Integrated oligoaniline-cross-linked composites of Au nanoparticles/ glucose oxidase electrodes: A generic paradigm for electrically contacted enzyme systems

Electropolymerizable glucose oxidase (GOx) was synthesized by the tethering of thioaniline units to the protein. The electropolymerization of the thioaniline-modified GOx in the presence of thioaniline-functionalized Au nanoparticles (NPs) yielded a three-dimensional bis-aniline-cross-linked Au NPs/GOx network. The bis-aniline bridging units are redox active and mediate the electron transfer between the enzyme redox sites and the electrode, and the Au NPs provide the three-dimensional conductivity for transporting the electrons to the electrode. The covalently linked GOx displays an effective electrical contact with the electrode (turnover rate of ca. 500 s^-1, which results in a sensitive and selective glucose-sensing electrode. The preparation of the electrode by means of electropolymerization, and the bioelectrocatalytic features of the electrode, suggest its feasibility as a miniaturized electrode with a sensing matrix and as an implantable glucose sensor in future applications.