An electrochemical nitric oxide biosensor based on immobilized cytochrome c on a chitosan-gold nanocomposite modified gold electrode.

Goldnanoparticle (AuNPs), chitosan (CS), cytochrome c (Cyt c) and Nafion were immobilized on the surface of a gold electrode to form a Nafion/Cyt c/CS-3-Mercaptopropionic acid (MPA)-AuNPs/cysteamine-MPA (SAMs)-Au electrode. The CS-MPA-AuNPs nanocomposite was characterized by UV-vis spectroscopy. Electrochemical behavior of modified electrode was analyzed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry. Uv-vis results showed that CS-MPA-AuNPs nanocomposite could improve electron transfer between Cyt c and electrode surface and keep the catalytic activity of Cyt c. A pair of well defined and reversible redox peaks could be observed for the modified electrode in a 0.1M phosphate buffer solution (PBS, pH 7.0). The anodic and cathodic peak potentials of Cyt c/CS-MPA-AuNPs/SAMs-Au electrode were at 0.006V and -0.043V (vs. Ag/AgCl), respectively. Particular electrocatalytic activity was shown by Cyt c on CS-MPA-AuNPs layer for nitric oxide (NO) reduction. The relationship between peak current and NO concentration was linear in the range of 1×10-7-21.5×10-7M with a detection limit of 0.45×10-7M (S/N=3).The sensitivity was 0.199μA/μM. The obtained results indicating that the newly developed biosensor was quite selective and stable which was used for accurate and exact detection of NO.