Direct electron transfer and electrocatalysis of microperoxidase immobilized on nanohybrid film

The nanohybrid film (NHF) consisted of multi-wall carbon nanotubes (MWTNs) with attached gold nanoparticles was used to immobilize protein. The NHF provides a favorable microenvironment for microperoxidase (MP-11) to perform direct electron transfer (DET) at glassy carbon electrode. The NHF and MP-11 attached covalently were confirmed by transmission electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. MP-11 immobilized on NHF surface exhibits a surface-controlled quasi-reversible cyclic voltammetric behavior. The electrochemical parameters such as apparent heterogeneous electron rate constant (k), formal potential (E0′) and the influence of pH on E0′ in the process were estimated by cyclic voltammetry. The MP-11 immobilized on the NHF retains its bioelectrocatalytic activity to the reduction of H2O2. The apparent Michaelis-Menten constant (Km) and stability of the H2O2 response were investigated. Moreover, it can catalyze O2 through four-electron to water in pH 7.0 buffer solution. The kinetic constants for O2 reduction (ks, αnα) were obtained. The NHF to immobilize protein with DET shows potential applicability of nanofabrication of biosensors and biofuel cells.