Ratiometric target-triggered fluorescent silicon nanoparticles probe for quantitative visualization of tyrosinase activity.

Tyrosinase is the key enzyme in the treatment of vitiligo. Development of rapid, simple, and visual methods for screening bioactive compounds with tyrosinase activity from natural compounds is interesting for new drug discovery. Herein, a novel visual ratiometric fluorescent assay for screening tyrosinase activators and/or inhibitors based on silicon nanoparticles (Si NPs) was explored. Inspired by the changes in both of the solution color and the fluorescence emission due to the sensing between Si NPs and dopamine (DA), we employed tyramine as the model substrate, which can transfer into DA by tyrosinase. It was found that the tyrosinase-incubated tyramine solution exhibited pale yellow under nature light or yellow fluorescence under UV light in the presence of Si NPs, where the color/fluorescence intensity were directly related to the concentration of tyrosinase. The established method showed good detection selectivity, and the LOD for tyrosinase was 0.14 U mL-1. Eventually, this assay was successfully applied to screen tyrosinase activators or inhibitors from a natural product-like library, and a tyrosinase activator with EC50 of 2.62 μM, more potent than the commonly used tyrosinase activator 8-MOP, was discovered.