Page 114 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 7
Abstract
One of the most common applications of magnesium (Mg) in the biomedical field is in cardiovascular stents where the main advantage of the material is its degradation capacity and elimination due to Mg is an essential elements for the body and its excess is easily handled by unary excretion. Yet, Mg is highly reactive and local high concen- trations of leaching Mg can have toxicological effects on the surrounding tissues. One of the strategies to address this problem is through the use of magnesium alloys in order to decrease the degradation rate and to improve the performance of the material at mechanical and biological level. A high variety of alloys have been evaluated to date, however one of the limitations of this alternative are the side effects produced by the alloying agents after the degradation of the material. Additionally, techniques that involve surface modification and use of coatings has been used to prevent leaching of free Mg. For this study, commercial pure Mg (c.p Mg) was modified through plasma elec- trolytic oxidation (PEO) technique in order to produce a protective coating primarily composed of magnesium oxide and magnesium hydroxide. As a product of this reaction, corrosion products are generated reason why it is needed to evaluate its influence under cells of the system. Primary human umbilical vein endothelial cells (HUVECs) and smooth muscle cells (SMCs) were object of study due to both cell types are mainly involved after the placement of a stent in a blood vessel. The effect of the changes in the concentration of Mg2+ and changes in the pH were evaluated in these two cell types. Additionally, the influence of corrosion products on integrity of monolayers of HUVECs was studied in a static and dynamic model. Finally a better approximation was obtained by the evaluation in an ex vivo model where pig aortic rings were exposed to Mg extracts and the integrity and functionality of the endothelium was evaluated. As conclusion it was observed that independently, Mg concentration and pH had an effect in the cell activity of the both cell types. In overall, the use of coatings produced by PEO showed an improvement in the biologi- cal performance of the material in comparison with the bare Mg.
Key words: endothelial cells, smooth muscle cells, magnesium, plasma electrolytic oxidation, degradation.
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