Developing an ESIPT-based ratiometric fluorescent probe with fast-response for cellular imaging of hydrogen sulfide

Hydrogen sulfide (H2S) plays a crucial role in various physiological processes and is implicated in the pathogenesis of several diseases. The fluorescent probe (E)-2-(3-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylstyryl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (BTCMN) has been designed to image H2S in living cells using the excited-state intramolecular proton transfer (ESIPT) mechanism. This probe is developed by coupling 2-(2′-hydroxyphenyl) benzothiazole (HBT) with dicyanoisophorone through a H2S-responsive CC bond. Upon interaction with H2S, BTCMN exhibits a remarkable fluorescent change from red to green. BTCMN, which has shown exceptional performance in detecting hydrogen sulfide (H2S) with super-fast response times, large Stokes shifts (252 nm), specific selection towards H2S, and low detection limits. Importantly, BTCMN has been successfully used for visualizing endogenous and exogenous H2S in HepG2 cells with low cytotoxicity. These features collectively contribute to its effectiveness as a fluorescent probe for detecting H2S in living cells.