Uricase based fluorometric determination of uric acid based on the use of graphene quantum dot@silver core-shell nanocomposites.

The authors describe a fluorescent "turn-on" assay for detection of uric acid (UA) based on the use of graphene quantum dots coated with a shell of silver (GQD@Ag). The fluorescence of the GQDs is quenched by the silver shell. However, if the silver shell was removed via etching with H2 O2 (which is produced by uricase catalyzed oxidation of UA), the fluorescence of the GQDs is restored. The resulting increase in fluorescence at 466 nm depends directly on the concentration of H2 O2 , which, in turn, depends on the concentration of UA. The method allows UA to be quantitated with a 2 μM detection limit. It was applied to the analysis of human urine samples and exhibited satisfactory results. The method is cost-effective, sensitive and selective for UA. In our perception, it provides a useful tool in clinical analysis and may be extended to other assays based on the use of oxidases. Graphical abstract Schematic of the reduction of Ag(I) and the growth of a silver shell on the surface of graphene quantum dots (GQDs) to form a GQD@Ag nanocomposite whose fluorescence is quenched. Uricase catalyzes the oxidation of uric acid (UA) to produce allantoin and H2 O2 which etches the silver shell. This results in the release of GQDs and increased fluorescence, allowing quantitative analysis of UA.