Colloid Stabilization by an Oppositely Charged Polysaccharide: Mechanism of Interaction and Interface Studied with Synchrotron X-Rays

The liposome surface is modeled by a 2-D lipid monolayer made of behenic acid forming a negatively charged interface. The properties at the air/liquid interface were examined by pressure-area isotherms in a Langmuir trough introducing diluted chitosan solution in the subphase. X-ray reflectivity of the interface was measured in the same conditions in order to determine the layer thickness of the chitosan adsorbed on the behenic acid monolayer formed on water. Influence of pH of the subphase and molecular weight of adsorbed chitosan was investigated. All these results allow confirming that the charge and the stability of the lipid layer are controlled by the nature of the polyelectrolyte and the nature of the medium. In particular, the use of biocompatible charged polysaccharides is of interest for biomedical applications.