A dual-response fluorescent probe for SO2 and viscosity and imaging application in lysosomes and zebrafish

A dual-response fluorescence probe (1), namely 2-(3-cyano-5,5-dimethyl-4-{2-[1-(2-morpholin-4-yl-ethyl)-2-oxo-1,2-dihydro-quinolin-3-yl]-vinyl}-5H-furan-2-ylidene)-malononitrile, was synthesized for detecting SO2 derivatives and viscosity by integrating 3-formyl-2-quinolinone with a terminal morpholine and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF). This probe shows a ratiometric response towards HSO3− with highly selective and sensitive response (detection limit 0.37 μM), fast response (within 30 s), and a wide working pH range (4.0–11.0). Also, the probe exhibited a significant fluorescence enhancement response to viscosity. Importantly, the as-synthesized probe was successfully applied to image HSO3− and viscosity in lysosome of living HeLa cells lysosome and in zebrafish. In addition, the probe was also used to monitor HSO3− in real water samples.