Physical separation of the aqueous phase and lipoidal lamellae from multilamellar liposomes: an analytical and preparative procedure.

An efficient and rapid method to separate the aqueous phase from lipoidal lamellae after mechanical disruption of multilamellar liposomes with preservation of the phospholipid bilayer organization has been designed. Liposome suspensions were subjected to a few short bursts of sonication at a temperature below the transition temperature (Tc) of the lowest melting phospholipid component. This was followed by ultracentrifugation. The aqueous supernatant contained more than 90% of the encapsulated aqueous elements (6-carboxyfluorescein, bovine serum albumin) and less than 1% of the lipids. The washed pellet consisted of lipoidal lamellae devoid of any encapsulated aqueous phase. The lipoidal lamellae contained more than 99% phospholipids and were contaminated with less than 0.1% aqueous components. Such a method should allow the localization of any component within the aqueous phase or lipoidal lamellae of the liposomes.