Osmotic behaviour and permeability properties of liposomes.

In this overview liposomes are described as bilayer-bounded vesicles which under defined conditions act as ideal osmometers according to the Boyle van't Hoff law. Investigations on osmotic volume changes, directly or indirectly by taking advantage of changes in light scattering, are considered and applications in permeability measurements are discussed. Solute-solvent interactions occurring in isotonic swelling experiments are analysed in view of an irreversible thermodynamic description. In a second part liquid crystalline lipid bilayers are characterized as highly selective permeability bilayers and the physical principles underlying this selectivity are considered. Attention is given to special physical and chemical conditions that may cause structural defects in the bilayer organization and can affect the selective permeability properties of the bilayer or completely deteriorate its barrier function. Finally an evaluation is given of intrinsic ionophoretic activity in lipid bilayers containing negatively charged lipids.