A novel electrochemical hydrogen peroxide biosensor based on hemoglobin capped gold nanoclusters–chitosan composite

Abstract

A biocompatible nanocomposite containing hemoglobin capped gold nanocluster (Hb-AuNCs) and chitosan was prepared and applied to the modification of a glassy carbon electrode (GCE) for the preparation of a highly sensitive hydrogen peroxide biosensor. The electrochemical behavior of Hb-AuNCs in the composite film was studied in phosphate buffer solution of pH 7.4 and a pair of quasi-reversible redox peak attributed to the electrode reaction of Hb's Fe(III)/Fe(II) redox couple was observed. The FTIR and UV-vis spectroscopy indicated that Hb entrapped in the composite film possesses substantial changes in its secondary structure so that it provided a high peroxidase-like enzyme activity attributing to the excellent electrical conductivity of the encapsulated gold nanoclusters. The AuNCs found to play a critical role as conductive holder and accumulator of redox active centers at the surface of GCEs. The fabricated biosensor showed fast response, acceptable stability, excellent sensitivity, and high electrocatalytic activity toward the reduction of hydrogen peroxide. The oxidation peak current was found to be linearly proportional to H₂O₂ concentration in the range of 55–700 nM with a limit of detection of 16.5 nM (at S/N = 3).