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。这两种性质往往相互抵消。因此，该项目解决了水凝胶结构，粘附性能和机械/流变行为之间的关系的理解。贻贝可以通过分泌形成贻贝足丝的贻贝足蛋白来牢固地附着在各种基质上，如岩石、金属、木材结构和海洋生物。被称为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的主要成分，并且对于实现显著的水下粘附至关重要。受这种自然机制的启发，我们的目标是通过将DOPA掺入水凝胶中来获得强粘附力。纳米颗粒将用于增强聚合物水凝胶的机械强度。纳米颗粒是具有聚合物刷作为壳的聚合物核/壳颗粒（球形聚合物刷，SPB）。它们的直径可以控制在几十到几百nm之间。为了控制这种强化机制，纳米颗粒和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（Zn 2+、Fe 2+）存在下的螯合。为了提供结构和构造的多种多样性，水凝胶基质将由交联的线性链组成，其中SPB被并入基质中，或者SPB与微凝胶（直径：50 nm至2.5 μ m）混合。为了理解结构和机械/流变性能之间的关系，将在不同的长度尺度（10 nm - mm）上分析结构和机械/流变性能。例如，将通过在不同长度尺度和不同载荷（nN至mN）下使用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之外，不同的频率范围对于理解流变特性也是感兴趣的。为此，将使用流变仪和QCM-D，并进行动态AFM实验。 另一个长期目标是提供一种生物相容性凝胶。在当前的提议中，我们将解决pH和二价阳离子如Zn 2+、Fe 2+的影响，其导致与DOPA单元的螯合。用不同的外部刺激触发系统对于药物递送系统或传感器是有趣的。大多数研究的凝胶将基于PAA。在少数情况下，将研究基于PNIPAM和PEG的凝胶，以引入对外部温度变化的额外灵敏度。中国和德国合作伙伴的专业知识是互补的，将产生强大的协同作用。最近，他们开始了一项合作，该项目将加强这一合作。

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.