School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue 639798, Singapore.
Langmuir. 2013 Sep 10;29(36):11375-84. doi: 10.1021/la4017992. Epub 2013 Aug 23.
The adhesion of lipid vesicles to solid supports represents an important step in the molecular self-assembly of model membrane platforms. A wide range of experimental parameters are involved in controlling this process, including substrate material and topology, lipid composition, vesicle size, solution pH, ionic strength, and osmotic pressure. At present, it is not well understood how the magnitude and direction of the osmotic pressure exerted on a vesicle influence the corresponding adsorption kinetics. In this work, using quartz crystal microbalance with dissipation (QCM-D) monitoring, we have experimentally studied the role of osmotic pressure in the adsorption of zwitterionic vesicles onto silicon oxide. The osmotic pressure was induced by changing the ionic strength of the solvent across an appreciably wider range (from 25 to 1000 mM NaCl outside of the vesicle, and 125 mM NaCl inside of the vesicle, unless otherwise noted) compared to that used in earlier works. Our key finding is demonstration that, by changing osmotic pressure, all three generic types of the kinetics of vesicle adsorption and rupture can be observed in one system, including (i) adsorption of intact vesicles, (ii) adsorption and rupture after reaching a critical vesicle coverage, and (iii) rupture just after adsorption. Furthermore, theoretical analysis of pressure-induced deformation of adsorbed vesicles and a DLVO-type analysis of the vesicle-substrate interaction qualitatively support our observations. Taken together, the findings in this work demonstrate that osmotic pressure can either promote or impede the rupture of adsorbed vesicles on silicon oxide, and offer experimental evidence to support adhesion energy-based models that describe the adsorption and spontaneous rupture of vesicles on solid supports.
脂质体在固体支持物上的附着是模型膜平台分子自组装的重要步骤。控制这个过程涉及到广泛的实验参数，包括基底材料和拓扑结构、脂质组成、囊泡大小、溶液 pH 值、离子强度和渗透压。目前，人们还不太清楚施加在囊泡上的渗透压的大小和方向如何影响相应的吸附动力学。在这项工作中，我们使用石英晶体微天平（QCM-D）监测，实验研究了渗透压在两性离子囊泡吸附到氧化硅上的作用。渗透压是通过改变溶剂的离子强度来诱导的，与早期工作相比，渗透压的变化范围要大得多（囊泡外从 25 到 1000 mM NaCl，囊泡内从 125 mM NaCl，除非另有说明）。我们的主要发现是证明，通过改变渗透压，可以在一个系统中观察到囊泡吸附和破裂的所有三种通用类型的动力学，包括（i）完整囊泡的吸附，（ii）达到临界囊泡覆盖后吸附和破裂，以及（iii）吸附后立即破裂。此外，对吸附囊泡的压力诱导变形的理论分析和对囊泡-基底相互作用的 DLVO 分析定性支持了我们的观察。总之，这项工作的发现表明，渗透压可以促进或阻碍吸附在氧化硅上的囊泡破裂，并提供实验证据支持描述囊泡在固体支持物上吸附和自发破裂的基于粘附能的模型。
