Interaction of different cell types with magnesium modified by plasma electrolytic oxidation.

Magnesium (Mg) is a material widely used in industrial applications due to its low weight, ductility, and excellent mechanical properties. For non-permanent implants, Mg is particularly well-suited because of its biodegradability, while its degradation products are not harmful. However, Mg is chemically reactive, and cytotoxic hydrogen gas is released as part of the degradation. This adverse degradation can be tuned using plasma electrolytic oxidation (PEO). With PEO, a surface layer of MgO/Mg(OH) is deposited on the surface of Mg in a controlled way. The electrolytes used during PEO influence the surface's chemistry and topography and thus expectedly the biological response of adhered cells. In this study, thin samples of commercial pure of Mg (c.p Mg) were modified by PEO guided by different electrolytes, and the biological activity was assessed on vascular cells, immune cells, and repair cells (adipose tissue-derived stromal cells, ASCs). Vascular cells were more vulnerable than ASCs for compounds released by surface-coated Mg. All surface coatings supported the proliferation of adhered ASC. Released compounds from surface-coated Mg delayed but did not block in vitro wound closure of fibroblasts monolayers. Preformed endothelial tubes were vulnerable for released compounds, while their supporting ASC was not. We conclude that PEO-based surface-coating of Mg supports adhesion and future delivery of therapeutic vascular repair cells such as ASC, but that the observed vulnerability of vascular cells for coated Mg components warrants investigations in vivo.