Formation of homogeneous liposomes with high trapping efficiency by the surface chemical method

A new physicochemical method for preparing homogeneous liposomes with high trapping efficiency has been developed. A lamellar liquid crystalline (LLC) phase formed in the egg yolk lecithin (EPC)/propylene glycol/glycerol/water four-component system is utilized in this method. The ratio of propylene glycol to glycerol is important for the preparation of fine liposomes. The roles of propylene glycol and glycerol in the preparation process were studied using phase diagrams, small angle X-ray diffraction and video-enhanced microscopy. It has been shown that propylene glycol and glycerol control the hydrophile-lipophile balance (HLB) of lecithin and that the liposome size changes according to the HLB. The lamellar liquid crystalline phase with a 1:1 propylene glycol:glycerol weight ratio expands for a low concentration of lecithin, and liposomes with minimum size (116 nm) are prepared by adding water to the LLC phase. It was found that the trapping efficiency of the liposomes prepared by this new method was 19.5%, while the trapping efficiency was 0.2% for the sonication method and 2.1% for the extrusion method.