A novel fluorescent off-on probe based on 4-methylumbelliferone for highly sensitive determination of tyrosinase

Tyrosinase (TYR), a copper-containing oxidase, has emerged as a predictive biomarker for certain cancers. It is still challenging to develop highly sensitive and selective fluorescent probes for monitoring TYR in biological systems. In this study, we designed a novel fluorescent probe to detect TYR through the nucleophilic substitution reaction of 3-bromomethylphenol with the fluorescent dye 4-methylumbelliferone. Under the catalytic oxidation of TYR, the recognition group of the probe was oxidized to o-benzoquinone, and then a cleavage reaction took place to remove the recognition group and release the fluorophore, so that the fluorescence recovered. The enhancement of the fluorescence intensity was directly related to the activity of TYR. The probe showed high selectivity and sensitivity to TYR with a LOD of 0.2 U mL(-1). The feasibility of this probe in real sample assays and cell imaging was also investigated with satisfactory results, providing a practical strategy for detecting TYR activity in biological systems.