Construction of ratiometric hydrogen sulfide probe with two reaction sites and its applications in solution and in live cells

Hydrogen sulfide (H 2 S), as the third multifunctional signaling biomolecule, it acts as a neuromodulator in the human brain and is recognized as an important gas transmitter in human physiology. The abnormal concentrations of H 2 S in human cells can result in several common diseases. Therefore, accurate, fast, and reliable methodologies are required for measuring the in vitro and in vivo concentrations of H 2 S to further investigate its function. In this study, a novel DR–SO 2 N 3 fluorescent probe containing the fluorophore Disperse Red 277 and a sulfonyl azide group was developed and exploited based on the structural characteristic of Disperse Red 277 that contains the active site easily can be attacked by HS − . Therefore, this probe featured two reaction sites that involved the reduction and Michael addition of H 2 S and exhibited rapid ratiometric fluorescence changes and high selectivity towards H 2 S with a 619-fold enhancement factor. Further, the density functional theory (DFT)/time-dependent density functional theory (TDDFT) studies are conducted to understand the photophysical properties of DR–SO 2 N 3 and the final product DRHS–SO 2 NH 2 , which makes the proposed mechanism more reasonable. Furthermore, the probe was successfully applied for the ratiometric fluorescence imaging of exogenous H 2 S in living cells.