College Park, Maryland      June 6 - 10 , 2004

W2-B3 (2:15 PM): Formation of Lipid Membranes Assembled on Ordered Nanocomposite and Nanoporous Silica Thin-Films: A Neutron Reflectivity Study

D. A. Doshi, A.M. Dattelbaum, E.B. Watkins, J. Majewski, A.P. Shreve (Los Alamos National Laboratory), A.N. Parikh (University of California-Davis)

Ordered nanocomposite and nanoporous silica thin-films are promising platforms for supporting lipid membrane architectures that mimic biological systems. In this study we have systematically investigated the viability and the interfacial characteristics of phospholipid membranes formed on ordered silica thin-films using neutron reflectivity. The non-destructive nature and long penetration depth of neutrons (compared to x-rays) makes neutron reflectivity an ideal technique to study the soft silica film-membrane and membrane-water interfaces. Silica thin-films used here were prepared via an evaporation induced self-assembly process, which involves the hierarchical organization of organic surfactant and inorganic silica building blocks. POPC (1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine) lipid membranes were then deposited on the silica thin-film surfaces by vesicle fusion. The nature of the silica thin-film surface was found to be critical for the vesicle fusion process. In case of vesicle fusion on a self-assembled nanocomposite silica film, where the templating surfactant is present, a low-density lipid membrane was formed. When the templating surfactant was removed via photo-calcination, a densely packed lipid bilayer formed on the surface. The silica surfaces were also modified with a self-assembled silane monolayer prior to lipid membrane formation. A detailed analysis of all the thin-film/lipid membrane interfaces and structures formed will be presented.

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