Dynamic modeling of direct electron transfer PQQ-GDH MWCNTs bioanode function

Abstract

Derivation of a steady state and dynamic model of direct electron transfer of the bioanode utilized in a self-powered glucose biosensor (SPGS) is described. The bioanode comprises of dense network of multi-walled carbon nanotubes (MWCNTs) functionalized with pyrroloquinoline quinone dehydrogenase (PQQ-GDH) to oxidize glucose substrate. The model is based on detail charge and mass balances for several dissolved chemical species, such as glucose substrate, oxidized and reduced form of the enzyme, enzyme-substrate complex and the product gluconolactone. The chemical and electrochemical reactions occur in bulk solution and at the electrode surface, respectively. The charge and mass balances are used to describe the ping-pong mechanism of PQQ-GDH reactions at the bioanode. A detailed model parameter is used to stimulate the current-voltage response curve and current-time evolution in the SPGS with glucose as the anodic substrate. Additionally, the model output includes the time-dependent production of current and current density-potential profile, which is used to explain the activation, concentration and ohmic losses that occurs at the bioanode. The model is validated against experimental current density and potential profiles. The stimulations show the effect of different parameters on the bioanode characteristics and illustrate some of the possible restrictions of the bioanode as well as provide an insight into the optimization of SPGS. The approach taken to develop the PQQ-GDH bioanode model can be applied to other SPGS systems and has potential applications for other biological, chemical and electrochemical systems.