A FRET probe based on flavonol-benzothiazole for the detection of viscosity and SO2 derivatives.

Sulfur dioxide (SO2) and viscosity play important roles in living organisms, and abnormal levels of them are associated with many diseases. Hence, a bifunctional fluorescence probe (E)-3-(2-(4-(4-(4-(6-fluoro-3-hydroxy-4-oxo-4H-chromen-2-yl)benzoyl)piperazin-1-yl)styryl)benzo-[d]thiazol-3-ium-3-yl)propane-1-sulfonate (HFBT) with fluorescence resonance energy transfer (FRET) properties was successfully constructed by using 3-hydroxyflavonol as the energy donor and benzothiazole sulphonate derivatives as the energy acceptor, and it can be used for the detection of SO2 derivatives (HSO3-/HSO32-) and viscosity. HFBT exhibits a large Stokes shift (245 nm), high resonance energy transfer efficiency (95.56 %), and excellent selectivity, anti-interference and low limit of detection (LOD = 0.057 μM) for HSO3-. The fluorescence intensity of HFBT at 596 nm gradually increases with the increase of viscosity. Interestingly, a visual HSO3- detection platform was successfully constructed and applied to the quantitative detection of HSO3- in food. Additionally, HFBT was successfully applied to imaging endogenous and exogenous HSO3- in cells. The successful development of HFBT provides an effective tool for the detection and imaging of HSO3- in food and cells.