For biomedical application, it is important to evaluate materials' functionality as well as biological safety. Most of the materials degrade inside the body, it is also important to investigate materials degradation behavior in the physiological environment. These properties of conventional medical materials were evaluated by in vivo animal tests, however their tests results often disagree with those of clinical trials. Furthermore, recent global movement concerning animal welfare limits the execution of animal tests. Therefore, we are challenging the development of new evaluation method by simulating physiological environment in vitro, which will contribute to more quick and efficient development of new medical devices.

Gas cavity formation behavior of a Mg-alloy screw was examined using our original evaluation method; model tissue system. The polymer coating suppressed corrosion reaction of the substrate, reducing the gas cavity volume formed in the model tissue, which is quantified by micro-X-ray CT analysis.