Evaluation of a resoruf in-based fluorescent probe for tyrosinase detection in skin pigmentation disorders

Purpose Skin pigmentation disorders,such as vitiligo and melasma,are difficult to diagnose in the early stages,but abnor-mal tyrosinase levels and tyrosinase activity are potential indicators.Some resorufin-based fluorescence probes(RBFPs)have been designed to detect tyrosinase in tumors,but they have not been used in skin pigmentation disorders.In this study,one of these RBFPs(synthesized by resorufin salt coupled with 3-(bromomethyl)phenol)was evaluated comprehensively.Methods The RBFP was tested in different kinds of mouse and human skin cells,as well as in in vivo models,including zebrafish,guinea pigs,and Sprague-Dawley rats.In addition,small interfering RNAs(siRNAs),kojic acid,and 1-phenyl-2-thiourea(PTU)were used to inhibit tyrosinase levels or tyrosinase activity.Results This probe successfully detected tyrosinase and emitted red fluorescence in melanoma cells and melanocytes.Fluorescence was also observable in zebrafish and on the skin of guinea pigs when using the RBFP.In mouse and human cells,the RBFP showed good selectivity to tyrosinase.Moreover,in the case of decreased tyrosinase levels or activity caused by siRNAs,kojic acid,or PTU,the probe was sensitive to these changes.Further,the RBFP showed no toxic effects at concentrations of<20μmol/L,both in vitro and in vivo.Conclusions Our findings indicate the value and limitations of the RBFP in tyrosinase detection,but suggest the need for further improvement of fluorescent probes in the diagnosis of skin pigmentation disorders.