Investigation of polymer-cushioned phospholipid bilayers in the solid phase by atomic force microscopy

The preparation and the structure of polymer-cushioned phospholipid bilayers (PCPBs) in the solid phase through vesicle fusion was studied by atomic force microscopy. It was found that the anionic phospholipid alpha -L-dipalmitoylphosphatidic acid could form a good PCPB on the polyethylenimine surface but not on that of poly(dimethyldiallyammonium chloride), indicating that the attractive electrostatic force alone cannot guarantee the fusion of the vesicles. The zwitterionic phospholipid alpha -L-dipalmitoylphosphatidylcholine could not form a good PCPB on either polymer surface. It was found that the PCPB rearranged to an alternate monolayer and trilayer structure while it was exposed to air and turned back to a bilayer structure when it was dipped into water again. Various factors affecting the PCPB formation were discussed. The preparation of such bilayers through the LB transfer method was also investigated.