Development and validation of an in vitro short-time testing method for the prediction of the in vivo behavior of absorbable metallic implant materials

生物可吸收镁植入物被认为是未来外科医学中有前途的生物材料。镁较差的耐腐蚀性在这种特殊的应用中是有益的，因为植入材料可以设计成一种方式，在规定的时间内完成其功能并最终完全溶解，因此不需要进一步的手术来移除植入物。另一方面，由于镁的腐蚀和降解行为以及相应的功能丧失难以预测，并且作为腐蚀产物会形成氢气，因此阻碍了镁的广泛临床应用。在这种情况下，降解过程可以通过等离子体电解氧化（PEO）涂层可调地延迟。因此，镁材料作为生物材料的体外鉴定是一个很大的挑战，因为材料的行为需要长时间的预测。以前应用的腐蚀行为评价方法是不一致的，几乎没有标准化。许多体外和体内研究认为细胞相容性和生物相容性是相互独立的。除了有效的体外测试外，还应通过标准化的镁样品细胞相容性分析来扩展方法，以可靠和完整地预测体内材料的行为。此外，长时间浸泡在模拟体液中的试验涉及细菌污染的风险。综上所述，在没有参考动物实验的情况下，对生物可吸收植入物应用的材料的鉴定通常有很大的需求。因此，需要一种短期腐蚀疲劳试验方法，该方法可以估计材料在人体中的行为，并且可以在体外加速。在计划研究项目的框架内，将以有前景的镁合金WE43 MEO为例，开发这种测试方法。此外，peo涂层对细胞和生物相容性以及降解行为的影响将被研究。

Bioresorbable magnesium implants are considered as promising biomaterials of the future in surgical oriented disciplines of medicine. The poor corrosion resistance of magnesium is beneficial in this particular application, because implant materials can be designed in a way, that they fulfil their function for a defined period of time and eventually dissolve completely, so that there is no need for a further surgery to remove the implant.On the other hand, widespread clinical applications of magnesium are prevented because the corrosion and degradation behavior and the corresponding loss of function is difficult to predict as well as hydrogen gas is formed as a corrosion product. In this context, the degradation process can be adjustably delayed through coating by means of plasma electrolytic oxidation (PEO).Therefore, in vitro testing for qualification of magnesium materials as biomaterials is a big challenge, because the material behavior has to be predicted for a long period of time. Previously applied methods for the evaluation of the corrosion behavior are inconsistent and barely standardized. Many in vitro and in vivo studies consider the cyto- and biocompatibility independent from each other. Besides a valid in vitro testing, methods should be extended by standardized cytocompatibilty analyses of magnesium specimens to predict in vivo material behavior reliably and completely. Furthermore, immersion tests in simulated body fluids over long exposure times involve the risk of bacterial contamination.In summary, there is a generally great demand for qualification of materials for application as bioresorbable implants without referring to animal experiments. Therefore, a short-term corrosion fatigue testing method would be desirable with which the material behavior in the human body can be estimated time accelerated as well as in vitro.Within the framework of the planned research project such a testing method shall be developed using the example of the promising magnesium alloy WE43 MEO. Furthermore, the influence of a PEO-coating on the cyto- and biocompatibility as well as the degradation behavior shall be investigated.