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Hydrogen sulfide (H2S), once regarded solely as a highly toxic gas, is now recognized as a crucial signaling molecule in plants, bacteria, and mammals. In humans, H2S signaling plays a role in numerous physiological and pathological processes, including vasodilation, neuromodulation, and cytoprotection. To exploit its biological functions and therapeutic potential, a wide range of H2S-releasing compounds, known as H2S donors, have been developed. These donors are designed to release H2S under physiological conditions in a controlled manner. Among them, self-reporting H2S donors are seen as a particularly innovative class, combining therapeutic delivery with real-time fluorescence-based detection. This dual functionality enables spatiotemporal monitoring of H2S release in biological environments, eliminating the need for additional sensors or probes that could disrupt cellular homeostasis. This review summarizes recent advancements in self-reporting H2S donor systems, organizing them based on their activation triggers, such as specific bioanalytes, enzymes, or external stimuli like light. The discussion covers their design strategies, performance in biological applications, and therapeutic potential. Key challenges are also highlighted, including the need for precise control of H2S release kinetics, accurate signal quantification, and improved biocompatibility. With continued refinement, self-reporting H2S donors offer great promise for creating multifunctional platforms that seamlessly integrate diagnostic imaging with therapeutic H2S delivery. 

Similar to hydrogen sulfide (H 2 S), its chalcogen congener, Hydrogen selenide (H 2 Se), is an emerging molecule of interest given its endogenous expression and purported biological activity. However, unlike H 2 S, detailed investigations into the chemical biology of H 2 Se are limited and little is known about its innate physiological functions, cellular targets, and therapeutic potential. The obscurity surrounding these fundamental questions is largely due to a lack of small molecule donors that can effectively increase the bioavailability of H 2 Se through their continuous liberation of the transient biomolecule under physiologically relevant conditions. Driven by this unmet demand for H 2 Se-releasing moieties, we report that γ-keto selenides provide a useful platform for H 2 Se donation via an α-deprotonation/β-elimination pathway that is highly dependent on both pH and alpha proton acidity. These attributes afforded a small library of donors with highly variable rates of release (higher alpha proton acidity = faster selenide liberation), which is accelerated under neutral to slightly basic conditions—a feature that is unique and complimentary to previously reported H 2 Se donors. We also demonstrate the impressive anticancer activity of γ-keto selenides in both HeLa and HCT116 cells in culture, which is likely to stimulate additional interest and research into the biological activity and anticancer effects of H 2 Se. Collectively, these results indicate that γ-keto selenides provide a highly versatile and effective framework for H 2 Se donation.