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

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 H₂O₂ (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 H₂O₂, 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 H₂O₂ which etches the silver shell. This results in the release of GQDs and increased fluorescence, allowing quantitative analysis of UA.