title: Effect of support corrugation on silica xerogel--supported phase-separated lipid bilayers.
abstract: Lipid bilayers supported by substrates with nanometer-scale surface corrugations hold interest in understanding both nanoparticle-membrane interactions and the challenges of constructing models of cell membranes on surfaces with desirable properties, e.g., porosity. Here, we successfully form a two-phase (gel-fluid) lipid bilayer supported by nanoporous silica xerogel. Surface topology, lateral diffusion coefficient, and lipid density in comparison to mica-supported lipid bilayers were characterized by atomic force microscopy, fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), and quantitative fluorescence microscopy, respectively. We found that the two-phase lipid bilayer follows the silica xerogel surface contours. The corrugation imparted on the lipid bilayer results in a lipid density that is twice that on a flat mica surface in the fluid regions. In direct agreement with the doubling of actual bilayer area in a projected area, we find that the lateral diffusion coefficient (D) of fluid lipids on silica xerogel (approximately 1.7 microm2/s) is lower than on mica (approximately 3.9 microm2/s) by both FRAP and FCS techniques. Furthermore, the gel-phase domains on silica xerogel compared to mica were larger and less numerous. Overall, our results suggest the presence of a relatively defect-free continuous two-phase lipid bilayer that penetrates approximately midway into the first layer of approximately 50 nm silica xerogel beads.
authors.affiliation: Department of Chemical Engineering & Materials Science, University of California, Davis, California 95616, USA.
authors.forename: Emel I
authors.initials: EI
authors.lastname: Goksu
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Nellis
authors.forename: Wan-Chen
authors.initials: WC
authors.lastname: Lin
authors.forename: Joe H
authors.initials: JH
authors.lastname: Satcher
authors.forename: Jay T
authors.initials: JT
authors.lastname: Groves
authors.forename: Subhash H
authors.initials: SH
authors.lastname: Risbud
authors.forename: Marjorie L
authors.initials: ML
authors.lastname: Longo
mesh_terms: D004058:Diffusion; D036681:Fluorescence Recovery After Photobleaching; D005782:Gels / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008422:Materials Testing; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013499:Surface Properties
chemical_list: D005782:Gels; D008051:Lipid Bilayers; D008055:Lipids; D008567:Membranes, Artificial; D012822:Silicon Dioxide