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Modelling Ion Migration in Bioactive Glasses

生物活性玻璃中的离子迁移建模

基本信息

批准号：
EP/G041156/1
负责人：
Antonio Tilocca
金额：
$ 0.42万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FG041156%2F1
关键词：
Modelling Ion Migration Bioactive Glasses

项目摘要

Bioactive glasses (bioglasses) are widely used in biomedicine as restorative and regenerative implants, which exploit their ability to bond to hard (bone, teeth) and soft (tendons, ligaments) tissues shortly after exposure to the body physiological environment. This ability reflects a reactive response of the material to the contact with physiological fluids, involving a series of physico-chemical processes, leading to the formation of a layer of bone-like apatite (Ap) on the glass surface within a few hours or days after implantation. The Ap layer provides a strong interface effectively bonding the material and the living tissues: this stable biomaterial-tissue link promotes the integration of the implant and is therefore central for its success. Since the 1980s many studies have led to significant developments in this field: the glass bioactivity, i.e., its ability to bond to bone and/or to induce tissue repair and regeneration, is usually assessed by measuring the rate of Ap formation in-vitro or in-vivo, and the importance of glass composition, particle morphology, surface texture, and thermal treatment is now well established. One major obstacle to further technological progress is that, despite their importance, structure-bioactivity relationships are still largely unknown for bioglasses, mostly due to lack of accurate structural data. The disordered and multicomponent nature of these materials hinders the application of standard experimental probes to access their structure, with the result that prediction and test of compositional effects mostly relies on inefficient and expensive trial-and-error approaches: while the range and level of bioactivity of typical melt-derived compositions has been determined, no rational interpretation of the sharp changes in bioactivity with the composition has been proposed. Any such interpretation requires a detailed knowledge of the atomistic structure, at least of the most common melt-derived bioglasses. Structural investigations of the traditional, melt-derived bioglasses are still highly needed: since the bioactivity level of many melt-derived compositions has been exactly measured, these structural investigations can provide direct insight into structure-activity effects, and the resulting knowledge should be transferable to glasses of different composition and/or obtained through different routes. Atomistic computer simulations can provide a high-resolution picture of structural and dynamical features of these materials, thus supporting a more rational approach to identify the links between the composition, the structure, and the bioactivity of these glasses. As for standard experimental techniques, bioactive glasses represent a significant challenge also to modelling approaches. Our recent computational studies have tackled the bulk structure of bioglasses: by modelling compositions of different, known bioactivity, we identified specific structural features marking bioactive or bio-inactive compositions; these bulk structural data and the corresponding insight obtained represent the essential baseline, upon which further specific investigations can be based. A still largely unexplored field is the diffusive dynamics of Na and Ca cations: their migration within the bulk structure plays a critical role in the bioactive mechanism, because the initial leaching of sodium ions into the physiological solution, and the subsequent release of Ca from the glass are both key steps in the bioactive mechanism. Very few data are available on the Na and Ca transport; the present project aims at investigating the diffusive mechanism of modifier cations in bioglasses, using Molecular Dynamics simulations. The final purpose is to identify possible correlations between the glass composition, the local coordination/structure and the transport of modifier cations, which can be linked to the bioactive properties, and therefore improve our current limited understanding of how these materials work.

生物活性玻璃（生物玻璃）在生物医学中被广泛用作修复和再生植入物，其利用其在暴露于身体生理环境后不久与硬（骨、牙齿）和软（肌腱、韧带）组织结合的能力。这种能力反映了材料对与生理液体接触的反应性反应，涉及一系列物理化学过程，导致植入后几小时或几天内在玻璃表面上形成骨样磷灰石（Ap）层。Ap层提供了一个强有力的界面，有效地将材料和活组织结合在一起：这种稳定的生物材料-组织连接促进了植入物的整合，因此是其成功的关键。自20世纪80年代以来，许多研究导致了该领域的重大发展：玻璃生物活性，即，其与骨结合和/或诱导组织修复和再生的能力通常通过测量体外或体内Ap形成的速率来评估，并且玻璃组成、颗粒形态、表面纹理和热处理的重要性现在已经得到很好的确立。进一步技术进步的一个主要障碍是，尽管它们的重要性，但结构-生物活性关系在很大程度上仍然是未知的，主要是由于缺乏准确的结构数据。这些材料的无序和多组分性质阻碍了标准实验探针的应用以访问它们的结构，结果是组成效应的预测和测试主要依赖于低效和昂贵的试错方法：虽然已经确定了典型熔体衍生组合物的生物活性范围和水平，还没有提出对组合物的生物活性的急剧变化的合理解释。任何这样的解释都需要对原子结构有详细的了解，至少是对最常见的熔体衍生的类原子结构有详细的了解。仍然非常需要对传统的熔融衍生的玻璃进行结构研究：由于已经精确测量了许多熔融衍生的组合物的生物活性水平，因此这些结构研究可以提供对结构-活性效应的直接洞察，并且所得到的知识应该可转移到不同组成的玻璃和/或通过不同途径获得的玻璃。原子计算机模拟可以提供这些材料的结构和动力学特征的高分辨率图像，从而支持更合理的方法来识别这些玻璃的组成，结构和生物活性之间的联系。至于标准的实验技术，生物活性玻璃也代表了建模方法的重大挑战。我们最近的计算研究已经解决了大规模的结构的玻璃：通过建模不同的，已知的生物活性的组合物，我们确定了特定的结构特征，标志着生物活性或生物非活性的组合物;这些大规模的结构数据和相应的洞察力获得代表的基本基线，在此基础上，进一步的具体调查可以基于。Na和Ca阳离子的扩散动力学仍然是一个尚未探索的领域：它们在体结构内的迁移在生物活性机制中起着关键作用，因为钠离子最初浸出到生理溶液中，以及随后从玻璃中释放Ca都是生物活性机制中的关键步骤。很少有数据可供Na和Ca的运输，本项目的目的是研究改性剂阳离子在玻璃中的扩散机制，使用分子动力学模拟。最终目的是确定玻璃组合物，局部配位/结构和改性剂阳离子的运输之间可能的相关性，这可以与生物活性特性相关联，从而改善我们目前对这些材料如何工作的有限理解。