Improved enzymatic assay for hydrogen peroxide and glucose by exploiting the enzyme-mimicking properties of BSA-coated platinum nanoparticles

Platinum nanoparticles (Pt NPs) covered with a bovine serum albumin scaffold and a particle size of 1.5 nm (BSA-Pt-S NPs) are shown to display enhanced multiple enzyme-mimicking activities including peroxidase, oxidase, and catalase-like activities. The peroxidase-like activity is characterized by robustness and low signal background. BSA-Pt-S NPs were used to design colorimetric assays for H2O2 and glucose. H2O2 latter reacts with 3,3 ',5,5 '-tetramethylbenzidine in the presence of BSA-Pt-S NPs to form a blue product with an absorption maximum at 652 nm. The assay works in the 5-250 mu M H2O2 concentration range. The glucose assay is based on its glucose oxidase-catalyzed oxidation to produce gluconic acid and H2O2 which then is colorimetrically quantified. Response is linear in the 10-120 mu M glucose concentration range, and the detection limit is 2 mu M (at S/N = 3). The method correlates well with the glucose standard method (R-2 = 0.997 in the 95% confidence interval) which confirms that glucose in human serum has been successfully detected.