Planar bilayer lipid membranes supported on mesoporous aerogels, xerogels, and Vycor((R)) glass: an epifluorescence microscopy study

摘要

We report the deposition and characterization of fluid synthetic biomembranes on various mesoporous materials. Planar phospholipid bilayers consisting of 97 mol% L-alpha-phosphatidylcholine (egg PC) and 3 mol% fluorescently labeled lipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (NBD-PE) were formed by fusion of similar to30 nm diameter unilamellar vesicles on four different silica-based substrates: aerogels, xerogels, Vycor(R) glass, and microscope cover glass. Epifluorescence microscopy was used to examine the micrometer-scale homogeneity of the resulting planar membranes. Fluorescence recovery after photobleaching analysis was used to determine the lateral mobility retained in the membranes. Diffusion coefficients of 0.6 +/- 0.2, 2 +/- 1, 1.7 +/- 1.1, and 2.5 +/- 0.4 mum(2)s(-1) were obtained for membranes supported on aerogels, xerogels, Vycor(R), and glass, respectively. In the same order, the average immobile lipid fractions, defined by the normalized magnitudes of recovery, were similar to75%, 81%, 94%, and 100%. Both lateral mobility and immobile fraction exhibited ranges of standard variations, especially pronounced for xerogels and Vycor(R), suggesting that the long-range translational dynamics of lipids in the supported membranes are sensitive to local defects and geometry of the underlying surface. Micrometer-scale clefts on the aerogel and xerogel surfaces limited the lipid lateral exchange, as shown by the reduced diffusivity and recovery. (C) 2004 Elsevier B.V. All rights reserved.