BSA-stabilized Au clusters as peroxidase mimetics for use in xanthine detection

In this paper, we demonstrated that bovine serum albumin (BSA) stabilized Au clusters exhibited highly intrinsic peroxidase-like activity. Unlike nature enzymes, the BSA-Au clusters have strong robustness and can be used over a wide range of pH and temperature. Because of ultra-small size, good stability and high biocompatibility in water solution compare with other kinds of nanoparticles as peroxidase mimetics, such as Fe3O4, FeS or graphene oxide, it is more competent for bioanalysis. Furthermore, we make use of the novel properties of BSA-Au clusters as peroxidase mimetics to detect H2O2. The as-prepared BSA-Au clusters were used to catalyze the oxidation of a peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to the oxidized colored product, and which provides a colorimetric detection of H2O2. As low as 2.0 × 10−8 M H2O2 could be detected with a linear range from 5.0 × 10−7 to 2.0 × 10−5 M via this method. More importantly, a sensitive and selective method for xanthine detection was developed using xanthine oxidase (XOD) and the as-prepared BSA-Au clusters. The detection limit of this assay for xanthine was 5 × 10−7 M and the proposed method was successfully applied for the determination of xanthine in urine and human serum sample.