Carbonothioate-Triggered Cascade Cyclization Enables High-Specificity Fluorescence Imaging of Hydrogen Polysulfides

Hydrogen polysulfides (H₂S_n; n > 1) are critical redox signaling molecules. While the biological functions of H₂S_n have received much attention, their exact action mechanisms are still poorly understood due to the lack of reliable detection methods. In this context, fluorescent probes for H₂S_n are emerging as powerful chemical tools to aid in unraveling its contributions to biology. Currently, most available H₂S_n probes are prone to interference from biothiols or hydrogen sulfide (H₂S). To address this challenge, herein, we report a unique carbonothioate-based trigger utilizing a cascade cyclization reaction for specific detection of H₂S_n. Using this strategy, eight new fluorescent probes (CTP 1-8) were prepared and evaluated. Among them, CTP-8 not only enables highly sensitive and selective detection of H₂S_n but also allows visualization of H₂S_n fluctuations in living cells and mice. Significantly, we demonstrate for the first time the fluorescence imaging of endogenous H₂S_n dynamics in insulin-resistant cells and type 2 diabetes mellitus (T2DM) mice. Besides, this carbonothioate-based trigger could also be potentially utilized in other fluorescent dye scaffolds that possess an optically tunable phenolic hydroxyl group. This work provides a useful approach for further investigations of H₂S_n biology as well as future probe development.