Construction of a novel cell-trappable fluorescent probe for hydrogen sulfide (H 2 S) and its bio-imaging application.

Fluorescence detection of H ₂ S 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 H ₂ S fluorescent probe Rho630-AM-H ₂ S with red light emission. Its application for H ₂ S fluorescence detection in living HeLa cells and zebrafish was investigated. As expected, Rho630-AM-H ₂ S showed a huge fluorescence turn-on response of about 20-fold at 630 nm and good selectivity toward H ₂ S 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-H ₂ S exhibited remarkably enhanced cell penetration ability, as an enormous fluorescence signal increase was observed at the red channel within 5 min after Rho630-AM-H ₂ S was incubated with HeLa cells. Finally, the probe Rho630-AM-H ₂ S was used to detect H ₂ S in living HeLa cells and zebrafish with great fluorescence enhancement in the red channel. Graphical abstract.