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 (ks) 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 (Km) 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. (author)