Abstract: In this paper, a phenothiazine fluorescent probe PTZ-C was synthesized using caffeic acid group as the recognition site of superoxide anion( $ O_{2}^{\cdot-} $), and $ O_{2}^{\cdot-} $ was detected by fluorescence activation. In the presence of $ O_{2}^{\cdot-} $, the electron-donating pyrocatechol of caffeic acid residues in PTZ-C can be oxidized to form electron-withdrawing o-benzoquinone, and the fluorescence resonance energy transfer occurs. A new peak appears at 470 nm, and the solution is observed to change from colorless fluorescence to blue fluorescence under ultraviolet lamp, and the response speed is within 5 s. Probe PTZ-C can specifically recognize $ O_{2}^{\cdot-} $, has strong anti-interference ability and a wide range of pH value, and the detection limit is 12.8 nmol/L. It shows good reversibility to the redox process of alternately adding $ O_{2}^{\cdot-} $ and ascorbic acid. In addition, it shows little cytotoxicity, and can be applied in endogenic $ O_{2}^{\cdot-} $ fluorescence imaging of macrophage RAW264.7.
Keywords: superoxide anion; phenothiazine; caffeic acid; fluorescent probe