Ceramic coatings containing calcium and phosphate on magnesium alloy MnE21

Ceramic coatings containing calcium and phosphate were prepared on magnesium alloy MnE21 using the plasma electrolytic oxidation technique. The surface morphology of the formed layers was analysed by scanning electron microscopy and also by roughness and layer thickness examinations. The phase composition was investigated by X-Ray photoelectron spectroscopy and energy dispersive X-Ray spectroscopy. Different layer thicknesses developed on the surface dependent on the voltage applied during PEO process. Special focus was set on the relation between surface characteristics (layer thickness and average roughness) and cytotoxicity of the alloy and the layer, respectively. Cytotoxicity testing (water-soluble tetrazolium 1 assay and live/dead staining) revealed that cytotoxicity increases with higher layer thickness and roughness. The uncoated reference samples were highly toxic. The best results regarding cytotoxicity provided the samples with the lowest layer thickness and roughness. Because MnE21 has never been used for biological applications, this study provides first results about a possible application as biodegradable implant material.