Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, United States.
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
Acta Biomater. 2018 Jan;65:436-449. doi: 10.1016/j.actbio.2017.11.006. Epub 2017 Nov 7.
The past decade has witnessed a significant upsurge in the development of borate and borosilicate based resorbable bioactive glasses owing to their faster degradation rate in comparison to their silicate counterparts. However, due to our lack of understanding about the fundamental science governing the aqueous corrosion of these glasses, most of the borate/borosilicate based bioactive glasses reported in the literature have been designed by "trial-and-error" approach. With an ever-increasing demand for their application in treating a broad spectrum of non-skeletal health problems, it is becoming increasingly difficult to design advanced glass formulations using the same conventional approach. Therefore, a paradigm shift from the "trial-and-error" approach to "materials-by-design" approach is required to develop new-generations of bioactive glasses with controlled release of functional ions tailored for specific patients and disease states, whereby material functions and properties can be predicted from first principles. Realizing this goal, however, requires a thorough understanding of the complex sequence of reactions that control the dissolution kinetics of bioactive glasses and the structural drivers that govern them. While there is a considerable amount of literature published on chemical dissolution behavior and apatite-forming ability of potentially bioactive glasses, the majority of this literature has been produced on silicate glass chemistries using different experimental and measurement protocols. It follows that inter-comparison of different datasets reveals inconsistencies between experimental groups. There are also some major experimental challenges or choices that need to be carefully navigated to unearth the mechanisms governing the chemical degradation behavior and kinetics of boron-containing bioactive glasses, and to accurately determine the composition-structure-property relationships. In order to address these challenges, a simplified borosilicate based model melt-quenched bioactive glass system has been studied to depict the impact of thermal history on its molecular structure and dissolution behavior in water. It has been shown that the methodology of quenching of the glass melt impacts the dissolution rate of the studied glasses by 1.5×-3× depending on the changes induced in their molecular structure due to variation in thermal history. Further, a recommendation has been made to study dissolution behavior of bioactive glasses using surface area of the sample - to - volume of solution (SA/V) approach instead of the currently followed mass of sample - to - volume of solution approach. The structural and chemical dissolution data obtained from bioactive glasses following the approach presented in this paper can be used to develop the structural descriptors and potential energy functions over a broad range of bioactive glass compositions.
Realizing the goal of designing third generation bioactive glasses requires a thorough understanding of the complex sequence of reactions that control their rate of degradation (in physiological fluids) and the structural drivers that control them. In this article, we have highlighted some major experimental challenges and choices that need to be carefully navigated in order to unearth the mechanisms governing the chemical dissolution behavior of borosilicate based bioactive glasses. The proposed experimental approach allows us to gain a new level of conceptual understanding about the composition-structure-property relationships in these glass systems, which can be applied to attain a significant leap in designing borosilicate based bioactive glasses with controlled dissolution rates tailored for specific patient and disease states.
过去十年，由于硼酸和硼硅酸盐基可吸收生物活性玻璃的降解速度比硅酸盐基快，因此其发展迅速。然而，由于我们对控制这些玻璃水腐蚀的基础科学缺乏了解，文献中报道的大多数硼酸/硼硅酸盐基生物活性玻璃都是通过“反复试验”的方法设计的。随着对其在治疗广泛的非骨骼健康问题中的应用的需求不断增加，使用相同的传统方法设计先进的玻璃配方变得越来越困难。因此，需要从“反复试验”方法转变为“材料设计”方法，以开发具有针对特定患者和疾病状态的功能离子可控释放的新一代生物活性玻璃，从而可以从第一性原理预测材料的功能和特性。然而，要实现这一目标，需要深入了解控制生物活性玻璃溶解动力学的复杂反应序列以及控制它们的结构驱动因素。虽然有相当多的文献发表了关于潜在生物活性玻璃的化学溶解行为和磷灰石形成能力，但这些文献中的大多数都是基于不同的实验和测量方案在硅酸盐玻璃化学方面进行的。因此，不同数据集的相互比较揭示了实验组之间的不一致。此外，还存在一些主要的实验挑战或选择，需要谨慎处理，以揭示硼基生物活性玻璃化学降解行为和动力学的机制，并准确确定组成-结构-性能关系。为了解决这些挑战，研究了简化的硼硅酸盐模型熔融淬火生物活性玻璃系统，以描述热历史对其分子结构和在水中溶解行为的影响。结果表明，玻璃熔体的淬火方法会根据热历史引起的分子结构变化，使研究玻璃的溶解速率提高 1.5×-3×。此外，建议使用样品表面积与溶液体积（SA/V）的方法而不是当前使用的样品质量与溶液体积的方法来研究生物活性玻璃的溶解行为。本文提出的方法获得的生物活性玻璃的结构和化学溶解数据可用于在广泛的生物活性玻璃组成范围内开发结构描述符和势能函数。
要实现设计第三代生物活性玻璃的目标，需要深入了解控制其降解速度（在生理流体中）的复杂反应序列以及控制它们的结构驱动因素。本文重点介绍了在揭示控制硼硅酸盐基生物活性玻璃化学溶解行为的机制时需要谨慎处理的一些主要实验挑战和选择。所提出的实验方法使我们能够对这些玻璃系统的组成-结构-性能关系获得新的概念性理解，这可以应用于设计具有针对特定患者和疾病状态的受控溶解速率的硼硅酸盐基生物活性玻璃方面取得重大飞跃。
