Construction of a near-infrared ratiometric fluorescent sensing system for pyrosulfite and its application in food, living cells, and anti-counterfeiting inks

Pyrosulfite, a widely used food additive known for its dual functions as both a preservative and antioxidant, is extensively applied in various fields, including food preservation, and pharmaceutical industry. However, excessive use may pose potential risks to human health. Here, a near-infrared fluorescence probe, 4-(1-cyano-4-(4-(dimethylamino-phenyl)-buta-1,3-dienyl)-1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)pyridinium, iodide, named CPB was first developed. It triggers a near-infrared fluorescence (700 nm) quenching reaction with pyrosulfite in almost pure buffered solution through nucleophilic addition of the C C bond. This probe was effectively used for the quantitative monitoring of pyrosulfite in various foods and living cells, demonstrating high sensitivity. A near-infrared ratiometric fluorescent detection system for pyrosulfite was then successfully constructed by combining CPB and 3-(7-diethylamino-2-oxo-2 H -chromen-3-yl)-2-pyridin-4-yl-acrylonitrile ( CPA ) fluorescent compound. The ratiometric fluorescent detection system of the hydrogel-encapsulated probes has been successfully employed for the quantitative analysis of pyrosulfite with high sensitivity (detection limit: 0.12 µM), being able to keenly capture minor concentration changes. The system equipped with the two probes has also shown potential applications in anti-counterfeit ink.