Vesicle formation in aqueous dimyristoyl phosphatidylcholine suspensions: a cryo-electron microscopy study

The swelling of phospholipid in water above the chain-melting transition temperature produces lamellar structures in various shapes and sizes. These structures are potentially useful as drug, gene or cosmetic delivery systems. Cryo-electron microscopy has been used to demonstrate that the morphology of the structures in aqueous dimyristoyl phosphatidylcholine suspensions is affected by the degree of agitation. Long, undulating bilayer tubes are created, as hydrating phospholipid crystals flow through water. The proportion of unilamellar bilayer tubes to multilamellar tubes can be manipulated by varying the degree of agitation. Evidence is presented to show that agitation can transform multilamellar bilayer structures into unilamellar structures. A mechanism for the formation of unilamellar and multilamellar vesicles from these structures is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.