A BODIPY-based turn-on fluorescent probe for the selective detection of hydrogen sulfide in solution and in cells

A new turn-on fluorescent probe, incorporating 7-nitrobenzoxadiazole (NBD) ether group into a BODIPY molecule, was synthesized and studied for the detection of H2S and biothiols in aqueous solution and in living cells. The design was based on thiol-induced thiolysis of the NBD ether bond and followed by the cleavage and the release of free meso-(4-hydroxybenzyl)-substituted BODIPY fluorophore. The BODIPY-based probe displayed highly sensitive and selective fluorescence enhancement respond to H2S over competing biothiols such as cysteine (Cys) and glutathione (GSH), mainly due to the weak reactivity of biothiols toward the probe. There was a good linearity between the fluorescence intensity and the concentrations of H2S in the range of 1-200 µM with a detection limit of 2.6 µM. The proposed reaction mechanism was confirmed by mass spectrometry and optical spectroscopy, and the mechanism of turn-on fluorescent response was further determinated by the density functional theory (DFT) calculations using Gaussian 03 program. Moreover, the probe was successfully applied for the fluorescence imaging of H2S in HeLa cells under physiological conditions (pH 7.4).