Department of Mechanical and Aerospace Engineering, "Sapienza" University of Rome, via Eudossiana, 18, 00184 Rome, Italy.
Department of Mechanical and Aerospace Engineering, "Sapienza" University of Rome, via Eudossiana, 18, 00184 Rome, Italy.
J Biomech. 2021 Aug 26;125:110586. doi: 10.1016/j.jbiomech.2021.110586. Epub 2021 Jun 24.
Bone tissue is composed at the nanoscale of apatite minerals, collagen molecules and water that form the mineralized collagen fibril (MCF). Water has a crucial role in bone biomineralization. We developed a 3D random walk model to investigate the water diffusion process within the MCF for three different scenarios, namely low, intermediate and high mineral volume fraction. The MCF geometric model is obtained after applying 6·10 translational and rotational perturbations to an ordered arrangement of mineral. Subsequently, we compute 300 random trajectories of water molecules within the MCF for each mineral volume fraction. Every trajectory is constituted of up to 500 k positions of the water particle. We determined the diffusion coefficient from the linear fit of the mean squared displacement of water molecules as a function of time. We investigate changes in the diffusivity values in relation to variation of bone mineral content. The analysis performed on the random walk data, for all mineralization conditions, leads to diffusion coefficients in good agreement with the diffusivity outcomes achieved from previous experimental studies. Thus, the 3D geometrical configuration adopted in this numerical study appears suitable for modelling the MCF with different volume fractions, from hypo- to hyper-mineralized conditions. We observed that low mineral content is associated with an increase of the water diffusion, while lower values of diffusivity are determined in hypermineralized conditions. In agreement with experimental data, our results highlight the influence of the structural alterations on the mass transport properties.
骨组织在纳米尺度上由磷灰石矿物质、胶原蛋白分子和水组成，这些物质形成了矿化胶原纤维（MCF）。水在骨生物矿化过程中起着至关重要的作用。我们开发了一种 3D 随机行走模型，以研究在 MCF 内的水扩散过程，共涉及三种不同的情况，即低、中和高矿物质体积分数。在对矿物的有序排列进行 6·10 次平移和旋转扰动后，获得 MCF 的几何模型。随后，我们为每个矿物质体积分数计算了 MCF 内水分子的 300 条随机轨迹。每条轨迹都由多达 500K 个水分子的位置组成。我们通过线性拟合水分子的均方位移与时间的函数，从扩散系数确定扩散系数。我们研究了扩散系数值随骨矿物质含量变化的变化。对所有矿化条件下的随机行走数据进行的分析导致扩散系数与从先前实验研究中获得的扩散系数结果非常吻合。因此，在这项数值研究中采用的 3D 几何构型似乎适合对具有不同体积分数的 MCF 进行建模，从低矿化到高矿化条件。我们观察到低矿物质含量与水扩散的增加有关，而在高矿化条件下则确定了较低的扩散系数值。与实验数据一致，我们的结果强调了结构改变对质量传输特性的影响。
