Stabilization Impact of Nano-particles to Polymeric Hydrogels

该项目的目的是控制（生物）粘合剂和机械稳定的水凝胶。这两种特性通常是相互抵消的。因此，该项目致力于理解水凝胶结构、粘附性能和机械/流变行为之间的关系。贻贝可以通过分泌贻贝足蛋白，形成贻贝足，从而牢固地附着在岩石、金属、木结构和海洋生物等各种基质上。一种名为3,4-二羟基苯基- l-丙氨酸（DOPA）的儿茶酚氨基酸是贻贝足蛋白质的主要成分，对于实现非凡的水下粘附至关重要。受这种自然机制的启发，我们的目标是通过在水凝胶中加入多巴来获得强附着力。纳米颗粒将用于提高聚合物水凝胶的机械强度。纳米颗粒是聚合物核/壳颗粒，聚合物刷作为外壳（球形聚合物刷，SPB）。它们的直径可以控制在几十到几百纳米之间，为了控制这种强化机制，纳米颗粒与水凝胶之间的相互作用将被定制：静电吸引、氢键和在二价金属阳离子（Zn2+, Fe2+）存在下的螯合。为了提供多种结构和结构，水凝胶基质将由交联的线性链组成，其中spb并入基质中，或者将spb与微凝胶（直径：50 nm至2.5微米）混合。随着应用的前景（例如条纹上的水凝胶），这些水凝胶将被转移到平面表面。为了理解结构和力学/流变特性之间的关系，结构和力学/流变学将在不同的长度尺度（10nm - mm）上进行分析。例如，在不同长度尺度和不同载荷（nN到mN）下，将通过不同压头尺寸的压痕来测量力学。除了不同的长度尺度和力范围外，不同的频率也有助于理解流变特性。为此，将使用流变仪和QCM-D，并进行动态AFM实验。进一步的长期目标是提供一种生物相容性凝胶。在目前的提案中，我们将解决pH和二价阳离子（如Zn2+， Fe2+）导致与DOPA单元螯合的影响。用不同的外部刺激触发系统对于药物输送系统或感觉系统来说是有趣的。大多数研究的凝胶将基于PAA。在少数情况下，将研究PNIPAM和peg基凝胶，以引入对外部温度变化的额外灵敏度。中德合作伙伴的专业知识是互补的，将产生强大的协同效应。最近，他们开始了一项合作，该合作将通过该项目得到加强。

The aim of the project is the control of (bio)adhesive and mechanically stable hydrogels. These two properties are often counteracting. Therefore the project addresses the understanding of the relationship between the hydrogel structure, the adhesion property and mechanical/rheological behavior. Mussels can hold strongly to various substrates like rocks, metal, wood structure and marine organisms by secreting mussel foot proteins, which form mussel byssus. A catecholic amino acid called 3,4-dihydroxyphenyl-L-alanine (DOPA) presents a major component of the mussel foot proteins and is crucial for achieving the remarkable underwater adhesion. Inspired by this natural mechanism we aim to obtain strong adhesion by incorporating DOPA within the hydrogel. Nanoparticles will be used to enhance the mechanical strength of the polymer hydrogels. The nanoparticles are polymeric core/shell particles with a polymer brush as a shell (spherical polymer brushes, SPB). Their diameter can be controlled between several tens up to several hundreds of nm. In order to control this strengthening mechanism the interaction between the nanoparticles and the hydrogels will be tailored: electrostatic attraction, hydrogen bonding and chelation in presence of divalent metal cations (Zn2+, Fe2+). In order to offer a large variety in structure and architecture the hydrogel matrix will consist either of cross-linked linear chains where the SPBs are incorporated within the matrix or they the SPBs are mixed with microgels (diameter: 50 nm to 2.5 mikrometer).With perspectives for applications (e.g. hydrogels on stripes) theses hydrogels will be transferred to planar surfaces. In order to understand the relation between structure and mechanical/rheological properties both structure and mechanics/rheology will be analysed on different length scales (10 nm - mm). For instance, the mechanics will be measured via indentation with different indenter sizes on different length scales and under different loads (nN to mN). Beside different length scales and force ranges also different frequency regimes are of interest for the understanding of rheological properties. For this purpose a rheometer and a QCM-D will be used and dynamic AFM experiment will be carried out. A further long-term goal will be to offer a biocompatible gel. In the current proposal we will address the effect of pH and divalent cations like Zn2+, Fe2+ which leads to chelation with the DOPA units. Triggering the system with different outer stimuli is interesting with respect to drug delivery systems or sensorics. Most of the studied gels will be based on PAA. In a few cases PNIPAM- and PEG-based gels will be studied in order to introduce an additional sensitivity against outer temperature changes. The expertise of the Chinese and the German partners is complementary and will lead to strong synergy. Recently, they started a cooperation which would be strengthen by this project.