Page 64 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 4
Abstract
Due to its mechanical properties, magnesium (Mg) is widely used in industrial and biomedical applications. However, Mg is highly reactive and unstable in aqueous solution. Several strategies are available to increase stability of reactive metals which include the use of alloys or surface coatings. An efficient method for surface coating is plasma electro- lytic oxidation (PEO). This is an electrochemical oxidation technique that allow to obtain a protective surface layer in a controlled manner. Controllable parameters such as voltage, current density, time and electrolytic solution facilitate the production of a coating with specified morphology, composition and surface energy. To date, the use of additives to the electrolytic solution improves the corrosion resistance of the material, reason why hexamethylenetetramine and mannitol, compounds never studied before in this context were added to a base solution of silicate and potassium hydroxide In the present study, these electrolyte solutions were used and parameters of anodizing were optimized to obtain homogenous surfaces with a variable roughness and thickness. Results from in vitro studies in NaCl demon- strated an improvement in the corrosion resistance. In addition, coatings were obtained by a two-step anodization procedure: firstly anodizing in an electrolyte solution containing sodium fluoride and secondly in an electrolyte solu- tion with hexamethylenetetramine and mannitol respectively. Results showed that the first layer acts as a protective layer which improves the corrosion resistance in comparison with the samples with a single anodizing step. In conclu- sion, these coatings are promising candidates to be used in biomedical applications in particular because the com- ponents are non-toxic for the body and the rate of degradation of the surface coating is lower than that of pure Mg.
Graphical Abstract
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