A nitrite biosensor based on the immobilization of Cytochrome c on multi-walled carbon nanotubes–PAMAM–chitosan nanocomposite modified glass carbon electrode

A novel nitrite biosensor was successfully prepared via immobilizing Cytochrome c (Cyt c) onto the multi-walled carbon nanotubes–poly(amidoamine) (PAMAM)–chitosan (MWNT–PAMAM–Chit) nanocomposite modified glass carbon electrode (GCE). Ultraviolet and visible (UV–vis) absorption spectrum, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to examine the native conformation and bioactivity of the immobilized Cyt c, and the electrochemical properties of the modified electrodes, respectively. The results indicate that the immobilized Cyt c retained its native characters, and the MWNT–PAMAM–Chit nanocomposite is a good platform for the immobilization of Cyt c as well as an excellent promoter for the electron transfer between Cyt c and electrode. The high reactive Cyt c π-cation, which can oxidize NO2− into NO3− in the solution, is generated at higher potential (>0.7 V) based on the further oxidation of Cyt c. The nitrite biosensor showed a fast response to nitrite (about 5 s) in two concentration intervals, one was from 0.1 to 29 μM, and the other from 29 to 254 μM. The low detection limit of 0.01 μM was obtained.