Structure of Three-Phase Emulsion Stabilized with Phospholipid Bilayer-Assembly and Its Stability.

Abstract

The present review concerning the thermal properties of phospholipid bilayers, solubilization of hydrocarbon in the bilayers, and emulsification of hexadecane with the bilayers, has been described by combing our recent publications and some of our fresh data in regard to the bilayer properties. Phospholipid bilayers of dimyristoylphosphatidylcholine, dimyristoylphosphatidylglycerol sodium salt, and dimyristoylphosphatidylglycerol ammonium salt were investigated. In the thermal properties of phospholipid bilayers, two new transition temperatures of T* and TI, which were found by us, were introduced other than the main transition of Tm. Dispersion of phospholipids took a long period of time to establish the favorable hydration of bilayer-assemblies, and to transform from Lα phase into a new gel phase, transition temperature of which was expressed by TI. From the solubilization studies of octane and hexadecane, we showed that the locus of solubilization for hydrocarbon in the phospholipid bilayers turned out to occur in the palisade layers, being dissimilar in that of the usual surfactant bilayers. Finally, we showed that emulsion of hexadecane prepared with these lipid dispersions at 25°C thermodynamically took the three-phase structure composed of oil phase, emulsifier phase of bilayers, and water phase, and confirmed that it was more stable than the thermal stability of emulsion whose surface was adsorbed by monolayer.