Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils.
Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils.
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DOI：
10.1016/j.jmbbm.2014.07.008
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发表时间：
2015-12
影响因子：
3.9
通讯作者：
Buehler MJ
中科院分区：
文献类型：
--
作者：
Depalle B;Qin Z;Shefelbine SJ;Buehler MJ
胶原蛋白是一种普遍存在的蛋白质，具有显著的力学性能。具有高弹性，断裂强度大，变形时能量耗散大。人体的大部分结缔组织由胶原原纤维组成，胶原原纤维由交错排列的原胶原分子组成，这些原胶原分子通过分子间交联连接。在这项研究中，我们报告了胶原蛋白的三维粗粒度模型，并分析了酶交联对胶原原纤维力学的影响。采用自底向上的方法在中尺度模式中实现了两种典型的不成熟交联和成熟交联。通过改变原纤维中交联的数量、类型和力学性能，并对模型进行拉伸试验，我们系统地研究了交联胶原原纤维的变形机制。我们发现交联原纤维表现出三相行为，这比使用以前的模型获得的结果更符合实验结果。纤维力学响应的特征是：(i)与胶原蛋白分子展开相对应的初始弹性变形，（ii）由分子滑动主导的线性状态，以及（iii）与对胶原蛋白分子骨干拉伸有关的第二种更硬的弹性状态，直到纤维断裂。我们的研究结果表明，交联的密度和类型通过增加相互连接的分子数量来决定大变形区的刚度，而交联的力学性能决定了纤维的破坏应变和强度。这些发现表明，交联在创建具有可调韧性和强度的互联纤维材料中起着至关重要的作用。
Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength.