Stabilization of Small, Unilamellar Phospholipid Vesicles by Sucrose during Freezing And Dehydration

Abstract

Phospholipid bilayers have been widely used as model membranes in the past. More recently they have become important in form of unilamellar vesicles which are useful in the study of membrane-mediated processes such as membrane fusion, interfacial catalysis, energy conduction and conversion and drug delivery and targeting. It is hoped that this research will eventually lead to technological application of lipid bilayers. Considering industrial applications of bimolecular layers the problem of long-term storage has to be addressed. It is well-known that small unilamellar phospholipid vesicles (SUV) are thermodynamically unstable. Moreover, when SUV of egg lecithin are subjected to freeze-thawing or to freezedrying they have been shown to aggregate and fuse yielding large multilamellar liposomes reminiscent of unsonicated egg lecithin dispersions^1,2. This paper describes the interaction of mainly sucrose with phosphatidylcholine SUV. It is addressed to the question of whether or not SUV can be stabilized in the presence of sugar and sustain freeze-thawing and dehydration with full retention of their structural and permeability properties.