A quinolinium-based colorimetric and NIR fluorescent dual-channel sensing platform for specific detection of bisulfite in food, traditional Chinese medicine and living cells

Sulfur dioxide (SO2) and its derivatives are commonly used in food processing, but excessive exposure to SO2 and its derivatives can pose serious health risks. In this study, we present a near-infrared "turn-on" probe, QSB-M, for the highly selective and sensitive detection of HSO3- . The recognition of HSO3 -by the probe results in a marked color change and a significant enhancement in near-infrared fluorescence, offering high sensitivity (limit of detection = 95.12 nM), rapid response, and minimal interference from environmental background signals. The recognition mechanism involves the specific addition of HSO3 - to the 4-position of the quinolinium moiety, triggering an intramolecular charge transfer effect that leads to both colorimetric and fluorescence dual responses. QSB-M was also successfully applied for in situ visualization of HSO3 -in various foods and traditional Chinese medicines (TCM), with recoveries ranging from 90 % to 115 %. Additionally, test strips and a smartphone-assisted sensing platform were developed, enabling direct detection of HSO3 -levels in foods and TCM without the need for complex instrumentation. Importantly, QSB-M exhibits low cytotoxicity, good mitochondrial-targeting ability, and has been successfully used for the in situ detection of both endogenous and exogenous HSO3 - in live MCF-7 cells.