Department of Mechanical and Process Engineering, Swiss Federal Institute of Technology, Zurich, Switzerland.
Biomech Model Mechanobiol. 2013 Aug;12(4):747-62. doi: 10.1007/s10237-012-0438-z. Epub 2012 Sep 13.
This study was directed to the measurement of the mechanical response of fetal membranes to physiologically relevant loading conditions. Characteristic mechanical parameters were determined and their relation to the microstructural constituents collagen and elastin as well as to the pyridinium cross-link concentrations analyzed. 51 samples from twelve fetal membranes were tested on a custom-built inflation device, which allows mechanical characterization within a multiaxial state of stress. Methods of nonlinear continuum mechanics were used to extract representative mechanical parameters. Established biochemical assays were applied for the determination of the collagen and elastin content. Collagen cross-link concentrations were determined by high-performance liquid chromatography measurements. The results indicate a distinct correlation between the mechanical parameters of high stretch stiffness and membrane tension at rupture and the biochemical data of collagen content and pyridinoline as well as deoxypyridinoline concentrations. No correlation was observed between the mechanical parameters and the elastin content. Moreover, the low stretch stiffness is, with a value of 105 ± 31 × 10(-3) N/ mm much higher for a biaxial state of stress compared to a uniaxial stress configuration. Determination of constitutive model equations leads to better predictive capabilities for a reduced polynomial hyperelastic model with only terms related to the second invariant, I 2, of the right Cauchy-Green deformation tensor. Relevant insights were obtained on the mechanical behavior of fetal membranes. Collagen and its cross-linking were shown to determine membrane's stiffness and strength for multiaxial stress states. Their nonlinear deformation behavior characterizes the fetal membranes as I 2 material.
本研究旨在测量胎儿膜对生理相关加载条件的机械响应。确定了特征机械参数，并分析了它们与胶原和弹性蛋白的微观结构成分以及吡啶交联浓度的关系。在定制的充气装置上测试了来自 12 个胎儿膜的 51 个样本，该装置允许在多轴应力状态下进行机械特性分析。使用非线性连续体力学方法提取具有代表性的机械参数。应用了已建立的生化测定法来确定胶原和弹性蛋白的含量。通过高效液相色谱测量来确定胶原交联浓度。结果表明，高拉伸刚度和破裂时膜张力的机械参数与胶原含量以及吡啶啉和脱氧吡啶啉浓度的生化数据之间存在明显的相关性。但是，机械参数与弹性蛋白含量之间没有相关性。此外，与单轴应力配置相比，在双轴应力状态下，低拉伸刚度的值为 105 ± 31 × 10(-3) N/mm，要高得多。确定本构模型方程可以为仅与右柯西-格林变形张量的第二不变量 I 2 相关的项的简化多项式超弹性模型提供更好的预测能力。本研究获得了有关胎儿膜机械行为的相关见解。胶原及其交联决定了多轴应力状态下膜的刚度和强度。它们的非线性变形行为将胎儿膜表征为 I 2 材料。
