Computer-aided design of degradable Mg-based metallic glasses for safe medical implantation

随着人类预期寿命的不断延长，人体内植入物的数量将不断增加。不断发展的生物材料领域已经可以生产人造牙齿和皮肤、人工耳蜗、人造角膜、冠状动脉支架和人造髋关节等。随着我们对植入物需求的增长，人们不断改进制造植入物的材料。镁基金属和合金通常用于骨科植入物，因为它们具有与人体骨骼相似的机械性能，并且它们可以溶解到体内已经存在的成分中。在过去，它们会引起问题，因为它们在放置在体内时会释放氢气，这可能是有害的，需要被移除。含有锌和钙的镁基金属玻璃的某些组合物不释放氢，因此，只要它们保持适当的机械性能，它们比现有材料更适合用作生物医学植入物。该项目的目的是使用计算机建模来设计和优化这些镁基金属玻璃，以便安全植入人体。计算机模拟的进步意味着现在可以研究这些三元金属玻璃等复杂材料的结构。我们将使用的分子动力学（MD）模拟将揭示玻璃中存在的原子结构和化学键的性质。在不释放氢的玻璃成分中，当注入体内时，已知在玻璃表面上形成钝化层，但仅针对玻璃的某些成分，我们将构建这些玻璃以及相关成分的体积和表面性质的精确模型。MD模拟将提供玻璃结构的原子级分辨率，我们将利用它来识别控制表面层形成和氢释放的特征，并了解如何控制这些特征。我们还将模拟玻璃表面与生理环境的相互作用，以充分了解体内发生的反应。通过对各种玻璃成分的模拟，以及对表面层成分依赖性的充分分析，我们将能够推断出导致钝化层形成的反应，并抑制氢的释放。一旦我们了解了控制表面层形成的特征，我们将优化用于生物医学植入的镁基金属玻璃，通过计算设计具有适当机械性能但也不释放氢的合适玻璃组合物。这将导致生物医学，特别是骨科应用的改进和安全的植入物的设计。

As human life expectancy continues to lengthen, there will be an increased number of implants in human bodies. The growing biomaterials field can already produce artificial teeth and skin, cochlear implants, artificial corneas, coronary stents and artificial hips, among others. As our need for implants grows, there is a continuing drive to improve the materials from which they are made.Magnesium-based metals and alloys are often used for orthopaedic implants, because they have similar mechanical properties to human bone, and they dissolve to components already present in the body. In the past, they have caused problems because they release hydrogen gas when placed in the body, which can be harmful and needs to be removed. Certain compositions of Mg-based metallic glass containing zinc and calcium, do not release hydrogen, and so, providing they retain the appropriate mechanical properties, they are much more suitable for use as biomedical implants than existing materials. The aim of this project is to use computer modelling to design and optimise these Mg-based metallic glasses for safe implantation into the human body.Advances in computer simulation mean that it is now possible to investigate the structure of complex materials such as these ternary metallic glasses. The molecular dynamics (MD) simulations we will use will reveal the atomic structure and the nature of the chemical bonds which exist in the glass. In the glass compositions which do not release hydrogen, a passivating layer is known to form on the surface of the glass when it is implanted in the body, but only for certain compositions of the glass.We will construct accurate models of the bulk and surface properties of these glasses, as well as those of related compositions. MD simulations will provide atomic-level resolution of the structure of the glass, and we will use this to identify the features which control the formation of the surface layer, and the release of hydrogen, and understand how these can be controlled. We will also model the interaction of the glass surface with the physiological environment, to gain a full understanding of the reactions which occur in the body. Through the simulation of a wide range of glass compositions, and full analysis of the compositional dependence of the surface layer, we will be able to deduce what reactions cause the formation of the passivating layer, and inhibit the release of hydrogen.Once we understand the features which control the formation of the surface layer, we will optimise Mg-based metallic glasses for use in biomedical implantation, by computational design of suitable glass compositions which have the appropriate mechanical properties but also do not release hydrogen. This will lead to the design of improved and safe implants for biomedicine, especially in orthopaedic applications.