Mediated bioelectrocatalytic reaction at an ultrathin redox polymer film on a glassy carbon electrode surface and effect of the ionic strength on the catalytic current

Intermolecular interactions between water-soluble pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) and an Os complex-containing redox polymer coated on a glassy carbon electrode surface were investigated, especially by focusing on their electrostatic interaction, in which the electrostatic interaction was changed by varying the ionic strength in the solution. The redox polymer showed a strong repulsive interaction between the positively charged Os complexes, especially at low ionic strengths. The polymer worked as a good electron-shuttling mediator between PQQ-GDH and the electrode to produce a steady-state catalytic current ascribed to the d-glucose oxidation. The catalytic current drastically increased with an increase in the ionic strength, presumably due to the reduction of the repulsive electrostatic interaction between the active site of the enzyme and the Os complex in the polymer and between the Os complexes. The electrostatic interaction governs the electrostatic interaction between the redox site of PQQ-GDH and the Os complexes, and the dynamics of the Os complexes on the electrode surface.