Generation of multilamellar and unilamellar phospholipid vesicles

Multilamellar and unilamellar vesicles can be generated by a variety of techniques which lead to systems with differing lamellarity, size, trapped volume and solute distribution. The straight-forward hydration of lipid to produce multilamellar vesicles (MLVs) results in systems which exhibit low trapped volumes and where solutes contained in the aqueous buffer are partially excluded from the MLV interior. Large trapped volumes and equilibrium solute distributions can be achieved by freeze-thawing or by ‘reverse phase’ procedures where the lipid is hydrated after being solubilized in organic solvent. Unilamellar vesicles can be produced directly from MLVs by extrusion or sonication or, alternatively, can be obtained by reverse phase or detergent removal procedures. The advantages and limitations of these techniques are discussed.