Development of a Ratiometric Fluorescent Probe with Zero Cross-Talk for the Detection of SO₂ Derivatives in Foods and Live Cells

Sulfur dioxide (SO₂) derivatives are extensively utilized as both a preservative for foods and an active gaseous signal molecule in various physiological and pathological processes, but their excessive intake would bring harmful effects on human health; so, the determination of SO₂ derivatives is of great importance. Herein, we developed a ratiometric fluorescent probe named 2-(2'-hydroxyphenyl)benzothiazole-3-ethyl-1,1,2-trimethyl-1H-benzo[e]indolium (HBT-EMBI) by introducing a hemicyanine unit of EMBI to an HBT group for the detection of SO₂ derivatives via an excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) effects. The probe displays some advantages, such as a colorimetric change from purple to colorless, a ratiometric fluorescence with zero cross-talk, and a remarkably large emission shift (Δλ = 164 nm) under a single-wavelength excitation. Accordingly, the probe HBT-EMBI has been successfully employed for the colorimetric and ratiometric determination of SO₂ derivatives in real food samples and the quantitative visualization of SO₂ derivative variations in HepG2 cells.