Creating functional vesicle assemblies from vesicles and nanoparticles.

Vesicles (liposomes) have been shown to be excellent vehicles for drug delivery, yet assemblies of vesicles (vesicle aggregates) have been used infrequently in this context. However vesicle assemblies have useful properties not available to individual vesicles; their size can cause localisation in specific tissues and they can incorporate more functionality than is possible with individual vesicles. This article reviews progress on controlling the properties of vesicle assemblies in vitro, applications of vesicle assemblies in vivo, and our recent creation of magnetic nanoparticle-vesicle assemblies. The latter assemblies contain vesicles crosslinked by coated Fe3O4 nanoparticles and this inclusion of magnetic functionality makes them magnetically responsive, potentially allowing magnetically-induced contents release. This article describes further studies on the in vitro formation of these magnetic nanoparticle-vesicle assemblies, including the effect of changing magnetic nanoparticle concentration, pH, adhesive lipid structure and bilayer composition. These investigations have led to the development of thermally-sensitive magnetic nanoparticle-vesicle assemblies that release encapsulated methotrexate on warming.