A near-infrared fluorescence probe for the detection of bisulfite in vivo and food samples

The evaluation of the HSO3− levels in the biological systems and food samples is of great significance in the understanding its physiological/pathological roles and realizing food security supervision. In this work, a near-infrared (NIR) emitted fluorescence probe (QNP) has been successfully developed to detect HSO3− in live animals and food samples. QNP was designed with a large π-conjugation structure by conjugating of quinolinium with 3H-naphtho[2,1-b]pyran moiety through a reactive C=C double bond. Spectroscopic titration, high resolution mass spectrometry (HR MS), 1H NMR titration and theoretical computation indicates that HSO3− attacks to the C=C double bond through an established 1,4-nucleophilic addition reaction leads to the interruption of the π-conjugation system of QNP, resulting in dramatic decline of the UV–vis absorption and fluorescence spectra. QNP was featured with near infrared emission (centered at 690 nm), high water-solubility (98% water), large Stokes shift (218 nm), perfect selectivity, fast response time (within 50 s) to HSO3−, reliability in broad pH range (6.5–11.5) and low cytotoxicity. The application of QNP in biological systems has been demonstrated by the monitoring of exogenous HSO3− in live adult zebrafish and nude mouse. Furthermore, the evaluation of HSO3− level in several food samples including sugar, white wine, canned fruits and jasmine tea drinks were also determined by fluorescence colorimetric method using QNP.