Bone water at the nanoscale: a molecular dynamics study.
Bone water at the nanoscale: a molecular dynamics study.
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纳米级的骨水：分子动力学研究。
DOI：
10.1080/10255842.2015.1069586
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发表时间：
2015
影响因子：
1.6
通讯作者：
Lemaire T
中科院分区：
文献类型：
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作者：
Lemaire T
骨是一种饱和多孔介质，呈现固相和流体相（主要是水）。人们普遍认为，骨骼呈现出三个层次的孔隙度，它们像一套俄罗斯娃娃一样，在微循环通路中分层地嵌套在一起（Cowin et al. 2009）。大孔对应于脉管系统（Havers和Volkmann管，典型直径为50 μm）。中孔形成由骨细胞腔隙和小管通道组成的腔隙-小管孔隙，其中包含骨细胞星形骨网络（典型尺寸为100 nm）。骨骼中最小的孔隙度与胶原-磷灰石结构内部的空隙相对应。Holmes等人在1964年测得它们的典型尺寸约为5纳米。由于在纳米尺度上观察到水的结合状态，因此通常忽略了纳米孔内的间隙性骨液流动，从而导致骨孔隙力学的双重多孔处理（Rohan et al. 2012）。由于通过量化其渗透性来深入了解骨输送液体的能力是当代骨生物力学的一个具有挑战性的课题（Lemaire等人，2012；Cardoso等人，2013），我们最近应用原子分子动力学（MD）模拟来描述羟基磷灰石（HAP）纳米孔结构中水的性质（Pham等人，2015）。这些模拟捕获了描述纳米流体动力学所需的重要表面和水合作用，而这在传统的骨液流动连续描述中是缺失的。这个原子研究提供了一个更好的理解分子水平的相互作用如何控制骨纳米孔内的流体流动。传统观点认为，在纳米尺度上，骨水只存在于孔隙中，而我们发现，可移动的水只存在于几纳米的孔隙中。这提供了一种目前尚未研究的骨内物质运输途径。
As a saturated porous medium, bone presents a solid phase and a fluid phase (mainly water). It is commonly accepted that bone presents three levels of porosity, which are nested hierarchically one inside another as a set of Russian dolls in microcirculatory pathways (Cowin et al. 2009). The macropores correspond to the vasculature (Havers and Volkmann canals, typical diameter of 50 μm). The mesopores form the lacuno-canalicular porosity made of the osteocytic lacunae and canaliculi channels that contains the osteocytes’ stellar network of bone (typical size of 100 nm). The smallest porosity level in bone corresponds to the spaces inside the collagen–apatite structure. Their typical size was measured by Holmes et al. 1964 at around 5 nm. Due to the observation of a bound state of water at this nanometric scale, the interstitial bone fluid flow within the nanopores is classically neglected, resulting in a twofold porous treatment of bone poromechanics (Rohan et al. 2012). Since obtaining insight into bone’s ability to transport fluid by quantifying its permeability is a challenging topic of contemporary bone biomechanics (Lemaire et al. 2012; Cardoso et al. 2013), we have recently applied atomistic molecular dynamics (MD) simulations to describe the properties of water confined within hydroxyapatite (HAP) nanoporous structures (Pham et al. 2015). These simulations captured important surface and hydration effects which are needed to describe nanohydrodynamics, and which are absent from conventional continuum descriptions of bone fluid flow. This atomistic study provides a better understanding of how molecular-level interactions control fluid flow within the nanopores of bone. Contrary to the classical idea that, at the nanoscale, bone water is only bound in the pores, we show that mobile water exists in pores of just a few nanometers. This offers a mass transport pathway within bone that is currently not studied at all.