Direct electrochemistry and electrocatalysis of cytochrome c immobilized on gold nanoparticles-chitosan-carbon nanotubes-modified electrode.

A robust and effective nanohybrid film based on gold nanoparticles (GNPs)/chitosan (Chit)/multi-walled carbon nanotubes (MWNTs) was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the nanohybrid film modified glassy carbon (GC) electrode by cyclic voltammetry. The direct electron transfer between Cyt c and the modified electrode was investigated in detail. Cyt c shows a couple of quasi-reversible and well-defined cyclic voltammetry peaks with a formal potential (E(0')) of -0.16 V (versus Ag/AgCl) in pH 7.0 phosphate buffer solution (PBS). The Cyt c/GNPs/Chit/MWNTs modified GC electrode gives an improved electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2). The sensitivity is 92.21 microA mM(-1) cm(-2) and the calculated apparent Michaelis-Menten constant (K(m)(app)) is 0.791 mM, indicating a high-catalytic activity of Cyt c. The catalysis currents increase linearly to the H2O2 concentration in a wide range of 1.5 x 10(-6) to 5.1 x 10(-4)M with a correlation coefficient 0.999. The detection limit is 9.0 x 10(-7)M (at the ratio of signal to noise, S/N=3). Moreover, the modified electrode displays rapid response (5s) to H2O2, and possesses good stability and reproducibility.