Electrochemistry and biosensing activity of cytochrome c immobilized on a mesoporous interface assembled from carbon nanospheres

We report on an amperometric biosensor for hydrogen peroxide. It is obtained via layer-by-layer assembly of ordered mesoporous carbon nanospheres and poly(diallyldimethylammonium) on the surface of an indium tin oxide (ITO) glass electrode and subsequent adsorption of cytochrome c. UV–vis absorption spectroscopy was applied to characterize the process of forming the assembled layers. Cyclic voltammetry revealed a direct and quasi-reversible electron transfer between cytochrome c and the surface of the modified ITO electrode. The surface-controlled electron transfer has an apparent heterogeneous electron-transfer rate constant (k _s ) of 5.9?±?0.2?s^?1 in case of the 5-layer electrode. The biosensor displays good electrocatalytic response to the reduction of H₂O₂, and the amperometric signal increase steadily with the concentration of H₂O₂ in the range from 5?μM to 1.5?mM. The detection limit is 1?μM at pH 7.4. The apparent Michaelis-Menten constant (K _m ) of the sensor is 0.53?mM. We assume that the observation of a direct electron transfer of cytochrome c on mesoporous carbon nanospheres may form the basis for a feasible approach for durable and reliable detection of H₂O₂.