Direct electrochemistry and electrocatalysis of cytochrome c based on chitosan–room temperature ionic liquid-carbon nanotubes composite

A robust and effective composite film combined the benefits of room temperature ionic liquid (RTIL), chitosan (Chi) and multi-wall carbon nanotubes (MWNTs) was prepared. Cytochrome c (Cyt c) was successfully immobilized on glassy carbon electrode (GCE) surface by entrapping in the composite film. Direct electrochemistry and electrocatalysis of immobilized Cyt c were investigated in detail. A pair of well-defined and quasi-reversible redox peaks of Cyt c was obtained in 0.1 mol L−1 pH 7.0 phosphate buffer solution (PBS), indicating the Chi–RTIL–MWNTs film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of H2O2. The catalysis current was linear to H2O2 concentration in the range of 2.0 × 10−6 to 2.6 × 10−4 mol L−1, with a detection limit of 8.0 × 10−7 mol L−1 (S/N = 3). The apparent Michaelis–Menten constant (Km) was calculated to be 0.45 ± 0.02 mmol L−1. Moreover, the modified electrode displayed a rapid response (5 s) to H2O2, and possessed good stability and reproducibility. Based on the composite film, a third-generation reagentless biosensor could be constructed for the determination of H2O2.