Department of Oral Maxillofacial Surgery, University Medical Center, 20246 Hamburg-Eppendorf, Germany.
Department of Materials Test Engineering (WPT), TU Dortmund University, 44227 Dortmund, Germany.
Int J Mol Sci. 2019 Sep 30;20(19):4859. doi: 10.3390/ijms20194859.
The degradation rate of magnesium (Mg) alloys is a key parameter to develop Mg-based biomaterials and ensure in vivo-mechanical stability as well as to minimize hydrogen gas production, which otherwise can lead to adverse effects in clinical applications. However, in vitro and in vivo results of the same material often differ largely. In the present study, a dynamic test bench with several single bioreactor cells was constructed to measure the volume of hydrogen gas which evolves during magnesium degradation to indicate the degradation rate in vivo. Degradation medium comparable with human blood plasma was used to simulate body fluids. The media was pumped through the different bioreactor cells under a constant flow rate and 37 °C to simulate physiological conditions. A total of three different Mg groups were successively tested: Mg WE43, and two different WE43 plasma electrolytically oxidized (PEO) variants. The results were compared with other methods to detect magnesium degradation (pH, potentiodynamic polarization (PDP), cytocompatibility, SEM (scanning electron microscopy)). The non-ceramized specimens showed the highest degradation rates and vast standard deviations. In contrast, the two PEO samples demonstrated reduced degradation rates with diminished standard deviation. The pH values showed above-average constant levels between 7.4-7.7, likely due to the constant exchange of the fluids. SEM revealed severe cracks on the surface of WE43 after degradation, whereas the ceramized surfaces showed significantly decreased signs of corrosion. PDP results confirmed the improved corrosion resistance of both PEO samples. While WE43 showed slight toxicity in vitro, satisfactory cytocompatibility was achieved for the PEO test samples. In summary, the dynamic test bench constructed in this study enables reliable and simple measurement of Mg degradation to simulate the in vivo environment. Furthermore, PEO treatment of magnesium is a promising method to adjust magnesium degradation.
镁（Mg）合金的降解速率是开发基于镁的生物材料的关键参数，可确保体内机械稳定性并最小化氢气的产生，否则会在临床应用中产生不良反应。然而，同一材料的体外和体内结果通常差异很大。在本研究中，构建了一个带有多个单生物反应器单元的动态测试台，以测量镁降解过程中产生的氢气体积，从而指示体内的降解速率。使用与人血浆相当的降解介质来模拟体液。在恒定流速和 37°C 下，将介质泵通过不同的生物反应器单元，以模拟生理条件。总共连续测试了三组不同的 Mg 组：Mg WE43 以及两种不同的 WE43 等离子体电解氧化（PEO）变体。将结果与其他检测镁降解的方法（pH 值、动电位极化（PDP）、细胞相容性、SEM（扫描电子显微镜））进行了比较。未陶瓷化的标本显示出最高的降解率和较大的标准偏差。相比之下，两个 PEO 样品的降解率降低，标准偏差减小。pH 值显示出 7.4-7.7 之间的平均恒定水平，这可能是由于流体的不断交换。SEM 显示 WE43 降解后表面出现严重裂纹，而陶瓷化表面的腐蚀迹象明显减少。PDP 结果证实了两种 PEO 样品的耐腐蚀性得到了改善。虽然 WE43 在体外显示出轻微的毒性，但 PEO 测试样品的细胞相容性令人满意。综上所述，本研究中构建的动态测试台能够可靠且简单地测量镁的降解，以模拟体内环境。此外，对镁进行 PEO 处理是一种调整镁降解的有前途的方法。
