Adsorption of phospholipid vesicles on solid surfaces
Sonicated vesicles have been prepared from dipalmitoylphosphatidylcholine (DPPC) and phosphatidylinositol (PI) and their mixtures covering a range of composition. The adsorption of lipid from the vesicle dispersions onto the surfaces of glass beads has been measured by a batch procedure using a radiochemical assay. Lipid deposition onto the glass surface occurs via vesicle adsorption rather than monomeric lipid adsorption and a fluorescent assay has been used to demonstrate that the vesicles disrupt on contact with the glass. The adsorption isotherms are of the Langmuir type and for pure DPPC the limiting areas at the glass-aqueous interface are 0.39 nm2 molecule–1 and 0.64 nm2 molecule–1 at 25 and 50 °C, respectively. These figures suggest that a monolayer of DPPC is formed at the interface. Limiting adsorption could not be correlated with the electrokinetic properties of the vesicles and was not markedly dependent on the acyl chain length for a series of diacylphosphatidylcholines.