A highly sensitive near-infrared ratiometric fluorescent probe for detecting nitroreductase and cellular imaging

Based on the selective reduction of nitro group to hydroxylamine or amino group by nitroreductase in the presence of NADPH as an electron donor, a near-infrared ratiometric fluorescent probe CyNNO2 was designed and synthesized. CyNNO2 containing a p-nitrobenzyl moiety as a reactive group can selectively respond to nitroreductase with a ratiometric fluorescence signal output. The limit of detection for nitroreductase is 0.0058 ng/mL. Moreover, the probe can be used to image the endogenous nitroreductase in A549 cells under hypoxic condition.