Immobilization of cytochrome c on polyaniline/polypyrrole/carboxylated multi-walled carbon nanotube/glassy carbon electrode: biosensor fabrication

A modified electrode PAN/PPY/cMWCNTs composed of polyaniline/polypyrrole (PAN/PPY) bilayer conducting polymer film, carboxylated multi-walled carbon nanotubes (cMWCNTs), and glassy carbon electrode (GCE) was fabricated and examined for their potential applicability in the third-generation amperometric biosensor. Cytochrome c (Cyt c) was immobilized on the surface of modified PAN/PPY/cMWCNTs/GCE and its chemical and electrochemical properties were investigated by Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry techniques. The modified Cyt c/PAN/PPY/cMWCNTs/GCE exhibited well-defined redox peaks with the formal potential and peak-to-peak separation -0.338 V and 0.068 V (vs. Ag/AgCl, 3 M KCl), respectively. The surface coverage concentration of Cyt c was estimated to be 8.0 × 10−9 mol cm−2. The application of the prepared Cyt c/PAN/PPY/cMWCNTs/GCE for detection of hydrogen peroxide (H2O2) showed a sensitivity of 101.6 μA mM−1 with a detection limit of 0.1 μM in a linear response range of 1 to 370 μM. According to the obtained results, the proposed PAN/PPY/cMWCNTs nanocomposite could act as a charge promoter to facilitate direct electron transfer between immobilized Cyt c and GCE, offering a high potential for application in third-generation amperometric biosensors.