Rapid and highly-sensitive uric acid sensing based on enzymatic catalysis-induced upconversion inner filter effect

In this work, a novel and simple fluorescence method for detection of uric acid (UA) based on NaYF4:Yb(3+), Tm(3+) upconversion nanoparticles (UCNPs) is developed. The proposed method is based on the fact that uricase can oxidize uric acid to allantoin and hydrogen peroxide, which, on its turn, can oxidize o-phenylenediamine (OPD) to the oxidized OPD (oxOPD). The fluorescence of UCNPs can be significantly quenched by oxOPD through inner filter effects (IFE). Under the optimized conditions, the UA concentration was proportional to the changes in fluorescence intensity of UCNPs. A linear response was obtained over the concentration range from 20 to 850μΜ with the low detection limit of 6.7μΜ for uric acid. More importantly, this method has the potential to detect uric acid in human serum samples, suggesting the nanosensor can be used in a complex biological sample matrix.