A reagentless nitric oxide biosensor based on the direct electrochemistry of hemoglobin adsorbed on the gold colloids modified carbon paste electrode

A novel hemoglobin (Hb) electrode has been presented through adsorbed Hb onto a gold colloids modified carbon paste electrode. Ultraviolet–visible (UV–vis) spectra suggested that the conformation of Hb in the resulting films retained its native structure. Cyclic voltammetry displayed that the adsorbed Hb showed a pair of well-defined redox peaks at about −0.351 V versus SCE in pH 7.0 buffer solutions. Gold colloids can enhance the electron transfer of Hb efficiently on the modified electrode, which was testified by electrochemical impedance spectroscopy (EIS). Hb on that modified electrode was proved to exhibit good electrocatalytic activity for the reduction of nitric oxide (NO). Based on this, a sensitive amperometric nitric oxide biosensor which showed a good response to the reduction of NO without any mediator was developed. Under optimum conditions, the biosensor responded linearly to NO in the concentration range from 9.0 × 10−7 to 3.0 × 10−4 M with a detection limit of 1.0 × 10−7 M at 3σ. The response showed Michaelis–Menten behavior at higher NO concentrations and the apparent Michaelis–Menten constant is estimated to be 105.8 μM, showing an good affinity for NO. Moreover, this studied biosensor showed high sensitivity and selectivity, good reproducibility, and long-term stability.