2021 年 46 巻 2 号 p. 84-90
Lipid vesicle (also called liposome) is a molecular aggregate consisting of closed lipid bilayers formed by mainly phospholipids in aqueous solutions. They can be utilized as carriers for drug delivery systems as well as encapsulation materials of other functional compounds. Recently a novel method for preparing lipid vesicles using water–in– oil–in–water (W/O/W) type multiple emulsions has been developed by the authors. Lipid vesicle formation in this method is achieved via two processes: multiple emulsification and solvent evaporation processes. The multiple emulsification process consists of two–step emulsification involving primary emulsification for obtaining water–in–oil emulsion followed by secondary emulsification for obtaining W/O/W multiple emulsion. In the solvent evaporation process, organic solvent is removed from the W/O/W multiple emulsions by evaporation, and then lipid vesicles are formed and dispersed in the aqueous phase. By this method, lipid vesicles with high encapsulation efficiency for hydrophilic molecules and controlled diameter can be obtained. In this review, the outline of this method for obtaining lipid vesicles is overviewed, and a possible mechanism of lipid vesicle formation and the effects of the type and concentration of water–soluble emulsifiers on encapsulation efficiency are discussed based on the authors’ studies.