Sensitive colorimetric detection of glutathione in human serum based on peroxidase-like activity of chitosan-stabilized gold nanoparticles.

A colorimetric sensor for the rapid and sensitive detection of GSH was developed. The hydrothermal method was utilized to synthesize chitosan-stabilized gold nanoparticles (CS-AuNPs). The synthesized CS-AuNPs were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffractograms (XRD), and Fourier transform infrared spectroscopy (FTIR). The CS-AuNPs are well-dispersed and possess a spherical shape with an average particle size of 10.05 ± 2.26 nm in aqueous solution. They show an intrinsic peroxidase-like activity, which could efficiently catalyze the decomposition of HO to produce •OH radicals. These radicals then oxidized 3, 3´, 5, 5´-tetramethylbenzidine (TMB), resulting in the formation of the blue oxidized product oxTMB, observed a visible color change (from colorless to blue), and oxTMB had an obvious absorption peak at 652 nm. The presence of GSH could inhibit the peroxidase-like activity of CS-AuNPs, thereby reducing the formation of oxTMB. The solution's blue hue underwent a reduction in absorption intensity. Based on this fact, a novel and sensitive colorimetric sensor for detection of GSH was constructed. Under optimal conditions, the results of detection had an excellent linear relationship between the concentration of GSH and ∆A within the range 0.5 ~ 50.0 × 10 mol/L. The limit of detection (LOD) for GSH was 2.10 × 10 mol/L, which was much lower than those in most previous works. Furthermore, for detection in real human serum samples, the recoveries of GSH and the relative standard deviations (RSD) in the serum were in the range 98.40 ~ 103.32% and 1.85 ~ 3.54%, respectively. Thus, this visual colorimetric method has good precision and can be used for GSH detection in practical applications, promising in the fields of bioanalysis and illness diagnostics.