Rhodol-derived turn-on fluorescent chemosensor for ultrasensitive detection of nitroreductase activity in bacteria and bioimaging in oral cancer cells

The detection of intracellular nitroreductase (NTR) activity is important for the study of hypoxia in organisms. In the present study, a Rhodol-derived fluorescent chemosensor (Rhod-NO2) was synthesized in a one-step procedure. Rhod-NO2 exhibits 110-fold fluorescence enhancement in the presence of NTR. Moreover, Rhod-NO2 demonstrates high NTR selectivity and sensitivity (LOD, 0.6 ng/mL). The mode of Rhod-NO2 binding to NTR was also revealed by molecular docking. In addition, the reaction and luminescence mechanisms were evaluated by MS and TDDFT theoretical calculations, respectively. Finally, Rhod-NO2 was successfully applied to monitor NTR production during Escherichia coli (E. coli) growth, and to visually analyze NTR production in malignant oral cancer cells under hypoxia. Thus, Rhod-NO2 represents a new molecular tool to further understanding of the biological function of NTR.