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 (E0′) 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 μA mM−1 cm−2 and the calculated apparent Michaelis–Menten constant (Kmapp) 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 × 10−6 to 5.1 × 10−4 M with a correlation coefficient 0.999. The detection limit is 9.0 × 10−7 M (at the ratio of signal to noise, S/N = 3). Moreover, the modified electrode displays rapid response (5 s) to H2O2, and possesses good stability and reproducibility.