Asymmetric lipid bilayer sandwiched in polyelectrolyte multilayer films through layer-by-layer assembly

Lipid bilayer of 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) was formed on the surface of a linearly growing polyanion/polycation polyelectrolyte multilayer (PEM) film prepared by the layer-by-layer (LbL) technique. The PEM films were prepared with two strong polyelectrolytes poly( sodium 4-styrenesulfonate) (PSS) as the polyanion and poly-(diallyldimethylammonium chloride) (PDADMAC) as the polycation. The DMPE was always deposited onto the PEM cushion terminated with positively charged PDADMAC. The surface charge of the DMPE-coated film depends on the pH of the buffer solution. Formation of PEM could be continued on the top of the lipid bilayer by tuning the headgroup charge of the DMPE. An asymmetric structure of polycation/lipid/polyanion sandwich'' was created in the case where anionic PSS was used as the first layer of the subsequent PEM. In this system, the DMPE lipid membrane was constructed as a charge asymmetric barrier sandwiched in the interior of the PEM films. The formation of PEM architectures incorporated with an asymmetric DMPE bilayer was confirmed by zeta potential, UV-vis absorption, quartz crystal microbalance (QCM) and neutron reflectometry experiments.