Modeling the water-bioglass interface by ab initio molecular dynamics simulations.
Modeling the water-bioglass interface by ab initio molecular dynamics simulations.
复制标题
通过从头算分子动力学模拟对水-生物玻璃界面进行建模。
DOI：
10.1021/am900198t
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发表时间：
2009
影响因子：
9.5
通讯作者：
A. Cormack
中科院分区：
文献类型：
--
作者：
A. Tilocca;A. Cormack
使用从头开始 (Car-Parrinello) 分子动力学 (CPMD) 模拟对高生物活性硅酸盐玻璃表面的水合进行建模，重点关注接触后玻璃-水界面立即发生的结构和化学变化，以及它们影响这些材料生物活性的方式。首先研究了水二聚体和三聚体在干燥表面上的吸附，然后研究了玻璃和液态水之间的扩展界面。 CPMD 轨迹提供了与这些材料的生物活性相关的初始阶段的原子学见解：玻璃与水性（生理）介质接触后，表面区域 Na+ 阳离子的初始富集在表面建立了占主导地位的 Na+-水相互作用，这使得水分子能够渗透到开放的玻璃网络中并开始部分溶解。 Na/H 交换界面模型表明，Ca2+-水相互作用主要是在 Na 的主要部分浸出到溶液中后建立的。强调了改性剂阳离子的另一个关键作用：它们提供了中和水离解和非桥氧 (NBO) 表面位点质子化所产生的 OH(-) 所需的路易斯酸度。 CPMD 模拟还强调了另一种质子跳跃机制，通过该机制可以在液态水膜中发生相同的过程。从模拟中可以看出，生物活性玻璃表面在与水介质接触后立即出现的主要特征是（a）通过水在欠配位的Si位点解离或NBO直接质子化形成的硅烷醇基团，（b）OH（-）基团通常由改性剂阳离子稳定并与质子化的NBO偶联，以及（c）小环，即使在暴露于液态水后也相对稳定且未打开。讨论了这些位点在生物活性过程中可能的作用和影响。
The hydration of the surface of a highly bioactive silicate glass was modeled using ab initio (Car-Parrinello) molecular dynamics (CPMD) simulations, focusing on the structural and chemical modifications taking place at the glass-water interface immediately after contact and on the way in which they can affect the bioactivity of these materials. The adsorption of a water dimer and trimer on the dry surface was studied first, followed by the extended interface between the glass and liquid water. The CPMD trajectories provide atomistic insight into the initial stages relevant to the biological activity of these materials: following contact of the glass with an aqueous (physiological) medium, the initial enrichment of the surface region in Na+ cations establishes dominant Na+-water interactions at the surface, which allow water molecules to penetrate into the open glass network and start its partial dissolution. The model of a Na/H-exchanged interface shows that Ca2+-water interactions are mainly established after the dominant fraction of Na is leached into the solution. Another critical role of modifier cations was highlighted: they provide the Lewis acidity necessary to neutralize OH(-) produced by water dissociation and protonation of nonbridging oxygen (NBO) surface sites. The CPMD simulations also highlighted an alternative, proton-hopping mechanism by which the same process can take place in the liquid water film. The main features of the bioactive glass surface immediately after contact with an aqueous medium, as emerged from the simulations, are (a) silanol groups formed by either water dissociation at undercoordinated Si sites or direct protonation of NBOs, (b) OH(-) groups generally stabilized by modifier cations and coupled with the protonated NBOs, and (c) small rings, relatively stable and unopened even after exposure to liquid water. The possible role and effect of these sites in the bioactive process are discussed.