Uncharged homopolymers such as poly(vinyl alcohol), polyvinylpyrrolidone (PVP) and methylcellulose were used for the stabilization of small unilamellar vesicles in aqueous media of various composition. Polymer-free and polymer-bearing liposomes from dimyristoylphosphatidylcholine and dipalmitoylphosphatidylcholine were prepared under standardized conditions. Sterically stabilized liposomes were formed by incorporating dissolved macromolecules in the membrane bilayer of vesicles. The stability of liposomal dispersions, at physiological pH values and in the presence of natural cyclodextrins (CDs), were studied. The physical stability of vesicles was tested by measuring the size distribution of liposomes by means of a Malvern Zetasizer 4 apparatus. It was shown that most of the polymers are efficient steric stabilizers for the vesicles. PVP of high molecular mass exhibited the most efficient stabilizing effect at each pH studied, indicating that the formation of a relatively thick polymer layer around the lipid bilayers ensures enhanced and prolonged physical stability of liposomes. Also, the polymers proved to be suitable for preventing the destruction of phospholipid bilayers that dissolved natural CDs cause. Using these macromolecules, vesicle stability and interactions in dispersions of liposomal colloids can be well controlled.
- Liposomal colloids
- Physical stability
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)