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

The preparation and the structure of polymer-cushioned phospholipid bilayer s (PCPBs) in the solid phase through vesicle fusion was studied by atomic f orce microscopy. It was found that the anionic phospholipid alpha -L-dipalm itoylphosphatidic acid could form a good PCPB on the polyethylenimine surfa ce but not on that of poly(dimethyldiallyammonium chloride), indicating tha t the attractive electrostatic force alone cannot guarantee the fusion of t he vesicles. The zwitterionic phospholipid alpha -L-dipalmitoylphosphatidyl choline could not form a good PCPB on either polymer surface. It was found that the PCPB rearranged to an alternate monolayer and trilayer structure w hile it was exposed to air and turned back to a bilayer structure when it w as dipped into water again. Various factors affecting the PCPB formation we re discussed. The preparation of such bilayers through the LB transfer meth od was also investigated.