NANOSTRUCTURED INTERFACES FOR BIOCATALYSIS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0216817
• Project Start Date: Nov 1, 2008
• Project End Date: Oct 31, 2013
• Program Code: [(N/A)]- (N/A)

Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824

Performing Department
Chemical Engineering

Non Technical Summary
In electrobiocatalysis, enzymes are used to catalyze chemical reactions that involve electron transfer. This approach could be used to produce a wide range of fuels and chemicals from biobased chemical intermediates. However, technical challenges associated with achieving rapid and efficient electron transfer between an electrode and the enzyme currently limit industrial applications. The Worden lab has developed novel nanostructured bioelectronic interfaces that address these challenges. We now propose to develop novel electrochemical bioreactors that combine oxidation and reduction reactions into a single process capable of forming two high-value products simultaneously. The initial focus will be on reductive bioconversion of glucose to the high-value sweetener mannitol. Mannitol is a sugar alcohol used in the pharmaceutical, chemical, and food ingredients industries. Currently, 50,000 tons/year of mannitol are produced by hydrogenation of 50% fructose/50% glucose syrups at a 30% yield.1 The proposed enzymatic process would be conducted under mild conditions and is expected to have higher specificity and yield. The proposed electrobiocatalytic reactor represents a generic platform that could be used to produce a wide variety of products, simply by interchanging enzymes. The ability to economically produce multiple high value products from glucose would improve the economic competitiveness of a biofuel-producing biorefinery. Because processes to upgrade biobased raw materials will be located in rural areas near the biomass source, this research will help stimulate rural economic development by creating new jobs. Moreover, the high profit margins possible by converting low-cost glucose into specialty chemicals via dehydrogenases would allow these bioconversions to be stand-alone commercial ventures that do not require the huge capital investment of a full biorefinery. The total impact of the new industrial development is expected to significantly exceed that due simply to new jobs created directly for biobased product formation. Rural economic development models enable estimation of the multiplier by which the total number of new jobs (direct plus those supporting the new industry and employees) can be estimated. Growth of ethanol cooperatives, in which local farmers organize to benefit from economies of scale, will provide further benefits. Environmental benefits should also result from the new technologies; the proposed enzymatically catalyzed reactions will generate fewer and less toxic by-products than conventional catalytic processes, which operate at high temperatures and pressures.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	2410	2020	40%
501	2410	2020	30%
511	2410	2020	30%

Knowledge Area
511 - New and Improved Non-Food Products and Processes; 501 - New and Improved Food Processing Technologies; 402 - Engineering Systems and Equipment;

Subject Of Investigation
2410 - Cross-commodity research--multiple crops;

Field Of Science
2020 - Engineering;

Keywords

bioelectronic

dehydrogenase

biocatalysis

bioreactor

cofactor

regeneration

redox

Goals / Objectives
The objectives of the proposed research are to (1) develop innovative bioelectrocatalytic reactors that achieve mediated electron transfer to dehydrogenases, (2) analyze the underlying electrochemistry, reaction kinetics, and mass-transfer that govern the reactor's performance, and (3) optimize the reactor's performance for coupled bioconversions having commercialization potential, such as production of mannitol from glucose. A novel and innovative bioreactor system will be developed using the following strategies: (1) segregating the oxidation and reduction reactions to allow conditions for each enzymatic reaction to be optimized independently; (2) using inexpensive, high surface area carbon electrodes for rapid reaction rates; (3) achieving efficient proton transfer between the two compartments; (4) immobilizing mediator, cofactor, and enzyme in molecular orientations that prevents loss to the surrounding solution while allowing efficient, multistep electron transfer; (5) using a renewable interface architecture that allows cofactor and enzyme to be replaced periodically without the need to remove the electrode material.

Project Methods
The proposed electrochemical bioreactor will convert glucose to mannitol in the cathodic compartment. The first enzyme, glucose isomerase, will convert the glucose into fructose. The second enzyme, mannitol dehydrogenase, will reduce fructose to mannitol. In preliminary studies, we have assembled the proposed multilayered bioelectronic interface and confirmed that it converts glucose into mannitol. This interface will be adapted to carbon electrodes for continuous mannitol production from glucose using the approaches described above. The renewable bioelectronic interface developed in the Worden lab uses polyelectrolyte multilayers (PEM) to hold the desired enzymes, cofactors, and mediators in a configuration that provides efficient, multistep electron transfer, and high stability. This approach also allows spent enzymes and cofactors to be periodically replaced without removing the electrode material from the reactor. The enzymes, NADH, and electron mediator were immobilized on an electrode to facilitate electron transfer from the electrode to mannitol dehydrogenase. Our prototype bioelectronic reactor is made from non-conductive plexiglass. It features inlet and outlet ports for both compartments, as well as a central port for inserting electrodes. A proton-permeable Nafion membrane separates the anode and cathode compartments. Reticulated vitreous carbon (RVC) electrode material having different pore sizes may be cut to size, inserted in to the bioreactor, then functionalized with mediator, cofactor and electrode. The initial design is based on the following key features: (1) high-surface area, flow-through design, (2) minimal biocatalyst thickness to promote transport between compartments, (3) independent control of electrode potential of each chamber. Electrons removed from the anode will be delivered through an external circuit to the cathode and protons generated at the anode will be transported into the cathodic compartment through the Nafion membrane. Several alternative approaches will be evaluated to further optimize the assembly method on glassy carbon (GC) electrodes. In one approach, TBO will first be electropolymerized to GC using well-established methods. The reaction does not affect TBO's permanent positive charge, so anionic PEM, such as poly(acrylic acid) (PAA), can be adsorbed to the surface, followed by a PEI layer, to which cofactor and enzyme are attached. In another approach, a PEM base layer will be adsorbed directly onto the carbon, then a second polyelectrolyte functionalized with mediator, cofactor, and enzyme will be adsorbed. Our ability to build bioelectronic interfaces by sequentially depositing layers having nanometer-scale thickness provides the capability to precisely control the composition, thickness, and electrochemical properties of the resulting bioelectronic interface. We have assembled alternating layers of mediator-modified PAA and Secondary ADH-enzyme-modified PEI to generate a functional, multilayered bioelectronic interface on carbon.

Progress 11/01/08 to 10/31/13

Outputs
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? I developed an experiment based on nanostructured bioelectronic interfaces for the teaching laboratory of a senior-level Biochemical Engineering course (CHE 481) I developed and teach. In this new bioelectronics experiment, students immobilize a c-type cytochrome on a nanostructured biomimetic interface and use it to characterize cytochrome-c-mediated reduction of ferricyanide. This experiment is an example of translating outcomes of our ongoing MAES research effort into educational opportunities. During Fall, semester, 2013, the new experiment was used for CHE 481, which has an enrollment of >40 students. How have the results been disseminated to communities of interest? The results have been disseminated through classroom instruction, peer-reviewed publications, conference presentations, and a patent application. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The Hatch funding has had impact in several ways. It supported in part a researcher in Dr. Worden's lab who produced and purified recombinant proteins, especially redox proteins, for several researchers who collaborate with Dr. Worden on development of nanostructured interfaces for biocatalysis. These researchers include MSU faculty. Second, results have been presented annually at the Hatch Multistate Research Project, S1041 "The Science and Engineering for a Biobased Industry and Economy." Third, Dr. Worden has incorporated content from his research into two courses he teaches, including CHE 481, Biochemical Engineering, CHE 882, Advanced Biochemical Engineering, and CHE 883, Multidisciplinary Bioprocessing Laboratory. Fourth, Dr. Worden participated in the Annual Meeting of the American Institute of Chemical Engineers where he and his graduate student presented three research papers related to bioelectronics. Fifth, Dr. Worden directs an Interdisciplinary Bioelectronics Training Program at Michigan State University, which serves as an outlet for research results. This research has produced a change in knowledge. Research led to a new bioelectronic interface for Geobacter cytochromes in E. coli and shown them to be electrochemically active. A nanostructured bioelectronic interface containing a periplasmic cytochrome (cytochrome PpcA) from Geobacter sulfurreducens was assembled on the gold electrode. The cytochrome was expressed heterogeneously in E. coli and purified using cation exchange chromatography. A gold electrode was contacted with a 5 mM ethanolic solution of 11-mercaptoundecanoic acid and 11-mercaptoundecanol (1:3 ratio) to form a self assembled monolayer. Cytochrome PpcA was bound to the self assembled monolayer via an amide linkage using 50 mM EDC and 5 mM NHS solutions. Unbound protein was rinsed away using 20 mM phosphate buffer. Cyclic voltammetry was then used to characterize the interface. A reduction wave for the immobilized cytochrome PpcA was observed, whose magnitude at -450 mV vs. Ag/AgCl increased in a dose-dependent manner with the concentration of the soluble electron acceptor (ferric NTA). We also characterized interactions between engineered nanomaterials (ENM) and nanostructured biomimetic interfaces containing a bilayer lipid membrane (BLM). Our approach has focused on measuring ENM-induced ion leakage either using a planar BLM (pBLM) suspended across an orifice or a tethered BLM (tBLM) attached to an electrode. The effect of silica-core nanoparticles and biodegradable polypropargyl glycolide nanoparticles on tBLM resistance (Rm) was studied using electrochemical impedance spectroscopy. Changes in the Rm following ENM exposure were analyzed using an empirical, exponential-decay model and a simple mechanistic kinetic model. Statistical analysis of the model parameters for each ENM showed that the method could distinguish between ENM having identical core nanoparticles but different surface functional groups. We have also adapted electrophysiology methods to study how 20-nm polystyrene nanoparticles (PNP) induce pores in pBLM. The PNP’s charge was varied by using either positive (amidine) functional groups or negative (carboxyl) functional groups. The pBLM’s charge was varied using dioleoyl phospholipids having cationic (ethylphosphocholine), zwitterionic (phosphocholine), or anionic (phosphatidic acid) headgroups. Both positive and negative PNP induced pBLM pores for all lipid compositions studied. The results demonstrated for the first time that PNP can induce ion-selective pores in pBLM, and that the degree of ion selectivity is influenced synergistically by the charges of both the lipid headgroups and functional groups on the PNP. These results provide insight into mechanisms by which ENM interact with biomembranes and may lead to improved nanostructured bioelectronic interfaces for generation of biobased fuels and chemicals.

Publications

• Type: Journal Articles Status: Published Year Published: 2013 Citation: Huang Y, Liu Y, Hassler BL, Worden RM, Mason AJ. 2013. A Protein-Based Electrochemical Biosensor Array Platform for Integrated Microsystems. Biomedical Circuits and Systems, IEEE Transactions on 7(1):43-51.

Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: OUTPUTS: First, the Hatch funding supported in part a researcher in Dr. Worden's lab who produced and purified recombinant proteins, especially redox proteins, for several researchers who collaborate with Dr. Worden on development of nanostructured interfaces for biocatalysis. These researchers include MSU faculty. Second, results have been presented annually at the Hatch Multistate Research Project, S1041 "The Science and Engineering for a Biobased Industry and Economy." Third, Dr. Worden has incorporated content from his research into two courses he teaches, including CHE 481, Biochemical Engineering, CHE 882, Advanced Biochemical Engineering, and CHE 883, Multidisciplinary Bioprocessing Laboratory. Fourth, Dr. Worden participated in the Electrofuels Program Meeting & Workshop, where he discussed bioelectronic applications to generate biofuels. Fifth, Dr. Worden directs an Interdisciplinary Bioelectronics Training Program at Michigan State University, which serves as an outlet for research results. PARTICIPANTS: PARTICIPANTS: Robert Mark Worden Lee Alexander and Rui Li. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This research has produced a change in knowledge. Research led to a novel method to electroactivate to carbon electrodes by polarization in aqueous electrolyte at potentials exceeding 2 V. Electroactivation by cyclic voltammetry in the range of -1.5 to 2.5 V yielded a broad redox peak centered at -0.15 V, suggesting the presence of a redox couple, likely dominated by the quinone/hydroquinone couple. Electroactivation also increased the electrode's ability to adsorb an azine redox polymer. This increased azine loading significantly increased NADH oxidation activity. A design of experiments approach was used to investigate the effect of applied potential (+1.5 V, +2.5 V, and +3.25 V) and activation time (15 s, 30 s, and 120 s) on electroactivation. The contour plots of capacitive surface area, current production in NADH oxidation, and current density against activation potentials and durations showed that capacitive surface area increased strongly and monotonically with activation potentials over the entire time range studied. Above an activation potential of about 2 V, surface area increased weakly with time to about 80 s, and then decreased slightly with time. Below 2 V, time had minimal effect on surface area. The current normalized to capacitive surface area was highest when low activation potentials are applied for over a long time. The total current generated showed a relatively sharp optimum at intermediate activation potential (2.5 V) and relatively short time (25 s). These results suggest that electrooxidation of the glassy carbon can increase electrode surface area and generate chemical moieties (e.g., quinones) on the electrode surface that catalyze NADH oxidation. However, excessive activation potential or time can degrade the catalytic moieties. Over the range of potentials and times tested, the constant potential activation method yielded a maximum NADH rate only 3 times larger than produced by electrodes without activation, suggesting that a constant potential activation method may not be as effective as one based on cyclic voltammetry. In collaboration with Dr. Gemma Reguera, we have expressed a Geobacter cytochrome OmcB in E. coli and shown it to be electrochemically active. We also submitted an international patent on in-vitro self-assembly of recombinant Geobacter PilA peptides produced in our Protein Expression Lab into in nanowires resembling those used by Geobacter cells to reduce metals in the environment. In collaboration with Dr. James Tiedje, we have elucidated a new mechanism by which Shewanella cells use soluble electron mediators to direct their movement and reduce metals in the environment. This discovery was published in 2012.

Publications

• R. Li, J.M. Tiedje, C.C. Chiu, R.M. Worden, Soluble Electron Shuttles Can Mediate Energy Taxis toward Insoluble Electron Acceptors, Environmental Science & Technology, 46 (2012) 2813-2820.
• S.R. Jadhav, S.R. Kota, Y. Zheng, R.M. Garavito, R.M. Worden, Voltage dependent closure of PorB Class II porin from Neisseria meningitidis investigated using impedance spectroscopy in a tethered bilayer lipid membrane interface, Journal of Colloid and Interface Science, In press (2012).
• C.J. Brigham, C.S. Gai, J. Lu, D.R. Speth, R.M. Worden, A.J. Sinskey, Engineering Ralstonia eutropha for Production of Isobutanol from CO2, H2, and O2, in: J.W. Lee (Ed.) Advanced Biofuels and Bioproducts, Springer New York, 2012, pp. 1065-1090.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: First, the Hatch funding supported in part a researcher in Dr. Worden's lab who produced and purified recombinant proteins, especially redox proteins, for several researchers who collaborate with Dr. Worden on development of nanostructured interfaces for biocatalysis. These researchers include MSU faculty. Second, results have been presented annually at the Hatch Multistate Research Project, S1041 "The Science and Engineering for a Biobased Industry and Economy." Third, Dr. Worden has incorporated content from his research into two courses he teaches, including CHE 481, Biochemical Engineering, CHE 882, Multidisciplinary Bioprocessing Laboratory. Fourth, Dr. Worden served on the NIH NANO Review Panel, where he used his expertise in the review of nanotechnology-related proposals. Fifth, Dr. Worden gave an invited lecture at the International Conference on Electrofuels, sponsored by the Society of Biological Engineering and American Institute of Chemical Engineers. PARTICIPANTS: Robert Mark Worden, Lee Alexander and Rui Li TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This research has produced a change in knowledge. NADH was immobilized through linker molecules glycine and aminoboronic acid. To test the existence and functionality of immobilized NADH, we developed a method to perform the EnzyChrom NAD/NADH Assay Kit using a NanoDrop instrument. Thirty uL assay kit working reagent was placed onto the NADH modified electrode under room temperature. After 15 min, the color of working reagent having access to NADH changed from light yellow to deep purple. For a quantities result, 2 uL of working reagent was loaded to a NanoDrop 1000 Spectrophotometer at 0 min and 15 min. Optical density (OD) at 565 nm was increased from 0.004 to 0.2 0.01, whereas working reagent on the electrode not modified by NADH could not produce either significant color change or OD change. The results showed that immobilized NADH could actively transfer electrons to enzyme in the working reagent. TBO was also immobilized on the electrode surface and verified by cyclic voltammetry in phosphate buffer pH 6.5. In addition, in collaboration with Dr. Gemma Reguera, we demonstrated, for the first time,in-vitro self-assembly of recombinant Geobacter PilA peptides produced in our Protein Expression Lab into in nanowires resembling those used by Geobacter cells to reduce metals in the environment. We obtained a provisional patent on this invention, which has potential applications in nanostructured bioelectronic interfaces that mimic electron-transfer mechanisms found in metal-reducing microbes including Geobacter and Shewanella. In collaboration with Dr. James Tiedje, we have elucidated a new mechanism by which Shewanella cells use soluble electron mediators to direct their movement and reduce metals in the environment. This discovery has been submitted for publication.

Publications

• Shewanella oneidensis MR-1 Chemotaxis in a Diffusion Gradient Chamber Li Rui; Auchtung Jennifer M.; Tiedje James M.; et al. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 45, 1014-1020 (2011)

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: First, the Hatch funding supported in part a researcher in Dr. Worden's lab who produced and purified recombinant proteins, especially redox proteins, for several researchers who collaborate with Dr. Worden on development of nanostructured interfaces for biocatalysis. These researchers include both MSU faculty and researchers at the company Neogen, which produces and markets food-safety test kits. Second, results have been presented annually at the Hatch Multistate Research Project, S1041 "The Science and Engineering for a Biobased Industry and Economy." Third, Dr. Worden developed a 1.5-h lecture highlighting the cross-disciplinary research activities conducted as part of this project for an invited presentation in the Basic Biotechnology (MMG 445) course. The lecture was recorded into an streaming Internet movie, which is now used in the online version of the Basic Biotechnology course. PARTICIPANTS: Robert Mark Worden Lee Alexander TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This research has produced a change in knowledge. A potentially superior electron mediator (Azure C) for nanostructured bioelectronic interfaces involving dehydrogenase enzymes has been investigated. NAD+ is normally reduced at potentials between -0.7 V and -0.8 V vs. Ag/AgCl, where significant water reduction lowers the efficiency of the overall process. To operate at more positive potentials, azure C (which has a reductive peak at -0.25V/s vs. Ag/AgCl and a primary amine) was tested as electron mediator for NAD+ reduction and NADH oxidation. Azure C was bound to chitosan matrix through Schiff base chemistry, and the azure C-modified chitosan was drop-cast onto polished glassy carbon electrodes to form a film. Cyclic voltammetric scans were collected with and without NADH in the solution to obtain the optimal potential for NADH oxidation, and constant potential amperometry was used to probe the azure C-modified electrodes' activity towards NADH at -0.25V vs. Ag/AgCl. Azure C was found to have activity for both NADH oxidation and NAD+ reduction. Cyclic voltammograms of azure C-modified electrodes showed a large current increase at potentials above 0 V vs. Ag/AgCl shows azure C's activity toward NADH oxidation in this potential range, and the highest activity occurs at 0.35V vs. Ag/AgCl. Azure C also showed activity toward NAD+ reduction at -0.25V vs. Ag/AgCl (Figure 5), as shown by the current increase peaks observed upon incremental additions of 1 mM NAD+ to the reaction. In addition, we have mass-produced protein components to be used in nanostructured bioelectronic interfaces that mimic electron-transfer mechanisms found in metal-reducing microbes including Geobacter and Shewanella. Our collaborators used genetic engineering to produce plasmids encoding genes for the key proteins, and we completed the mass-production and purification of these proteins. successfully assembled the recombinant nanowire subunits in vitro. Results are being held for filing invention disclosures.

Publications

• Kohli, N., Lee, I., Richardson, R.J., and Worden, R.M. "Theoretical and Experimental Study of Bi-Enzyme Electrodes with Substrate Recycling", Journal of Electroanalytical Chemistry, 641, 104-110, (2010).
• Greiner, A. J.; Richardson, R. J.; Worden, R. M.; Ofoli, R. Y. "Influence of lysophospholipid hydrolysis by the catalytic domain of neuropathy target esterase on the fluidity of bilayer lipid membranes," Biochimica Et Biophysica Acta-Biomembranes 1798(8), 1533-1539, (2010).

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Results of this study have been disseminated in several ways. They have been published in peer reviewed publications; presented at conferences, including the USDA CSREES Nanotechnology Grantees Meeting Sept. 27-29 in Santa Fe, NM and the annual meeting of the Hatch Multistate Research Project, "The Science and Engineering of a Biobased Industry and Economy;" and published in three Ph.D. dissertations published during 2009. PARTICIPANTS: Robert Mark Worden (principal investigator) TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This research has produced a change in knowledge, which resulted in several publications in 2009, including three Ph.D. dissertations. A Ph.D. dissertation entitled, "Engineering surfaces for bioelectronic applications" was published by Brian Hassler. This dissertation described bioelectronic interfaces that facilitate electron transfer between the electrode and a dehydrogenase enzyme have potential applications in biosensors, biocatalytic reactors, and biological fuel cells. The dissertation described novel methods to fabrication a renewable bioelectronic interface in which poly(ethyleneimine) (PEI) was used to couple the cofactor and enzyme to the electrode. By decreasing the pH the surface-bound carboxylic acid group protonates disrupting the ionic bonds and releasing the enzyme and cofactor. After neutralization, fresh PEI, enzyme, and cofactor can be reassembled, allowing the interface to be reconstituted. Renewable bioelectronic interfaces were also fabricated on a glassy carbon electrode. However, these interfaces are limited in their reaction capacity, because it contains a single enzyme monolayer. Also, a novel approach was developed, in which multiple, nanostructured bioelectronic cassettes are stacked in series to yield multilayered bioelectronic interfaces having higher reaction capacities. An approximate analytical solution for bioelectronic interfaces containing reversible enzymes and mediators was developed that takes into account reversible enzyme kinetics, reversible mediator kinetics, substrate diffusion, product diffusion, and electron diffusion. A second Ph.D. dissertation entitled "Design and Characterization of Nanostructured Biomimetic Interfaces Containing Bilayer Lipid Membranes," was published by Sachin Jadhav. The central theme of this work is to develop robust, nanostructured biomimetic interfaces that display protein activities, are easy to fabricate, and are directly addressable by various analytical techniques. Three different BLM interfaces, namely planar unsupported BLMs, supported BLMs (sBLM), and tethered BLMs (tBLM), were fabricated and characterized using electrochemical techniques. A third Ph.D. dissertation, entitled, ""Dynamics of Embedded Fluorophores in Model Bilayer Lipid Membranes" was published by Aaron Greiner. This dissertation described fundamental studies to investigate nanostructured biomimetic interfaces that contained lipid bilayers. These interfaces are well suited to display the activity of membrane proteins. The model enzyme studied, neuropathy target esterase esterase, whose activity is believed to influence nerve impulse transmission. Our group had previously developed a nanostructured bioelectronic interface that translated enzymatic activity into an electrical signal.

Publications

• Kohli, N., Lee, I., Richardson, R.J., and Worden, R.M. (2009) "Theoretical and Experimental Study of Bi-Enzyme Electrodes with Substrate Recycling", Journal of Electroanalytical Chemistry, in press.
• Greiner AJ, Pillman, HA, Worden RM, Blanchard GJ, and Ofoli RY (2009) "Effect of Hydrogen Bonding on the Rotational and Translational Dynamics of a Headgroup-Bound Chromophore in Bilayer Lipid Membranes" J. Phys. Chem. B, 113 (40): 13263-13268.
• Yang, C.; Huang, Y.; Hassler, B.; Worden, R. M.; Mason, A.J. (2009) "Amperometric Electrochemical Microsystem for a Miniaturized Protein Biosensor Array", IEEE Transactions on Biomedical Circuits and Systems, 3, 160-168.
• Yang, C; Jadhav, SR; Worden, RM; and Mason AJ (2009) "Compact Low-Power Impedance-to-Digital Converter for Sensor Array Microsystems" IEEE Journal of Solid-State Circuits, 44 (10): 2844-2855.
• Hassler, B.L (2009) "Engineering Surfaces for Bioelectronic Applications", Ph.D. Dissertation, Michigan State University.
• Greiner, A.J. (2009) "Dynamics of Embedded Fluorophores in Model Bilayer Lipid Membranes", Ph.D. Dissertation, Michigan State University.
• Jadhav, S. (2009) "Design and Characterization of Nanostructured Biomimetic Interfaces Containing Bilayer Lipid Membranes," Ph.D. Dissertation, Michigan State University.