Liposome/Emulsion Transition Induced by α-Tocopheryl Acetate

The destruction of liposomes and their transition into multiple emulsions induced by the addition of α-tocopheryl acetate (Toc) were investigated. With the increase of incorporated Toc in lipid bilayers composed of hydrogenated soybean lecithin (HSL), the polarity in the hydrophobic region of the bilayers decreased. When the added Toc exceeded its capacity to be incorporated, the excess formed multiple emulsions. There were two characteristic Toc/HSL molar ratios defined as R1 and R2. R1 is the molar ratio at which the alteration in the physical properties of membranes becomes significant. R2 is the molar ratio at which emulsions begin to be formed, that is, the capacity of Toc in HSL membranes. In our system, these ratios were ca. 0.03 and 0.6, respectively. The proportion of the emulsions can be successively predicted by the mean field approach. The physical effect of Toc on phospholipid membranes and the transition mechanism from liposomes to multiple emulsions are discussed.