A hypoxia-activated near infrared fluorescent probe for cyclooxygenase-2 and in vivo imaging for tumor and inflammation

[Display omitted] •A novel hypoxia-activated COX-2 specific fluorescent probe YZP1 was designed and synthesized.•Under hypoxia condition and the reduction of Cytochrome P450 reductase, a remarkable “off-on” fluorescence change was observed for YZP1 with the fluorescence quantum yield increasing from 0.0028 to 0.125.•The specificity of the probe YZP1 to COX-2 was demonstrated by both in vitro living cell imaging and in vivo imaging in mouse inflammation model and tumor xenograft model. Tumor is one of the most serious diseases, and its early diagnosis is of great significance for improving the prognosis and patient survival rate. Herein, aiming at the detection of cyclooxygenase-2 (COX-2), which plays an important role in tumorigenesis, we synthesized a NIR fluorescent probe YZP1, by using near infrared fluorescent dye Cy5.5 as the fluorophore and indomethacin (IMC) as the targeting group. Due to the quenching effect of azo group, the fluorescence of YZP1 was quenched. Under hypoxia condition and the reduction of Cytochrome P450 reductase, the azo bond of YZP1 was broken, and the fluorescence quantum yield increased from 0.0028 to 0.125. Furthermore, when HeLa cells were co-incubated with YZP1 under hypoxia condition, remarkable red fluorescence were observed, and the ratio of fluorescence intensity between hypoxic and normoxic cells could reach 9 folds. After treated with the celecoxib, an inhibitor of COX-2, of different concentrations, the fluorescence will be weakened gradually, which verify the binding of YZP1 and COX-2. Finally, by using mouse inflammation model and tumor xenograft model, the in vivo imaging ability of YZP1 was also demonstrated.