Preparation and the Mechanism of Liposome Formation

Abstract

Several large scale liposome preparation methods are presented and the mechanism of liposome formation by various methods is discussed. This film hydration methods and various solvent-injection hydration techniques appear to be the most promising in the large scale applications. In the former ones, liposomes are formed upon swelling of dry lipid films in aqueous phases, while in the latter ones, liposomes form upon injecting solutions of lipids in organic solvents into aqueous solutions followed by removal of the organic solvent. In both cases, however, liposomes are normally processed further in order to obtain smaller and more homogeneous preparations. Methods where lipid powder mixtures are directly hydrated and demulsification procedures, in which liposomes are produced by depleting organic phases from different lipid emulsions, are also described. Various intermediate structures and their free energy states are discussed in relation to possible mechanism of liposome formation.