Supported phospholipid bilayer formation on hydrophilicity-controlled silicon dioxide surfaces

We investigated the influence of surface hydroxyl groups (-OHs) on the supported planar phospholipid bilayer (SPB) formation and characteristics. We prepared SiO2 surfaces with different hydrophilicity degree by annealing the SiO2 layer on Si(100) formed by wet chemical treatments. The hydrophilicity reduced with irreversible thermal desorption of -OHs. We formed SPB of dimyristoylphosphatidylcholine on the SiO2 surfaces by incubation at a 100-nm-filtered vesicle suspension. The formation rate was faster on less hydrophilic surfaces. We proposed that a stable hydrogen-bonded water layer on the SiO2 surface worked as a barrier to prevent vesicle adhesion on the surface. Theoretical calculation indicates that water molecules on vicinal surface -OHs take a stable surface-unique geometry, which disappears on an isolated -OH. The surface -OH density, however, affected little the fluidity of once formed SPBs, which was measured by the fluorescence recovery after the photobleaching method. We also describe the area-selective SPB deposition using surface patterning by the focused ion beam.