Recent Developments On Activatable Turn-On Fluorogenic Donors of Hydrogen Sulfide (H₂S)

Hydrogen sulfide (H₂S) is considered the third member of the gasotransmitter family, along with nitric oxide (NO) and carbon monoxide (CO). Besides its role in physiological and pathophysiological conditions, the promising therapeutic potential of this small-molecule makes it advantageous for various pharmaceutical applications. The endogenous production of H₂S at a lower concentration is crucial in maintaining redox balance and cellular homeostasis, and the dysregulation leads to various disease states. In the event of H₂S deficiency, the exogenous donation of H₂S could help maintain the optimal cellular concentration of H₂S and cellular homeostasis. Over the last several years, researchers have developed numerous small-molecule non-fluorogenic organosulfur compounds as H₂S donors and investigated their pharmacological potentials. However, reports on stimuli-responsive turn-on fluorogenic donors of H₂S have appeared recently. Interestingly, the fluorogenic H₂S donors offer additional advantages with the non-invasive real-time monitoring of the H₂S release utilizing the simultaneous turn-on fluorogenic processes. The review summarizes the recent developments in turn-on fluorogenic donors of H₂S and the potential biological applications that have developed over the years.