Cascade reaction-based trinal-site probe for sensing and imaging of cysteine and glutathione

Biothiols, such as glutathione (GSH) and cysteine (Cys), play important roles in many physiological processes, and variations in their levels are related to different diseases. Many fluorescence probes have been developed to understand the function of biothiols, but only few of such probes can detect both Cys and GSH. Herein, a new strategy for specific colorimetric and fluorescent detection of Cys and GSH by different cascade reactions was developed. By utilizing this strategy, we designed and synthesized two fluorescent probes, namely, CR1 and CR2, for detection of Cys and GSH under physiological conditions. CR1 contains a stronger electron-withdrawing substituent group and provides high selectivity and sensitivity for Cys and GSH. This probe is based on the mechanism of Cys-induced native-chemical-ligation-cyclization and GSH-induced transthioesterification–cyclization cascade reactions, with detection limits of 0.029 and 0.371 μM, respectively. CR1 can be successfully applied for imaging Cys and GSH in living cells with low cell toxicity.