Rational Atomic Engineering of Prussian Blue Analogues as Peroxidase Mimetics for Colorimetric Urinalysis of Uric Acid

Nanoparticles of Prussian blue (PB) and its cyanometallate structural analogues are validated as multienzyme mimetics, while there remains a need for improved activities of PB-based nanozymes through rational atomic engineering on the species and amount of doping metal. Herein, we find that the doping of a second divalent 3d metal ion (Co2+, Ni2+, and Cu2+) into the PB framework results in discriminated peroxidase-like activity, by catalyzing the oxidation reaction of 3,3 ',5,5 '-tetramethylbenzidine (TMB) with H2O2. The order of the catalyzed reaction generally follows Cu2+-doped PB (CuPB) > PB > Co2+-doped PB (CoPB) > Ni2+-doped PB (NiPB). Besides the atomic preference over Cu doping, the amount of doped Cu2+ is rationally engineered for the optimization of peroxidase-like activity. By coupling the optimized CuPB nanoparticles with natural uricase, we develop a cascade reaction system for measuring the uric acid level in human urine specimens, the results of which are well correlated with the standard values determined on instrumentation (R2 = 0.975). Due to the simplicity of the platform and capability of preparing CuPB nanozyme in a large scale, we envisage the method to be translated into urinalysis of uric acid, especially packaged as a type of assay kits for point-of-care testing.