Xinyan Tracy Cui University of Pittsburgh
Diane Hoffman-Kim Brown University
Silvia Luebben TDA Research, Inc.
Christine E. Schmidt The University of Texas-Austin
QQ1: Electroactive and Conductive Polymers for Biomedical Applications
Tuesday PM, November 27, 2007
Room 204 (Hynes)
9:30 AM - **QQ1.1
A Biopolymer Composite that Catalyzes the Reduction of Oxygen to Water.
Jiangfeng Fei 1 , Hyun-Kon Song 1 , Tayhas Palmore 1 2 Show Abstract
1 Division of Engineering, Brown University, Providence, Rhode Island, United States, 2 Division of Biology and Medicine, Brown University, Providence, Rhode Island, United States
A biopolymer composite consisting of polypyrrole, ABTS, and laccase (PAL) was electrodeposited onto the surface of an electrode and shown to catalyze the reduction of dioxygen to water under acidic conditions. The catalytic activity of this biopolymer composite is highest at pH 4, decreasing with increasing pH. The activity of laccase immobilized within this polymer composite was found to be higher than laccase dissolved in solution when methanol was present or at elevated temperatures.
10:00 AM - **QQ1.2
Controlling the Electrode – Cellular Interface Using Organic Conductors.
Gordon Wallace 1 Show Abstract
1 ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
10:30 AM - **QQ1.3
Neural Contacts with Conjugated Polymers in Fibre Geometries.
Olle Inganas 1 4 , Maria Asplund 1 3 4 , Mahiar Hamedi 1 , Robert Forchheimer 2 4 , Hans Holst 3 Show Abstract
1 Biomolecular and organic electronics, IFM, Linkoping University, Linkoping Sweden, 4 Organic Bioelectronics (OBOE), Linköping University, Linköping Sweden, 3 Neuronics, Karolinska Sjukhuset, Stockholm Sweden, 2 Image Coding, ISY, Linköping University, Linköping Sweden
The interfaces of artificial electrode materials and biological neural systems require sufficient charge capacity of electrodes to elicit a neural pulse. To make possible dense interfaces for applications such as an artifical retina, microstructured electrodes are required. A materials class fulfilling these demands are conducting polymer hydrogels, on which neural cells thrive and differentiate. Such porous threedimensional electrodes, can also be designed to include biochemicals, suitable for stimulation of neural (stem) cell differentiation. Electronic fibre based structures with a multitude of electrochemical transistors can be used to adress multiple micro electrodes.
11:00 AM - QQ1: Invited
11:30 AM - **QQ1.4
Conducting Polymers to Improve and Stabilize the Electrode-tissue Interface for Development of Biologically-integrated Prosthetic Devices.
Sarah Richardson-Burns 1 , Caroline Dove 1 , Daniel Margul 2 , Antonio Peramo 1 , Jeffrey Hendricks 2 , Melanie Urbanchek 3 , Paul Cederna 3 , Amanda Thornton 4 , Steven Goldstein 4 , David Martin 1 Show Abstract
1 Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan, United States, 4 Orthopedics, University of Michigan, Ann Arbor, Michigan, United States
The pursuit of bio-integrated artificial limbs continues to motivate development of novel materials necessary for bridging the biotic-abiotic interface and for joining ionically and electronically conductive systems. Bioprosthetic devices intended for long-term functional contact with the body rely on their ability to establish and maintain communication with target tissues. These devices must accommodate multiple device-tissue interfaces, specifically bone/frame, peripheral nerve/wire, muscle/sensor-actuator, and skin/protective coating. Integration at the device-tissue interface can be increased through the use of bioactive or biomimetic materials that can physically and biochemically interact with surrounding/interfacing tissue. However for use in devices that interface electrically-responsive tissues such as the nervous system, muscle, or bone, materials should also facilitate electronic-ionic communication between the electrodes and the target cells. Hence our laboratory has developed strategies to increase tissue integration, biocompatibility, electrical sensitivity, and charge transfer capacity at the device-tissue interface through the use of inherently conductive polymers and conducting polymer-protein composites. Here we describe the synthesis, characterization, and functional investigation of novel conductive biomaterials for interfacing prosthetic devices with peripheral nerve, skeletal muscle, and bone. Electrically conductive peripheral nerve scaffolds were prepared by coating acellularized mouse muscle tissue with the conducting polymer, poly (3,4-ethylenedioxythiophene) (PEDOT) by chemical and electrochemical polymerization. These scaffolds have been implanted into a transected rat peroneal nerve to assess their utility for nerve guidance and repair and electrophysiological measurements. In vitro studies on interactions between cardiac myoblasts and differentiated myocytes with the PEDOT-coated acellular muscle tissue scaffolds are also underway. We have also prepared bone cell scaffolds comprised of poly(lactic-co-glycolic acid) (PLGA) and hydroxyapatite coated with PEDOT. Consistent with previous studies on PEDOT interactions with neural cells, we have found MC3T3 osteoblasts adhere to and proliferate on PEDOT substrates. After 5 days in culture on PEDOT, osteoblasts express alkaline phosphatase an early indicator of bone mineralization. Tests are underway to assess whether electrical stimulation via PEDOT substrates and scaffolds is osteoconductive. Our findings will contribute to our long-term goal to develop materials that mediate large variations in mechanical properties, charge transport, and biological activity to function at the interface between engineered devices and living tissue. This work was supported by the Department of Defense Multidisciplinary University Research Initiative (MURI) program administered by the Army Research Office under grant W911NF0610218.
12:00 PM - **QQ1.5
Biomimetic Electroconductive Hydrogels: Biologically Inspired Co-networks of Polypyrrole and Poly(hydroxyethyl methacrylate) Containing Poly (ethylene glycol) and Phosphorylcholine.
Anthony Guiseppi-Elie 1 , Stephen Finley 1 , Walter Torres 1 Show Abstract
1 , Clemson University, Clemson , South Carolina, United States
12:30 PM - **QQ1.6
Biocatalysis for Material Science and Drug Discoveries.
Ferdinando Bruno 1 , Subhalakshmi Nagarajan 2 , Ramaswamy Nagarajan 3 , Donna McIntosh 4 , Susan Braunhut 5 , Jayant Kumar 6 , Lynne Samuelson 7 Show Abstract
1 , US Army RDECOM Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, United States, 2 , Departments of Chemistry and Physics, Center for Advanced Materials, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 3 , Department of Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 4 , Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 5 , Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 6 , Departments of Chemistry and Physics, Center for Advanced Materials, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 7 , US Army RDECOM Natick Soldier Research, Development and Engineering Center, Lowell, Massachusetts, United States
A novel biomimetic route for the synthesis of conducting homopolymers and copolymers from aniline, phenol, pyrrole and 3,4-ethylenedioxy-thiophene in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG-Hematin) and the enzyme horseradish peroxidase (HRP) were used to catalyze the copolymerization of different monomers. UV-vis, FTIR, XPS, TGA and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of a polyelectrolyte, such as SPS, in this complex provides a unique combination of properties such as processability and water-solubility.Additionally catechins, the active compounds found in green tea, were polymerized and found to exhibit very interesting anti-carcinogenic properties. Here we report a unique enzymatic approach for the synthesis of water-soluble poly(catechins) with enhanced stability and potent anti-proliferative effects on human cancer cells in vitro. Various stereoisomers of catechin [(+), (-), (±)] and (-)-epicatechin have been biocatalytically polymerized using HRP in ethanol/buffer mixtures. This one-pot biocatalytic polymerization is carried out in ambient conditions yielding water-soluble poly(catechins). These synthesized poly(catechins) were tested for their growth inhibitory properties using a variety of normal and cancerous human epithelial cell lines. The poly(catechins) exhibit statistically significant greater growth inhibitory effects when compared to the monomers and exhibited specificity, inhibiting the growth of breast, colorectal and esophageal cancer cells while having little effect on normal epithelial cell growththus achieving a high therapeutic ratio. The synthesis, characterization and the growth inhibitory effects of these novel water-soluble poly(catechins) will also be presented.
QQ2: Electroactive and Conductive Polymers for Biomedical Applications - Actuators and Tissue Engineering
Tuesday PM, November 27, 2007
Room 204 (Hynes)
2:30 PM - **QQ2.1
Conjugated Polymer Actuators for Biomedical Applications.
Elisabeth Smela 1 Show Abstract
1 , University of Maryland, College Park, Maryland, United States
Conjugated polymers actuators are attractive for use as artificial muscles in biomedical applications since their motion can be electrochemically controlled at low voltage, since they combine reasonably high strain and stress, since they operate in aqueous electrolytes, and since they have been shown to be biocompatible. Potential applications include micro-manipulators, valves, steerable catheters, and autonomous micro-robots. There are a number of challenges facing implementation, however, such as building a more complete understanding of actuation behavior and performance.Conjugated polymer actuators come in a variety of form factors, with one of the most common being bending bilayers. We have established methods for microfabricating such bilayers, and using them to rotate rigid components. One application of these actuators that we are pursuing is cell-based sensors, in which the actuators are used to open and close lidded vials that contain cells. These structures are microfabricated on a CMOS chip containing sensors and circuitry. The actuators must operate in cell medium at 37 °C in the presence of cultured cells, for which the actuators must be specially designed. This requires a fundamental understanding of the actuation mechanisms, leading to predictive models.Broadly speaking, the actuation mechanism in conjugated polymers is the ingress and egress of ions, which maintain charge neutrality upon the oxidation or reduction (redox) of the polymer backbone: upon ion ingress, the volume of the polymer expands, and upon egress it reversibly contracts. The actuation strain is proportional to the redox charge that has been consumed, and also depends on the ion. Operation of the actuators in biofluids, which are typically complex mixtures of anions and cations, therefore requires an understanding of the role of the ions in order to predict device behavior. In cation-transporting polymers, such as polypyrrole doped with dodecylbenzenesulfonate, PPy(DBS), in aqueous electrolytes, for example, in the alkali cation series, Li+ gives that largest volume change since it has the largest hydration shell, and thus the largest effective volume. This ion is also the fastest. To be able to use these actuators more widely, the interactions of the ions with the polymer, the role of the solvent, and the electro-chemo-mechanical couplings in the system are also needed.There has been much progress in this field in the last decade, and conjugated polymer actuators have reached the point where practical applications have become feasible. The biomedical arena is a natural one for this technology, and the next few years are expected to yield a wide variety of new devices.
3:00 PM - QQ2.2
Modulating Neural Activities via Electroactive Polymers.
Xinyan Cui 1 2 3 , William Stauffer 1 3 Show Abstract
1 Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 , McGowan Institute for Regenerative Medincine, Pittsburgh, Pennsylvania, United States, 3 , Center for Neural Basis of Cognition, Pittsburgh, Pennsylvania, United States
A new system capable of individually addressable targeted delivery of small amounts of neurochemicals is being developed, which can be easily integrated into pre-existing multielectrode arrays (MEAs). The system utilizes the unique properties of electroactive conducting polymers, which can be synthesized by electropolymerization with ionic drug molecules incorporated. Upon an electrical potential change, the polymer undergoes redox reactions that lead to the release of drug from the electrodes, with the release quantity controlled by the strength and duration of electrical stimulus. As a proof of principle demonstration, we coated the Pt black electrodes of multi-electrode arrays with polypyrrole (PPy) doped with various neurochemicals including AMPA receptor antagonist CNQX(6-cyano-7-nitroquinoxaline-2,3-dione), NMDA receptor antagonist AP5 (D-2-amino-5-phosphonopentanoate) and neurotransmitter glutamate. Drug molecules can be released in a linear fashion upon electrical stimulation. The coating can be optimized to have low impedance ensuring the good recording capability of the electrodes. By applying a negative current pulse to the modified electrodes, CNQX can be released to affect the local cells. Repeatedly we found that when CNQX is released from an electrode that is actively recording neural spikes, the mean firing rate decreased by 87±2% for ~ 30s and recovered. Reducing the duration of the stimulus resulted in less reduction of firing rate. The activity of neurons on neighboring electrodes was unaffected. In the case of the excitatory glutamate, the same current stimulus delivered to PPy/glutamate electrodes elicited a 100% increase in firing rate for 10 seconds. The fact that both inhibitory and excitatory effects can be obtained through polymer loaded with inhibitory and excitatory neurochemicals respectively suggests that the effect we observed is indeed due to the released neurochemicals, not the electrical stimuli or some electrochemical byproducts of the polymer or the culture media.
3:15 PM - QQ2.3
Electroactive Behavior of a Tunable Nanostructured Polymer.
Ravi Shankar 1 2 , Tushar Ghosh 2 , Richard Spontak 1 3 Show Abstract
1 Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Fiber & Polymer Science, North Carolina State University, Raleigh, North Carolina, United States, 3 Chemical Engineering, North Carolina State University, Raleigh, North Carolina, United States
3:30 PM - QQ2.4
Electroactive Controlled Release from Multilayer Thin Films.
Daniel Schmidt 1 , Kris Wood 1 , Nicole Zacharia 1 , Paula Hammond 1 Show Abstract
1 Chemical Engineering Department, MIT, Cambridge, Massachusetts, United States
A number of challenges exist in the field of drug delivery, such as improving localization and efficiency of delivery and tailoring drug release profiles. Many of these challenges can be addressed by “smart”, implantable drug delivery platforms that can administer precise quantities of drugs in response to external stimuli (e.g. electric or magnetic fields or changes in temperature, pH, or ionic strength). Electroactive controlled release is advantageous given that the timing of release can be precisely controlled remotely and an electric field can be easily applied locally compared to other stimuli. Here we demonstrate the fabrication of an electroactive, polymeric thin film drug delivery platform constructed via electrostatic layer-by-layer (LbL) assembly. The films are comprised of positively charged polymers, negatively charged Prussian Blue (PB) nanoparticles, and encapsulated polymeric model drugs. The electroresponsive component of the films is the Prussian Blue, an FDA-approved iron hexacyanoferrate material. Upon application of a small electric potential (+1.25 V), the PB nanoparticles are oxidized from a negatively charged state to a neutral state, leading to rapid film destabilization mediated by electrostatic repulsion between adjacent like-charged polymers. This causes film dissolution and controlled release of incorporated model drugs. Furthermore, on/off switchable release can be achieved from a single film by simply removing the applied potential to restabilize the film, then reapplying the potential. Release profiles and film stability can also be altered through surface modification of the PB nanoparticles with polymers. This technology represents a new, inexpensive, and versatile platform for the fabrication of nanostructured, field-activated (remote-controlled) drug delivery systems.
3:45 PM - QQ2.5
Development of Biodegradable and Electrically Conducting Biomaterials for Nerve Regeneration.
Silvia Luebben 1 , Shawn Sapp 1 , Emily Chang 1 , Christine Schmidt 2 , Hyma Durgam 2 , Zin Khaing 2 Show Abstract
1 , TDA Research, Inc., Golden, Colorado, United States, 2 , University of Texas at Austin, Austin, Texas, United States
In the US more than one million people suffer serious peripheral nerve injuries every year and 20,000 procedures are carry out annually to repair severed peripherals nerves. Nerve guidance channels (NGCs) are hollow conduits used to bridge large gaps of severed peripheral nerves. Current NGC’s materials have many drawbacks that often preclude their use or cause failure of the procedure. Therefore, new biomaterials that actively promote nerve regeneration are needed for the fabrication of improved NGCs.Electrically conducting biomaterials are of interest because they can be used to deliver electrical stimulation to responsive cells like osteoblasts, endothelial cells, and neurons. Polypyrrole (PPy) is an electrically conducting polymer that is not cytotoxic and has been demonstrated to favor the regeneration of damaged peripheral nerves in rats. Because PPy is a semiconductor, it can be used to deliver electric stimuli to cultured cells, accelerating their growth, migration and proliferation. Unfortunately, existing studies of the biological uses of conducting polymer materials has been limited to insoluble films with little to no control over composition (type of dopant and doping level), morphology and conductivity. Furthermore, PPy is not biodegradable, and NGCs made of PPy must be removed from the body upon healing, requiring a second surgery and causing additional site morbidity. Finally, PPy, like most conducting polymers, is insoluble and infusible, and has poor mechanical properties. Therefore, it is very difficult to process it into the necessary form. Together, these properties limit the practical applications of PPy in tissue engineering. Here we present the successful development of a biodegradable form of PPy that is electrically conducting, biodegradable, and can be processed from solution. Moreover, TDA’s conducting biomaterial was found to support neuron-like cell growth in vitro and allow the growth of a healthy nerve cable when used as the internal coating in nerve guidance channels in vivo. We also demonstrated that different electrode configurations promote the growth of different neuron-like phenotypes in the in vitro stimulation experiments.
4:30 PM - QQ2.6
Electroactive Polymer Bioreactor to Apply Mechanical Stimuli to Cells.
Manuel Aschwanden 1 , Raoul Enning 1 , Antje Rey 1 , Andreas Vonderheit 1 , Alfredo Franco-Obregon 2 , Andreas Stemmer 1 Show Abstract
1 Nanotechnology Group, ETH Zurich, Zurich Switzerland, 2 Institute for Biomedical Engineering, ETH Zurich, Zurich Switzerland
Mechanical forces serve as an anabolic stimulus for cells. In particular the development programs of all structural tissues, such as bones, muscles, and connective tissues, is modulated by mechanical stimuli. Normal functioning of many more tissues, including blood vessels, skin, and nervous tissue, is influenced by mechanical forces. Tools for studying these processes, although highly anticipated, have been slow in coming. Available bioreactors capable of applying mechanical stimuli to growing cells and tissue in vitro by means of flexible membranes actuated by pins or pressure suffer from very limited spatial and temporal resolution. Additionally, there is little flexibility in the geometric arrangement of the applied mechanical stimuli. To overcome these limitations, we have developed a novel transparent bioreactor based on electroactive polymers that can stimulate cells and tissue with a wide range of temporal and spatial force patterns. Our bioreactor is fully compatible with standard incubators (requiring only a small electrical lead into the incubator) and also allows for convenient observation under a light microscope while cells and tissue are actuated.Our electroactive polymer bioreactors are made from acrylic elastomer films (VHB 4910, 3M), pre-strained by a factor of 300% x 300% for optimal performance. Compliant carbon black electrodes of suitable geometry are contact-printed onto the acrylic elastomer films using poly(dimethylsiloxane) (PDMS) stamps. The electrodes are arranged such that the volume containing cells and tissue remains field-free. The top electrode of the electroactive polymer actuator and an electrode reaching into the cell medium are grounded to ensure that the high voltages (up to 4 kV) applied to the actuator do not affect the potential and ion distribution in the liquid medium. The side of the electroactive polymer actuator facing the liquid compartment is sealed with an additional layer of an acrylic elastomer film (VHB 9460, 3M), pre-strained by a factor of 300% x 300% to a film thickness of 3 µm. This actuator assembly is mounted in a polymethylmethacrylate (PMMA) holder that also serves as liquid container. To obtain a biocompatible layer inside the liquid container, a 15 µm thin PDMS layer is spin-coated onto the acrylic sealing layer, sterilized by UV treatment, and coated with fibronectin. Stretch magnitudes of 10% and higher can be achieved at frequencies from static up to 10 Hz. So far, we have analysed the response of HeLa, C2C12 myoblasts, and Vero cells to different strains (0–15%) and frequencies (0.1–0.3 Hz). The cells were uni-directionally stretched for 8 hours and afterwards fixed and stained with phalloidin Alexa Fluor 488. The fluorescent actin filaments were imaged with a fluorescence light microscope to observe the change of the cytoskeleton caused by the mechanical stimuli.
4:45 PM - QQ2.7
Polyethylenedioxythiophene (PEDOT) Coatings for Neural Stimulation and Recording Electrodes.
Stuart Cogan 1 Show Abstract
1 , EIC Laboratories, Inc., Norwood, Massachusetts, United States
Electrodeposited polyethylenedioxythiophene (PEDOT) was investigated as a high charge-capacity, low impedance coating for neural stimulation and recording electrodes. PEDOT was deposited onto single-shaft penetrating PtIr microelectrodes with areas from 200-4000 μm2 and onto thin-film multielectrode arrays of gold electrodes (area=2000-125600 μm2) patterned on flexible polyimide substrates. Several strategies for obtaining adherent PEDOT on metal electrodes were investigated. Adhesion layers of sputtered iridium oxide and electrodeposited gold were most effective in providing stable PEDOT coatings, particularly on PtIr microelectrodes. The PEDOT was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and potential transient measurements during current pulsing. Using current pulsing protocols similar to those anticipated for intracortical and retinal prostheses, the charge-injection capacity of PEDOT was determined as a function of electrode area and potential bias in the interpulse period. Charge-injection capacities of >10 mC/cm2 with 0.6 ms pulses (50 Hz) were obtained and are approximately twice those possible with iridium oxide electrodes pulsed to the same potential limits. Voltage transients recorded during pulsing showed features arising from impedance changes accompanying PEDOT reduction and are also discussed. The stability and electrochemical response of PEDOT-coated penetrating microelectrode arrays for a chronic study of stimulation and recording in cat cortex are also presented.
5:00 PM - QQ2.8
Work Behaviors and Training Effects of Artificial Muscles based on Cation Driven Polypyrrole.
Keiichi Kaneto 1 , Hirotaka Suematsu 1 , Tomokazu Sendai 1 , Keintaro Yamato 1 , Wataru Takashima 1 Show Abstract
1 Life Science and Systems Engineering, Kyushu Institute of Technology,, Kitakyushu Japan
Conducting polymers shows electrochemomechanical deformation (ECMD) and the behaviour can be used as artificial muscles. The artificial muscles expand and shrink either by positive or negative biases, depending on the preparation procedures of conducting polymer films. In this paper, results on the tensile load dependence of polypyrrole (PPy) muscles are reported with discussion of the energy conversion efficiency and training effects. Polypyrrole films were electrodeposited on metal electrodes in an aqueous solution of pyrrole and dodecylbenzensulfonic acid (DBS). The actuators were operated presently in an aqueous 1M LiCl electrolyte. The change of the film length was measured as the function of tensile load.The PPy/DBS film contracts upon oxidation (cation driven), since the long DBS anion was entangled and immobilized, and cations were dedoped instead. Hence, the film lifted weights by oxidation with increasing the Young’s Modulus. It was found that the initial strain of ca.5 % at the zero load decreased to the half at ca. 3MPa, and the current response lasted longer with increasing stresses. This fact was found to be resulted from somehow the fatigue of electrical contact between the film and electrode. The electrical input energy was calculated to be about 85 mJ at 1-4 MPa, being almost constant. The mechanical out put energy was estimated from the work of lifting weights to be 0.1 mJ at 3 MPa tensile load. The maximum energy conversion efficiency of PPy/DBS was obtained to be 0.12%. During the tensile load test of artificial muscles, it was found that PPy/DBS films showed an interesting feature of training effects. The stroke of expansion and contraction increased significantly, when the contraction length was measured after the muscle had experienced large tensile loads for several times. The fact is conjectured to be due to the realignment of fibrils along the direction of tensile load or becoming anisotropic behaviours. The results including the PPy/DBS film operated in NaCl and KCl will be discussed in detail. References S. Hara, T. Zama, N. Tanaka, W. Takashima and K. Kaneto, Chem. Letters., 34 (2005) 784. Keiichi Kaneto, Hisashi Fujisue, Kentaro Yamato and Wataru Takashima, Thin Solid Films, Available online 27 April 2007, Thin Solid Films, Available online 27 April 2007,
5:30 PM - QQ2.10
A Novel Electroactive Hydrogel Microfiber with Improved Actuation.
Yahya Ismail 1 , Su Ryon Shin 1 , Min Kwin Shin 1 , Sung Il Jung 1 , Seon Jeong Kim 1 Show Abstract
1 , Hanyang University, Seoul Korea (the Republic of)
A new type of electro actuating hydrogel /electroactive polymer micro fiber for artificial muscles was fabricated through wet spinning of a chitosan solution followed by in situ chemical polymerization of aniline. The fiber showed a reasonable electrical conductivity of 2.856 x 10-2 S/cm and EDS data showed the presence of polyaniline inside the fiber, which gradually decreased moving towards the center of the fiber. SEM images correspond to an agglomerated granular morphology for the polyaniline particles coated on the surface of chitosan fiber. Cyclic voltammograms showed that electrochemical property of the fiber was imparted by polyaniline. This novel biomaterial showed enhanced chemical and electrochemical actuation in response to pH and electrical stimulus. The actuation characteristics were found to depend on polymerization conditions. The strain ratio and response time during the electrochemical actuation was highly dependent on the pH of the electrolyte. An isotonic strain of 0.39% during the electro actuation in aqueous HCl of pH =1 along with a strain of 6.7% corresponding to pH actuation was realized in the microfiber.
5:45 PM - QQ2.11
Digital Auscultation Revamped Using Ionomeric Polymer Transducers.
David Griffiths 1 , Daniel Cooper 1 , Barbar Akle 1 , Donald Leo 1 , Pavlos Vlachos 1 Show Abstract
1 Mechnical Engineering, Virginia Tech, Blacksburg, Virginia, United States
Auscultation began with the development of the stethoscope by Rene Laennec in 1816. It remained fairly unchanged for another 90 years until Rappaport and Sprague released a binaural stethoscope with a bell and diaphragm to resolve both high and low frequencies. The stethoscope is an invaluable tool when used by the right physician. A study by Mangione et al stated that less than 20% of the 12 most common cardiac sounds are not accurately identified by family practitioners. An electronic stethoscope allows for acquisition of body sounds in digital format. Using both spectral and temporal based algorithms, pulmonary and cardiac sounds can be identified and used to assist the family practitioner in their assessment with greater accuracy than previously obtainable. However, both classic and electronic stethoscopes do not allow repeatable sound interrogation with high sensitivity, frequency dynamic range and proper diagnostic classification of disease. This work aims to overcome these limitations for interrogating cardiac sounds and develop a novel reliable and inexpensive medical modality.Ionomeric polymer transducers (IPT) are an exciting new technology that are most commonly used as actuators, having the ability to generate large bending strain and moderate stress at low applied voltages. Although the actuation capabilities of IPTs have been extensively studied, the sensing performance of these transducers has yet to be exploited. The work presented herein aims to use IPTs to develop an electronic stethoscope for digital auscultation with a large dynamic range and high sensitivity.Ionic polymers are generally fabricated by coating an ion exchange membrane, typically Nafion, with a flexible electrode. It has been shown that the electrode thickness has an impact on the efficiency of IPTs in both sensing and actuation. The traditional impregnation reduction fabrication technique of IPTs has little control on the electrode thickness. However, a new Direct Assembly Process, developed by our group , for fabrication of IPT allows for experimentation with varying conducting materials and direct control of electrode architecture, which allows for the tailoring of the transducer.The final version of this paper will demonstrate the potential of IPTs for cardiac auscultation. Multiple IPTs will be characterized using various geometries and signal conditioners under controlled conditions. There are no off the shelf signal conditioning circuits currently available, therefore customized signal conditioners are designed to measure the output signal. Comparisons between these different circuits will be presented within the context of transfer functions and signal to noise ratios. A prototype electronic stethoscope will be designed and tested on multiple subjects. Pickup of S1 and S2 sounds will be quantified for a base metric to stipulate a working design. The frequency components will be compared to previous works for validation of the results.
QQ3: Poster Session
Wednesday AM, November 28, 2007
Exhibition Hall D (Hynes)
9:00 PM - QQ3.1
Development of Reliable Ionic Polymer-Metal Composite (IPMC) Actuators by Surface Coating.
Hyung-Kun Lee 1 , Nak-Jin Choi 1 , Kang-Ho Park 1 Show Abstract
1 IT-NT group/Nanosensor team, Electronics and Telecommunications Research Institute (ETRI), Daejeon Korea (the Republic of)
Actuators based on ionic polymer-metal composites (IPMCs) have been shown to be capable of generating large displacement upon the application of low voltages. The conventional IPMCs swollen with water have limitations in application because of dehydration and electrolysis of water. To develop IPMCs reliable from these intrinsic problems of water, we have prepared IPMCs swollen with ionic liquids that are well known for their high electrochemical stability along with no measurable vapor pressure. However we found that the leakage of electrolytes from IPMC during actuation in a long period has been occurred resulting in decreasing actuation ability. Within this work, we report that effect of polyurethane (PU) coating on surface electrodes of IPMCs by preventing electrolyte leakage phenomenon. The preservation of the electrolytes inside IPMCs by PU coating plays a role in increasing displacement of actuation. Furthermore, it is found that the polymer-coating treatment on IPMC’s surface increases reliability as well as displacement because the polymer coating is thought to be effective in preventing electrode from contacting with air that results in oxidation of electrodes.
9:00 PM - QQ3.10
Preparation and Properties of Fine Super-Flexible Biosensors for In Vivo Measurements.
Mikito Yasuzawa 1 , Hiroki Takaoka 1 2 Show Abstract
1 Department of Chemical Science and Technology, The University of Tokushima , Tokushima Japan, 2 , Toyo Precision Parts MFG, Kashihara, Nara, Japan
Real-time monitoring of compounds such as glucose and lactate is very important for the effective treatment of diseases and the investigation of biological mechanism and drug effect. Therefore, much effort has been devoted for the development of an effective sensor for in vivo continuous monitoring. Miniaturization of the sensor device is an important subject, since smaller devices are less invasive, both physically and psychologically. A finer device will excite fewer pain receptors in the skin and will cause less tissue damage and less pain. However, since the miniaturization lead to easy distortion and fraction of the sensor, it was difficult to fabricate finer sensor device than 200 μm diameter with enough strength to maintain its function implanted in the body. In this study, super-flexible Ni-Ti alloy wire was applied as core material and platinum thin film was coated on its surface in order to perform as platinum electrode. Glucose oxidase (GOx) was immobilized on the platinum surface using electrodeposition technique and biocompatible polyurethane film was coated on the electrode in order to eliminate the absorption of proteins exist in the biological fluid. A glucose sensor with a diameter of less than 200 μm was prepared and showed good performance in both in vitro and in vivo.
9:00 PM - QQ3.11
Conductive Polymer Films to Dynamically Control Protein-protein Interactions.
Megan O'Grady 1 , Kevin Parker 1 Show Abstract
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
9:00 PM - QQ3.12
Rheological Characteristics of Polyaniline Films During Electrochemical Cycles.
Makoto Ookawa 1 , Kentaro Yamato 1 , Wataru Takashima 1 , Keiichi Kaneto 1 Show Abstract
1 , Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology,, Kitakyushu Japan
Upon electrochemical oxidation and reduction, conducting polymers swell and shrink with changing the electrical conductivity. The electrochemomechanical deformation (ECMD) has being intensively studied to develop soft actuators or artificial muscles. Attractive features of soft actuators based on conducting polymers are low driving voltage (less than 2V), large strain (up to 39%) and large stress (several MPa). One of demerits of electrochemical actuators is creeping phenomenon or permanent elongation under heavy tensile loads and also slow response. We surmise that the creeping is a kinetic property of the polymer, and we have examined the mechanism of creeping during the electrochemical deformation as has been studied the function of frequency. Polyaniline films were prepared by casting an N-methyl-2-pyrrolidone (NMP) solution of emeraldine base powder on glass substrates at 60 °C. Films with the thickness of 20 µm were cut into pieces with typical areas of 1.0x10.0 mm. A film was electrochemically cycled in a 1M HCl (pH 0) electrolyte by the sine wave potentials between -200 mV and +550 mV (vs. Ag/AgCl). The magnitude and phase shift (tan δ) of maximum deformation were measured as the function of frequency ranging 0.1 mHz to 20 mHz. The deformation was obtained by taking the ratio of deformed length to the original length of film in %. The deformation decreased monotonically from 8% (0.1 mHz) to 2% (20 mHz). However, the tan δ being 2 at 0.1mHz increased to the maximum of ca. 3.8 at around 1mHz and then decreased to 1.5 at 20 mHz. The tan δ peak appears at the transition frequency from viscous to elastic characteristics in viscoelastic polymer.It is speculated that the frequency of the maximum tan δ is the specific frequency, where the solvated water are released from anions, thought the details are not known at the present stage.
9:00 PM - QQ3.13
Mechano-Chemoelectrical Effects in Polyprrole Film for Tensile Sensing.
Kawamura Shunsuke 1 , Wataru Takashima 1 , Keiichi Kaneto 1 Show Abstract
1 , Graduate Shcool of Life Science and Systems Engineering ,Kyushu Institute of Technology, Kitakyushu Japan
It is well known that conducting polymers are deformed by electrochemical oxidation and reduction due to doping and undoping of bulky ions. The effect is named electrochemomechanical deformation (ECMD) and has been extensively studied to apply in biomimetic soft actuators or artificial muscles. On the other hand, as the reversed phenomenon it was found that conducting polymers, polyaniline generated current or voltage by applying the mechanical tensile forces in an electrochemical cell. The phenomenon is named Mechano-chemoelectrical (MCE) effects, which can be used as force sensors with further understanding of detailed mechanisms.In the present report, the mechanisms of MCE effects in the conducting polymer, polypyrrole (PPy) are mentioned. Polypyrrole films exhibit distinguished features such as highest tensile strength and largest ECMD strain and stress among the conducting polymers. PPy films were prepared by electrochemical polymerization in aqueous electrolyte of dodecylbenzene sulfonic acid (DBS). The film expanded upon reduction, indicating that cations are involved in redox reaction and named cation driven film. A piece of rectangular film with 4×10mm and the thickness of 30 μm was suspended in 1M NaCl electrolyte. By the application of tensile forces to the film, the deformation (elongation) and the induced current against counter electrode were observed at given voltages vs. reference electrode of Ag/Ag+. When the film potential was kept at -600 mV against the reference electrode, the tension of 1MPa resulted in 13% elongation of the film and induction of a negative current of 50 μA (reduction current). The negative current corresponded to reducing and expanding the film at this potential region. The release of tension resulted in contraction to the original film length and positive current (same to oxidation). Therefore, the result can be explained by a model that the equilibrium state between inside of the film and electrolyte was interrupted by the expansion or elongation of film. Namely, the tension or expansion of film requires dopant of Na+ ion flowing into the film, corresponding reduction of the film. The MCE effects were reproducibly observed many times at any given voltages, similar to ECMD effect. It will be interesting to enhance the MCE effects in the future investigation and utilized the effect as tension sensors and electricity generators.References: W. Takashima et al., Synth. Met. 85 (1997) 1395. W. Takashima et al., Electrochem. Commun. in press.
9:00 PM - QQ3.14
Novel Hydrogel and Conducting Polymer-based Skin Surface Electrode Design.
Nicolas Alba 1 , Xinyan Cui 1 2 3 Show Abstract
1 Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 , McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States, 3 , Center for the Neural Basis of Cognition, Pittsburgh, Pennsylvania, United States
The development of effective electrodes for clinical EEG recording presents a number of unique challenges from the perspective of materials and biomedical engineering. Electrodes must be cheap, non-toxic, durable, simple to apply with minimal skin preparation, and capable of recording for extended periods of time without discomfort or reduction in performance. The largest obstacle to electrode performance is the ionic current barrier presented by the stratum corneum and hair of the scalp, which are typically defeated by parting, shaving, and surface abrasion, which can be time consuming and uncomfortable for the patient. We propose a novel electrode design which could eliminate much of the skin preparation necessary for recording, and thus enable multi-channel high resolution EEG to be more practical and simple to execute.Potentiostatic impedance spectroscopy was used as an initial test for evaluating electrode performance, and was performed using a two-point method across human inner forearm skin (counter electrode skin was abraded, but working electrode skin was left intact). Testing was performed on four subjects, with twelve electrodes tested in total. After an initial stabilization period, electrode impedances averaged to 15.7 ± 9.0 kOhm cm-2 at 10 Hertz, well below the values obtained from commercially available 3M ECG electrodes tested on non-abraded forearm skin. Long term testing indicated that impedances remained stable after over seven hours of recording. Testing was also performed using a clinical EEG recording apparatus on non-abraded skin on human forehead and temple. Impedance and EEG recording were performed using a three-point method, with the counter located on well-abraded skin behind the ear. Impedances were found to remain below 10 kOhm after an initial stabilization period, and recorded waveforms were comparable to those recorded by a conventional gold cup and paste electrode on abraded skin, though significantly less preparation time was required.
9:00 PM - QQ3.15
Improved Electroluminescence Efficiency of Photo-Patternable Polyfluorene with Oxetane-Functionalized Charge-Transporting Molecules.
Jin-Baek Kim 1 , Ji Young Park 1 , Jong Hee Lee 1 , Se Jin Gu 1 , Su Min Kim 1 , Hong-Ku Shim 1 Show Abstract
1 Department of Chemistry and School of Molecular Science (BK21), KAIST, Daejeon Korea (the Republic of)
9:00 PM - QQ3.16
An Electroactive, Degradable Thiophene and Ester-Based Copolymer for Neural Applications.
Nathalie Guimard 1 , Jonathan Sessler 1 , Christine Schmidt 2 Show Abstract
1 Chemistry, University of Texas at Austin, Austin, Texas, United States, 2 Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States
9:00 PM - QQ3.17
Performance Parameters in Field-actuated Electrostrictive, Low Modulus Fluoroalkoxy Polyphosphazene Elastomers.
Rafil Basheer 1 , Roy Kornbluh 2 Show Abstract
1 , Materia Chemica LLC, Rochester Hills, Michigan, United States, 2 , SRI International, Menlo Park, California, United States
9:00 PM - QQ3.2
Preparation of Conducting Polymer Actuators using Ionic Liquid and Electrochemomechanical Properties.
Kentaro Yamato 1 , Kenji Tabata 1 , Wataru Takashima 1 , Keiichi Kaneto 1 Show Abstract
1 Graduate School of Life Science and Systems Engineering, Kyushu Institute of technology, Kitakyushu Japan
Conducting polymers swell and shrink upon electrochemical oxidation and reduction, respectively. The swelling is induced by the insertion of counter ions and the conformation change due to the delocalization of pi-electron upon oxidation and called as an electrochemomechanical deformation (ECMD). So far the largest strain of 39%, stress of 22-34MPa and strain rate of 11%/s in polypyrrole(PPy) films have been obtained, which can be compared with those of natural muscles of 30%, 0.4MPa and 300%/s, respectively. However, there are some problems to be worked out such as low energy efficiency, short cycling lifetime and unstable behaviors. These problems are originated from over oxidation, side reactions of dissolved oxygen and impurity in the driving electrolyte. Therefore, we employed ionic liquids as driving electrolyte. Ionic liquids are room temperature molten salts and they have excellent properties as electrolytes such as nonvolatility, nonflammability, high-ionic conductivity wide potential window and electrochemical stability.PPy films were prepared by galvanostatic polymerization from a Methyl Benzoate /Dimethyl Phthalate mixed solution of 0.25M pyrrole and 0.2M Lithium bis(trifluoromethanesulfonyl)imide(LiTFSI) on platinum electrode at 0°C at 0.2mA/cm2 for 8 hours. Thus obtained TFSI-doped PPy (PPyTFSI) film was 33μm in the thickness and 75S/cm in the conductivity. The ECMD was measured in water/propylene carbonate (PC) solution of LiTFSI by cycling between -0.9 and +0.7V versus Ag/AgCl at 2mV/s. The ECMD of the 1st cycle was as large as 24%, however, the magnitude monotonically decreased to 21.2% at 2nd, 3rd 19.2%, 4th 17.2%, 5th 15.3%, 6th 13.8%, and 7th 12.4%. On the other hand, in the case of ionic liquid of 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMITFSI)(MP:-50°C, conductivity:2.2mS/cm, potential window : -2.4 to +3.0V)/PC mixed solution showed excellent behavior in ECMD. Namely, the ECMD of the 1st cycle was 24.7%, and stayed constant more than 7th cycles. These ECMD values showed better stability than the LiTFSI electrolyte solution alone.
9:00 PM - QQ3.3
Investigation of Bone Cell Growth on Single Walled Carbon Nanotube Networks.
Wojtek Tutak 1 , Ki Ho Park 2 , Federico Sesti 2 , Manishkuma Chhowalla 1 Show Abstract
1 Materials Science and Engineering, Rutgers, The State University of New Jersey , Piscataway, New Jersey, United States, 2 Physiology & Biophysics , Robert Wood Johnson Medical School , Piscataway, New Jersey, United States
One of the major goals of bone bioengineering is to identify new biocompatible materials that can not only sustain cell growth and proliferation but also actively promote healing to shorten recovery processes. Single walled carbon nanotubes (SWNTs) can play a prominent role in this effort due to their unique structural and chemical characteristics. The unique possibility to chemical functionalize CNTs makes these material the ideal substrate for a variety of compounds that can promote healing.We report a systematic investigation of SWNT networks as scaffolds for bone cell growth. Toward this end we examined the effects of purified High Pressure Carbon Monoxide processed (HiPCo) SWCNT on osteoblastic osteosarcoma UMR-106 and preosteoblastic MC3T3-E1 cells. UMR 106 and MC3T3-E1 cells were plated on 1 cm2 CNTs substrate at a density 7000 cell/ml and cultured under controlled conditions. Samples were collected every 2-3 days for a period of 28 days. Notably, we found that CNTs substrates affected the proliferation of UMR and MC3T3-E1 cells differently. While we did not detect significant differences between the rate of proliferation of UMR cells grown on CNTs substrates versus standard plastic or glass substrates, MC3T3-E1 cells exhibited a significant increase in the rate of proliferation when cultured with SWNT substrates. We conclude that CNTs sustain osteoblastic osteosarcoma growth and induce higher proliferation rate in preosteoblastic bone cells.
9:00 PM - QQ3.4
Decoration and Characterization of CNTs with Hydroxyapatite: DNA Nano-composite.
Rizwan Wahab 1 , Sg Ansari 1 , Young soon Kim 1 , Song min Woo 1 , Hyoung Kee Seo 1 , Hyung-Shik Shin 1 Show Abstract
1 School of Chemical Engineering , Chonbuk National University, Jeonju, Chollabukto, Korea (the Republic of)
Carbon nanotubes and its modification by the chemical or biological molecule have attracted great interest in the scientific community for its new and interesting applications in the areas of electrochemistry, bio-sensing and biological systems. The properties of the tiny nanotubes can be tuned and controlled by modifying their surfaces and attaching biological molecules on the functionalized/modified surface of these nanotubes. Calcium phosphate is a known attractive biomedical material with its excellent biocompatibility and non-toxicity for carbon nanotubes. Several forms of these materials can be used as scaffolds for tissue engineering, drug delivery agents, non-viral gene carriers, prosthetic coating and composites. Among many phases of calcium phosphates, hydroxyapatite is the most studied material for number of above mentioned biomedical applications. In this paper we are presenting the interaction of 100bp DNA on the surface of hydroxyapatite modified functionalized carbon nanotubes. The MWCNTs were functionalized by the reported acid treatment method. The characteristic vibrational and stretching modes of hydroxyl (-OH) group was observed at 3401 and 1632cm¬-1 whereas as the weak carbonyl (C=O) group was presented at 1708cm¬-1.the morphological observation clearly reveals that on the surface of carbon nanotubes hydroxyapatite particles attached. The 100base pair DNA Ladder is seen to form a web like structure on the surface of hydroxyapatite modified carbon nanotubes.Furthermore, the surface states of the hydroxyapatite, carbon nanotubes DNA nanocomposite was also characterized by the X-ray photoelectron spectroscopy.
9:00 PM - QQ3.6
Single Walled Carbon Nanotube Fluorescence as a Tool for Glucose Detection in Vivo.
Paul Barone 1 , Michael Strano 2 Show Abstract
1 Chemcial and Biomolecular Engineering, University of Illinois - Urbana-Champaign, Urbana, Illinois, United States, 2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Single walled carbon nanotubes (SWNT) fluoresce from 900 to 1600 nm affording them unique advantages over conventional fluorophores for use in in vivo applications. However, one of the main challenges in harnessing these advantages is maintaining SWNT stability in solution while imparting the necessary analyte selectivity. We demonstrate that coating the nanotubes in a partially hydrophobic dextran polymer allows detection of glucose based on changes in SWNT fluorescence. The prospects and feasibility of using such a system in vivo are discussed and elaborated on by imaging of SWNT fluorescence through tissue.
9:00 PM - QQ3.7
High Sensitivity Biological and Chemical Sensors through Argon and Hydrogen Modified Carbon Nanotube Ensembles.
Jeffrey Nichols 1 , Prabhakar Bandaru 1 Show Abstract
1 Materials Science Program, Department of Mechanical Engineering, UC, San Diego, La Jolla, California, United States
The small size, large surface area to volume ratio, and ease of functionalization of carbon nanotubes (CNTs) makes them very appealing for chemical sensor applications. Combined with fast electron transfer kinetics, resulting in rapid current response and high sensitivity, CNTs can be used in a variety of biomedical applications. Such favorable electrochemical behavior has been attributed to the presence of defects on CNT walls or at CNT tips, which serve as chemically active sites for electron transfer reactions. Consequently, controlling the defect density in CNTs may provide new ways to engineer highly sensitive and selective biochemical sensors, even without functionalization, which is the objective of the present study. Defects were systematically incorporated into vertically aligned multi-walled CNTs through reactive ion etching (RIE) using argon and hydrogen gases. Raman spectroscopy was then used to characterize the amount and nature of disorder within the nanotube samples. For both gases, increasing etch time lead to increased disorder, with argon causing nanotube charging (through the formation of dangling bonds) and hydrogen terminating dangling bonds and decreasing the nanotube correlation length/grain size. Amperometric measurements involving the addition of 1 mL aliquots of 5mM glucose were then performed on as produced, and Ar and hydrogen treated MWCNT electrode ensembles. While the electrochemical behavior of the untreated and Ar etched CNT ensembles were found to be similar, the current response in this case did not return to the original baseline following successive glucose additions. A very large, reversible, and stable current response was observed for the MWCNT electrode treated with hydrogen for ~ 10 minutes. The differences in behavior seem to suggest that the biochemical sensing capabilities of MWCNTs can be tuned by the incorporation of different defect natures and densities. Additional results will be presented on the electrochemical sensing of biologically important entities such as dopamine and ascorbic acid, and the influence of defects in carbon nanotubes for their use in biomedical applications.
9:00 PM - QQ3.8
Nanostructured Thin Films Incorporating Carbon Nanotubes and Phthalocyanines: Processing at the Nanoscale and Applications in Sensing.
Jose Siqueira 1 , Luiz Gasparotto 2 , Osvaldo Oliveira 1 , Valtencir Zucolotto 1 Show Abstract
1 Physics Institute of São Carlos, University of São Paulo, São Carlos Brazil, 2 Chemistry Department, Federal University of São Carlos, São Carlos Brazil
Nanostructured composites containing carbon nanotubes (CNTs) have been widely exploited as candidate materials for many technological applications, mainly due to their mechanical and electrical properties. One of the strategies recently employed for CNT manipulation is the layer-by-layer (LbL) technique, through which the CNT molecules are assembled in a multilayer structure in conjunction with different materials. In this study we investigated the assembly characteristics and sensing abilities of LbL nanocomposites of polyamidoamine dendrimers (PAMAM)-incorporating multi-walled carbon nanotubes (PAMAM-NT) assembled in conjunction with nickel tetrasulfonated phthalocyanine (NiTsPc). The sequential adsorption of the PAMAM-NT/NiTsPc layers was monitored via UV-Vis. and micro-Raman spectroscopies, which pointed to an exponential growth of the multilayers deposited on ITO-coated glass substrates. Specific interactions between –NH3+ and –SO3- groups from PAMAM and NiTsPc, respectively, were observed via FTIR analysis. The films displayed a well-defined electroactivity (redox pair at 0.86 V and 0.87 V vs Ag/AgCl), charge-transfer controlled process and high electrochemical stability. The presence of CNTs in the nanostructured films enhanced the electrochemical response of the NiTsPc, and as a consequence, its electrocatalytic properties toward dopamine (DA), which could be detected at concentrations lower than 10-5 M. We performed a 22 factorial design to evaluate the influence of two variables on DA detection, namely DA concentration and number of PAMAM-NT/NiTsPc bilayers and no correlation between the variables was observed.
9:00 PM - QQ3.9
Influence of Environmental Factors on Electrical Conductivity of Single DNA Molecule using Single-walled Carbon Nanotube Electrodes.
Harindra Vedala 1 , Somenath Roy 1 , Melissa Doud 2 , Kalai Mathee 2 , Wonbong Choi 1 Show Abstract
1 Department Mechanical and Materials engineering, Florida International University, Miami, Florida, United States, 2 Department of Biological Sciences, Florida International University, Miami, Florida, United States
We have demonstrated that single-walled carbon nanotubes (SWNT) can be used as nanoscale electrodes to detect charge transport through single oligo-DNA molecule dielectrophoretically trapped between these electrodes. In comparison to metal electrodes, SWNT provide superior dimensional compatibility with single DNA molecule. As the intrinsic conductivity of the DNA molecule is strongly influenced by environmental factors such as water molecules, we have investigated the DNA conductivity both in ambient and various vacuum conditions. In addition, effect of counterions variation on DNA conductivity was studied by comparing the current-voltage characteristics of the dried DNA molecule, suspended previously in two different buffers namely, sodium acetate and tris(hydroxymethyl) aminomethane (TRIS). A two order of higher magnitude of current signal was observed for the DNA molecule suspended in TRIS. This study would provide better understanding of the native electrical properties of an oligo-DNA molecule to facilitate the development of future DNA-based nanoelectronic and sensor devices.
Xinyan Tracy Cui University of Pittsburgh
Diane Hoffman-Kim Brown University
Silvia Luebben TDA Research, Inc.
Christine E. Schmidt The University of Texas-Austin
QQ4: Carbon Nanotubes for Biomedical Applications
Wednesday AM, November 28, 2007
Room 204 (Hynes)
9:45 AM - QQ4.1
Biologically Active and 3D Electrically Conducting Polymer Scaffolds for Neural Engineering.
Christine Schmidt 1 Show Abstract
1 Depts. of Biomedical Engineering and Chemical Engineering, The University of Texas - Austin, Austin, Texas, United States
10:00 AM - QQ4.2
Single-Walled Carbon Nanotube-Polyelectrolyte Multilayers and Freestanding Films for Neural Tissue Interfacing.
Edward Jan 1 , Nicholas Kotov 1 Show Abstract
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Many neurological disorders and injuries, such as Parkinson’s disease, epilepsy, and stroke, require a biomaterial to generate and record electrical activity in the damaged or diseased tissue. The tissue-material interface is extremely critical to the proper functioning, performance, and lifetime of implantable electrodes and devices. We have explored the use of layer-by-layer (LBL) assembled single-wall carbon nanotube (SWNT)-polyelectrolyte composite thin films for interfacing neural tissues. LBL assembled SWNT thin films are perfect for this application because they have exceptional tensile strength, high flexibility, good electrical conductivity and chemical stability. Their nano-fibrous topology provides high interfacial area for charge transport and tissue contact. Their biocompatibility has been examined and verified using a multi-parameter cytotoxicity assay. We have demonstrated the the differentation of both mouse embryonic neural stem cells and human peripheral blood dervived neural stem cells on these LBL assembled SWNT thin films. In addition, we have observed different cell morphology on thin films of different topology. Our findings suggest that SWNT thin films are biocompatible with the most sensitive cell types and have tremendous potential for neuroprosthetic applications.
10:15 AM - QQ4.3
Au Cluster Decorated Single-wall Carbon Nanotubes as Biosensor Platforms.
Jeong-O Lee 1 , Byoung-Kye Kim 2 1 , Hye-Mi So 1 , Hyunju Chang 1 , Ki-jeong Kong 1 , Ju-Jin Kim 2 Show Abstract
1 Fusion-Biotechnology Research Center, Korea Research Institute of Chemical Technology, Daejeon Korea (the Republic of), 2 Department of Physics, Chonbuk National University, Chonju Korea (the Republic of)
We demonstrate the Au-cluster decorated single wall carbon nanotubes (SWNT) as effective biosensor platforms. Nanoscale Au clusters was formed on the side walls of carbon nanotubes in transistor geometry by using electroless deposition, electrochemical deposition and simple physical evaporation techniques. The effect of Au cluster decoration appears as a hole doping in electrical transport characteristics regardless of the decoration method. Thiolated single stranded probe DNAs were successfully immobilized on Au clusters decorating single-walled carbon nanotube field effect transistors (SWNT-FET), and this appear as a decrease in conductance that could be explained by the decrease of Au work function upon adsorption of thiolated DNA oligomers. While a target ssDNA with a single mismatch does not give any change in electrical conductance, clear increase of conductance observed with matching ssDNA, thereby showing the possibility of SNP (single nucleotide polymorphism) detection using Au-cluster decorated SWNT-FETs.
10:45 AM - QQ4.5
Detection of Viral Proteins using Human Receptor Functionalized Carbon Nanotubes.
Michelle Chen 1 , Samuel Khamis 1 , Sujit Datta 1 , A.T. Charlie Johnson 1 , Yian-Biao Zhang 2 , Mandakini Kanungo 2 , Alexander Ho 2 3 , Paul Freimuth 2 , Daniel van der Lelie 2 , Barbara Panessa-Warren 2 , James Misewich 2 , Stanislaus Wong 2 3 Show Abstract
1 , University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 , Brookhaven National Laboratory, Upton, New York, United States, 3 , State University of New York at Stony Brook, Stony Brook, New York, United States
We present proof-of-concept experiments for developing a highly-sensitive and fast-response miniaturized single-walled carbon nanotube field-effect transistor (SWNT-FET) biosensor for electrically detecting adenovirus using ligand-receptor-protein specificity. SWNTs are mildly oxidized to form carboxylic groups on the surfaces without compromising the electronic integrity of the nanotubes. Then the human coxsackievirus and adenovirus receptor (CAR) is covalently functionalized onto the nanotube surface via diimide-activated amidation process. Upon exposure of the device to adenovirus protein, Ad12 Knob, specific binding of Ad12 Knob to CAR decreases the current that flows through the SWNT-FET device. For control experiment, the CAR-SWNT device is exposed to YieF, which does not bind specifically to CAR, and no current change is observed. To further confirm the biological activity of CAR protein that is immobilized on nanotube surface, the specific binding of such CAR to Rhodamine labeled Knob is tested. We also verify the biological activity of Knob protein through binding to its labeled conjugate antibody. AFM analysis is done to show height increase of a few nanometers at specific spots where the CAR-Knob complex are covalently linked to the nanotube surface. Therefore, our results show that the human receptor protein CAR does immobilize on SWNT surface while fully retains its biological activity. Moreover, the specific binding of CAR to its complementary adenovirus Knob can be electrically detected using individual SWNT-FET devices. These findings suggest that CAR-functionalized SWNT-FETs can ably serve as biosensors for detection of environmental adenoviruses. Acknowledgement: Work conducted in the laboratory of ATCJ was supported by the JSTO DTRA and the Army Research Office Grant #W911NF-06-1-0462, as well as partial support by the Nano/Bio Interface Center through the National Science Foundation under contract NSEC DMR-0425780. MC acknowledges support from Laboratory for Research on the Structure of Matter (NSF DMR00-79909), and US Department of Energy, grant No. DE-FG02-98ER45701. YZ DVL, JM, and SSW acknowledge support of this work through the U.S. Department of Energy Office of Basic Energy Sciences under contract DE-AC02-98CH10886.
11:30 AM - QQ4.6
Carbon Nanotube-Protein Nano-Architectiures for Cancer Cell-Specific Scaffolding.
Sofia Sotiropoulou 1 , Diego Rey 2 , Carl Batt 1 Show Abstract
1 Food Science, Cornell University, Ithaca, New York, United States, 2 Biomedical Engineering, Cornell University, Ithaca, New York, United States
Topographical patterns as well as mechanical and physicochemical surface properties have been found to affect cell adhesion and proliferation, with the exact cues guiding these phenomena still being investigated. Carbon nanotubes have lately emerged as one of the most interesting systems to study biology at the nanoscale due to their extremely small dimensions that allow minimal perturbation while their electrical, mechanical and chemical properties allow simultaneous monitoring of analytically significant parameters with high sensitivity. The ability of CNTs to target living cells has been explored only for soluble systems. The possibility to promote the same interactions in three dimensional systems is very intriguing, since it will provide a platform to control the spatial adhesions of cells, a research area with significant implications in tissue engineering, biosensors and cell arrays. We therefore undertook an effort to use substrate grown CNT- architectures to pattern cells and more specifically to target endothelial mammalian colon carcinoma cells. In order to target these cells a site –specific functionalization approach was undertaken to conjugate the humanized single-chain variable domain fragment antibody (A33scFv) that recognizes the A33 cell surface glycoprotein expressed in the SW1222 colon cancer cell lines. For reasons of comparison, cells that do not express the A33 antigen (HT29) were also seeded on the CNT-patterned surfaces, serving as a negative control. Live cell assay using fluorescence microscopy was performed to monitor the adhesion and proliferation of the cells on the CNT surfaces. The fluorescence images clearly showed preferential adhesion of the SW1222 cells on the CNT conjugated with the scFvA33 antibody. Pristine tubes actually inhibited cell attachment (cells were observed outside the patterned areas) an observation attributed to the highly hydrophobic character of the pristine CNT. This indicates that the mechanical strength and surface roughness are not the main parameters for colon cancer cells to adhere, rather a more specific interaction. This was further indicated by the lower number of HT29 cells found on antibody-functionalized CNT patterns. Further investigation of the interaction was performed on fixed cells using confocal fluorescence microscopy and SEM imaging. Both techniques pointed to the fact that that CNTs-scFvA33 patterns act as specific adhesion points for the cells to attach and proliferate and more so for the SW1222 (+A33) cells. It is therefore determined that the SW1222 cells, expressing the A33 antigen were effectively targeted by CNT-scFvA33 conjugates atrend not observed for either pristine tubes or cells that do not express the same glycoprotein.
11:45 AM - QQ4.7
Optical Properties of Carbon Nanotubes: Near-Infrared Induced Hyperthermia as Therapy for Brain Tumors.
Lewis Gomez 1 , Meng-Tse Chen 2 , Weijun Wang 3 , Thomas Vernier 2 5 , Tom Chen 3 , Martin Gundersen 2 4 , Chongwu Zhou 1 2 4 , Paul Pagnini 6 Show Abstract
1 Chemistry , University of Southern California, Los Angeles, California, United States, 2 Materials Science, University of Southern California, Los Angeles, California, United States, 3 Health Sciences, University of Southern California, Los Angeles, California, United States, 5 MOSIS: Information Science Institute, University of Southern California, Los Angeles, California, United States, 4 Electrical Engineering, University of Southern California, Los Angeles, California, United States, 6 Keck School of Medicine, University of Southern California, Los Angeles, California, United States
12:00 PM - QQ4.8
Fabrication and Characterization of Individually Controlled Multi-pixel Carbon Nanotube Cathode Array Chip for Micro-RT Application.
Sigen Wang 1 2 , Zhijun Liu 2 , Lei An 2 , Otto Zhou 2 , Sha Chang 1 , Alfred Kleinhammes 1 Show Abstract
1 Department of Radiation Oncology, University of North Carolina, Chapel Hill, North Carolina, United States, 2 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina, United States
New Presenation Time/Paper Number/PresenterQQ4.8 @ 11:00 AM to QQ5.11 @ 4:30 PMFabrication and Characterization of Individually Controlled Multi-pixel Carbon Nanotube Cathode Array Chip for Micro-RT Application. Alfred Kleinhammes
12:15 PM - QQ4.9
Voltage Gated Channels through Aligned Carbon Nanotube Membrane.
Mainak Majumder 1 , Xin Zang 1 , Xin Su 1 , Bruce Hinds 1 Show Abstract
1 Chemical and Materials Engineering, Univ. of Kentucky, Lexington, Kentucky, United States
Carbon nanotubes have three key attributes that make them of great interest for novel membrane applications 1) atomically flat graphite surface allows for ideal fluid slip boundary conditions 2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance and 3) CNT are electrically conductive allowing for electrochemical reactions and application of electric fields gradients at CNT tips. Towards this goal, a composite membrane structure containing vertically aligned carbon nanotubes passing across a polystyrene matrix film have been fabricated. Fabrication steps, material characterization and ionic diffusion transport properties are described. In general, the transport mechanisms through CNT membrane are a) ionic diffusion is near bulk expectation with no enhancement from CNT b) gas flow is enhanced by ~1-2 order of magnitude due to specular reflection off of flat graphitic surface c) and pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 ORDERS OF MAGNITUDE FASTER than conventional Newtonian flow due to atomically flat graphite planes inducing nearly ideal slip conditions and approach that of aquaporin protein channels. Plasma oxidation during the fabrication process introduces carboxylic acid groups on the CNT tips that are modified using carbodiimide mediated coupling between carboxylic acid on the CNTs and accessible amine groups of the functional molecule. The entrances to CNT’s cores were thus functionalized with aliphatic amines of different lengths, charged dye molecule and an aliphatic amine elongated by spacers containing poly-peptides and the simultaneaous permeation of two differently sized but equally charged molecules was studied. Using a hindered diffusion to model observed selectivities was consistent only with a geometry of only CNT tip functionalization, not along the length of CNT core. Bio-chemical gating of CNTs is also seen by tethering desthiobiotin to CNT tips with the reversible binding to streptavidin. The complete ATP cycle (phosphylation/dephosphylation) can be performed on CNT tips with corresponding modulation of flux across CNT membrane. The functional density of tethered charge molecules can be substantially increased by the use of electrochemical grafting of diazonium salts. Functionality can be forced to occur at the CNT tip entrances by fast fluid flow of an inert solvent through the core during electrochemical functionalization. The selectivity between Ru(bi-pyridine)3^2+ and methyl viologen ^2+ flux is found to be as high as 23 with -130mV bias applied to the membrane with tethered anionic dye molecule. Changes in the flux and selectivity support a model where charged tethered molecules at the tips are drawn into the CNT core at positive bias hindering/gating flux across the membrane. Applications of this system towards programmed transdermal drug delivery of nicotine and fentanyl are discussed.
12:30 PM - QQ4.10
Electrical Stimulation of Encapsulated Neural Cells in Nano-Featured Polymer Scaffolds.
Rajesh Pareta 1 , Thomas Webster 1 Show Abstract
1 , Brown University, Providence, Rhode Island, United States
Encapsulation of neural cells in poly(lactic-co-glycolic) acid (PLGA) was achieved using co-axial electrospinning. Co-axial electrospinning consists of two concentric capillaries compared to only one capillary in conventional electrospinning. This allows for the processing of two liquid solutions simultaneously. Neural cells suspended in hydrogel were injected in the inner capillary, while the carbon nanotubes suspended in PLGA were injected in the outer capillary at controlled flow rates. On the application of a high voltage, a compound jet formed at the capillaries exits and results in a co-electrospun fiber of nerve cells encapsulated in PLGA. In this study, the voltage varied from 0 to 10 kV and various flow rates were tested to achieve a stable cone-jet mode in electrospinning. The cell density in the media varied from 1 to100 million cells/ml and the polymer solution concentration varied from 0.1 to 10 mg/ml. This resulted in a three dimensional scaffold with nano-features on the polymer surface, which were collected on the grounded substrate. Nerve cells were found to be viable after the electrospinning process. Electrical stimulation was applied to these scaffolds to see the effect on neural cell differentiation and proliferation. This technique may be very useful for the development of cell encapsulated scaffolds for tissue engineering applications such as nervous system regeneration.
12:45 PM - QQ4.11
Membrane-free Enzymatic Biofuel Cell with Carbon Nanotube Electrodes on Porous Silicon.
Fan Yang 1 , Zafar Iqbal 1 Show Abstract
1 Chemistry & Environmental Science, New Jersey Institute of Technology, Newark, New Jersey, United States
Emerging interest in biofuel cells is being driven by their unmatched, highly selective biocatalytic activity, near-room temperature and neutral pH operation, and the increasing need for biomedical power sources and related biosensors. In this talk we will report on the fabrication and characterization of a membrane-free, direct electron transfer glucose oxidation and oxygen reduction enzymatic biofuel cell based on carbon nanotubes. The bioelectrode design used comprised of a porous silicon (po-Si) current collecting flow-field platform on which both single-walled and multiwalled carbon nanotubes (SWNTs and MWNTs, respectively) electrodes were synthesized directly and then functionalized with carboxylic groups. Anodic and cathodic enzymes: glucose oxidase (GOx) and laccase, respectively, were then electrochemically immobilized on the nanotube sidewalls and tips. Membrane-free biofuel cells consisting of po-Si/SWNTs and po-Si/MWNTs electrodes with immobilized GOx and laccase were studied with 4 mM glucose in pH 7 buffer solution as fuel and oxygen as oxidant. The maximum power density of 0.32 mW/cm2 obtained for the SWNT-based biofuel cell was substantially higher than that of the corresponding biofuel based on MWNTs. Enhancement of the power density to 2.2 mW/cm2 was obtained when free standing SWNT membranes functionalized with GOx and bilirubin oxidase (BOD) were used as anode and cathode respectively.
QQ5: Electroactive and Conductive Polymers for Biomedical Applications - Sensors
Wednesday PM, November 28, 2007
Room 204 (Hynes)
2:30 PM - QQ5.1
Conjugated Polymers for Signal-amplifying Biosensor and Sensor Arrays.
Jinsang Kim 1 2 3 , Kangwon Lee 1 , Jean-Marie Rouillard 2 , Laura Povlich 3 , Erdogan Gulari 3 Show Abstract
1 Materials Sci and Eng, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
We have developed conjugated polymer-based biosensors to detect clinically important biological materials. We developed a solution-based sensory system and a solid state microarray system, respectively. Our signal amplifying sensors are designed to achieve high sensitivity by means of the energy harvesting property and highly emissive property of conjugated polymers. Receptors are rationally designed to provide specificity toward a target analyte to realize high selectivity. In this presentation, we will discuss water soluble poly(p-phenyleneethynylene)s (PPEs) for the detection of specific DNA sequence in solution. Single strand oligonucleotides and molecular beacons are tethered to the two chain ends of the water-soluble PPEs to form the PPE-DNA and PPE-DNA beacon hybrid system, respectively, for DNA detection. DNA detection results using the PPE-DNA hybrid system confirmed large signal amplification by means of efficient Förster energy transfer from the energy harvesting PPE to the fluorescent dye attached to the complementary analyte DNA. DNA detection study of the PPE-DNA beacon also showed not only signal-amplifying property but also self-signaling property. We also discuss our signal amplifying DNA microarray that have been achieved through the development of uniquely stable oxadiazole-containing conjugated polymers and on-chip oligonucleotide synthesis.1.Kangwon Lee, Jean-Marie Rouillard, Trinh Pham, Erdogan Gulari, and Jinsang Kim “Signal Amplifying Conjugated Polymer-DNA Hybrid Chips” Angew. Chem. Int. Ed. 2007, 46, 4667. 2.Kangwon Lee, Laura K. Povlich, Jinsang Kim “Label-free and Self-signal Amplifying Molecular DNA Sensors Based on Bioconjugated Polyelectrolytes" Adv. Func. Mat. 2007 in press.
2:45 PM - QQ5.2
Nanostructured Conducting Polymers and Bioactive Polymer Nanofibers for Nerve Regeneration, Precisely Controlled Release of Drugs, and Surface Modification of Biosensors.
Mohammad Reza Abidian 1 , David Martin 2 3 1 , Joseph Corey 4 , Daryl Kipke 1 Show Abstract
1 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Neurology, University of Michigan, Ann Arbor, Michigan, United States
The interface between biosensors and living tissue plays a significant role in the long-term performance of these devices. It is thought that biocompatible polymer coatings can stabilize the interface between microelectrode and living tissue. The ability of neural electrodes to record high signals over extended periods of time remains a significant problem. Here we propose that nanostructured conducting polymer and bioactive polymer nanofiber coatings can improve the interface between microelectrodes and living tissue. We have suggested that stabilization occurs: 1) when there is a smooth gradient of mechanical properties between the stiff electrode and soft tissue, 2) neutrophins and anti-inflammatory drugs are controllably delivered at the site of implantation to improve neural cell attraction and prevent scar tissue formation, 3) the transport of charge carriers between device and neuron at the site of implantation is improved. In case of nerve regeneration, textured implants for neural guidance also hold promise approach for controlled neural regeneration. We developed a new approach for preparing anti-inflammatory drug and neutrophin loaded conducting polymer nanotubes and bioactive polymer nanofibers. The fabrication process includes the electrospinning of a biodegradable polymer (here poly(lactide-co-glycolide)) into which a drug has been incorporated (here the anti-inflammatory agent dexamethasone) followed by electrochemical deposition of a conducting polymer (here poly(3,4-ethylenedioxythiophene). We have also developed methods to create oriented conducting polymer nanotubes that can precisely control the local release of neurotrophic proteins, and can provide guidance for directed neurite outgrowth. Dorsal root ganglion explants, neuroblastoma SH-SY5Y cells and PC12 cells were cultured on these aligned nanotubes. The wall thickness of the PEDOT nanotubes varied from 50-100 nm, and the nanotube diameter ranged from 100-600 nm. We demonstrated that the impedance of the neural microelectrodes can be significantly decreased (about 2 orders of magnitude, from 800 ± 20 kΩ to 8 ± 2 kΩ) and the charge transfer capacity significantly increased (about 3 orders of magnitude, from 0.001 ± 10-4 µC to 4.9 ± 0.6 µC) by creating conducting polymer nanotubes on the electrode surface. UV spectrophotometry and enzyme-linked immunosorbent assay was used to determine the release profile of dexamethasone and nerve growth factor. The drugs can be released either precisely from the nanotubes in a desired fashion by electrical stimulation as low as 0.5 V of the nanotubes or slowly from polymer nanofibers through hydrogel scaffolds.These polymer-modified neural probes were implanted in cortex of male rats and their performance was monitored by impedance spectroscopy, signal amplitude, and noise level over periods of at least 7 weeks. The polymer-coated sites were found to outperform control sites with respect to signal-to-noise ratio and impedance.
3:00 PM - QQ5.3
Label-free Identification of Genomic DNA at the Single Molecule Level.
Somenath Roy 1 , Harindra Vedala 1 , Wonbong Choi 1 Show Abstract
1 Mechanical and Materials Engg., Florida International University, Miami, Florida, United States
3:15 PM - QQ5.4
Signal-amplifying and Label free DNA Microarray Chips by Combining Conjugated Polymer and Intercalating Dye.
Kangwon Lee 1 , Katharina Maisel 1 , Jean-Marie Rouillard 2 , Erdogan Gulari 2 , Jinsang Kim 1 2 3 Show Abstract
1 Materials science and engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Macromolecular science and engineering, University of Michigan, Ann Arbor, Michigan, United States
A traditional DNA microarray is composed of oligonucleotides or ssDNA fragments can cannot generate a sensory signal by themselves, requiring appropriate fluorescence labeling of analyte ssDNA. In this presentation, we will discuss a signal amplifying and label free DNA-micoarray using energy harvesting conjugated polymers and intercalating dyes. We developed a new series of conjugated polymers, oxadiazole-containing conjugated polymers, that have high quantum yield and unique stability in rigorous reaction conditions. The new poly(oxadiazole-co-phenylene-co-fluorene) having amine side chains was immobilized on the glass substrate through a covalent bond. Oligonucleotides were then directly synthesized on the polymer-coated substrate. During the harsh DNA synthesis steps, the polymer did not loose its emissive property. We have tested DNA detection capability of the DNA microarray by using SYBR green I as a double-stranded intercalating dye. Our DNA microarray showed excellent selectivity and sensitivity by means of large signal amplification of SYBR green I fluorescence through efficient Förster energy transfer (FRET) from the energy-harvesting conjugated polymer layer.
3:30 PM - QQ5.5
Reagentless Conducting Polymer-based Biosensor for in vivo Monitoring of Cytokines.
Wei Liao 1 , Tracy Cui 1 2 3 Show Abstract
1 Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Center for Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Neural prosthetics often suffer from undesired chronic inflammatory tissue response. This can lead to neuronal loss and formation of glial sheath, which would serve as a barrier to neural signal transduction. In vivo monitoring of neuro-inflammatory cytokines (Interleukins, TNF-α, MCP-1, PDGF) may improve our understanding of device induced inflammatory responses. Furthermore, early detection of the onset and degree of inflammation and releasing drugs accordingly may lead to improved long term performance of such implanted devices. For this reason, biosensor applying aptamer as probe and electrochemical impedance spectroscopy as the detection method has been developed. Aptamers, certain kinds of DNA or RNA molecules which can bind variety of molecules, have the overwhelming advantages over antibodies of low cost and ease of control. Platelet-derived growth factor BB (PDGF-BB), one of the important cytokines involved in neural inflammation, has been selected as our detection target. Typically during the faradic electrochemical impedance measurements for in vitro biosensing, an electroactive molecule (mediator) is present in the sample solution for amplifying the change of charge transfer resistance. Adding mediator molecules to the tissue is not practical for in vivo sensing applications. An ideal alternative is to trap the mediator onto the sensor surface without completely sacrificing its mobility. For this purpose, electropolymerization of pyrrole was performed for simultaneous immobilization of aptamer and mediator in the porous polymer film. The impedance spectroscopy revealed that the electron transfer resistance decreased significantly upon the binding of PDGF-BB with the negatively-charged aptamer probe. The detection limit has been determined as low as 1 ng/ml, which is below the regular concentration of PDGF-BB 10 ng/ml in the body. High selectivity has been demonstrated by comparing the specific binding with PDGF-BB and the non-specific adsorptions of BSA, thrombin and lysozyme. In conclusion, a reagentless biosensor, which integrates the virtues of conducting polymer, the specificity of aptamer and the sensitivity of electrochemical impedance measurement, has been successfully developed for the purpose of in vivo cytokine detection.
3:45 PM - QQ5.6
Polydiacetylene Liposomes for Selective Pottasium Detection with Dual Signaling.
Jiseok Lee 3 , Jinsang Kim 1 2 3 Show Abstract
3 Macromolecular Science and Engineering, University of Michigan, Philadelphia, Pennsylvania, United States, 1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
In this presentation, we will describe the development of polydiacetylene (PDA) liposome-based potassium sensors having dual detection modes. Our PDA liposome sensors have single-stranded DNA with a G-rich sequence as a probe at the liposome surface. The Guanine rich single stranded DNA can fold into G-quadruplexes by intramolecular hydrogen bonding interactions with potassium ions. In our sensors design, this conformational change of DNA perturb the ene-yne backbone of PDA and produce a red fluorescence signals as well as a color change from blue to red. Self-assembled diacetylene vesicles were prepared by using a mixture of an N-hydroxysuccinimide-containing diacetylene and a carboxybutylamido-modified diacetylene. The self-assembled diacetylene vesicles were printed onto an amine-modified glass substrate using a microarray system. A single-stranded DNA with the G-rich sequences was covalently tethered to the diacetylene liposomes on the glass substrate. Finally, the conjugated polydiacetylene sensor for detection of potassium ion was prepared through the polymerization of the DNA-tethered diacetylenes. The PDA sensors selectively and sensitively detect potassium even in the presence of sodium.
4:30 PM - QQ5.7
Glucose Biosensors Based on Hygroscopic Insulator Field-Effect Transistors.
Kathleen Sirois 1 , Benjamin Vaughan 1 , Warwick Belcher 1 , Paul Dastoor 1 Show Abstract
1 Physics, University of Newcastle, Callaghan, New South Wales, Australia
Biosensing, which involves the detection of an analyte via specific reactivity with biological recognition elements followed by the transduction of this reaction to an electrical signal, is attracting increasing attention in the pharmaceutical, environmental and food industries . Organic field-effect transistors (OFETs) based on poly(3-hexylthiophene) present the advantages of low manufacturing cost, high sensitivity and selectivity, which makes them desirable for biosensing applications . The OFET is a three terminal device in which a potential applied to a gate electrode induces an electric field through an insulating layer controlling the charge carrier density through a conductive channel between the source and drain electrodes.One problem with this design is that these conventional OFET devices require high operating gate voltages. To lower the operating voltage a hygroscopic gated-insulator layer has been introduced between the gate electrode and the conductive channel . In this device, a potential typically applied to the gate electrode induces ionic drift within the insulator layer resulting in oxidation or reduction of the source/drain channel and allowing the hygroscopic field-effect transistor (HIFET) to perform at lower voltages than usual OFET devices and to operate under ambient atmosphere.The first successful glucose biosensing using a HIFET has been performed by coupling the FET to an electrochemical cell. The catalytic oxidation of glucose by glucose oxidase in the electrochemical cell leads to a variation in the gate potential of the coupled HIFET and thus sensing. Recent results of the development of these devices will be presented.REFERENCES1. C. Reese, M. Roberts, M.-M Ling et al. Mater. Today, 2004, 20-27.2. J. T. Mabeck and G. G. Malliaras, Anal. Bioanal. Chem., 2006, 384, 343-353.3. H. G. O. Sandberg, T. G. Bäcklund, R. Österbacka et al. Adv. Mater., 2004, 16, 1112-1115.
4:45 PM - QQ5.8
Organic Electrochemical Transistors in Sensing Applications.
Daniel Bernards 1 , George Malliaras 1 Show Abstract
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Organic electrochemical transistors (OECTs) have recently gained interest as a platform for sensing applications given their low cost, ease of processing and compatibility with a variety of systems. In their simplest form, the conductivity of an organic semiconductor is modulated by application of a bias through an electrolyte; however, OECTs generally cannot sense uncharged analytes or discriminate between ion types. As a result they usually lack specificity and must be integrated with other components for sensing applications. One possible route to introduce specificity is the incorporation of bilayer lipid membranes (BLMs), where specificity is determined by the addition of ion channels. In this way, an OECT acts to amplify ionic currents that are governed by the characteristics of a particular ion channel. We have incorporated BLMs into typical OECTs as a means to control device characteristics and have shown that ion channels can be successfully used to control the selectivity of OECTs.A second method to functionalize OECTs is to add enzymes that are particular to a desired analyte. Using this approach it is possible to sense analyte concentrations over several orders of magnitude. In addition to double layer formation, Faradaic reactions contribute to the gate current in this mode of operation and can dominate device response. Due to this complexity it is not straightforward to understand device characteristics, and optimizing sensor performance is tedious. Using a model that describes OECT behavior, we have developed a model to account for the Faradaic reactions present in enzymatic based sensors, which can successfully be used in device optimization. In this way we have been able to systematically improve the response of sensors based on this configuration.
5:00 PM - QQ5.9
Water-soluble Conjugated Polymer-antibody Conjugates for In-vitro Cell Imaging.
Kangwon Lee 1 , Moon Soo Choi 2 , Charles Seiler 3 , Taek Seung Lee 2 , Kojo Elenitoba-Johnson 3 , Megan Lim 3 , Jinsang Kim 1 4 5 Show Abstract
1 Materials science and engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejeon Korea (the Republic of), 3 Pathology, University of Michigan, Ann Arbor, Michigan, United States, 4 Chemical engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Macromolecular science and engineering, University of Michigan, Ann Arbor, Michigan, United States
Immunofluorescence bioimaging with small fluorescent molecules or inorganic quantum dot have been well studied and have shown potentials for immunofluorscence labeling. However, conventional cell staining using small molecules for immunofluorescence microscopy requires high cost and time consuming-multiple steps for sample preparation (fixing the cell, blockings, incubation with primary and secondary antibodies). Moreover, semiconducting quantum dots have a critical problem of potential cytotoxicity because heavy-metal can be released through the capping layers of the quantum dots. In this presentation, we will discuss our development of water-soluble conjugated poly(p-phenyleneethynylenes) (PPEs) as a fluorescent probe to image living cells. Two different PPEs (PPE-P and PPE-BTD50) containing carboxylic moiety as a pendent group were prepared. PPE-P was completely water-soluble and emitted intense blue fluorescence at 460 nm whereas PPE-BTD50 showed red-fluorescence at 630 nm in water. To provide specific recognition capability to the conjugated polymers we attached appropriate antibodies to the polymer by using the pendant carboxylic moiety through carbodiimide chemistry. We used CD20 antibody for B-cell recognition. Polymer-CD20 bioconjugates were incubated in the cell. Polymer-CD20 showed excellent selectivity between the target B-cells whereas and T-cells a negative control and produced excellent fluorescent imaging . Cross-selectivity tests were also performed using another antibody CD3 for Jurkats after CD3 and CD20 were bioconjugated with PPE-P and PPE-BTD50 respectively. Our study show that rationally designed emissive water-soluble conjugated polymers can provide an alternative convenient immunofluorescent labeling strategy.
5:15 PM - QQ5.10
A Greener Route to the Synthesis of Electrically Conducting Polypyrrole.
Ramaswamy Nagarajan 1 , Subhalakshmi Nagarajan 2 , Jayant Kumar 3 , Ferdinando Bruno 4 , Lynne Samuelson 4 Show Abstract
1 Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Chemistry, University of Massachusetts Lowell , Lowell, Massachusetts, United States, 3 Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 4 Nano Materials Science Team, US Army RDECOM Natick Soldier Center, Natick, Massachusetts, United States
Polypyrrole (PPY) has been known to be one of the less toxic and more biocompatible electrically conducting polymers with potential applications in the areas of biosensing, drug delivery, transduction and actuation. Most synthetic protocols used for the synthesis of PPY involve very low pH conditions and oxidants that are not compatible with biological systems. For the purpose of creating biosensors based on PPY, it is important to develop a route for synthesizing PPY in the presence of the desired biological entities. Horseradish peroxidase (HRP) has been reported to catalyze the polymerization of aniline under mild conditions (pH ~ 4.5). However this biocatalyst is not effective for synthesis of PPY under these conditions. Here we present a biocatalytic approach for polymerizing pyrrole in relatively benign conditions thus widening the utility of PPY in biological/sensing applications. The polymerization of pyrrole is catalyzed by Soybean peroxidase (SBP) in aqueous media and in the presence of a polyelectrolyte such as polystyrene sulfonate (PSS). Using this method, water-soluble electrically conducting form of PPY can be obtained at pH > 4. PSS acts as the charge-balancing dopant that also improves the solubility of the polymeric complex. Detailed synthesis, spectral characterization and electrical properties of the PPY-PSS complex will be presented. This biocatalytic approach is greener and amenable for use with biological entities thus enhancing the scope for using PPY in new and unique applications.