Mitochondria-targetable colorimetric and far-red fluorescent sensor for rapid detection of SO2 derivatives in food samples and living cells.

Sulfur dioxide (SO2) derivatives are intertwined with many physiological and pathological processes in living systems, and excess intake of them are associated with various diseases. Herein, we have rationally constructed a novel colorimetric and far-red fluorescent probe for HSO3- based on a rhodamine analogue skeleton bearing a 3-quinolinium carboxaldehyde moiety. The novel probe exhibited a significant far-red fluorescence "Turn-on" response to HSO3-, along with obvious color change from reddish to purple via the specific 1,4-nucleophilic addition reaction of HSO3- with the quinolinium moiety in 3-(4-(2-carboxyphenyl)-7-(diethylamino)chromenylium-2-yl)-1-methylquinolin-1-ium hypochlorite trifluoromethanesulfonate (AQCB). The AQCB had excellent water-solubility, and presented rapid response (<15 s),highsensibility(LOD = 49 nM) and selectivity toward HSO3-. In addition, the probe was able to detect the content of HSO3- in food samples with satisfactory results. Furthermore, the probe possessed good cell membrane and could be successfully applied for imaging HSO3- in the mitochondria of living cells.