Gold nanoclusters as switch-off fluorescent probe for detection of uric acid based on the inner filter effect of hydrogen peroxide-mediated enlargement of gold nanoparticles

Herein we report a novel switch-off fluorescent probe for highly selective determination of uric acid (UA) based on the inner filter effect (IFE), by using poly-(vinylpyrrolidone)-protected gold nanoparticles (PVP-AuNPs) and chondroitin sulfate-stabilized gold nanoclusters (CS-AuNCs) as the IFE absorber/fluorophore pair. In this IFE-based fluorometric assay, the newly designed CS-AuNCs were explored as an original fluorophore and the hydrogen peroxide (H(2)0(2)) -driven formed PVP-AuNPs can be a powerful absorber to influence the excitation of the fluorophore, due to the complementary overlap between the absorption band of PVP-AuNPs and the emission band of CS-AuNCs. Under the optimized conditions, the extent of the signal quenching depends linearly on the H(2)0(2) concentration in the range of 1-100 mu M (R-2 =0.995) with a detection limit down to 0.3 mu M. Based on the H(2)0(2)-dependent fluorescence IFE principle, we further developed a new assay strategy to enable selective sensing of UA by using a specific uricase-catalyzed UA oxidation as the in situ H(2)0(2) generator. The proposed uricase-linked IFE-based assay exhibited excellent analytical performance for measuring UA over the concentration ranging from 5 to 100 mu M (R-2=0.991), and can be successfully applied to detection of UA as low as 1.7 mu M (3 sigma) in diluted human serum samples.