Structure-regulated mitochondrial-targeted fluorescent probe for sensing and imaging SO2 in vivo

SO2 and its derivatives play an important role in the antioxidation and anticorrosion of food and medicine. In biological systems, abnormal levels of SO2 lead to the occurrence of many biological diseases. Hence, the development of suitable tools for monitoring SO2 in mitochondria is beneficial for studying the biological effect of SO2 in subcellular organelles. In this research, DHX-1 and DHX-2 are fluorescent probes designed on the basis of dihydroxanthene skeletons. Importantly, DHX-1 (650 nm) and DHX-2 (748 nm) show near-infrared fluorescence response toward endogenous and exogenous SO2, which showed advantages of great selectivity, good sensitivity and low cytotoxicity, and the detection limit is 5.6 μM and 4.08 μM of SO2, respectively. Moreover, DHX-1 and DHX-2 realized SO2 sensing in HeLa cells and zebrafish. Moreover, cell imaging demonstrated that DHX-2 with a thiazole salt structure possesses good mitochondria-targeting ability. Additionally, DHX-2 was perfectly achieved by in situ imaging of SO2 in mice.