ORGANIZATION AND DEFECTS IN LAMELLAR AGGREGATES: IMPLICATIONS FOR DIFFUSION, PHASE TRANSITIONS, AND TRANSPORT IN LIPOSOMES.

Polymerized vesicles and liposomes are under close scrutiny as long-lived, stable substitutes for their natural and synthetic unpolymerized counterparts. A monomer surfactant containing one or more polymerizable groups is dispersed in water at the appropriate temperature and concentration to form lamellar bilayers. Polymerization is then initiated while the monomer surfactant is in the lamellar liquid crystalline state. These bilayers are usually dispersed in excess water as multibilayer aggregates known as liposomes or multilayered vesicles (MLV). Both polymerized and unpolymerized liposomes and vesicles have a wide variety of applications to slow-release and site specific drug delivery, membrane-mediated chemistry, and as model systems for investigations of biological membranes. This paper examines the fundamental forces that determine bilayer organization and defects in liposomes. Models of liposome morphology are presented along with a discussion of liquid crystal defects in bilayer aggregates.