Keller C A, Kasemo B
Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
Biophys J. 1998 Sep;75(3):1397-1402. doi: 10.1016/S0006-3495(98)74057-3.
We have measured the kinetics of adsorption of small (12.5-nm radius) unilamellar vesicles onto SiO2, oxidized gold, and a self-assembled monolayer of methyl-terminated thiols, using a quartz crystal microbalance (QCM). Simultaneous measurements of the shift in resonant frequency and the change in energy dissipation as a function of time provide a simple way of characterizing the adsorption process. The measured parameters correspond, respectively, to adsorbed mass and to the mechanical properties of the adsorbed layer as it is formed. The adsorption kinetics are surface specific; different surfaces cause monolayer, bilayer, and intact vesicle adsorption. The formation of a lipid bilayer on SiO2 is a two-phase process in which adsorption of a layer of intact vesicles precedes the formation of the bilayer. This is, to our knowledge, the first direct evidence of intact vesicles as a precursor to bilayer formation on a planar substrate. On an oxidized gold surface, the vesicles adsorb intact. The intact adsorption of such small vesicles has not previously been demonstrated. Based on these results, we discuss the capacity of QCM measurements to provide information about the kinetics of formation and the properties of adsorbed layers.
我们使用石英晶体微天平（QCM）测量了小尺寸（半径12.5纳米）单层囊泡在二氧化硅、氧化金和甲基封端硫醇自组装单分子层上的吸附动力学。作为时间函数的共振频率偏移和能量耗散变化的同步测量提供了一种表征吸附过程的简单方法。所测量的参数分别对应于吸附质量和形成过程中吸附层的机械性能。吸附动力学具有表面特异性；不同的表面会导致单层、双层和完整囊泡的吸附。在二氧化硅上形成脂质双层是一个两相过程，其中完整囊泡层的吸附先于双层的形成。据我们所知，这是完整囊泡作为平面基底上双层形成前体的首个直接证据。在氧化金表面，囊泡完整吸附。此前尚未证明如此小的囊泡能完整吸附。基于这些结果，我们讨论了QCM测量提供有关形成动力学和吸附层性质信息的能力。
