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

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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.