Characterization and In Vitro Behavior of PEO Coated Mg Modified with Antibacterial Ag(I) and Cu(II) Complexes.

The use of Mg-based biomaterials with a number of their advantageous properties are overshadowed by uncontrollable metal corrosion. Moreover, the use of implants goes alongside with the threat of pathogens-associated complications. In this study, PEO coated Mg biomaterial loaded with antibacterial Ag(I) and Cu(II) complexes is produced and tested to meet both appropriate protective characteristics as well as sufficient level of antibacterial activity. To achieve a suitable level of anticorrosion protection phosphate and fluoride-phosphate electrolytes are used in the PEO process. Investigation of the surface thickness and morphology done by means of cross-section analysis and scanning electron microscopy (SEM), as well as electrochemical impedance spectroscopy (EIS) assay show precedence of the fluoride containing PEO coating and make it the material of choice for further modification with Ag(I) and Cu(II) complexes. The presence of the complexes on the PEO surface is confirmed by energy dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES) are used to estimate the complexes' chemical state and depth of penetration in the coating surface. Based on the results of antibacterial assay, the modified coatings are found to be active against both Gram-positive and Gram-negative bacteria.

Influence of the amount of intermetallics on the degradation of Mg-Nd alloys under physiological conditions.

The influence of amount of intermetallics on the degradation of as-extruded Mg-Nd alloys with different contents of Nd was investigated via immersion testing in DMEM+10% FBS under cell culture conditions and subsequent microstructural characterizations. It is found that the presence of intermetallic particles Mg41Nd5 affects the corrosion of Mg-Nd alloys in two conflicting ways. One is their negative role that their existence enhances the micro-galvanic corrosion. Another is their positive role. Their existence favours the formation of a continuous and compact corrosion layer. At the early stage of immersion, their negative role predominated. The degradation rate of Mg-Nd alloys monotonously increases with increasing the amount of intermetallics. Mg-5Nd alloy with maximum amount of intermetallics suffered from the most severe corrosion. With the immersion proceeding (≥7 days), then the positive role of these intermetallic particles Mg41Nd5 could not be neglected. Owing to the interaction between their positive and negative roles, at the later stage of immersion the corrosion rate of Mg-Nd alloys first increases with increasing the content of Nd, then reaches to the maximum at 2 wt. % Nd. With a further increase of Nd content, a decrease in corrosion rate occurs. The main corrosion products on the surfaces of Mg-Nd alloys include carbonates, calcium-phosphate, neodymium oxide and/or neodymium hydroxide. They are amorphous at the early stage of immersion. With the immersion proceeding, they are transformed to crystalline. The existence of undegradable Mg41Nd5 particles in the corrosion layer can enhance the crystallization of such amorphous corrosion products.