UNS: Enhancing charge transport in enzymatic bio-electrodes using an iron-sulfur-based synthetic electron-transport-chain

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Fernando, 1511303Enzymatic biofuel cells work on the same general principles as all fuel cells, they use a catalyst to separate electrons from a parent molecule and force it to go around an electrolyte barrier through a wire to generate an electric current. The enzymatic biofuel cell uses enzymes derived from living cells. The enzymes that allow the fuel cell to operate must be "immobilized" (attached) near the anode and cathode in order to work properly; if not immobilized, the enzymes will diffuse into the cell's fuel and most of the liberated electrons will not reach the electrodes, compromising its effectiveness. The overall effectiveness of all enzyme-based electrochemical devices is dependent on the ability of the molecules that attach enzymes to the electrode to successfully harvest and transport charges from the outer oxidizing point (enzyme active-site) to the inner electrode surface. Redox enzymes are naturally-occurring sensing devices that can act as power plants due to their ability to generate an electron stream in the presence of the enzyme-specific analyte. When these enzymes are wired to electrodes (outside a living cell or ex vivo), their ability to harness these electrons (or electricity) diminishes significantly due to the thermodynamic limitations associated with the coenzymes (that are essential for proper functioning of the enzyme). The common coenzymes, nicotinamide-adenine-dinucleotide (NAD) and Flavin-adinie-dinucleotide (FAD), are resistant to cyclic oxidation and reduction ex vivo; and require special molecules known as electron mediators to help extract electrons from the cofactor to transfer to the final target. Long molecular wires help eliminate the thermodynamic issue but themselves create electron transport (kinetic) issues due to increased resistance. Nature has found a way to circumvent the thermodynamic and kinetic electron transport issues associated with redox enzymes by using an array of unique molecules, the iron-sulfur complexes ([Fe-S]), to wire the enzyme (apoenzyme and coenzyme) complex to the supporting surfaces (like those found in biological electron transport chains). [Fe-S] complexes seem to have a unique combination of properties that facilitate unimpeded electron transport in biological systems.The objective of this project is to evaluate the reaction and electron transport kinetics of enzymatic electrodes of which NAD and FAD based enzyme systems are directly attached using common iron sulfides and select [Fe-S] complexes (mimicking the critical iron-sulfur link(s) in biological electron transport chains). The PI will evaluate the possibility of fabricating a highly effective molecular wire for transporting electrons ex vivo.A major educational objective is to integrate research into education via an undergraduate course and a graduate level course. Research Experience for Academic Change (REACH) is a program in which students who are academically at risk will be paired with academically successful students and provided with research opportunities early in their undergraduate program. The PI plans to evaluate whether their early exposure to practical research helps resuscitate their excitement and confidence concerning their engineering education and degree programs.