| Abstract: | The processes of adsorption of two neutral polymers (poly(vinyl pyrrolidone), PVP and poly(vinyl alcohol), PVA) were investigated on liposomes composed of soy lecithin/dicetyl phosphate/cholesterol = 25:2:3 (molar ratio). The liposomes were prepared in buffered solution at pH = 7.4 and mixed with the solution of the measured polymers in the desired polymer/lipid (w/w) ratios. Adsorption was measured by determination of the equilibrium bulk concentration of the polymer. In the case of PVA quantitative adsorption measurements with a specific reagent were possible. Adsorption isotherms were recorded at 25 ± 1°C. It was concluded that adsorbed and unadsorbed PVA molecules are in equilibrium even at low polymer/ lipid ratios. The results were confirmed by dynamic laser light scattering (DLS), and thermal activity monitoring (TAM) experiments. Another group of the liposomes was prepared in 60 mM ammonium sulphate (pH = 5.0) and we filled the vesicles with a test dye, acridine orange (AO) using the pH-gradient (remote loading) method. The AO release property of liposomes was tested with a special vertical diffusion cell after we had made PVA adsorb on their surface in different PVA/lipid (w/w) ratios. |
