Electrochemical Features of Bilirubin Oxidase Immobilized on Different Carbon Nanostructures

Abstract

An electrode interface was prepared using a mixture of a cheap carbon nanomaterial KetjenBlack (KB) and carbon nanotubes (CNT) dispersed in a biopolymer chitosan. Bilirubin oxidase (BOD) was proved to adsorb effectively on such a nanointerface, retaining its catalytic activity for reduction of dioxygen to water, which was proved by cyclic voltammetry. Moreover, three distinct cathodic redox reactions were determined in the absence of oxygen, suggesting that KB/CNT template provides a suitable micro and nanoporosity for direct electron transfer between BOD and the modified electrodes revealing all three known active sites of BOD. Furthermore, BOD was adsorbed on graphene oxide with subsequent electrochemical reduction of graphene oxide into a conductive graphene film with BOD trapped within the matrix. Two active sites of BOD were observed on the electrode modified by graphene suggesting the enzyme is oriented in a different way compared to the KB/CNT nanointerface due to changes in the nature of functional groups within the nanocomposite, changed porosity of the nanointerface or as a result of electrochemical perturbation of the matrix during reduction of graphene oxide. A more detailed fundamental investigation of the influence of the nanointerface matrix on an adsorption and orientation of BOD will without any doubt allow us to tailor ability of such composites to reduce dioxygen to water with high efficiency, what is a feature important for construction of robust and effective biocathodes of enzymatic biofuel cells.