Novel designed azo substituted semi-cyanine fluorescent probe for cytochrome P450 reductase detection and hypoxia imaging in cancer cells

A hypoxia activated fluorescent probe AZO-Cy which contains an azo group conjugated to the electron withdrawing part of the fluorescent dye was synthesized. In the presence of NADH, AZO-Cy displayed high selectivity and sensitivity to cytochrome P450 reductase (CPR) under low p(O(2)). The probe showed high anti-interference capability in the presence of other biothiols and ions. In A549 cell imaging, the fluorescence intensity is increased about 11-fold under hypoxia compared to normoxia conditions. Further inhibitor experiments showed that CPR is not the only reductase that can take part in the process of azo bond reduction. The probe AZO-Cy displayed high oxygen sensitivity in the identified different hypoxic status of tumor cells which provides huge potential application toward in vivo hypoxia detection.