A Curcumin-Based Turn-on Fluorescent Probe for Superoxide Anion in Living Cells

Superoxide (O₂^•-) plays a pivotal role in diverse physiological and pathological processes, a thorough understanding of its molecular mechanisms relies on dependable detection techniques. In this study, we designed and synthesized DFCD, a novel curcumin-based fluorescent probe with a switching mechanism, for the highly selective and sensitive detection of O₂^•-. By employing diphenylphosphinyl chloride as the reactive group, DFCD operates through a photoinduced electron transfer (PET) mechanism and exhibits significant fluorescence enhancement at 574 nm upon reaction with superoxide anion. The probe demonstrates a detection limit of 0.11 µM, excellent selectivity over competing reactive species and ions, good stability at physiological pH, and minimal cytotoxicity. Live-cell imaging confirms that DFCD is capable of monitoring endogenous superoxide anion dynamics in HeLa cells under various stimuli. Furthermore, DFCD proves highly effective for imaging macrophage inflammatory responses, providing a robust tool for studying superoxide-driven oxidative stress in inflammatory models. Collectively, these findings establish DFCD as a valuable imaging probe for studying superoxide-related oxidative stress at the cellular level.