Comparing medium pressure dielectric barrier discharge (DBD) plasmas and classic methods of surface cleaning/activation of pure Mg for biomedical applications

Abstract

Pure magnesium (Mg), being a lightweight biodegradable material, is increasingly attracting attention for its use in biomedical applications. However, surface contaminations arising from material machining can result in a deleterious degradation behavior thus a poor implant biocompatibility performance. Therefore, this paper represents a comparative study tackling the surface chemistry, cytocompatibility and degradation of Mg discs subjected to classical grinding and chemical treatments and to unconventional medium pressure (5 kPa) plasmas operated in Ar and NH3/He. Results reveal that both plasmas remove more than 40% of the carbonaceous contaminations while introducing surface oxygen (and nitrogen) containing functionalities. However, grinding only removes 34% of the initial surface carbon. Despite being the most efficient in eliminating the organic layer, the chemical treatment leads to an excessive surface oxidation. In vitro tests involving mesenchymal stem cells reveal that plasma-treated samples outperform their ground and chemically cleaned counterparts in terms of cell-surface affinity as more spread out cells with significantly bigger areas are detected, suggesting higher cell attachment. Moreover, plasma does not alter the degradation rate of Mg discs, thus providing a striking insight for their application in tissue engineering. Overall, one can conclude that the eco-friendly and economical sub-atmospheric plasma is an effective alternative synergistically cleaning and improving the cytocompatibility of Mg surfaces.