Lipidic composite vesicles based on poly(NIPAM), chitosan or hyaluronan: behaviour under stresses

Giant Unilamellar Vesicles (GUVs) consisting in self-closed lipid bilayers of 0.5-100 µm diameter are considered as oversimplified models of cells because of their biological membrane and micrometric size while Large Unilamellar Vesicles (LUVs) of 100-500 nm diameter have applications in drug delivery. To improve structural and mechanical properties of these vesicles, we have developed two categories of composite polymer-vesicles. The first category is prepared by encapsulating solutions or networks of poly (N-isopropyl-acrylamide) (polyNIPAM) chains. PolyNIPAM exhibiting a Low Critical Solution Temperature (LCST) at 32°C, composite NIPAM-vesicles are thermo-responsive. The second category of vesicles is obtained by adsorption of polyelectrolytes (chitosan or hyaluronan or both layer-by-layer) on their outer surface. Chitosan and hyaluronan are respectively positively and negatively charged polymers; both are biocompatible and allow to tune the net charge of the vesicles. All these composite vesicles hold promise as passive mechanical models of cells and as drug carriers because of their improved structural and mechanical properties and enhanced resistance to various mechanical or chemical stresses if compared to unmodified vesicles. Poly (NIPAM) vesicles present the additional advantage to be potential thermo-responsive drug carriers, collapsing reversibly at 32°C with a release of 98% of their internal solution.