Mitochondria-targeting near-infrared fluorescence/afterglow sensing assay for the rapid detection of HClO and its application in the early detection of Alzheimer's disease

Hypochloric acid (HClO) in living organisms is generated by the catalysis of myeloperoxidase (MPO). As an inflammatory signaling molecule, it can lead to neuronal cell death in the process of neuroinflammation, which is closely related to the etiology of Alzheimer's disease (AD). Therefore, it is of great significance to develop effective tools for the localization of HClO in the early pathological process of AD. Therefore, a near-infrared (NIR) fluorescent probe HCy-1 targeting mitochondria for brain HClO detection was developed in this work. The reaction time between HCy-1 and HClO is short (within in 10 minutes), and the rapid detection of hypochlorous acid can be realized by naked eyes. HCy-1 also shows high selectivity and sensitivity to HClO with a detection limit of 34.5 nM, and the fluorescence intensity of HCy-1 at 715 nm is increased over 38 times after the incubation of HClO. HCy-1 can be used to detect both exogenous and endogenous HClO in PC-12 nerve cells and RAW 264.7 cells, and it can also be used for oxidative stress imaging analysis in AD cell model. For in vivo experiments, HCy-1 showed a strong ability to penetrate the blood-brain barrier, and the fluctuation of HClO could be detected in AD mice. More importantly, the special structure of hemicyanine was used to perform afterglow imaging under in vitro light irradiation, which proved that HCy-1 could detect the early onset of AD in a lower background.