A new coumarin-based "OFF-ON" fluorescent sensor for H₂S detection in HeLa cells

A new "OFF-ON" coumarin-based fluorescent probe for H₂S detection was designed and successfully developed through O-sulfonylation between a dabsyl quencher and 7-hydroxy-4-methylcoumarin as a fluorescent reporter, based on a FRET approach. This H₂S responsive probe, utilizing H₂S assisted thiolysis of a sulfonate ester as the sensing strategy, demonstrated excellent performance towards H₂S with a limit of detection (LoD) of 1.64 µM, along with superb selectivity, good stability and high specificity towards H₂S without interference from other biomarkers and analytes. Moreover, dabsyl-7-hydroxy-4-methylcoumarin (dabsylcoumarin) is capable of permeating the cell membrane and effectively visualizing the level of H₂S in the living HeLa cells without cytotoxicity.