Water adsorption and desorption on chemically inert, biorepulsive surfaces

该项目的主要目的是更好地了解聚乙二醇和低聚乙二醇（分别为PEG和OEG）基有机表面对蛋白质吸附和生物污染的惰性背后的机制。假设，根据最普遍的观点，这些性质背后的关键因素是PEG/OEG部分的水化作用，我们计划对一系列模型OEG表面上水吸附和解吸的动力学和热力学进行系统研究，并研究水在吸附过程中的湿润和成核行为。作为合适的测试系统，我们将在金和银底物上采用一系列OEG取代烷硫酸酯（OEG- at）的自组装单层（sam）。通过改变OEG片段的长度或改变其堆积密度和用其他物质稀释OEG- at部分，这些单层膜的生物排斥特性将以一种良好控制的方式进行调整。上述变化将以这样一种方式进行，即目标表面的宏观润湿特性将保持不变或仅略有变化，这应该可以解开水化和随后的界面润湿。此外，OEG-AT SAMs的末端基团也将发生变化，以获得进一步解决水化和界面润湿问题的工具。将特别关注水的成核行为和吸附的初始阶段，其中水化应起主导作用，因为水的吸附应首先以OEG- ats sam的OEG部分的水化形式发生，然后在sam -气氛界面（界面相）形成冰膜。通过设计oeg - at分子和各自的sam来改变水覆盖范围和系统地改变水化能力，我们应该能够监测从水化到润湿状态的转移，以及区分水化相和界面相，并具体得出它们的参数。观察到的行为和导出的动力学和热力学参数以及水化程度等将与OEG-AT sam对蛋白质吸附和生物污染的倾向或惰性相关。最后，利用几种互补的光谱技术，推导出水化相中水分子的结合构型及其在界面相中的结构和形态。此外，我们计划在吸附水的初始阶段监测OEG片段的结构和构象的变化。实验结果和推导出的参数将与现有理论模拟的预测结果进行比较，这既是对各自模型正确性的检验，也是促进理论进一步改进和发展的一种手段。

The main objective of the proposed project is a better understanding of the mechanism behind the inertness of poly- and oligo(ethylene glycol) (PEG and OEG, respectively) based organic surfaces to protein adsorption and biofouling. Assuming, in accordance with the most accepted viewpoint, that the key factor behind these properties is hydration of the PEG/OEG moieties, we plan a systematic study of the kinetics and thermodynamics of water adsorption and desorption on a series of model OEG surfaces as well as investigation of the wetting and nucleation behavior of water during the adsorption. As suitable test systems we will take a series of self-assembled monolayers (SAMs) of OEG substituted alkanethiolates (OEG-ATs) on gold and silver substrates. The biorepulsive properties of these monolayers will be tuned in a well-controlled fashion by either varying the length of the OEG segments or by changing their packing density and diluting the OEG-AT moieties with other species. The above changes will be performed in such a way that the macroscopic wetting properties of the target surfaces will be kept constant or vary slightly only, which should make possible to untangle the hydration and subsequent interfacial wetting. Additionally, the terminal group of the OEG-AT SAMs will be varied to obtain a further tool to untangle hydration and interfacial wetting. A particular attention will be paid to the nucleation behavior of water and to the initial stages of adsorption, where the hydration should play the dominant role since the adsorption of water should first occur in the form of hydration of the OEG part of the OEG-ATs SAMs followed by the formation of the ice film at the SAM-ambience interface (interfacial phase). Varying the water coverage and systematically varying the capability of hydration by design of the OEG-ATs molecules and respective SAMs, we should be able to monitor the transfer from the hydration to wetting regime as well as to distinguish between the hydration and interfacial phases and to derive specifically their parameters. The observed behavior and derived kinetic and thermodynamic parameters as well as extent of hydration, etc., will be correlated with the proneness or inertness of the OEG-AT SAMs to protein adsorption and biofouling. Finally, using several complementary spectroscopic techniques, information about the binding configuration of the water molecules in the hydration phase and their structure and morphology in the interfacial phase will be derived. In addition, we plan to monitor the changes in the structure and conformation of the OEG segments at the initial stages of the water adsorption. The experimental results and derived parameters will be compared with predictions of available theoretical simulations, both as a test of correctness of the respective models and as a means to stimulate a further improvement and development of theory.