Department of Physics, Ludwig-Maximilians-Universitat, D-80539 Munich, Germany.
Biointerphases. 2007 Sep;2(3):109-18. doi: 10.1116/1.2790852.
This work reports a novel tethered lipid membrane supported on silicon oxide providing an improved model cell membrane. There is an increasing need for robust solid supported fluid model membranes that can be easily deposited on soft cushions. In such architecture the space between the membrane and the substrate should be tunable in the nanometer range. For this purpose a SiO(2) surface was functionalized with poly(ethylene glycol) (PEG)-lipid tethers and further modified with poly(ethylene glycol) making a biologically passivated substrate available for lipid bilayer deposition. First, a short chain self-assembled alkenyl silane film was oxidized to yield terminal COOH groups and then functionalized with amino-terminated PEG-lipids via N-hydroxysuccinimide chemistry. The functionalized silane film was then additionally passivated by functionalization of unreacted COOH groups with amino-terminated PEG of variable chain length. X-ray photoelectron spectroscopy (XPS) analysis of dry films, carried out near the C 1s ionization edge to characterize chemical groups formed in the near-surface region, confirmed binding of PEG-lipid tethers to the silane film. XPS further indicated that backfilling with PEG caused the lipid tails to stick up above the PEG layer which was confirmed by the x-ray reflectivity measurements. Lipid vesicle fusion on these surfaces in the presence of excess water resulted in the formation of supported membranes characterized by very high homogeneity and long range mobility, as confirmed by fluorescence bleaching experiments. Even after repeated drying-hydrating cycles, these robust surfaces provided good templates for high fluidity elevated membranes. X-ray reflectivity measurements of the tethered membranes, with a resolution of 0.6 nm in water, showed that these fluid membranes are elevated up to 8 nm above the silicon oxide surface.
这项工作报道了一种新型的固定在氧化硅上的脂双层膜，为改进的模型细胞膜提供了一种方法。需要坚固的、易于沉积在柔软衬底上的固态支撑流体模型膜的需求日益增长。在这种结构中，膜和基底之间的空间应该可以在纳米范围内进行调节。为此，在 SiO2 表面用聚乙二醇（PEG）-脂键合来固定脂双层膜，并进一步用聚乙二醇进行修饰，得到了可用作脂双层沉积的生物钝化衬底。首先，短链自组装烯基硅烷薄膜被氧化，生成末端的 COOH 基团，然后通过 N-羟基琥珀酰亚胺化学与氨端 PEG-脂进行功能化。然后，通过用不同链长的氨端 PEG 对未反应的 COOH 基团进行功能化，进一步对功能化的硅烷薄膜进行钝化。X 射线光电子能谱（XPS）分析干膜，在 C 1s 离化边缘附近进行，以表征近表面区域形成的化学基团，证实了 PEG-脂键合到硅烷薄膜上。XPS 进一步表明，用 PEG 进行回充会导致脂尾突起到 PEG 层之上，这一点通过 X 射线反射率测量得到了证实。在存在过量水的情况下，这些表面上的脂质囊泡融合导致了支撑膜的形成，其具有非常高的均一性和长程流动性，这一点通过荧光漂白实验得到了证实。即使在重复的干燥-水合循环之后，这些坚固的表面仍然为高流动性的抬高膜提供了良好的模板。用分辨率为 0.6nm 的 X 射线反射率测量对固定脂双层膜进行测量，结果表明这些流体膜被抬高到距离氧化硅表面 8nm 以上。
