A reductant-resistant ratiometric, colorimetric and far-red fluorescent probe for rapid and ultrasensitive detection of nitroxyl

Development of selective fluorescent probes for rapid and ultrasensitive detection of nitroxyl (HNO) is of great importance for biomedical researchers to investigate the detailed functions and mechanisms of HNO in living systems. Herein, based on an internal charge transfer (ICT) mechanism, we developed a novel ratiometric, colorimetric and far-red fluorescent probe (HNO-TCF) for the rapid and ultrasensitive detection of HNO in living cells. HNO-TCF exhibits high HNO-selectivity even in the presence of a high concentration of biological reductants including glutathione (GSH), hydrogen sulfide (H₂S) and ascorbate (AA), which might be ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. The ICT-based fluorescent probe HNO-TCF displays a large (185 nm) red-shifted absorption spectrum and the color changes from yellow to blue upon addition of HNO. In addition, the results showed that HNO-TCF could quantitatively detect HNO in the range of 0 to 4 μM with a detection limit of 10 nM by ratiometric absorption and fluorescence spectrometry methods. Importantly, HNO-TCF was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.