Construction of a novel cell-trappable fluorescent probe for hydrogen sulfide (H2S) and its bio-imaging application.

Fluorescence detection of H2S in living organisms is greatly advantageous because it is nondestructive and can be used for in situ analysis. We have constructed a novel rhodamine analogue dye (Rho630) by extending the conjugated system of rhodamine to create a novel cell-trappable H2S fluorescent probe Rho630-AM-H2S with red light emission. Its application for H2S fluorescence detection in living HeLa cells and zebrafish was investigated. As expected, Rho630-AM-H2S showed a huge fluorescence turn-on response of about 20-fold at 630 nm and good selectivity toward H2S in solution. An MTT assay demonstrated that the probe showed negligible cytotoxicity in the concentrations typically used in fluorescence imaging experiments. Cell imaging experiments revealed that compared with compound 4 without cell-trappable unit modification, Rho630-AM-H2S exhibited remarkably enhanced cell penetration ability, as an enormous fluorescence signal increase was observed at the red channel within 5 min after Rho630-AM-H2S was incubated with HeLa cells. Finally, the probe Rho630-AM-H2S was used to detect H2S in living HeLa cells and zebrafish with great fluorescence enhancement in the red channel. Graphical abstract.