Selective colorimetric and fluorescence detection of nitroreductase enzymes in living cells.

Rhodamine dyes bearing aromatic nitro group has been synthesized for nitroreductase enzyme chemosensing applications. The probe is showing very selective turn-on fluorescent response towards nitroreductase enzymes and in hypoxic conditions. The sensor displays a remarkable fluorescent enhancement at 557 nm (λex = 500 nm) without the interference of other biologically relevant species under hypoxic conditions in a physiological medium. The nitro group in the sensor is reduced by the nitroreductase enzyme to the amino group, resulting in the hydrolysis of the probe and subsequent release of highly fluorescent rhodamine 6G dye is observed. This rhodamine based fluorescent probe has been utilized for the imaging of nitroreductase enzymes as well as hypoxia in live cells.