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

[Display omitted] •Rhodol-derived turn-on fluorescent chemosensor EBI-NO2 was synthesized using a one-step method.•The chemosensor had high selectivity towards NTR, and its detection limit was as low as 0.6 ng/mL.•The reaction mechanism was verified using MS, molecular docking and theoretical calculations.•The chemosensor was successfully applied in real-time monitoring of NTR produced during growth of Escherichia coli (BL21) and in visualization of NTR in oral cancer cells (Cal-27) under hypoxia. 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.