Stabilization Impact of Nano-particles to Polymeric Hydrogels

该项目的目标是控制(生物)粘合剂和机械稳定的水凝胶。这两个特性往往相互抵消。因此，该项目致力于了解水凝胶结构、粘附性和力学/流变性之间的关系。贻贝可以通过分泌贻贝足部蛋白而强烈地附着在岩石、金属、木材结构和海洋生物等各种底物上，形成贻贝的足部。一种儿茶性氨基酸，称为3，4-二羟基苯基-L-丙氨酸(DOPA)，是贻贝足部蛋白的主要成分，对实现显著的水下粘附性至关重要。受这一自然机制的启发，我们的目标是通过在水凝胶中加入DOPA来获得强大的粘附性。纳米粒子将用于提高聚合物水凝胶的机械强度。纳米粒子是以聚合物刷为壳的聚合物核/壳粒子(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。为了控制这种增强机制，纳米粒子和水凝胶之间的相互作用将被定制：静电吸引、氢键和在二价金属离子(锌、铁)存在下的螯合作用。为了提供多样化的结构和结构，水凝胶基质将由交联线性链组成，其中SPBS被结合在基质中，或者他们SPBS与微凝胶(直径：50 nm到2.5微米)混合。从应用的角度(例如条状水凝胶)，这些水凝胶将转移到平面表面。为了了解结构和力学/流变性之间的关系，将在不同的长度尺度(10 nm-mm)上分析结构和力学/流变学。例如，将通过在不同长度尺度和不同载荷(Nn到Mn)下用不同压头尺寸的压痕来测量力学性能。除了不同的长度、尺度和作用力范围外，不同的频率范围对于理解流变特性也是有意义的。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的凝胶。在当前的提案中，我们将讨论pH和二价阳离子(如锌、铁)的影响，这些阳离子会导致与DOPA单元的螯合。在药物输送系统或感官方面，用不同的外部刺激触发系统是很有趣的。大多数研究的凝胶将以PAA为基础。在少数情况下，将研究基于PNIPAM和聚乙二醇凝胶的凝胶，以引入对外部温度变化的额外敏感性。中德合作伙伴的专业知识具有互补性，将产生强大的协同效应。最近，他们开始了合作，这个项目将加强合作。

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.