Improved direct electron transfer-type bioelectrocatalysis of bilirubin oxidase using thiol-modified gold nanoparticles on mesoporous carbon electrode

Abstract

Ketjen Black (KB), a mesoporous carbon material, was modified with gold nanoparticles (AuNPs) and 4-mercaptobenzoic acid (MBA). The MBA/AuNP-modified KB was utilized as an effective scaffold for the direct electron transfer (DET)-type bioelectrocatalytic reduction of dioxygen by bilirubin oxidase from Myrothecium verrucaria (BOD). Owing to the MBA/AuNP modification, the limiting current density of the steady-state catalytic wave was doubled and the half-wave potential of the catalytic wave was shifted to the positive direction by 140mV. The kinetic analysis of the steady-state catalytic wave indicated that the modification narrowed the orientation distribution of the adsorbed BOD and shortened the mean length between the redox copper site of BOD and the electrode surface. The electrostatic attraction and π–π interactions between BOD and MBA are likely responsible for the favorable orientation of the enzyme.