A Near-Infrared Fluorescent Probe for the Rapid Detection of Nitroxyl in Living Cells.

Nitroxyl (HNO) plays an important role in various physiological activities. It has the potential to be used as a treatment for certain diseases such as alcohol poisoning, acute hypertension, and atherosclerosis. However, traditional methods for detecting HNO are challenging due to its rapid polymerization and elimination into N2O. Therefore, it is crucial to establish direct and effective HNO detection methods to comprehend these physiological processes better. In this study, a new near-infrared fluorescent probe called HXM-P based on the intramolecular charge transfer (ICT) mechanism was designed and synthesized. This probe employs 2-((6-hydroxy-2,3dihydro-1 H-xanthen-4-yl)methylene)malononitrile as a fluorophore and 2-(diphenylphosphine) benzoate as a recognition group. The results showed that probe HXM-P can detect HNO with high sensitivity (1.07 × 10- 8 M). A good linear correlation was observed between the fluorescence intensities at 640 nm and the concentrations of HNO in the range of 0-80 µM (R2 = 0.997). Moreover, probe HXM-P exhibited a rapid response rate (within 15 s) toward HNO, and the fluorescent intensity reached a plateau within 5 min, making it easier to track the highly reactive and short-lived HNO in living systems. Additionally, HXM-P was successfully employed for imaging HNO in HepG2 cells.