Mitochondria-targeted reversible ratiometric fluorescent probe for monitoring SO2/HCHO in living cells.

Sulfur dioxide (SO2) maintains a certain steady state balance in the body, high concentration SO2 will be harmful to human health. Seeking a suitable detection method to monitor sulfur dioxide in real time becomes an urgent requirement owing to the transient nature of sulfur dioxide in organisms. Here, a novel NIR ratiometric fluorescent probe for detection of SO2 was developed based on a conjugation of coumarin and indol salt with excellent water solubility. The probe Mito-CI displayed highly sensitive (69 nM), fast response time (30 s), large Stokes shift (174 nm) and the NIR fluorescence emission wavelength (655 nm). In the reversibility process of the SO3--probe Mito-CI system induced by HCHO in vitro was also detected. Besides, cell imaging showed that Mito-CI possesses mitochondria-targeted ability. Particularly, Mito-CI was proved to reversibly detect SO2/HCHO in living cells.