Structure-regulated mitochondrial-targeted fluorescent probe for sensing and imaging SO₂in 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.