Mobile phospholipid bilayers on a polyion/alkylthiol layer pair

The formation of phospholipid bilayers on a polymer/alkylthiol layer pair was investigated by surface plasmon resonance (SPR). The organic layer pair between the lipid membrane and the solid gold surface consisted of a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on a gold surface followed by a thin layer of hydrated cationic poly(diallyldimethylammonium chloride) (PDDA). The lipid layers were formed by vesicular fusion of small unilamellar vesicles of an anionic lipid 1-stearoyl-2-oleoyl-phosphatidylserine (SOPS), a zwitterionic lipid 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), and mixtures of these two lipids with different compositions. In the case of pure SOPS and lipid mixtures with a POPC composition below 25%, the lipid layer thickness was approximately that of a single bilayer, while multilayers tended to build up with higher concentrations of POPC. The electrostatic interaction of the cationic PDDA with the negatively charged lipid membrane is most probably the driving force for the adsorption of a single bilayer. Fluorescence recovery after photobleaching (FRAP) experiments showed that single bilayers supported on the PDDA/alkylthiol layer pair were mobile at room temperature with lateral diffusivities of approximately (1-2) x 10(-9) cm(2)/s. A membrane fusion peptide wt-20 of the influenza virus was bound to the supported bilayers as detected by SPR. This suggests the potential of this model membrane system for use as a biosensor.