electrode-Electrolyte System at kHz Frequencies: Assessment of Electromagnetic Intermodulation Distortion Technique for Biomedical Application.
Rohit Pande 1 2 , Leiming Xie 1 , Wanda Wosik 1 2 , Krzysztof Nesteruk 3 , Jarek Wosik 1 2 Show Abstract
1 Texas Center of Superconductivity , University of Houston, Houston, Texas, United States, 2 Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, 3 Institute of Physics, Polish Academy of Sciences, Warszawa Poland
Dielectric spectroscopy is an efficient electromagnetic technique for investigating linear/nonlinear responses. It is also used as a powerful tool in studies of biological systems. Non-linear systems do not follow superposition theorem and when excited with sinusoidal signal, they produce additional signals (harmonics) that distort the output response. Such distortions are conventionally identified using one-tone total harmonic distortion (THD) technique. In our work, we have employed a much more sensitive method known as two-tone intermodulation distortion (IMD) technique, which has an additional advantage of probing biological non-linearites at very lower power levels. It also allows to reduce any thermally induced effects. IMD uses two equal amplitude signals at frequencies f1 and f2 to excite the device under test (DUT). For nonlinear cases, Fourier transformed output shows higher order tone products called intermodulation products (IMPs). Usually, IMD spectra contain many higher order terms, but the fundamental and third order IMPs are sufficient reference points. Another benefit is small bandwidth.Our IMD setup includes ultra low distortion two-tone generator DS360, spectrum analyzer SR785, Agilent power meter N1912A and especially constructed LCR resonator as the DUT. The LCR resonator (operating at 20 kHz to 100 kHz and bandwidth 1 kHz) consists of a parallel plate sample holding capacitor and a ferrite core based adjustable inductor. Capacitor electrodes (17.5 mm x 15 mm) were patterned on 2000 Å gold layer deposited on glass and insulated by thin teflon film. The two input frequencies f1 and f2 were selected so that they match with the LCR resonance peak and are separated by approximately 100 Hz. This locates f1, f2 and the third order IMPs 2f1-f2 and 2f2-f1 within the resonator’s pass-band, thus enhancing the sensitivity.We measured IMD spectrum for DI Water, 0.01M, 0.1M and 1M NaCl solutions and yeast suspensions in water. Control experiment with DI water did not show any IMPs. IMD spectra obtained for NaCl solutions showed third order IMPs. The output power of these IMPs showed the dependence on ion concentration, which relates to the electrode-electrolyte interface (EEI). To simulate the degree of nonlinearity in the system we used a double layer (DL) model. Using DL concept we calculated the EEI current density and identified its capacitive and conductive components. As a result we could simulate the amplitudes of third order IMPs. The ratio of the third order terms for 1M/0.01M and 1M/0.1M were calculated from experiments and compared to those obtained from capacitive and conductive power expansion series. It was found that both capacitive and conductive components of EEI current contribute almost equally to the observed non-linearity. IMD spectrum for yeast samples under different degree of oxygenation and a method of correction for “intrinsic” interface nonlinearity will be presented and discussed.
9:00 PM - HH4.37
Photosystem I as a Biomolecular Reactor for Solar Energy Conversion toward Hydrogen Generation.
Amy Manocchi 1 , David Baker 1 , James Sumner 1 , Scott Pendley 1 , Margaret Hurley 1 , Kang Xu 1 , Barry Bruce 2 , Cynthia Lundgren 1 Show Abstract
1 , US Army Research Laboratory, Adelphi, Maryland, United States, 2 , University of Tennessee Knoxville, Knoxville, Tennessee, United States
The ever increasing world energy demand, coupled with heightened concerns of global warming, has generated considerable interest in alternative energy sources. Countless research groups have focused on developing hydrogen fuel cells as an alternative energy source; however the on-demand production of clean hydrogen fuel remains challenging. Therefore, there is a critical need for the development of an environmentally friendly route to the production of hydrogen gas in vitro. Nature has perfected the conversion of light energy to chemical energy via photosynthesis through a finely tuned network of protein reaction centers. Photosystem I (PSI), a thylakoid reaction center protein, is particularly instrumental in photosynthesis. Upon excitation by light, PSI undergoes complex unidirectional electron transfers across multiple redox centers within the protein. This light-induced charge separation is then utilized in the production of energy in the plant in the form of ATP. Our goal is to mimic photosynthesis through the fabrication of a photocatalytic biohybrid system of PSI and inorganic materials in order to produce hydrogen gas, rather than ATP. This presentation shows our recent work in understanding PSI as a biomolecular reactor for solar energy conversion, and our progress toward a biomimetic hydrogen generating device. We highlight the controlled surface assembly of wild-type and modified PSI complexes onto various modified electrode surfaces and the optimization of charge transfer from the electrode surface to PSI. Finally, we demonstrate the photoelectrochemical activity of these surface assembled PSI complexes.
9:00 PM - HH4.39
Au Nanocrystals for Enzyme-Free Electrochemical Biosensors.
Yu-Ho Won 1 , Lia Stanciu 1 Show Abstract
1 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Metal and semiconductor nanocrystals have been recently widely investigated due to their unique properties. Among these, Au nanocrystals have attracted intense attention owing to their potential applications in fields such as catalysis, biosensing, or biological labeling. These unique properties are dramatically influenced by their size and shape.Here, we report on the fabrication of Au nanocrystals with different morphologies and their subsequent testing in enzyme-free electrochemical biosensor configurations. Specifically, Au nanoparticles (NPs) on silica, Au NPs, and Au nanorods (NRs) with aspect ratios of 1:3 and 1:5, were coated on screen printed electrodes and their capabilities for hydrogen peroxide detection were evaluated in a three-electrode system configuration. The electrodes modified with Au nanocrystals showed biosensing properties without any enzyme being attached or immobilized at their surface. The hydrogen peroxide detection limit of the biosensors was in the range of 6.48 ~ 9.38 μM (signal to noise = 3). The biosensors with Au NPs, Au NRs (1:3), and Au NRs (1:5) showed the sensitivities of 11.13, 54.53, and 58.51 μA/mM, respectively. These results indicate that morphologies of Au nanocrystals significantly influence the sensitivity of the biosensors. In addition, the enzyme-free biosensors with Au nanocrystals were stable for 2 months. Au nanocrystal-based enzyme-free system, which is proposed in this study, can be used as a platform for various electrochemical biosensors without the disadvantages brought by the inherent instability and problems related to orientation control of enzymes. Thus, the reported Au nanocrystals-based hydrogen peroxide biosensors were stable for 2 months. The principles derived from the proposed Au nanoparticle-based enzyme-free system has the potential to be useful for other enzyme-free electrochemical biosensor configurations.
9:00 PM - HH4.4
Fabrication of Nanoneedle Array for High-Throughput Biomarker Detection in a Lab-on-a-Chip Device.
Rahim Esfandyarpour 1 2 3 , Hesaam Esfandyarpour 1 2 3 , Ronald W Davis 1 2 3 , Sam Emaminejad 1 Show Abstract
1 , stanford university, Stanford, California, United States, 2 , Stanford University, Stanford, California, United States, 3 , Stanford University, Stanford, California, United States
Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization and label-free operation. We introduce the Nanoneedle, a label-free biosensor, which has the potential of measuring single molecule interactions useful for protein biomarker detection and DNA sequencing.Coaxial Nanoneedle Biosensor as a real time, label free and direct electrical detection platform, shows a promise to overcome the current limitations of biosensors. The basic device consist of two conductive layers ( 100 nm each) with an insulator layer (30 nm) in between. The tip of the Needle interfaces the solution. Impedance is measured in between the conductive layers. Probe molecules are immobilized at the surface of the tip. Binding of the analyte results in modulation of the impedance. The system is optimized for the high sensitivity and low concentration detection. A preliminary study was performed to prove feasibility of the direct impedance biosensor for detection of protein or nucleic acids, due to the ionic current and impedance modulation. In addition, there are a lot of interest in high throughput proteomics and cancer biomarker multiplexing both for research and clinical applications. One of the major benefits of Nanoneedle sensor is the feature of parallel processing and array format of the device in microfluidic channels.
9:00 PM - HH4.40
Observation of Local Ionic Concentration of the Selected Cations with Sub-Micro Pipette.
Jong Wan Son 1 , Tomohide Takami 1 , Joo-Kyung Lee 1 , Tomoji Kawai 1 , Bae Ho Park 1 Show Abstract
1 Physics, Konkuk University, Seoul Korea (the Republic of)
Selected cationic currents in aqueous NaCl and KCl solutions with concentrations from 0.01 to 1.0 M were measured using sub-micro pipette probes. A polyvinyl chloride film was prepared in the sub-micro pipette probes, and the film contains crown ether ligands that filter potassium or sodium ions. The currents of the survived ions were detected through a silver wire electrode and the currents were recorded with a sub-picoampere current measurement system developed from the techniques of TΩ-gap impedance scanning tunneling microscopy. The ionic currents increased with the concentration of the corresponding solutions. The Debye-Hückel-Onsager (DHO) equation can be applied at low concentrations less than 0.1 M, whereas it does not work at high concentrations because the surrounding ions and water molecules relax the microscopic structure of the ions and the hydrodynamic effect arises from the coupling of the ion velocity with the natural currents of the system.
9:00 PM - HH4.41
High Surface Area Chemiresistive Biosensor for Efficient and Faster Detection of Analyte.
Dhiman Bhattacharyya 1 , Karen Gleason 1 Show Abstract
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Chemiresistive biosensors detect the changes in resistance when analyte molecules specifically bind to the sensor surfaces. Chemiresistive biosensing technique is attractive because it is label-free and can be developed for faster detection of analytes avoiding a long sample preparation time as it is required in other techniques such as in polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), or by avoiding the necessity to carry heavy weight instruments, such as surface plasmon resonance (SPR). Overall, chemiresistive biosensors can be portable, selective, highly sensitive and stable. In this work, oxidative chemical vapor deposition (oCVD) technique is employed for deposition of conducting polymer thin films on the electro-spun fiber mats. The dry oCVD process allowed us to deposit uniform and conformal conducting –OH functional copolymeric film on the electro-spun fiber mat in a single step. For the proof-of-concept of the biosensor application, avidin molecules were covalently immobilized to the –OH functional groups of the conducting copolymer on the e-spun mat. Various concentrations of biotin solutions were employed as the analytes because avidin is known to have very high selectivity towards biotin and they have a very high association constant. Therefore, these experiments proved the specificity of the biosensor devices. Moreover, the responses and the response times of the devices were significantly improved when the high surface area electro-spun mat were used as a substrate than a flat substrate.
9:00 PM - HH4.42
Density Functional Theory (DFT) Computations of Biological Molecules for Organic Semiconductors.
Michael Korn 1 , Marissa Estep 1 Show Abstract
1 Biology & Chemistry, Liberty University, Lynchburg, Virginia, United States
Computations of the highest occupied molecular orbital (HOMO) energies and lowest unoccupied molecular orbital (LUMO) energies and therefrom the band gap (Eg) of some 20+ biological molecules have been performed using Density Functional Theory at the B3LYP/6-31G* level with the aim to identify compounds suitable as bio-based organic semiconductors [1,2]. Compounds investigated comprise molecules with aromatic cores, such as caffeine, adenine, pterin, luciferin, indigo, and several bioconjugates. Results show HOMO energies between -5.03 eV and -6.61 eV, LUMO energies between -0.17 eV and -2.99 eV, and Eg values between 2.50 eV and 5.50 eV. The most promising candidate identified is indigo with a HOMO energy of -5.26 eV, a LUMO energy of -2.76 eV, and Eg of 2.50 eV. Cai, D., Marques, M. A. L., Milne, B. F., Nogueira, F. J. Phys. Chem. Lett. 2010, 1, 2781-2787. Bettinger, C. J., Bao, Z. Adv. Mater. 2009, 21, 1-5.
9:00 PM - HH4.44
Enzyme/ SWNTs Based Biosensor for D-Glucose Detection.
Jinyoung Lee 1 , Malima Asanterabi 1 , Jungho Seo 1 , Sivasubramanian Somu 1 , Ahmed Busnaina 1 Show Abstract
1 Mechanical Engineering, Northeastern University, Boston, Massachusetts, United States
Electrochemical detection method for detecting D-glucose in solution is being adopted widely due to their simplicity and relative ease of calibration. However, the response time of the sensors based on electrochemical detection is really slow. Also these devices are based on three electrode configuration and are operated in in-vitro mode. For specific applications such as those involve monitoring in intensive care as well as constant monitoring of patients a glucose sensor with faster response is needed. In addition, currently available glucose sensors are huge in size and hence cannot be implemented in the in-vivo mode. Here we report on the development of a simple yet highly sensitive micron scale SWNT based glucose biosensors with instantaneous response to the presence of glucose. The principle of operation of the device is conductance based and consists on only two terminals. The device comprises of D-glucose oxidase/highly organized SWNTs channel attached to electrical leads. The SWNTs bundle was made using template guided fluidic assembly method. The GOD was attached using non-covalent bonding with the help of 1-pyrenebutanoic acid succinimidyl ester as a linker molecule. Raman characterization revealed that the D/G band ratio changed by 15% after the immobilization of D-glucose oxidase on SWNT through non-covalent fundtionalization. When glucose molecules attached to the D-glucose oxidase, an increase in resistance as large as 85% was observed. This increase in resistance is a measure of the concentration of glucose. Once these devices are washed in water they regenerate and can be used thousands of time. The developed D-glucose glucose sensor has detection range of 0~40 mM. In addition, due to its inherent small size, the biosensor can be used for in-vivo mode application. Thus employing simple directed assembly and non-covalent functionlization process we have fabricated D-glucose oxidase /SWNT hybrid sensors and were able to achieve instantaneous response for glucose detection.
9:00 PM - HH4.45
Non-Covalent Surface Anchoring of Lipophilic Nucleic Acids: Preparation, Characterization and Sensing Applications.
Roey Elnathan 1 , Anke Kolbe 2 Show Abstract
1 nano and chemistry, Tel-Aviv Universirty, Tel-Aviv Israel, 2 , Zernike Institute University of Groningen, Groningen Netherlands
Biofunctional interfaces between biomolecules and solid inorganic substrates (such as semiconductor materials) have been the focus of enormous interest in basic and applied science due to the vast potential applications of these hybrid structures in fields including proteomics, microarray technology, and biosensors. It is anticipated that these hybrid biointerfaces will be able to perform specific functions, such as biorecognition in the context of an electrical, mass, and optical measurements, better than either purely organic or inorganic systems.Here, we demonstrate a new method for the non-covalent reversible anchoring of novel multi-lipophilic arm DNA probes on self-assembled monolayer-modified gold electrodes, silicon semiconductor surfaces and glass surfaces. Using hydrophobic self-assembled monolayers as an anchoring basis, lipid-DNA hybrid target molecules showed to be inserted into the monolayer structure, through their lipid tails, upon incubation for different periods of time. Thus, the surface coverage of the target DNAs can be controlled by simply modulating their initial concentration and the incubation time. Interestingly, heating the DNA-inserted monolayer surfaces at temperatures >80oC leads to release of the DNA-lipid structures from the surface, without affecting the integrity of the hydrophobic self-assembled monolayers. This release process leaves behind a DNA-free surface which can be repeatedly modified with DNA-lipid probe molecules for additional cycles. Furthermore and notably, the influence of mixed monolayers, with hydrophobic molecules of different lengths, on the surface density of lipophilic-DNA target molecules was also studied, and reveals results highly dependent on the nature of the monolayer composition and structure used as basis for the DNA-lipid insertion process. Finally, using these novel lipid-DNA hybrid molecules, we show the influence of the number of lipophilic tails, two or four, on their insertion capabilities and on the stability of the resulting DNA-inserted layers.
9:00 PM - HH4.46
Solar-Powered Microbial Photoelectrochemical Cells for Renewable Energy Generation.
Fang Qian 1 2 , Gongming Wang 2 , Yongqin Jiao 1 , Mona Hwang 1 , William Smith 1 , Michael Thelen 1 , Yat Li 2 Show Abstract
1 Physical and Life Sciences Directorate, Lawrence Livermore National Lab, Livermore, California, United States, 2 Department of Chemistry and Biochemistry, University of California, Santa Cruz, California, United States
We report a self-biased, solar-powered microbial photoelectrochemical cell (solar MPC) that can generate sustainable electricity through coupling the microbial catalysis with solar energy conversion. The model device consists of a p-type Cu2O nanostructured photocathode and a Shewanella-colonizing anode, which can harvest solar energy and chemical energy from biodegradable organic matter, respectively. The photocathode and bioanode are interfaced electrically by matching the redox potentials of outer-membrane cytochromes of Shewanella cells and the electronic bands of Cu2O. At zero bias, a 25-mL solar MPC yielded a net photocurrent of 0.2 mA under weak white light illumination (20 mW/cm2); the rate-limiting steps under different illumination conditions were identified. The design criteria, challenges and promise of realizing such bio/semiconductor hybrid energy conversion systems will be discussed. This work was performed under the auspices of the U.S. Department of Energy Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
9:00 PM - HH4.5
Controlling the Mechanisms of Axonal Pathfinding and Electrical Connectivity for Neuronal Cells Patterned on 2-Dimensional Substrates.
Jonathan Poli 1 , Elise Spedden 1 , James White 2 , Min Tang-Schomer 2 , David Kaplan 2 3 , Cristian Staii 1 Show Abstract
1 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States, 2 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 3 Chemical Engineering, Tufts University, Medford, Massachusetts, United States
In the developing brain chemical and geometrical cues are an essential source of information used by neurons when wiring up the nervous system. Over the past decade, many of the molecular cues and the signaling pathways through which they operate have been identified using traditional biological techniques. However, our current understanding of the mechanisms by which the guidance factors control the path that growing axons/dendrites follow to reach their targets and form functional electrical connections remains qualitative. A current limitation for the study of neural network formation is the ability to precisely control the growth and interconnectivity of small numbers of neurons. Here we present a combined Atomic Force Microscopy – Fluorescence Spectroscopy approach for patterning neurons on 2-dimensional substrates and precisely controlling their location, growth and interconnectivity. We demonstrate that this approach allows one to: a) form simple neuronal circuits in well-controlled geometries; b) guide the formation of functional synapses between neurons, and c) measure the electrical activity of small groups of neurons. We discuss the implications of these results for our current understanding of the fundamental mechanisms that govern the development of electrical connections between neurons, as well as new insights that these results might provide for designing nerve-biomaterial interfaces for prosthetic devices.
9:00 PM - HH4.6
Spectroscopic and Electrochemical Detection of Thrombin/5’-SH or 3’-SH Aptamer Immobilized on (Porous) Gold Substrates.
Jinkyu Roh 1 , Younghun Kim 1 Show Abstract
1 Chemical Engineering, Kwangwoon University, Seoul Korea (the Republic of)
Thrombin, also known as coagulation factor II, is a multifunctional serine protease that catalyzes the conversion of soluble fibrinogen (factor I) into long, sticky threads of insoluble fibrin (factor Ia). Factor Ia induced by factor II forms a mesh that traps platelets, blood cells, and plasma to enable physiological and pathological blood coagulation. During the coagulation process, the concentration of thrombin in blood varies from nM to μM levels, and thus it is important to detect thrombin in blood serum for clinical and diagnostic applications. To achieve this goal, it has been suggested that a 15-mer aptamer strongly binds with thrombin to form a G-quartet structure of the aptamer. Generally, 5’-end thiol-functionalized aptamer has been used as an anti-thrombin binder. Herein, we evaluated whether a 3’-SH aptamer has same affinity for thrombin as a 5’-SH aptamer. Thiol functionalized aptamers were easily immobilized on gold substrate, and for binding with thrombin, the 15-mer aptamer folded into a chair-form quadruplex with the adjacent 5’ and 3’ ends in the corner of the quadruplex, and 2 staked G-quartets were linked with TT and TGT loops. Therefore, the two aptamers should have similar affinities for thrombin; and in SPR analysis, both the 3’-SH aptamer and the 5’-SH aptamer acted as effective aptasensors. In electrochemical analysis, both aptamers demonstrated similar current changes. Specifically, although the configuration of the 3’-SH aptamer was similar to that of the 5’-SH aptamer, the addition of several functional groups to the 5’-end of the anti-thrombin aptamer would allow for suppressing the formation of the G-quartet structure. To enhance the current signal in CVs, porous gold substrate, which has a high pore size and surface area compared to gold thin film, was introduced and showed a 5-fold larger current signal without change of sensitivity. Further studies should be conducted to investigate the LOD when using porous gold to develop highly sensitive aptasensors.
9:00 PM - HH4.7
Chirality and Selectivity of Pyridyl-Substituted Porphyrin Ring for Monitoring Neurotransmitters in the Presence of Interfering Agents.
Joon-Hyung Jin 1 , Min-Jung Song 1 , SungWoo Hwang 1 Show Abstract
1 , Korea University, Seoul Korea (the Republic of)
Porphyrin-modified self-assembled monolayer (PSAM) was prepared on transparent conducting oxide (TCO) substrates. We employed two different porphyrin derivatives tetra-4-pyridylporphyrin and tetra-4-carboxyphenylporphyrin. The PSAM/TCO electrodes showed an excellent selectively for monitoring adrenaline, dopamine, and serotonin simultaneously in the presence of interfering agents including ascorbic acid and urea. The selectivity and chiral activity were characterized via square wave voltammetry (SWV) by observing separate peak potentials of each neurotransmitter. The measured values for the peak potential separation between neurotransmitters were at least 50 mV. Photocatalytic effects of the PSAM layer on selective detection of neurotransmitters were also investigated using a laboratory-made Teflon electrochemical cell. Characterization of electrochemically-inactive pyridyl-substituted porphyrin and corresponding electrodes were conducted by electrochemical impedance spectroscopy (EIS).
Shachar Richter Tel Aviv University
David Waldeck University of Pittsburgh
David Lederman West Virginia University
Jason Davis University of Oxford
HH5: Charge Transfer, Spectroscopy, and Devices
Wednesday AM, November 30, 2011
Room 204 (Hynes)
9:30 AM - **HH5.1
Metal Bonded P450 CYP2C9 as a Platform to Study Heme Electron Transfer.
Peter Gannett 1 Show Abstract
1 Basic Pharmaceutical Sciences, West Virginia University, Morgantown, West Virginia, United States
Electron Transfer in ferroxoreductases has been a long standing problem. A variety of approaches have been explored to determine the factors that modulate the process and the mechanism involved. A major problem is that there are no direct methods available to directly measure electron transfer. Our approach to the measurement of electron transfer in ferroxoreductases is to directly wire them directly into circuits. Here, we describe three approaches we have taken including and electrochemical cell, when captured between electrodes made by a break-junction approach, and conducting probe atomic force microscopy. The solution system contained CYP2C9 bonded to a gold electrode via an eight carbon linker. Bonding was required implying either participation of the linker in electron transfer and/or the effect of bonding on orienting the heme relative to the planar electrode. In the second approach, CYP2C9 was captured between two platinum electrodes and conduction was dependent upon the absence or presence of substrate indicating involvement of the heme. Due to the technical difficulties associated with this second approach, a third utilizing isolated CYP2C9 bonded to gold post and conducting probe AFM is being developed. The relative merits of these systems and data obtained from them with respect to ferroreductase electron transfer will be described. (Supported by NIH GM081348, WV EPSCoR HEPC.dsr.09013, NSF DMR-1004431 and EPS-1003907)
10:00 AM - HH5.2
Myoglobin-Based Single Electron Transistors.
David Lederman 1 , Debin Li 1 , Peter Gannett 2 Show Abstract
1 Department of Physics, West Virginia University, Morgantown, West Virginia, United States, 2 Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, West Virginia, United States
Experiments were performed on single electron transistors (SETs) where the quantum dot element is the heme-group of the myoglobin protein. The heme-group is composed of a single iron atom in a prophyrin ring, which is intrinsically small and thus has energy levels separated by > 100 meV. We used Pt break-junctions on SiO2/Si substrates to fabricate the devices. We observed several SET-characteristic phenomena, including Coulomb diamonds and inelastic tunnelling behaviour due to interaction with the vibrational modes of the enzyme. The Coulomb diamond behaviour was modeled and the parameters thus extracted (i.e., energy levels, contact capacitances, and tunneling rates) were reasonable and consistent with known values from bulk myoglobin. Because biomolecules such as myoglobin are stable at room temperature, these experiments demonstrate that SET room-temperature operation may be feasible in the near future. This work is supported by NSF (grant EPS-0554328) and the WVNano Initiative at WVU.
10:15 AM - HH5.3
Doped Biomolecules in Miniaturized Electric Junctions.
Elad Mentovich 1 2 , Bogdan Belgorodsky 1 , Michael Gozin 1 , Hagai Cohen 3 , Shachar Richter 1 2 Show Abstract
1 Chemistry, Tel Aviv University, Tel Aviv Israel, 2 Center for nanoscience and nanotechnology, Tel Aviv University, Tel Aviv Israel, 3 Department of Chemical Research Support, Weizmann Institute of Science , Rehovot Israel
Control over molecular scale electrical properties within nano junctions is demonstrated, utilizing site-directed C60 targeting into protein macromolecules as a doping means. The protein molecules, self-assembled in a miniaturized transistor device, yield robust and reproducible operation. Their device signal is dominated by an activity center that inverts affinity upon guest incorporation and thus controls the properties of the entire macromolecule. We show how the leading routs of electron transport can be drawn, spatially and energetically, on the molecular level and, in particular, how the dopant effect is dictated by its 'strategic' binding site. Our findings propose the extension of microelectronic methodologies to the nanometer scale and further present a promising platform for ex-situ studies of biological mechanisms.
10:30 AM - HH5.4
Chemically Resolved Electrical Measurements at Selected Sites of Organic and Bio Molecular Layers.
Hagai Cohen 1 Show Abstract
1 , Weizmann, Rehovot Israel
A novel technique for chemically resolved electrical measurements (CREM), based on x-ray photoelectron spectroscopy (XPS), is used for studying the electrical properties of organic systems at selected molecular sites. CREM is an essentially contact-free method, where both the input current and (output) voltage measurement are carried out by means of electrons transmitted through the vacuum to or from the sample. CREM can probe the electrostatic potential at specific chemical addresses and, thus, draw detailed information on intra-molecular dielectric response mechanisms, approaching in certain cases atomic resolution. Here, basic principles of the CREM method will be discussed, with particular emphasis on its application to self-assembled monolayers, starting with small silane molecules and ending in protein macromolecules. The unique advantages of the technique and its drawbacks will be discussed. References1.I. Doron Mor et al., Nature 406, 382 (2000).2.H. Cohen, Applied Physics Letters 85, 1271 (2004).
11:15 AM - **HH5.5
ECSTM/STS Single Molecule Investigation of 2e-/2H+ Redox Reactions.
Paolo Facci 1 Show Abstract
1 NANO-S3, CNR, Modena Italy
The hydroquinone/benzoquinone redox couple involves the exchange of two electrons and two protons in its oxidation/reduction reaction in aqueous buffered solutions (1). We have employed Electrochemical Scanning Tunneling Microscopy and Spectroscopy (ECSTM, ECSTS) to study the interfacial electron transfer properties of hydroquinone incorporated in a Self Assembled Monolayer on a Au(111) substrate (2). The exchange of electrons between the STM tip and the substrate is regulated by the redox levels of the sandwiched molecule and shows the presence of two regions of tunneling enhancement in the tunneling current/overvoltage relationship. The two regions can be attributed to the presence of two one-electron transfer processes whose equilibrium positions shift upon pH variations. By changing the link between quinone and substrate from a thiolated alkyl chain to an oligo-phenylenevinylene thioacetate chain, it was possible to vary the spacing between the detectable electronic levels, corroborating theoretical predictions on the involved electron transport mechanism that foresee different behaviors of the current/overvoltage relationship as a function of the ratio between bias voltage and redox level spacing (3). This is the first time a redox molecule involving the exchange of both electrons and protons is studied by ECSTM and ECSTS. In light of the reported results, hydroquinone/benzoquinone redox couple appears as an intriguing candidate to implement an electrochemically and/or pH gated single molecule transistor.References1. M. Quan, D. Sanchez, M.F. Wasylkiw, D.K. Smith, J. Am. Chem. Soc. 2007, 129, 12847.2. P. Petrnagolini, A. Alessandrini, L. Berti, P. Facci J. Am. Chem. Soc. 2010, 132, 7445. 3. P. Petrangolini, A. Alessandrini, M. Capobianco, P. Facci, 2011, submitted.
11:45 AM - HH5.6
Optical Trapping, Biosensing, and Spectroscopy in a Single Plasmonic Platform.
Arif Cetin 1 , Cihan Yilmaz 2 , Ahmet Yanik 1 , Sivasubramanian Somu 2 , Ahmed Busnaina 2 , Hatice Altug 1 Show Abstract
1 Electrical Engineering, Boston Univ, Boston, Massachusetts, United States, 2 Mechanical Engineering, Northeastern University , Boston, Massachusetts, United States
In this work, we propose a plasmonic platform composed of gold nanopillars which allows biosensing applications, ultrasensitive vibrational spectroscopy and optical trapping at the same time. Perpendicular incident light is used to excite the structure which is one of the significant advantageous over other platforms based on angled illumination source. The tight localization of plasmonic excitation in nanopillar structure leads to narrow resonances in the spectrum. Hence, we achieve high refractive index sensitivities, ~675 nm/RIU with high figure of merit (FOM) values, ~112.5. This FOM value is one order of magnitude higher than the preceding plasmonic structures based on the localized Surface Plasmon (SP) modes. In our structure, SPs are localized at specific hot spots on top surface of the gold nanopillars which lead large near-field intensities with enhancement factors of ~10000, highly desirable for surface enhanced Raman spectroscopy. The near-field intensities are mostly collected in the vicinity of the structure which allows high optical field-biological analyte overlap for biosensing and vibrational spectroscopy applications. The location of the plasmonic hot spots with high near-field enhancements depend on the polarization direction of the incident source. We achieve high optical forces, ~350 pN/W/µm^2, from these hot spots which allows optical trapping of nanoparticles with low power excitation source. Since the location of the hot spots highly depends on the direction of polarization, we can utilize the direction of this strong optical force by polarization control for optical manipulation of the biological molecules in the vicinity of the nanopillar arrays. Our proposed structure serves for optical trapping of bioparticles, spectroscopy measurement and real-time biodetection at the same time and on the same platform which could attract many attentions from wide range of researches and studies.
12:00 PM - HH5.7
Large Conductance Changes in Peptide Single Molecule Junctions Controlled by pH.
Richard Nichols 1 , Lisa Scullion 1 , Thomas Doneux 2 , Laurent Bouffier 3 , Simon Higgins 1 , David Fernig 4 , Donald Bethell 1 Show Abstract
1 Chemistry, Liverpool University, Liverpool Belgium, 2 Chimie Analytique et Chimie des Interfaces, Université Libre de Bruxelles, Brussels Belgium, 3 Institut des Sciences Moléculaires, NSYSA, Institut des Sciences Moléculaires, Pessac France, 4 Structural and Chemical Biology, Liverpool University, Liverpool United Kingdom
This presentation concerns the electrical properties of junctions involving single peptide molecules (gold-peptide-gold) and their response to solution pH. The study of charge transfer across molecular and bimolecular junctions has been given great impetus in recent years by the development of new experimental techniques for forming single molecular junctions and advanced method for computing the conductance of such junctions. Since charge transfer is often highly sensitive to bridge length and molecular or bimolecular conformation; changes in these can have a huge impact on the conductance of single molecule electrical junctions. We report here on the use of pH is used to control the conformation and effective length of single molecule junctions containing defined peptide sequences which include ionisable glutamic acid residues. These groups in our target peptide result in an oligo-peptide structure highly sensitive to pH. In low pH solutions the peptide molecular bridge exists in its more compact alpha-helical state. On the other hand, at high pH deprotonation leads to electrostatic repulsion between the charged carboxylate groups of the glutamic acid residues. This promotes more extended conformations of the peptide “wire”. The STM-based I(s) method is used to measure the single molecule conductance of gold-peptide-gold two-terminal junctions in buffered electrolyte solution at low pH (2) and higher pH (7). In its more compact alpha-helical state at low pH, a relatively high single molecule conductance of has been recorded, with the conductance then dropping to a low level when the pH is raised to higher pH values where the glutamic acid residues are deprotonated. This large pH-controlled drop in conductance shows that oligo-peptides can provide particularly sensitive motifs for controlling long-range electron transfer and possible future application in bio-electronics. The STM measurements are complemented by electrochemical measurements of charge transport across self-assembling monolayers of the peptide. These measurements quantify the rate constant for charge transfer across the peptide monolayer and how it varies with pH. REFERENCES: 1.L. Scullion, T. Doneux, L. Bouffier, D. G. Fernig, S. J. Higgins, D. Bethell and R. J. Nichols Large Conductance Changes in Peptide Single Molecule Junctions Controlled by pH Journal of Physical Chemistry C, 2011, 115, 8361-8. 2.T. Doneux, L. Bouffier, L. V. Mello, D. J. Rigden, I. Kejnovska, D. G. Fernig, S. J. Higgins and R. J. Nichols Molecular Dynamics and Electrochemical Investigations of a pH-Responsive Peptide Monolayer Journal of Physical Chemistry C, 2009, 113, 6792-9.
12:15 PM - HH5.8
Electrochemically Transduced Logic Gate on Molecular Level.
Dirk Mayer 1 2 , Yaqing Liu 1 2 , Andreas Offenhaeusser 1 2 Show Abstract
1 Peter Gruenberg Institute, PGI-8, Forschungszentrum Juelich GmbH, Juelich Germany, 2 , JARA-Fundamentals of Future Information Technology, Juelich Germany
Organic molecules or biomolecules that are able to generate a detectable response to an external stimulus are of great scientific interest since they can be used for data processing, as for instance information storage, transformation, and communication. Logic gates such as AND, OR, INHIBIT, XOR, XNOR, and NOR Boolean functions have been realized on the molecular level and are able to process information. In order to achieve practical applications, the future of biomolecular logic elements is strongly related to the successful linkage of biomolecules onto a conductive or semi-conductive support. We realized different functions with electric readout by immobilizing robust, redox-active oligopeptides such as microperoxidase-11 on a solid-state surface and applying different redox probes as input signals. The different functional units presented here have in common that they are all based on (bio)-electrochemical rectifiers (ECR). An electrochemical rectification is characterized by an unidirectional redox current which is transferred between redox probes in solution and a metal electrode functionalized with the molecular redox mediator. The unidirectional current develops due to selective electron transport from the functionalized electrode to the redox probe or vice versa such that the redoxmediator controls the read-out of the coupled redox system. A high forward current can be observed if electrons are continuously transferred from the source to the drain via states of lower energy. (Bio)-electrochemical rectifiers can be combined to perform higher logic operations similar to conventional diode rectifiers. Here, an electrode functionalized by a redox mediator acted as an ECR for two different redox inputs of opposite sign. When integrating the resulting cathodic and anodic current rectifier, a XOR logic gate characteristic was observed with high switching ratio between output signals “1” and “0”. The strategy to link different surface bound and unbound redox centers to electrified interfaces can be further expanded to the development of other molecular logic gates with electrical readout, which might pave the way to integrate logic and sensing operations for advanced sensor performance. The opportunity to process different sensory inputs (for instance biomarkers) by a logic gate will improve the reliability of senor responses by suppressing cross sensitivity.
12:30 PM - HH5.9
Orthogonal Processing for Intergrated Pattering of Biomolecules and Organic Electronics.
Priscilla Taylor 1 , Kari Midthun 2 , Carol Newby 1 , Jin Kyun Lee 3 , Barabara Baird 2 , Christopher Ober 1 Show Abstract
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States, 3 Department of Polymer Science and Engineering, Inha University, Incheon Korea (the Republic of)
Orgnanic electronic materials interface better with biology than do conventional inorganic electronic materails such as silicon. Future bioelectronic devices will require fabrication routes that can pattern organic electronic materials like P3HT and PEDOT:PSS in close proximity to active biomolecules. However, both organic electronic materials and biomolecules are easily damaged by the aggressive solvents used to process conventional photoresists.Recently, orthogonal processing has been shown to be a viable method of patterning organic electronic materials. By using non-damaging fluorous solvents it allows patterning of organics in a process directly analogous to conventional high-throughput lithographic patterning.Due to the low intermolecular forces in fluorous solvents thay are also non-damaging to biomolecules. Assays were done to investigate the effect of the solvents on protein binding and found there was no decrease in bioactivity after imersion in hydrofluoroethers or after coating and stripping of the fluorinated resist. Using such a fluorinated resist system multiple proteins were patterened on a single surface via nanoimprint lithography down to dimesions of 5 microns.In a further development the same fluorinated resist is shown to allow integration of patterning both bioactive molecules and organic electronic materials on a substrate. Various interdigitated and connected patterns of metal, organic electronic material and proteins were achieved using both photolithography and nanoimprint lithography.1. A. A. Zakhidov, J.-K. Lee, H. H. Fong, J. A. DeFranco, M. Chatzichristidi, P. G. Taylor, C. K. Ober, G. G. Malliaras, Adv. Mater., 20, 348 (2008)
HH6: Cellular Bioelectronics
Wednesday PM, November 30, 2011
Room 204 (Hynes)
2:30 PM - HH6.1
Nanowire Transistor Three-Dimenional Probes for Intracellular and Tissue Recording.
Quan Qing 1 , Erik Nelson 1 , Zhe Jiang 1 , Ruixuan Gao 1 , Charles Lieber 1 Show Abstract
1 Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Conventional techniques for extracellular recording, such as metal microelectrodes, may fail to measure slow and subthreshold signals produced by electrogenic cells. In contrast, intracellular recording methods, such as patch-clamp micropipettes can capture all of the fine features of cell activity, although this technique has limits due to solution exchange between cytosol and pipette, and current leakage at the pipette-cell junction. Solid-state nanoelectronic devices are uniquely suited for use as biological detectors due to their high sensitivity, biologically relevant size scale and biocompatibility. In particular, they can form non-invasive cellular interfaces with living cells through biomimetic processes associated with membrane fusion and cell internalizaiton. The bottom-up synthetic integration of a nanoscale field effect transistor (nanoFET) at the tip of acute-angle kinked silicon nanowire enables formation of three-dimensional (3D) detectors that can access the intracellular cytoplasm. While such chip-based 3D nanoFETs provide many advantages for intracellular recording, they are limited for many studies due to the requirement of a supporting substrate. Here we report for the first time the fabrication of free-standing 3D nanoFET probes and their precise positioning using 3D micromanipualtors within selected cells and cellular structures. Intra- and extracellular signals from cultured cardiomyocytes, neurons as well as acute brain slices will be described and discussed. These novel nanometer-sized, substrate-free FET detectors combine the advantages of the nanoFET-cell interface with the flexibility and accuracy of micropositioning, and thus enabling unique opportunities to study live cells in-vitro and in-vivo.
2:45 PM - HH6.2
Vertical Nanowire Probes as a New Tool for Intracellular Communication with Neural Cells.
Ki-Young Lee 1 3 , Soeun Kim 1 , Il-Soo Kim 1 , Du-Won Jeong 2 , Ju-Jin Kim 2 , Hyewhon Rhim 3 , Jae-Pyeong Ahn 4 , Seung-Han Park 5 , Heon-Jin Choi 1 Show Abstract
1 School of Advenced Materials Science and Engineering, Yonsei Univ, Seoul Korea (the Republic of), 3 Center for Theragnosis, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Department of Physics, Chonbuk National University, Jeonju Korea (the Republic of), 4 Advanced Analysis Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 5 Department of Physics, Yonsei Univ, Seoul Korea (the Republic of)
The probing of a neuronal activity in extra- and intracellular modes on a single-cell level is crucial for the understanding of a whole nervous system. Typical method, such as a patchclamp, is useful to identify the electrical activity of neurons with a good signal-to-noise ratio as well as temporal resolution. However, these techniques burst the cell membrane and alter the internal milieu of the cell, preventing long-term and/or repetitive monitoring. Meanwhile the neuron-nanomaterial hybrid devices are powerful systems, which allow obtaining integrated information by non-invasive and long-term recording or stimulation of individual living neuron cell. Among nanomaterials developed to date, nanowires (NWs) are the unique material, which has a diameter on a nanometer scale, high aspect ratio (<103) and single crystallinity and thus are ideal building blocks for probing single cell activity on a submicron scale. We synthesized vertical Si nanowires in a controlled manner and the optimum conditions including diameter, length, and nanowire density were determined by culturing cells on the nanowires. For intracellular interfacing, vertical nanowire probes were then fabricated with a CMOS process including sequential deposition of passivation- and electrode layer on the nanowires, and a subsequent partial etching process. The fabricated nanowire probes with a diameter of about 60 nm were intracellular interfaced with a GH3 cell and measured the spontaneous action potential. It successfully measured the action potential, which rapidly reached a steady state with average peak amplitude of ~10 mV, duration of ~140 ms, and period of 0.9 Hz. The outcomes of this study can thus be easily extended to the signaling of neural networks such as cultured primary neurons or brain slices, where it is necessary to measure long-term cellular activity in a large working area.
3:00 PM - HH6.3
In Vitro Cell Sensing with Semiconductor-Based Biosensing Technology.
Toshiya Sakata 1 , Haruyo Sugimoto 1 Show Abstract
1 Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
In our laboratory, we focus on a direct detection of ions or ionic molecules through ion-channels at cell membrane, because most of cell functions are closely related to transferring of charged conductors from cell to cell. In this study, we have clarified that a principle of semiconductor devices based on field effect realizes it in a direct, label-free, real-time and noninvasive manner for cell functional analysis. The principle of semiconductor-based biosensing devices is based on the potentiometric detection of charge density changes induced at a gate insulator/solution interface accompanied by specific bio-molecular recognition events. Ionic charges of ions or bio-molecules at the gate insulator electrostatically interact with electrons in silicon crystal across the thin gate insulator resulting in the threshold voltage change. Particularly, we are interested in ion transportations through membrane proteins such as ion-channels and ion-pumps at cell membrane and trying to detect ionic behaviors based on biological phenomena using a cell-coupled gate semiconductor (CGS). The semiconductor-based biosensing devices have good advantages of label-free, real-time and noninvasive method and we can make an arrayed device for a multi target analysis by use of the conventional semiconductor processes. In the point of detection of cell functions, we propose the device structure with three components such as target, signal transduction interface and detection device. Since we utilize the CGS, we are trying to design the signal transduction interface in order to detect ion charges specifically and selectively based on each cell function. In order to detect drug effect on cancer cells, we need to detect ion charges based on programmed cell death “apoptosis” using the CGS and develop the signal transduction interface to trap them. The previous work showed the possibility of potassium ions, chloride ions and water release in the early stage of apoptosis. Therefore, we have focused on potassium ion release based on apoptosis and succeeded in the real-time, direct and noninvasive monitoring of their flow. In particular, this result was accomplished by use of crown ether monolayer to trap selectively potassium ion as signal transduction interface of the CGS. Moreover, we have found the possibility of multi target detection for high throughput screening of drug effect using the CGS with some transfected cancer cells in this study. Using the CGS, furthermore, we have succeeded in a real-time and noninvasive monitoring of various cell functions, as follows. - Interaction between substrate and transporter at cell membrane for drug effect detection - Embryo activity based on in vitro fertilization (IVF) for assisted reproductive technology (ART) - Glucose response of pancreatic be-ta cells for insulin secretion - Differentiation of stem cells such as murine or human iPS cells - Autophagy for accommodation to starvation - Other cell functions
3:15 PM - HH6.4
Metallic Nanopillars for Highly Efficient Electrical Cellular Interface.
Chong Xie 1 , Lindsey Hanson 2 , Carter Lin 3 , Bianxiao Cui 2 , Yi Cui 1 Show Abstract
1 Material Sciences and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry, Stanford University, Stanford, California, United States, 3 Applied Physics, Stanford University, Stanford, California, United States
The small scale of nanomaterials and nanostructures makes them one of the best man-made candidates to interact with biological systems at subcellular or even molecular level. It has been the focal point of the research interests to electrically interface live cells with one dimensional nanostructures, such as nanowires and nanopillars. In this work, we achieve improved electrical coupling between biological cells and solid state devices by using arrays of vertically aligned nanopillar electrodes. Their tight attachment to the cell membrane allows us to acquire intracellular-like action potential signals non-destructively from cultured cardiomyocytes, which could enable various biomedical applications.
3:30 PM - HH6.5
Electrical Control of Protein Conformation and Cell Function on a Conducting Polymer Surface.
Alwin Wan 1 , Emily Chandler 2 , Rebecca Schur 1 , Christopher Ober 1 , Claudia Fischbach 2 , Delphine Gourdon 1 , George Malliaras 3 Show Abstract
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Biomedical Engineering, Cornell University, Ithaca, New York, United States, 3 Centre Microélectronique de Provence, Ecole Nationale Supérieure des Mines de Saint Etienne, Gardanne France
The interface between electronic materials and biological systems is central to governing the behaviour of bioelectronics systems, and organic electronics are particularly well-suited for use in such systems due to their simultaneous (and coupled) ability to conduct ions and electrons. In particular, electrochemically-active conducting polymers experience many property changes as a function of redox state, and some of these changes have directly affect the behaviour of cells and biomolecules that are adsorbed to the polymer. To this end, we have developed a technology utilizing a conducting polymer surface that offers unprecedented control over the molecular conformation of adsorbed proteins. Such control is of substantial interest, as a protein’s conformation is directly related to its bioactivity and function, and the ability to precisely and easily control the conformation of surface-adsorbed proteins would find useful applications in basic research, medical diagnostics, and tissue engineering.We have focused in particular on the important extracellular matrix (ECM) protein fibronectin (Fn), which mediates cell adhesion, migration, differentiation, and growth, in processes ranging from embryonic development to wound-healing. By applying a moderate voltage (or voltage gradient) to a device made from the conducting polymer poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonate (PEDOT:TOS), we varied the conformation of adsorbed Fn from compact to extended. Further, the full range of conformations was found to be biologically relevant, as all of the achieved conformations supported varying levels of cell adhesion and growth.This device allowed us to further study cell behaviour as a function of ECM protein conformation. By establishing single conformations over large areas, we were able to study biological responses such as cell secretory behaviour and adhesion characteristics. We found that fibroblasts exhibited increased secretion of vascular endothelial growth factor (VEGF), and decreased integrin-mediated adhesion, on reduced PEDOT:TOS surfaces as compared to oxidized. Future studies will utilize this platform to investigate other cellular behaviours including: proliferation, differentiation, and secretions of other important factors. This novel bioelectronic technology provides a model platform for studying the specific role of ECM mechanics in regulating cellular functions.
3:45 PM - HH6: Cell
HH7: Energy Harvesting Biomaterials and Devices
Wednesday PM, November 30, 2011
Room 204 (Hynes)
4:15 PM - HH7.1
Application of Wide Band Gap Semiconductors to Increase Photocurrent in a Protein Based Photovoltaic Device.
Arash Takshi 1 , Houman Yaghoubi 1 , John Madden 2 , J. Thomas Beatty 3 Show Abstract
1 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 Electrical and Computer Engineering, University of British Columbia (UBC), Vancouver, British Columbia, Canada, 3 Microbiology and Immunology, University of British Columbia (UBC), Vancouver, British Columbia, Canada
Reaction centers (RCs) from natural photosynthetic cells are photoactive proteins which generate electron-hole pairs in presence of light. Conventionally, a highly ordered monolayer of immobilized RCs on the surface of metallic electrodes has been utilized for making photovoltaic (PV) devices. For efficient collection of either electrons or holes, semiconducting electrodes with appropriate energy levels must be applied which requires a suitable linker for immobilizing RCs. In a new approach presented in this work, a solution of suspended RCs with mediators has been applied as the electrolyte to build electrochemical based PV devices. In this approach, mediators transfer charges from the RCs to the electrodes via diffusion (indirect charge transfer). Various metallic and semiconducting materials, including Carbon, Au, Pt, Indium Tin Oxide (ITO), SnO2, WO3, have been tested as the electrodes. The combination of WO3 and carbon electrodes has shown the largest cell potential (0.339V) with a photocurrent of 5.1 μA/cm2 which is at least three times larger than the other combinations. Also, the photocurrent in this device is found to be one order of magnitude lager than that in a cell with immobilized RCs on a carbon electrode (conventional approach).
4:30 PM - HH7.2
Electrospun Polypeptide-Based Piezoelectric Nanofibers for Sensing and Energy Harvesting Applications.
Dawnielle Farrar 1 2 3 , Kailiang Ren 2 , Derek Cheng 2 , William Wilson 2 , James West 3 4 , Michael Yu 2 Show Abstract
1 , Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, United States, 2 Materials Science & Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 3 Electrical & Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 4 Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Electrospinning is a versatile and cost-effective method for the fabrication of polymeric fibers with sub-micrometer diameter. Although several patents and recent publications have discussed the production of piezoelectric fibers via electrospinnig, to date, direct evidence of poled molecular dipoles and its correlation to fiber piezoelectricity have not been demonstrated. Here, we show for the first time that electrospinning can be used as a one-step method to produce polar polymer fibers with electric dipoles permanently poled in the direction of the fiber axis, resulting in high non-linear optical (NLO) activity and thermally stable piezoelectricity. This was achieved by electrospinning poly(γ-benzyl α, L-amino acid) (PBLG), a liquid crystalline, α-helical poly(α-amino acids) with macroscopic dipoles pre-aligned in the direction of helical axis which can couple synergistically with external electric field and shear force. The electrospun fibers exhibited a d33 piezoelectric coefficient of 25 pC/N which did not deteriorate, even after 100 °C thermal treatment for over 24 hrs. To the best of our knowledge, this is one of the highest thermally stable piezoelectric coefficients reported for poled polymers. The piezoelectric PBLG fibers could be used as flexible, light-weight sensors/transducers and as energy harvesting devices.
4:45 PM - HH7.3
Free-Floating Reaction Centers (RCs) versus Attached Monolayer of RCs in Bio-Photovoltaic Devices.
Houman Yaghoubi 1 , Arash Takshi 1 , John Madden 2 , J. Thomas Beatty 3
1 Department of Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 Department of Electrical and Computer Engineering , University of British