A Fast-Response Red Shifted Fluorescent Probe for Detection of H₂S in Living Cells

Near-infrared (NIR) fluorescent probes are attractive tools for bioimaging applications because of their low auto-fluorescence interference, minimal damage to living samples, and deep tissue penetration. H₂S is a gaseous signaling molecule that is involved in redox homeostasis and numerous biological processes in vivo. To this end, we have developed a new red shifted fluorescent probe 1 to detect physiological H₂S in live cells. The probe 1 is based on a rhodamine derivative as the red shifted fluorophore and the thiolysis of 7-nitro 1,2,3-benzoxadiazole (NBD) amine as the H₂S receptor. The probe 1 displays fast fluorescent enhancement at 660 nm (about 10-fold turn-ons, k₂ = 29.8 M^-1s^-1) after reacting with H₂S in buffer (pH 7.4), and the fluorescence quantum yield of the activated red shifted product can reach 0.29. The probe 1 also exhibits high selectivity and sensitivity towards H₂S. Moreover, 1 is cell-membrane-permeable and mitochondria-targeting, and can be used for imaging of endogenous H₂S in living cells. We believe that this red shifted fluorescent probe can be a useful tool for studies of H₂S biology.