Characterization of liposomes. The influence of extrusion of multilamellar vesicles through polycarbonate membranes on particle size, particle size distribution and number of bilayers

Abstract The influence of extrusion on number of bilayers, particle size (ps) and particle size distribution (psd) of multilamellar vesicles (composition on a molar basis: phosphatidylcholine/phosphatidylserine/cholesterol, 10:1:4) is investigated. Ps and psd are investigated with freeze-fracture electron microscopy, average number of bilayers 〈 N 〉, with small angle X-ray scattering and 31 P-NMR. The encapsulated volume ( E ) is determined using carboxyfluorescein as marker. From E and the volume/surface ratio of the liposomes, determined from the psd, 〈 N 〉 was also calculated. Determined and calculated number of bilayers are in reasonable agreement. Extrusion reduces 〈 N 〉.