Mitochondria targeted dual-fluorescent probe for bio-imaging viscosity and F− with different fluorescence signals

The F− ion and viscosity both affect the physiological state of mitochondria and to the best of our knowledge no fluorescent probe is reported for the dual detection of mitochondrial viscosity and F− ion through different signals. DMAS-Si is weakly red fluorescent due to free intramolecular rotation between dimethylaminophenyl and pyridinium moieties and PET from silyloxy to the pyridinium moiety. In viscous medium (glycerol 90 %), the rotation is restricted and 18-fold increase in red-fluorescence (λem 637 nm) is observed. On reaction with F− ion, the desilylations followed by release of quinone-methide from DMAS-Si gives intense green fluorescence (λem 515 nm) due to formation of DMAS. DMAS-Si can detect as low as 50 nM F−. DMAS-Si shows good permeability to HeLa cells and preferably targets mitochondria. It has been used for imaging of increased viscosity in mitochondria of HeLa cells in the presence of nystatin through red fluorescence and exogenous F− ion by appearance of green fluorescence.