New fluorescent turn-off probes for highly sensitive and selective detection of SO2 derivatives in a micellar media

Abstract

In this work, two isoxazole derivatives (1 and 2) were synthesized and characterized using common spectroscopic tools. The chemosensor behavior of 1 and 2 toward various analytes was explored and we found that both probes follow a ‘switch-off’ mechanism during SO2-derivatives sensing, with limits of detection near 10−6 and 10−5M, respectively. A recognition mechanism is proposed, based on a Michael-type addition reaction toward the probes, induced by SO2-derivatives and favored by micellar media. Typical interferences like glutathione (GSH) and cysteine (Cys) were inhibited by the presence of the cationic micelles of cetylpyridinium bromide (CPB) and the zwitterionic micelle of sulfobetaine (SB3-14); the detection limits were considerably improved. Thus, on the basis of these results, it is suggested that the use of these kinds of surfactants can be considered as a strategy for optimizing the detection of sulfite via its addition reaction to activated olefins containing isoxazole. Finally, probe 1 was chosen as the best sensor since it was assessed to detect SO2-derivatives in real samples (red and white wines) and in a biological system (Caco-2 cells) with very good results.