Department of Mechanical Engineering, Indian Institute of Technology Delhi, Haus Khas, New Delhi, 110016, India.
Department of Mechanical Engineering, Indian Institute of Technology Delhi, Haus Khas, New Delhi, 110016, India.
J Mech Behav Biomed Mater. 2023 Nov;147:106147. doi: 10.1016/j.jmbbm.2023.106147. Epub 2023 Sep 29.
Multi-directional deformation exhibited by annulus fibrosus (AF) is contributed by chemo-mechanical interactions among its biomolecular constituents' collagen type I (COL-I), collagen type II (COL-II), proteoglycans (aggrecan and hyaluronan) and water. However, the nature and role of such interactions on AF mechanics are unclear. This work employs a molecular dynamics-cohesive finite element-based multiscale approach to investigate role of COL-I-COL-II interchanging distribution and water concentration (WC) variations from outer annulus (OA) to inner annulus (IA) on collagen-hyaluronan (COL-HYL) interface shear, and the mechanisms by which interface shear impacts fibril sliding during collagen fiber deformation. At first, COL-HYL interface atomistic models are constructed by interchanging COL-I with COL-II and increasing COL-II and WC from 0 to 75%, and 65%-75% respectively. Thereafter, a multiscale approach is employed to develop representative volume elements (RVEs) of collagen fibers by incorporating COL-HYL shear as traction-separation behaviour at fibril-hyaluronan contact. Results show that increasing COL-II and WC increases interface stiffness from 0.6 GPa/nm to 1.2 GPa/nm and reduces interface strength from 155 MPa to 58 MPa from OA to IA, contributed by local hydration alterations. A stiffer and weaker interface enhances fibril sliding with increased straining at the contact - thereby contributing to reduction in modulus from 298 MPa to 198 MPa from OA to IA. Such reduction further contributes to softer mechanical response towards IA, as reported by earlier studies. Presented multiscale analysis provides deeper understanding of hierarchical structure-mechanics relationships in AF and can further aid in developing better substitutes for AF repair.
纤维环（AF）的多向变形是由其生物分子成分的胶原 I（COL-I）、胶原 II（COL-II）、蛋白聚糖（聚集蛋白聚糖和透明质酸）和水之间的化学机械相互作用贡献的。然而，这些相互作用对 AF 力学的性质和作用尚不清楚。本工作采用分子动力学-内聚有限元多尺度方法，研究了从外纤维环（OA）到内纤维环（IA）的 COL-I-COL-II 交换分布和水浓度（WC）变化对 COL- 透明质酸（COL-HYL）界面剪切的作用，以及界面剪切如何影响胶原纤维变形过程中纤维滑动的机制。首先，通过用 COL-II 交换 COL-I 并将 COL-II 和 WC 分别从 0 增加到 75%和 65%-75%，构建 COL-HYL 界面原子模型。然后，采用多尺度方法，通过将 COL-HYL 剪切作为纤维-透明质酸接触处的牵引-分离行为，将 COL-HYL 剪切作为牵引-分离行为，来开发胶原纤维的代表性体积元（RVE）。结果表明，COL-II 和 WC 的增加会使界面刚度从 0.6 GPa/nm 增加到 1.2 GPa/nm，使界面强度从 OA 到 IA 从 155 MPa 降低到 58 MPa，这是由于局部水合作用的改变所致。更硬和更弱的界面会增强纤维滑动，从而在接触处增加应变，使模量从 OA 到 IA 从 298 MPa 降低到 198 MPa。这种减少进一步导致对 IA 的机械响应更软，这是早期研究报告的结果。提出的多尺度分析提供了对 AF 中层次结构-力学关系的更深入理解，并可以进一步帮助开发更好的 AF 修复替代品。
