Mobile phospholipid bilayers on a polyion/alkylthiol layer pair

The formation of phospholipid bilayers on a polymer/alkylthiol layer pair w as investigated by surface plasmon resonance (SPR). The organic layer pair between the lipid membrane and the solid gold surface consisted of a self-a ssembled monolayer of 11-mercaptoundecanoic acid (MUA) on a gold surface fo llowed by a thin layer of hydrated cationic poly(diallyldimethylammonium ch loride) (PDDA). The lipid layers were formed by vesicular fusion of small u nilamellar vesicles of an anionic lipid 1-stearoyl-2-oleoyl-phosphatidylser ine (SOPS), a zwitterionic lipid 1-palmitoyl-2-oleoylphosphatidylcholine (P OPC), 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 mu ltilayers tended to build up with higher concentrations of POPC. The electr ostatic 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 show ed that single bilayers supported on the PDDA/alkylthiol layer pair were mo bile 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 wa s bound to the supported bilayers as detected by SPR. This suggests the pot ential of this model membrane system for use as a biosensor.