New paradigms for relating the microstructure of cartilage to its large scale mechanics: The Roles of Rigidity-Percolation and Double Gel Network Structure in Non-Linear Response

将软骨微观结构与其大规模力学联系起来的新范例：刚性渗透和双凝胶网络结构在非线性响应中的作用

基本信息

批准号：
1536463
负责人：
Itai Cohen
金额：
$ 34.81万
依托单位：
Cornell University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-08-01 至 2019-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536463&HistoricalAwards=false
关键词：
New paradigms relating microstructure cartilage

项目摘要

Cartilage, the smooth tissue that coats bones in joints, is a remarkable material that can last decades and outperform any man-made substance in its unique combination of material properties. There are several aspects of cartilage's microstructure that contribute to its longevity. First, the matrix that gives rise to these mechanical properties is comprised of two interpenetrating polymer networks, a design that has recently been shown to inhibit crack formation. Second, the mechanical properties of cartilage change with depth such that energy damping occurs almost entirely in a thin region near its surface. The PIs have recently developed a theoretical model that explains how variations in the concentration of the polymer networks lead to this localization of energy absorption to the tissue surface. This project uses an array of experimental techniques to test this model and extend its applicability to extreme deformations where cartilage can be damaged. By chemically treating the tissue to remove essential molecular components and testing the tissue response in their absence, the PIs will determine which elements of the matrix are essential for generating cartilage's unique combination of mechanical properties. A better understanding of the macromolecular origins of cartilage mechanical properties will give insight into how diseases such as arthritis develop, guide approaches to tissue repair therapies, and more broadly, provide mechanical design criteria for fabrication of robust materials that can endure extreme loading.Articular cartilage has unique material properties that enable it to endure millions of loading cycles per year while protecting underlying tissues. The structural and compositional origins of its compressive properties have been known for decades. However, there is no equivalent understanding of the underlying mechanisms associated with its shear behavior. Recently the investigators introduced a rigidity percolation theory, previously established to explain the properties of reconstituted polymer networks, to explain the linear response of cartilage shear mechanics. This theory is that the observed orders of magnitude variation in the shear modulus of cartilage arises from small concentration differences of matrix constituents that are poised near a rigidity percolation threshold. Furthermore, the theory makes novel predictions about molecular mechanisms of non-linear shear behavior and gives new insight into mechanical changes that occur from biochemical and mechanical damage. This project will test these predictions and determining if rigidity percolation can be used as a new paradigm for the macromolecular origins of the mechanical shear properties of articular cartilage. Specifically, using chemical and mechanical degradation techniques, predictions made by the model about the critical extracellular matrix elements that give rise to cartilage's macroscale mechanical properties will be tested. Finally, this project will extend the applicability of the model to describe how the microscopic structure of cartilage is altered when it is sheared beyond the linear regime.

软骨是一种在关节中覆盖骨骼的光滑组织，它是一种持续数十年的非凡材料，并且以其独特的材料特性组合以胜过任何人造物质。软骨微观结构有几个方面有助于其寿命。首先，产生这些机械性能的基质由两个互穿聚合物网络组成，该设计最近已显示出抑制裂纹形成。其次，软骨的机械性能随深度变化，使能量阻尼几乎完全发生在其表面附近的薄区域中。 PI最近开发了一个理论模型，该模型解释了聚合物网络浓度的变化如何导致能量吸收到组织表面的定位。该项目使用一系列实验技术来测试该模型，并将其适用性扩展到可能损坏软骨的极端变形。通过化学处理组织以去除必需的分子成分并在不存在的情况下测试组织反应，PIS将确定矩阵的哪些元素对于生成软骨的机械性能的独特组合至关重要。更好地理解软骨机械性能的大分子起源，将深入了解诸如关节炎等疾病如何发展，指导性方法的方法，组织修复疗法以及更广泛的疾病，为能够忍受极端负荷的强大材料提供了机械设计标准，可以使极端货物具有少量的cy量的独特材料。其压缩特性的结构和成分起源已知数十年。但是，对与其剪切行为相关的潜在机制没有等效的理解。最近，研究人员介绍了一种刚性渗透理论，该理论以前是为了解释重构聚合物网络的特性，以解释软骨剪切力学的线性响应。该理论是，在软骨的剪切模量中观察到的数量级变化的顺序是由矩阵成分的小浓度差异引起的，这些基质成分的浓度差异在刚性渗透阈值附近。此外，该理论对非线性剪切行为的分子机制做出了新的预测，并为生化和机械损害发生的机械变化提供了新的见解。该项目将测试这些预测，并确定是否可以将刚性渗透用作关节软骨机械剪切特性的大分子起源的新范式。具体而言，使用化学和机械降解技术，该模型对导致软骨的宏观机械性能的关键细胞外基质元件做出的预测将进行测试。最后，该项目将扩展模型的适用性，以描述软骨的显微镜结构在剪切超过线性状态时如何更改。