Division of Biomedical Engineering, Department of Materials Science and Engineering, Uppsala University, Sweden.
Department of Medical Cell Biology, Science for Life Laboratory, Uppsala University, Sweden.
Biomater Sci. 2023 May 2;11(9):3144-3158. doi: 10.1039/d2bm02074b.
Silicon nitride (SiN) coatings may reduce unwanted release of metal ions from metallic implants. However, as SiN slowly dissolves in aqueous solutions, additives that reduce this dissolution rate would likely increase the lifetime and functionality of implants. Adding iron (Fe) and carbon (C) permits tuning of the SiN coatings' mechanical properties, but their effect on SiN dissolution rates, and their capacity to reduce metal ion release from metallic implant substrates, have yet to be investigated. Such coatings have recently been proposed for use in spinal implants; therefore, it is relevant to assess their impact on the viability of cells expected at the implant site, such as microglia, the resident macrophages of the central nervous system (CNS). To study the effects of Fe and C on the dissolution rate of SiN coatings, compositional gradients of Si, Fe and C in combination with N were generated by physical vapor deposition onto CoCrMo discs. Differences in composition did not affect the surface roughness or the release of Si, Fe or Co ions (the latter from the CoCrMo substrate). Adding Fe and C reduced ion release compared to a SiN reference coating, which was attributed to altered reactivity due to an increase in the fraction of stabilizing Si-C or Fe-C bonds. Extracts from the SiN coatings containing Fe and C were compatible with microglial viability in 2D cultures and 3D collagen hydrogels, to a similar degree as CoCrMo and SiN coated CoCrMo reference extracts. As Fe and C reduced the dissolution rate of SiN-coatings and did not compromise microglial viability, the capacity of these additives to extend the lifetime and functionality of SiN-coated metallic implants warrants further investigation.
氮化硅（SiN）涂层可以减少金属植入物中金属离子的不必要释放。然而，由于 SiN 会在水溶液中缓慢溶解，因此添加可以降低溶解速率的添加剂可能会延长植入物的使用寿命和功能。添加铁（Fe）和碳（C）可以调整 SiN 涂层的机械性能，但它们对 SiN 溶解速率的影响，以及它们减少金属植入物基底中金属离子释放的能力，尚未得到研究。这些涂层最近被提议用于脊柱植入物；因此，评估它们对植入部位预期细胞（如小胶质细胞，中枢神经系统（CNS）的常驻巨噬细胞）活力的影响是相关的。为了研究 Fe 和 C 对 SiN 涂层溶解速率的影响，通过物理气相沉积在 CoCrMo 盘上生成了 Si、Fe 和 C 与 N 的组合成分梯度。组成差异不影响表面粗糙度或 Si、Fe 或 Co 离子的释放（后者来自 CoCrMo 基底）。与 SiN 参考涂层相比，添加 Fe 和 C 降低了离子释放，这归因于由于稳定的 Si-C 或 Fe-C 键的比例增加而导致的反应性改变。含有 Fe 和 C 的 SiN 涂层提取物与小胶质细胞在 2D 培养物和 3D 胶原水凝胶中的活力相容，与 CoCrMo 和 SiN 涂覆的 CoCrMo 参考提取物的相容性相似。由于 Fe 和 C 降低了 SiN 涂层的溶解速率并且不损害小胶质细胞活力，因此这些添加剂扩展 SiN 涂层金属植入物的使用寿命和功能的能力值得进一步研究。
