Comparison of Molecular-Wires for Enhancing Charge Transport of Enzymatic Electrode Assemblies: A Glycerol Bioanode Model

Abstract

Biomolecules are inherently less conductive. Therefore, bio-electronic devices that depend on conventional biomolecules to tether enzymes onto electrode supports and to shuttle electrons between the enzyme and the electrode suffer from charge dissipation. This results in bioanondes with decreased current-voltage responses as a result of ohmic losses. Reducing the internal resistance is the simplest way of increasing the current-voltage response associated with bioanodes and has yet been an unmet challenge. A novel iron (II) sulfide (FeS) based molecular wiring system was developed for immobilizing glycerol dehydrogenase on a gold electrode surface. Amperometric and potentiometric analyses with glycerol dehydrogenase-based model electrodes confirmed the ability of this single-molecule to remarkably amplify, about ten-fold increase in current and up to 24% increase in voltage outputs, as compared to electrodes fabricated with the conventional Pyrroloquinoline quinone-based composite molecular wiring system. FeS achieves the dual purpose of anchoring the enzyme to the gold electrode while also mediating electron shuttling between coenzyme and the electrode surface. This dual functionality allows usage of a single-molecular wire to foster electrical communication between the enzyme and the electrode instead of the conventional multi-molecular wiring system and in turn reducing the internal resistance of the electrode. The resulting increase in current/voltage response opens up a wide range of possibilities for developing efficient bio-electrodes for bioelectronics applications.