Nature uses lipid membranes as a universal wrap around cells, and there is increasing evidence of the membrane$,1ry(Bs role in controlling critical cell functions by reorganizing itself into lipid rafts. Rafts consist of laterally phase separated lipids whose occurrence coincides with changes in the local cell surface topography, local valency, and membrane integrity. These structural changes seem to correlate with several critical cell functions including cell signaling and viral infection mechanisms, and the molecular processes regulating these changes are still largely unknown.
Inspired by Nature, we use model lipid membranes to study simplified processes that alter the surface topography, the apparent activity/valency of functionalized membranes, the membrane permeability and fusogenicity, with the aim to potentially contribute to the understanding and control of related collective membrane behavior. We design and study such simplified pH-dependent processes on model functionalized lipid bilayers in the form of giant and of small unilamellar vesicles. Giant lipid vesicles are used as templates to study the morphology, reversibility, and kinetics of formation and growth of phase separated lipid domains. Integration of these processes on nanometer-sized lipid vesicles used as drug delivery carriers may precisely control their interactions with diseased cells increasing therapeutic efficacy while minimizing toxicities by simultaneously addressing a number of transport-related obstacles within tumors or targeted cells. Examples of improving the therapeutic potential in liposomal chemotherapy and alpha-particle radiotherapy will be presented.