Selective fluorescent probes for live-cell monitoring of sulphide

Aqueous sulphides, including hydrogen sulphide, have important roles in biological signalling and metabolic processes. Here we develop a selective sulphide-trapping strategy involving sulphide addition to an aldehyde; the resulting hemithioacetal undergoes a Michael addition with an adjacent unsaturated acrylate ester to form a thioacetal at neutral pH in aqueous solution. Employing this new strategy, two sulphide-selective fluorescent probes, SFP-1 and SFP-2, were synthesized on the basis of two different fluorophore templates. These probes exhibit an excellent fluorescence increase and an emission maximum shift (SFP-1) in response to Na2S and H2S in a high thiol background as found under physiological conditions. We show the utility of the probes for the selective detection of sulphides, and the capacity of our probes to monitor enzymatic H2S biogenesis and image free sulphide in living cells.