A novel dual-ratiometric-response fluorescent probe for SO2/ClO- detection in cells and in vivo and its application in exploring the dichotomous role of SO2 under the ClO- induced oxidative stress.

Intracellular reactive sulfur species and reactive oxygen species play vital roles in immunologic mechanism. As an emerging signal transmitter, SO2 can be generated as the anti-oxidant, while SO2 is also a potential oxidative stress-inducer in organism. Aiming to elucidate in-depth the dichotomous role of SO2 under oxidative stress, we designed a dual-response fluorescent probe that enabled the respective or successive detection of SO2 and ClO-. The probe itself emits the red fluorescence (625 nm) which can largely switch to blue (410 nm) and green fluorescence (500 nm) respectively in response to SO2 and ClO-, allowing the highly selective and accurate ratiometric quantification for both SO2 and ClO- in cells. Moreover the ultrafast (SO2: <60 s; ClO-: within sec) and highly sensitive (detection limits: SO2: 3.5 nM; ClO-: 12.5 nM) detection were achieved. With the robust applicability, the developed probe was successfully used to quantify SO2 and endogenous ClO- in respectively the HeLa cells and the RAW 264.7 cells, as well as to visualize the dynamic of SO2/ClO- in zebrafish. The fluorescent imaging studies and flow cytometry analysis confirmed the burst-and-depletion and meanwhile the oxidative-and-antioxidative effects of intracellular SO2 under the NaClO induced oxidative stress.