Rational development of an ESIPT-based fluorescent probe with large Stokes shift for imaging of hydrogen sulfide in live cells

It is crucial to monitor hydrogen sulfide (H2S) because H2S plays a vital role in the regulation of many physiology and pathology processes. Many evidences indicate that endogenous H2S is closely associated with many diseases such as inflammation and cancers. Herein, we reported a novel fluorescent probe BTDI to monitor the fluctuation of H2S based on the excited-state intramolecular proton transfer (ESIPT) mechanism both ex vivo and in vivo. The selectivity of BTDI for H2S is significantly higher than that for biothiols and other potential anions. After the probe responded to H2S, the nucleophilic addition reaction of the H2S with probe BTDI resulted the shifting of maximum emission peak from 630 nm to 542 nm and the fluorescent signals change from red to green emission along with a large Stokes shift (240 nm). Moreover, BTDI can be successfully applied to detect extracellular and endogenous H2S in living cells through fluorescent cell-imaging, which provides a promising tool for the specific recognition of H2S in complex biological systems.