Highly Selective Fluorescent Probe for Imaging H₂Se in Living Cells and in Vivo Based on the Disulfide Bond

Hydrogen selenide (H₂Se) is an important metabolite of dietary Se compounds and has been implicated in various pathological and physiological processes. The development of highly sensitive and selective methods for the sensing of H₂Se is therefore very important. Herein, we developed a fluorescent probe (hemicyanine (Hcy)-H₂Se) for detecting H₂Se based on a new H₂Se-specific receptor unit, 1,2-dithiane-4,5-diol. Hcy-H₂Se showed high selectivity toward H₂Se over thiols (RSH), hydrogen sulfide (H₂S), and selenocysteine (Sec) and was further exploited for the fluorescence imaging of H₂Se both in living cells and in vivo. Furthermore, with the aid of Hcy-H₂Se, we demonstrated that H₂Se can be generated and gradually accumulated in HepG2 cells under hypoxic conditions and in the solid tumor after treatment with Na₂SeO<sub>3