Visual and colorimetric detection of uric acid in human serum and urine using chitosan stabilized gold nanoparticles

In this paper, the chitosan stabilized gold nanoparticles was developed as a catalyzed 3,3′,5,5′-tetramethylbenzidine - H2O2 system for visual and colorimetric detection of uric acid. In theory, uric acid can be catalyzed by uricase to produce H2O2, and the chitosan stabilized gold nanoparticles were successfully synthesized by chemical reduction and showed an intrinsic peroxidase-like activity. The chitosan stabilized gold nanoparticles could effectively catalyze decomposition of H2O2 to generate OH radicals. The peroxidase substrate 3,3′,5,5′-tetramethylbenzidine is oxidized in the presence of OH radicals, resulting in a visible color change (from colorless to blue). This convenient, novel and sensitive method could be used for detection of uric acid based on the chitosan stabilized gold nanoparticles, with a linear range from 0.1 to 30 μM, and a limit of detection (S/N ratio of 3) as low as 0.04 μM. Furthermore, the detection method has been successfully applied to human serum and urine samples by visual observation. The recoveries of uric acid in human serum and urine were in the range of 96.1–103.1% and 95.2–97.7%, respectively. These results revealed that the visual colorimetric method may provide an alternative to clinical medicine and daily monitoring.