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

Hydrogen sulfide (H2S), 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 H2S 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 H2S to further investigate its function. In this study, a novel DR-SO2N3 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 H2S and exhibited rapid ratiometric fluorescence changes and high selectivity towards H2S 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-SO2N3 and the final product DRHS-SO2NH2, which makes the proposed mechanism more reasonable. Furthermore, the probe was successfully applied for the ratiometric fluorescence imaging of exogenous H2S in living cells.