A rapid-response and near-infrared fluorescent probe for imaging of nitroxyl in living cells.

Nitroxyl (HNO), generated from nitric oxide (NO) in biological system, plays distinct biological roles in physiological process, but the role of endogenous HNO in biosystems still remains unclear, because of lacking of specific and sensitive detector to monitor HNO in real time. The conventional methods indicate the level of HNO through detecting the ultimate product nitrous oxide (N2O) of HNO dimerization and dehydration, which could easily result in inaccurate data. Therefore, developing an assay that can directly apply to detect HNO is of significance for understanding the function mechanism of HNO in biological system. In this study, we describe a near-infrared fluorescent probe 4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl) phenyl-2-(diphenylphosphanyl)-benzoate (CPN) that employs (2-(4-hydroxystyryl) -4H-chromen-4-ylidene) malononitrile (CP-OH) as a fluorophore and 2-(diphenylphosphino) benzoate as a recognition group. This probe, CPN, shows rapid-response to HNO which compared to other current probes. The fluorescent intensity reaches plateau in 20 min in vitro and in 2 min in vivo, respectively, which is important to monitor dynamic and transient state of HNO in biological system. In addition, CPN probe with a large Stokes' shift (150 nm) and near-infrared emission (700 nm) that is suitable for biological imaging. This probe has a potential of elucidating the biological function of HNO in biosystem.