This paper reports on electrochemical and optical characteristics of flexible, transparent microelectrodes, which consist of thin poly-(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) spun onto indium-tin-oxide (ITO) electrodes for potential applications in biomedical optoelectronic devices. Although PEDOT:PSS/ITO combined films have been extensively investigated for applications in optical devices, such as solar cells and LEDs, PEDOT:PSS/ITO films for use in electrophysiological recording have not been well-characterized yet. In this work, PEDOT:PSS coated ITO microelectrodes with various diameters of 10 μm, 37 μm, 50 μm and 80 μm were microfabricated and characterized, and their properties were compared with plain ITO microelectrodes. Experimental results demonstrate that PEDOT:PSS coated ITO electrodes exhibit decreased electrochemical impedance, well-performed stability in saline, and increased charge storage capacity while preserving excellent optical transparency and mechanical flexibility. Equivalent circuit models were fitted to the experimental results to analytically extract interface capacitance, charge transfer resistance and solution resistance at the electrode-electrolyte interface.

The increased manufacturing of nanoparticles for use in cosmetics, foods, and clothing necessitates the need for an effective system to monitor and evaluate the potential environmental impact of these nanoparticles. The goal of this research was to develop a plant-based sensor network for characterizing, monitoring, and understanding the environmental impact of TiO nanoparticles. The network consisted of potted with a surrounding water supply, which was monitored by cameras attached to a laptop computer running a machine learning algorithm. Using the proposed plant sensor network, we were able to examine the toxicity of TiO nanoparticles in two systems: algae and terrestrial plants. Increased terrestrial plant growth was observed upon introduction of the nanoparticles, whereas algal growth decreased significantly. The proposed system can be further automated for high-throughput screening of nanoparticle toxicity in the environment at multiple trophic levels. The proposed plant-based sensor network could be used for more accurate characterization of the environmental impact of nanomaterials.

Influenza A virus (FLUAV), the causative agent of influenza infection, has received extensive attention due to the recent swine-origin H1N1 pandemic. FLUAV has long been the cause of annual epidemics as well as less frequent but more severe global pandemics. Here, we describe a biosensor utilizing electrically active magnetic (EAM) polyaniline-coated nanoparticles as the transducer in an electrochemical biosensor for rapidly identifying FLUAV strains based on receptor specificity, which will be useful to monitor animal influenza infections and to characterize pandemic potential of strains that have transmitted from animals to humans. Pandemic potential requires human-to-human transmissibility, which is dependent upon FLUAV hemagglutinin (HA) specificity for host glycan receptors. Avian FLUAV preferentially bind to α2,3-linked receptors, while human FLUAV bind to α2,6-linked receptors. EAM nanoparticles were prepared by synthesizing aniline monomer around gamma iron (III) oxide (γ-FeO) cores, yielding 25-100-nm diameter nanoparticles that were structurally characterized by transmission electron microscopy and electron diffraction. The EAM nanoparticles were coated with monoclonal antibodies specific to H5N1 (A/Vietnam/1203/04). Specificity of binding between glycans and H5 was demonstrated. The biosensor results were correlative to supporting data from a surface plasmon resonance assay that characterized HA/glycan binding and α-H5 antibody activity. This novel study applies EAM nanoparticles as the transducer in a specific, portable, easy-to-use biosensor with great potential for disease monitoring and biosecurity applications.

Reducing the size of a nanofluidic channel not only creates new opportunities for high-precision manipulation of biological macromolecules, but also makes the performance of the entire nanofluidic system more susceptible to undesirable interactions between the transported biomolecules and the walls of the channel. In this manuscript, we report molecular dynamics simulations of a pressure-driven flow through a silica nanochannel that characterized, with atomic resolution, adsorption of a model protein to its surface. Although the simulated adsorption of the proteins was found to be nonspecific, it had a dramatic effect on the rate of the protein transport. To determine the relative strength of the protein-silica interactions in different adsorbed states, we simulated flow-induced desorption of the proteins from the silica surface. Our analysis of the protein conformations in the adsorbed states did not reveal any simple dependence of the adsorption strength on the size and composition of the protein-silica contact, suggesting that the heterogeneity of the silica surface may be a important factor.

Cancer is recognized as a serious health challenge both in the United States and throughout the world. While early detection and diagnosis of cancer leads to decreased mortality rates, current screening methods require significant time and costly equipment. Recently, increased levels of certain micro-ribonucleic acids (miRNAs) in the blood have been linked to the presence of cancer. While blood-based biomarkers have been used for years in cancer detection, studies analyzing trace amounts of miRNAs in blood and serum samples are just beginning. Recent developments in deoxyribonucleic acid (DNA) nanotechnology and DNA computing have shown that it is possible to construct nucleic-acid-based chemical networks that accept miRNAs as inputs, perform Boolean logic functions on those inputs, and generate as an output a large number of DNA strands that can readily be detected. Since miRNAs occur in blood in low abundance, these networks would allow for amplification without using polymerase chain reaction. In this study, we report initial progress in the development of a DNA-based cross-catalytic network engineered to amplify specific cancer-related miRNAs. Subcomponents of the DNA network were tested individually, and their operation in serum, as well as a mixture of serum with sodium dodecyl sulfate, is demonstrated. Preliminary simulations of the full cross-catalytic network indicate successful operation.

Nanowire FETs (NWFETs) are promising building blocks for nanoscale bioelectronic interfaces with cells and tissue since they are known to exhibit exquisite sensitivity in the context of chemical and biological detection, and have the potential to form strongly coupled interfaces with cell membranes. We present a general scheme that can be used to assemble NWs with rationally designed composition and geometry on either planar inorganic or biocompatible flexible plastic surfaces. We demonstrate that these devices can be used to measure signals from neurons, cardiomyocytes, and heart tissue. Reported signals are in millivolts range, which are equal to or substantially greater than those recorded with either planar FETs or multielectrode arrays, and demonstrate one unique advantage of NW-based devices. Basic studies showing the effect of device sensitivity and cell/substrate junction quality on signal magnitude are presented. Finally, our demonstrated ability to design high-density arrays of NWFETs enables us to map signal at the subcellular level, a functionality not enabled by conventional microfabricated devices. These advances could have broad applications in high-throughput drug assays, fundamental biophysical studies of cellular function, and development of powerful prosthetics.

Sequencing a single molecule of deoxyribonucleic acid (DNA) using a nanopore is a revolutionary concept because it combines the potential for long read lengths (>5 kbp) with high speed (1 bp/10 ns), while obviating the need for costly amplification procedures due to the exquisite single molecule sensitivity. The prospects for implementing this concept seem bright. The cost savings from the removal of required reagents, coupled with the speed of nanopore sequencing places the $1000 genome within grasp. However, challenges remain: high fidelity reads demand stringent control over both the molecular configuration in the pore and the translocation kinetics. The molecular configuration determines how the ions passing through the pore come into contact with the nucleotides, while the translocation kinetics affect the time interval in which the same nucleotides are held in the constriction as the data is acquired. Proteins like α-hemolysin and its mutants offer exquisitely precise self-assembled nanopores and have demonstrated the facility for discriminating individual nucleotides, but it is currently difficult to design protein structure ab initio, which frustrates tailoring a pore for sequencing genomic DNA. Nanopores in solid-state membranes have been proposed as an alternative because of the flexibility in fabrication and ease of integration into a sequencing platform. Preliminary results have shown that with careful control of the dimensions of the pore and the shape of the electric field, control of DNA translocation through the pore is possible. Furthermore, discrimination between different base pairs of DNA may be feasible. Thus, a nanopore promises inexpensive, reliable, high-throughput sequencing, which could thrust genomic science into personal medicine.

Plasmon resonances are computed for nanoshells of prolate and oblate spheroidal shape. Both longitudinal and transverse resonances are investigated as a function of aspect ratio and shell thickness. Formulas for the surface charge density on the outside and inside shell surfaces are derived.

An automated technique is presented for mechanically exfoliating single-layer and few-layer transition metal dichalcogenides using controlled shear and normal forces imposed by a parallel plate rheometer. A thin sample that is removed from bulk MoS or MoTe is initially attached to the movable upper fixture of the rheometer using blue dicing tape while the lower base plate also has the same tape to capture and exfoliate samples when the two plates are brought into contact then separated. A step-and-repeat exfoliation process is initiated using a preprogrammed contact force and liftoff speed. It was determined that atomically thin films of these materials could be obtained reproducibly using this technique, achieving single-layer and few-layer thicknesses for engineering novel 2D transistor devices for future electronic technologies. We show that varying the parameters of the rheometer program can improve the mechanical exfoliation process.

Increasingly targeted in drug discovery, protein-protein interactions challenge current high throughput screening technologies in the pharmaceutical industry. Developing an effective and efficient method for screening small molecules or compounds is critical to accelerate the discovery of ligands for enzymes, receptors and other pharmaceutical targets. Here, we report developments of methods to increase the signal-to-noise ratio (SNR) for screening protein-protein interactions using atomic force microscopy (AFM) force spectroscopy. We have demonstrated the effectiveness of these developments on detecting the binding process between focal adhesion kinases (FAK) with protein kinase B (Akt1), which is a target for potential cancer drugs. These developments include optimized probe and substrate functionalization processes and redesigned probe-substrate contact regimes. Furthermore, a statistical-based data processing method was developed to enhance the contrast of the experimental data. Collectively, these results demonstrate the potential of the AFM force spectroscopy in automating drug screening with high throughput.