Fluorogenic hydrogen sulfide (H₂S) donors based on sulfenyl thiocarbonates enable H₂S tracking and quantification

Hydrogen sulfide (H₂S) is an important cellular signaling molecule that exhibits promising protective effects. Although a number of triggerable H₂S donors have been developed, spatiotemporal feedback from H₂S release in biological systems remains a key challenge in H₂S donor development. Herein we report the synthesis, evaluation, and application of caged sulfenyl thiocarbonates as new fluorescent H₂S donors. These molecules rely on thiol cleavage of sulfenyl thiocarbonates to release carbonyl sulfide (COS), which is quickly converted to H₂S by carbonic anhydrase (CA). This approach is a new strategy in H₂S release and does not release electrophilic byproducts common from COS-based H₂S releasing motifs. Importantly, the release of COS/H₂S is accompanied by the release of a fluorescent reporter, which enables the real-time tracking of H₂S by fluorescence spectroscopy or microscopy. Dependent on the choice of fluorophore, either one or two equivalents of H₂S can be released, thus allowing for the dynamic range of the fluorescent donors to be tuned. We demonstrate that the fluorescence response correlates directly with quantified H₂S release and also demonstrate the live-cell compatibility of these donors. Furthermore, these fluorescent donors exhibit anti-inflammatory effects in RAW 264.7 cells, indicating their potential application as new H₂S-releasing therapeutics. Taken together, sulfenyl thiocarbonates provide a new platform for H₂S donation and readily enable fluorescent tracking of H₂S delivery in complex environments.