Hydrogen selenide in biological systems: from synthetic donors to fluorescent probes.

Analogous to hydrogen sulfide (H2S), the more strongly reductive hydrogen selenide (H2Se) functions as a key endogenous mediator, exerting significant influence on signal transduction, redox regulation, and cytoprotection. However, the in vivo generation of H2Se via molecular donors and the real-time monitoring of its fluctuations remain challenging due to inherent instability. To tackle these challenges, several H2Se donors, including organic small molecule, inorganic salt, and composite nanoparticles, have been developed to ensure controlled H2Se delivery. Meanwhile, various kinds of fluorescent probes have been developed as powerful tools for the real-time visualization of H2Se at both cellular and organismal levels. This review will summarize the development of H2Se donors and fluorescent probes and emphasize the underlying obstacles that still exist in this field, with the aim of providing a deeper understanding of the biological functions of endogenous H2Se and facilitate its exploration across interdisciplinary fields.