Bioelectrochemical sensor based on PQQ-dependent glucose dehydrogenase

Bioelectrochemical responses of pyrroloquinoline quinone (PQQ) dependent glucose dehydrogenase (PQQ-GDH) have been studied with the use of two principal electrode configurations: (i) glassy carbon electrode, coated with Nafion layer, containing sorbed N-methylphenazonium (NMP), and overcoated by an enzyme layer, crosslinked by glutaraldehyde, and (ii) glassy carbon electrode, containing an electropolymerized layer of either Toluidine blue, or o-phenylenediamine, or pyrrole, and overcoated by a crosslinked enzyme layer. When operated within the potential window of 0.0–0.3 V, Nafion-coated and NMP-soaked bioelectrode shows an anodic current response to glucose without the presence of electron transfer mediator in solution. The current–concentration profile obtained resemble to that, typical for enzyme catalyzed reaction. Other configurations studied showed bioelectrochemical response to glucose only in the presence of soluble mediator NMP. Without any mediator, no electrochemical responses have been registered. It indicates that direct electron transfer between PQQ-GDH and all types of electrodes modified during current work is undetectable.