An ESIPT-based ratiometric fluorescent probe for the imaging of nitroxyl in living cells

Nitroxyl is a highly reactive compound that irreversibly dimerizes and subsequently dehydrates to yield nitrous oxide and water, making its direct detection in cells or in vivo difficult. In this paper, a novel fluorescent probe 1 based on the excited state intramolecular proton transfer (ESIPT) mechanism for the detection of nitroxyl was developed for the first time. It consists of 2-(2'-hydroxyphenyl)-benzothiazole as the fluorophore, linked via an ester moiety to a diphenylphosphinobenzoyl group. The probe exhibited high sensitivity and selectivity toward nitroxyl in the presence of biologically relevant species. Moreover, the potential for biological applications of the probe was confirmed by employing it for fluorescence imaging of nitroxyl in living cells.