A highly selective near-infrared fluorescent probe for imaging H(2)Se in living cells and in vivo

Hydrogen selenide (H(2)Se), a highly reactive Se species, is an important selenium metabolism intermediate involved in many physiological and pathological processes. This compound is of scientific interest with regard to the real-time monitoring of H(2)Se in living cells and in vivo to understand the anti-cancer mechanism of selenium. However, monitoring H(2)Se in living cells is still challenging due to the lack of straight forward, highly selective and rapid methods. Here, we developed a novel small-molecule fluorescent probe, NIR-H(2)Se, for imaging endogenous H(2)Se. NIR-H(2)Se exhibited high selectivity toward H(2)Se over selenocysteine (Sec), H(2)S and small molecule thiols and was successfully used to image the H(2)Se content in HepG2 cells during Na(2)SeO(3)-induced apoptosis. Increased H(2)Se content and reduced ROS levels were observed under hypoxic conditions compared to normoxic conditions, which indicated that the cell apoptosis induced by Na(2)SeO(3) under a hypoxic environment is via a non-oxidative stress mechanism. Thus, this probe should serve as a powerful tool for exploring the physiological function of H(2)Se and Se anticancer mechanisms in a variety of physiological and pathological contexts.