Electrochemical current rectification at bio-functionalized electrodes

In the present paper, we demonstrate the electrochemical rectification of a redox current which is transferred between redox probes (ferricyanide) in solution and a gold electrode functionalized with the biomolecular redox mediator microperoxidase-11 (MP-11). MP-11 is the redox active, heme-containing domain of the biological electron shuttle cytochrome c (cyt c). In our system, a unidirectional current develops due to selective electron transport from the bio-functionalized electrode to ferricyanide such that MP-11 controls the read-out of our coupled redox system. The electrode was functionalized by adding a monolayer of undecanethiol (UDT) to promote the physisorption of MP-11 and inhibit the direct electron transfer between redox probe and electrode. The relative position of redox donator, mediator, and acceptor equilibrium potentials defines the charge transport and a potential-dependent electrochemical current rectification. The results of our investigations demonstrate that functional building blocks of proteins can be reassembled into new conceptual devices with operation modes deviating from their native function, which could prove highly useful in future design of biosensors and bioelectronic systems.