An activatable near-infrared fluorescent probe with large Stokes shift for visualizing peroxynitrite in Alzheimer’s disease models

[Display omitted] •An activatable NIR fluorescent probe CDCI-ONOO for detecting ONOO− was developed.•CDCI-ONOO exhibited a large Stokes shift, high selectivity, and high sensitivity.•Realized in vivo imaging of neuronal cells and Alzheimer’s disease models. Alzheimer’s disease (AD), characterized by its incurable nature and prevalence among the elderly, has remained a focal point in medical research. Increasing evidence suggests that peroxynitrite (ONOO−) serves as a crucial biomarker for the diagnosis of AD. In this study, we present a novel, easily available, high-yield, and cost-effective near-infrared (NIR) fluorescent probe, CDCI-ONOO. This probe utilizes a coumarin-dicyanoisophorone conjugate as the fluorophore and diphenylphosphinic chloride as the recognition site, enabling the detection of ONOO− both in vitro and in vivo. Upon interaction with ONOO−, CDCI-ONOO exhibits a distinct maximum emission peak at 715 nm with a substantial Stokes shift of 184 nm. The probe demonstrates excellent selectivity and sensitivity (LOD = 144 nM), along with noticeable colorimetric and fluorescence changes after the reaction. Comprehensive analyses using high-performance liquid chromatography (HPLC), high-resolution mass spectrometry (HRMS), and density functional theory (DFT) calculations confirm that the reaction with ONOO− restores the initially quenched Intramolecular Charge Transfer (ICT), resulting in the formation of CDCI-OH, a product that emitting fluorescence in the near-infrared region. Furthermore, we demonstrated the successful application of CDCI-ONOO for ONOO− detection in neuronal cells and imaging of ONOO− in the brains of mice. These findings underscore the potential of CDCI-ONOO as a near-infrared fluorescent probe for in vivo ONOO− detection, offering a significant avenue for advancing our understanding of AD pathology and diagnosis.