An endoplasmic reticulum-targeting fluorescent probe for the visualization of superoxide anion (O2•−) in living cells during ferroptosis

Superoxide anion (O2•−) plays critical roles during ferroptosis, and real-time tracking O2•− at endoplasmic reticulum (ER) is critical for deeply exploring its functions for ferroptosis. Herein, we constructed an ER-targeting fluorescent probe (ER-S) for tracking intracellular O2•− during ferroptosis. ER-S utilizes triflate unit and p-toluenesulfonamide as a recognition site for O2•− and ER-targeting moiety, respectively. When responding to O2•−, the probe ER-S experienced double reaction steps including nucleophilic reaction between triflate group with O2•− and cyclization reaction. The probe ER-S displayed excellent sensitive and selective response towards O2•−. Fluorescent imaging data indicated that ER-S showed desirable ER-targeting property and can track endogenously produced O2•− by PMA and rotenone. Moreover, erastin-induced ferroptosis was demonstrated to cause an increase in endogenous O2•− levels, and VE, DHLA and rutin can significantly block the excessive generation of O2•− during ferroptosis.