Mitochondria-targeted and FRET based ratiometric fluorescent probe for SO2 and its cell imaging

SO2 can react with water to form sulphite (SO32-) and bisulphite (HSO3-) ions, after it is inhaled into the body. Aberrant levels of SO2 and its derivatives in cells are related with a variety of diseases. So, it is important to monitor the level of SO2 and its derivatives in biological systems. Up to now, few probes have been reported for ratiometric detection of bisulfites in mitochondria. And the response speed of most reported probes were slow. It limited their application in real time detection of SO2. Here, using benzopyrylium as energy acceptor and mitochondria-targeted group, a FRET fluorescent probe CBP for SO2 was developed. CBP can detect SO2 with excellent selectivity over various analytes, including glutathione, homocysteine, cysteine and some common reactive oxygen species. The recognition process is accompanied by the color of the solution changing from purple to yellow, which allows naked eye detection for SO2. Its response is very fast (< 1 min) and the detection limit is low (17.7 nM). In addition, probe CBP can be located in mitochondria and successfully used for the imaging of intracellular SO2 in EC-109 cells.