Fast responding of mitochondrial HClO using a coumarin-based fluorescent probe in living cells and zebrafish

As an important reactive oxygen species (ROS), hypochlorous acid (HClO) plays pivotal role in the human immune system and ensures the normal function of the organisms. HClO is derived from mitochondria and can regulate intracellular redox balance. Nevertheless, abnormal HClO levels is related to immune system disorders, neurodegenerative injury and cancer. Therefore, fast and sensitive monitoring HClO in mitochondria is extremely significant for some diseases indication. Herein, we designed a mitochondrial-targeted probe HDCl to detect HClO in living cells, which was a hybrid of coumarin, quaternized pyridine (mitochondrial target site) and N, N-dimethylthiocarbamate (DMTC, hypochlorous acid recognition site). The probe HDCl present high sensitivity, high selectivity and ultrafast (<5 s) responding properties for HClO in phosphate buffer solution (PBS) with the very low detection limit of 2.8 nM and trigger a significant enhanced fluorescent signal at 641 nm. Additionally, with a massive Stokes shift (176 nm), HDCl has been successfully applied to imaging HClO in mitochondria of living cells and in zebrafish.