A thiol-activated near-infrared fluorescent H2S donor for visualizing H2S release and its applications.

Hydrogen sulfide (H2S), a critical endogenous signaling molecule, is involved in diverse physiological processes, and H2S donors have emerged as promising therapeutic agents. While organic donors address the uncontrolled release limitations of inorganic counterparts, most thiol-activated systems depend exclusively on cysteine (Cys), risking cellular thiol imbalance. To overcome this limitation, we developed AD-SH, a novel benzopyran salts-based NIR fluorescent H2S donor responsive to multiple biothiols. AD-SH exhibits high selectivity and sensitivity toward all intracellular biothiols (e.g., cysteine, glutathione, and homocysteine) without preferentially depleting a single Cys. Importantly, its near-infrared (NIR) fluorescence enables real-time tracking and visualization of H2S release. With excellent biocompatibility, photostability, and in vivo imaging performance in mice, AD-SH demonstrates its strong potential for live-cell imaging and dynamic H2S release tracking.