Cell-Trappable BODIPY-NBD Dyad for Imaging of Basal and Stress-Induced H 2 S in Live Biosystems.

H 2 S is a gaseous signaling molecule that is involved in many physiological and pathological processes. In general, the level of intracellular H 2 S (<1 μM) is much lower than that of GSH (∼1-10 mM), leading to the remaining challenge of selective detection and differentiation of endogenous H 2 S in live biosystems. To this end, we quantitatively demonstrate that the thiolysis of NBD amine has much higher selectivity for H 2 S over GSH than that of the reduction of aryl azide. Subsequently, we developed the first NBD-based cell-trappable probe 1 ( AM-BODIPY-NBD ) for highly selective and ultrasensitive imaging of intracellular H 2 S. Probe 1 demonstrates a 207-fold fluorescence enhancement at 520 nm after reaction with H 2 S/esterase to produce a bright BODIPY (quantum yield 0.42) and a detection limit of 15.7 nM. Probe 1 is water-soluble, cell-trappable, and not cytotoxic. Based on this excellent chemical tool, relative levels of basal H 2 S in different cell lines were measured to reveal a positive correlation between endogenous H 2 S and the metastatic potential of colon and breast cancer cells. In addition, H 2 S biogenesis in vivo was also validated by probe 1 both in tobacco leaves under viral infection and in zebrafish after tail amputation. It is anticipated that probe 1 will have widespread applications in imaging and for investigating different H 2 S-related biological processes and diseases.