A self-correcting fluorescent assay of tyrosinase based on Fe-MIL-88B-NH₂ nanozyme

A self-correcting fluorescent assay of tyrosinase (TYR) was developed by utilization of Fe-MIL-88B-NH₂ as a peroxidase-like nanozyme and a capture probe. Fe-MIL-88B-NH₂ nanozyme was selected as an electron donor, and the oxidization product (dopamine-o-quinone) acts as an energy acceptor. First, TYR catalyzes the oxidation of tyramine hydrochloride to dopamine and then to dopamine-o-quinone. Second, Fe-MIL-88B-NH₂ with intrinsic peroxidase-like activity decomposes H₂O₂ to produce ·OH radicals, which further accelerate the oxidation of dopamine to dopamine-o-quinone. Excessive H₂O₂ and ·OH radicals reduce the interferences from ascorbic acid at the same time providing a self-correcting ability. Dopamine-o-quinone reacts with -NH₂ groups on the ligand of Fe-MIL-88B-NH₂ through Michael reaction which results in fluorescence quenching. Under 365-nm excitation, the fluorescence emission intensity at 452 nm gradually decreased with increasing TYR concentration varying from 0 to 10 U mL^-1. The linear range is from 1 to 5 U mL^-1 and the detection limit is 0.05679 U mL^-1. This self-correcting fluorescent assay of tyrosinase exhibits good sensitivity and selectivity which is also successfully applied for tyrosinase inhibitor detection. Schematic representation of fluorescent assay for tyrosinase determination based on Fe-MIL-88B-NH₂ nanozyme. A self-correcting fluorescent assay for tyrosinase was developed based on the Fe-MIL-88B-NH₂ nanozyme.