Detection of hypochlorous acid fluctuation via a selective near-infrared fluorescent probe in living cells and in vivo under hypoxia stress

 Hypoxia stress is a common concern for both medicine and biology, which can induce the cellular injury and death by excess production of reactive oxygen species (ROS). Hypochlorous acid (HOCl), one of the ROS, plays a crucial role in oxidative damage to tissue proteins in the pathogenesis of various diseases. Therefore, excess production of HOCl might be an important factor for the damage of hypoxia stress. However, most of the present methods cannot meet the demand of real-time detection on account of the labile and reactive chemical properties of HOCl. Herein, we design a near-infrared fluorescent probe Cy-HOCl for the selective imaging of HOCl in cells and in vivo. Cy-HOCl includes two moieties: a 4-amino-3-nitrophenol group as the response unit; a near-infrared heptamethine cyanine fluorophore as the fluorescent modulator. Cy-HOCl exhibits excellent selectivity and sensitivity towards the detection of HOCl. The hypoxia response behavior of Cy-HOCl is evaluated in cells to clarify the relationship between HOCl and hypoxia. The probe is also applied to measure HOCl in ex vivo-dissected organs of acute ischemia mouse model, as well as used for real-time monitoring the changes of HOCl in hypoxic zebrafish model.