Peroxidase-like activity of chitosan stabilized silver nanoparticles for visual and colorimetric detection of glucose

Chitosan stabilized silver nanoparticles (Ch-Ag NPs) were successfully synthesized by a one-step method and were found to possess intrinsic peroxidase-like activity, could catalytically oxidize substrates, such as TMB, and OPD, by H2O2 to produce a typical colour reaction such as from colorless to blue for TMB and from colorless to red for OPD. Our results demonstrate that the Ch-Ag NPs exhibit higher thermal and pH durance than HRP, thus could be suitable in a wider range of harsh conditions. Results of electron paramagnetic resonance (ESR) suggest that the catalyse-mimic activity of the Ch-Ag nanostructures effectively catalyzed the decomposition of H2O2 into OH radicals. Based on this finding, a simple, sensitive and selective visual and colorimetric method with TMB as substrate has been designed for glucose detection when combined with glucose oxidase (GOx). This colorimetric method can be used for detection of glucose in biological samples with a detection limit as low as 100 nM and a dynamic range from 5.0 x 10(-6) to 2.0 x 10(-4) M.