RMS Foundation, Bischmattstrasse 12, CH-2544 Bettlach, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012 Bern, Switzerland.
RMS Foundation, Bischmattstrasse 12, CH-2544 Bettlach, Switzerland.
Acta Biomater. 2023 Oct 1;169:566-578. doi: 10.1016/j.actbio.2023.08.012. Epub 2023 Aug 16.
One of the most widely used materials for bone graft substitution is β-Tricalcium phosphate (β-TCP; β-Ca(PO)). β-TCP is typically produced by sintering in air or vacuum. During this process, evaporation of phosphorus (P) species occurs, leading to the formation of a calcium-rich alkaline layer. It was recently shown that the evaporation of P species could be prevented by co-sintering β-TCP with dicalcium phosphate (DCPA; CaHPO; mineral name: monetite). The aim of this study was to see how a change of sintering atmosphere could affect the physico-chemical and biological properties of β-TCP. For this purpose, three experimental groups were considered: β-TCP cylinders sintered in air and subsequently polished to remove the surface layer (control group); the same polished cylinders after subsequent annealing at 500 °C in air to generate a calcium-rich alkaline layer (annealed group); and finally, β-TCP cylinders sintered in a monetite-rich atmosphere and subsequently polished (monetite group). XPS analysis confirmed that cylinders from the annealed group had a significantly higher Ca/P molar ratio at their surface than that of the control group while this ratio was significantly lower for the cylinders from the monetite group. Sintering β-TCP in the monetite-rich atmosphere significantly reduced the grain size and increased the density. Changes of surface composition affected the activity of osteoclasts seeded onto the surfaces, since annealed β-TCP cylinders were significantly less resorbed than β-TCP cylinders sintered in the monetite-rich atmosphere. This suggests that an increase of the surface Ca/P molar ratio leads to a decrease of osteoclastic resorption. STATEMENT OF SIGNIFICANCE: Minimal changes of surface and bulk (< 1%) composition have major effects on the ability of osteoclasts to resorb β-tricalcium phosphate (β-TCP), one of the most widely used ceramics for bone substitution. The results presented in this study are thus important for the calcium phosphate community because (i) β-TCP may have up to 5% impurities according to ISO and ASTM standards and still be considered to be "pure β-TCP", (ii) β-TCP surface properties are generally not considered during biocompatibility assessment and (iii) a rationale can be proposed to explain the various inconsistencies reported in the literature on the biological properties of β-TCP.
β-磷酸三钙（β-TCP；β-Ca(PO)) 是最常用于骨移植替代的材料之一。β-TCP 通常通过在空气中或真空中烧结来生产。在此过程中，磷（P）物种会蒸发，导致形成富含钙的碱性层。最近的研究表明，通过将β-TCP 与二水磷酸钙（DCPA；CaHPO；矿物名称：磷灰石）共烧结可以防止 P 物种的蒸发。本研究的目的是观察烧结气氛的变化如何影响β-TCP 的物理化学和生物学性质。为此，考虑了三个实验组：在空气中烧结的β-TCP 圆柱体，然后抛光以去除表面层（对照组）；在空气中在 500°C 退火后具有相同表面的抛光圆柱体，以生成富含钙的碱性层（退火组）；最后，在富含磷灰石的气氛中烧结的β-TCP 圆柱体，然后抛光（磷灰石组）。XPS 分析证实，与对照组相比，退火组的表面 Ca/P 摩尔比明显更高，而磷灰石组的 Ca/P 摩尔比明显更低。在富含磷灰石的气氛中烧结β-TCP 可显著减小晶粒尺寸并提高密度。表面组成的变化影响接种在表面上的破骨细胞的活性，因为退火的β-TCP 圆柱体比在富含磷灰石的气氛中烧结的β-TCP 圆柱体的吸收明显减少。这表明表面 Ca/P 摩尔比的增加会导致破骨细胞吸收减少。意义声明：表面和体相（<1%）组成的微小变化对破骨细胞吸收β-磷酸三钙（β-TCP）的能力有重大影响，β-TCP 是最广泛用于骨替代的陶瓷之一。本研究中的结果对于磷酸钙界具有重要意义，因为（i）根据 ISO 和 ASTM 标准，β-TCP 可能含有高达 5%的杂质，但仍被认为是“纯β-TCP”，（ii）在生物相容性评估中通常不考虑β-TCP 表面性质，以及（iii）可以提出一个合理的理由来解释文献中关于β-TCP 生物学性质的各种不一致之处。
