A near-infrared fluorescent probe for in situ imaging of SO2 flux in drug-induced liver injury

Sulfur dioxide (SO2) has been widely applied as an important additive in various foods and drugs due to its antioxidant, antiseptic and bleaching properties. SO2 in living organisms plays a key biological role as an antioxidant in a variety of life activities. However, abnormal levels of SO2 in both food and living organisms could cause harm and even serious illness, such as diseases related to the respiratory and cardiovascular systems and cancers. Therefore, it is of great practical significance to accurately determine the level of SO2 in food and organisms. In this work, we synthesized a novel near-infrared ratiometric fluorescent probe (NTO) using xanthene and benzopyran as the matrix for the detection of SO2. NTO demonstrates a rapid response (within 8 s), high selectivity, excellent sensitivity (LOD = 3.64 μM) and a long emission wavelength (800 nm), which could be applied to SO2 monitoring in a complex environment. NTO showed a high recovery (90%-110%) of SO2 in food samples such as beer and rock sugar. The results of HeLa cell experiments indicate that NTO has excellent fluorescence labeling ability for SO2 in endoexogenous-sulfide metabolism. In addition, we applied it to mice with acetaminophen (APAP)-induced acute liver injury and observed changes in SO2 during liver injury. Based on these results, we believe that this will provide a convenient visual tool for the detection of the SO2 content in food safety and biomedicine.