Physicochemical characteristics of liposomes formed with internal wool lipids

The bilayer-forming capability of internal wool lipids and their physicochemical properties were studied in an attempt to enhance our understanding of the lipid structure present in wool and other keratinized tissues. Internal wool lipids were extracted and analyzed, and the mixture obtained [sterol esters (10%), free fatty acids (24%), sterols (11%), ceramides (46%), and cholesteryl sulfate (9%)] was shown to form stable liposomes. A phase-transition temperature of 60 degrees C was obtained from nuclear magnetic resonance spectra for this lipid mixture. The spontaneous permeability of these vesicles was lower than that of phosphatidylcholine liposomes bur slightly higher than that of the vesicles formed with lipids extracted from other keratinized tissues with higher amounts of cholesterol. The transmission electron micrographs showed large vesicular aggregates of approximately 300 nm, which seem to be made up of smaller structures of approximately 20 nm in size. This particular structure could account for the large diameters and small internal volumes found by dynamic light-scattering and spectrofluorometric measurements.