Hydrolysis-Based Small-Molecule Hydrogen Selenide (H₂Se) Donors for Intracellular H₂Se Delivery

Hydrogen selenide (H₂Se) is a central metabolite in the biological processing of selenium for incorporation into selenoproteins, which play crucial antioxidant roles in biological systems. Despite being integral to proper physiological function, this reactive selenium species (RSeS) has received limited attention. We recently reported an early example of a H₂Se donor (TDN1042) that exhibited slow, sustained release through hydrolysis. Here we expand that technology based on the P═Se motif to develop cyclic-PSe compounds with increased rates of hydrolysis and function through well-defined mechanisms as monitored by ³¹P and ⁷⁷Se NMR spectroscopy. In addition, we report a colorimetric method based on the reaction of H₂Se with NBD-Cl to generate NBD-SeH (λ_max = 551 nm), which can be used to detect free H₂Se. Furthermore, we use TOF-SIMS (time of flight secondary ion mass spectroscopy) to demonstrate that these H₂Se donors are cell permeable and use this technique for spatial mapping of the intracellular Se content after H₂Se delivery. Moreover, these H₂Se donors reduce endogenous intracellular reactive oxygen species (ROS) levels. Taken together, this work expands the toolbox of H₂Se donor technology and sets the stage for future work focused on the biological activity and beneficial applications of H₂Se and related bioinorganic RSeS.