Experimental study of the electrically induced optical birefringence in suspension of densely packed giant lipid vesicles

Optical birefringence Δn ∼ –10−7, induced in suspension of giant lipid vesicles by high-frequency (500 kHz) AC electric field was measured. The liquid phases inside and outside the vesicles were iso-osmolar solutions of sucrose and glucose (0.22 mol/L). The two solutions have different optical densities and different specific weights. The estimated volume fraction of the vesicles in the studied suspension was 48 v%. The amplitude of the applied electric field was varied in the interval 5 ÷ 30 V/mm. The observed effect was supposed to be a result from the electro-deformation of the giant vesicles leading to an optical anisotropy. The measured value of Δn in our case is in the same range as for suspensions of large unilamellar vesicles with considerably higher lipid concentrations, as reported in the literature.