Construction of a super large Stokes shift near-infrared fluorescent probe for detection and imaging of superoxide anion in living cells, zebrafish and mice.

As one of the major reactive oxygen species (ROS), superoxide anion (O) is engaged in maintaining redox homeostasis in the cell microenvironment. To identify the pathological roles in related disorders caused by abnormal expression of O, it is of great significance to monitor and track the fluctuation of O concentration in vivo. However, the low concentration of O and the interference caused by tissue autofluorescence make the development of an ideal detection methodology full of challenges. Herein, a "Turn-On" chemical response near-infrared (NIR) fluorescence probe Dcm-Cu-OTf for O detection in inflamed models, was constructed by conjugating the NIR fluorophore (dicyanisophorone derivative) with an O sensing moiety (trifluoromethanesulfonate). Dcm-Cu-OTf exerted about 140-fold fluorescence enhancement after reacting 200 μM O with an excellent limited of detection (LOD) as low as 149 nM. Additionally, Dcm-Cu-OTf exhibited a super large Stokes shift (260 nm) and high selectivity over other bio-analytes in stimulated conditions. Importantly, Dcm-Cu-OTf showed low toxicity and enabled imaging of the generation of O in the Lipopolysaccharide (LPS)-stimulated HeLa cells, zebrafish, and LPS-induced inflamed mice. The present study provided a potential and reliable detection tool to inspect the physiological and pathological progress of O in living biosystems.