Biodegradable magnesium-based supports as novel treatment modalities for vascular disease

Monica Echeverry-Rendon, University of Antioquia, Medellin, Colombia

Magnesium (Mg) is a material widely used in industrial applications due its low weight, ductility and good mechanical properties. For non-permanent implants Mg is considered as a good option because it is biodegradable and its products of degradation are not harmful for the human body. However, Mg is chemically reactive and hydrogen gas is released as part of the degradation. However, physico-chemical modification of the material can alleviate this problem because this reduces the degradation rate. Using the plasma electrolytic oxidation (PEO) technique, a surface layer of MgO/Mg(OH)2 is produced in a controlled way. Thus the degradation rate of the Mg can be carefully tuned and reduced. An additional advantage of PEO is that properly designed surfaces can be produced that improve adhesion and function of e.g. therapeutic stem cells. To date, little is known about the influence of the microenvironment in vitro or in vivo on the degradation of Mg, irrespective of coating. The aim of this project was to develop a magnesium-based stent with tunable degradation to deliver therapeutic cells that augment healing of vascular lesions. The optimal device would show a turnover that synchronises with the progress of the tissue healing. Samples of c.p Mg (99.98%) were anodized in a basic solution using a DC power supply. Characterization of the samples in terms of wettability, morphology and composition were carried out. Cytotoxicity, proliferation and cell-material interaction was studied with adipose-derived stromal/stem cells (ASC). Scratch wound-assay with fibroblast cells was carried out by using conditioned medium obtained from Mg with coating or bare uncoated. Finally, effect of materials under laminar flow condition and endothelial cells (HUVECs) were carried out (IBIDI flow system). The corrosion resistance of Mg was improved after generation of a surface coating using the PEO technique. In contrast to c.p Mg, all PEO-surface treated coating were non-cytotoxic and fully hemocompatible i.e. these did not cause hemolysis. In conclusion, degradation rate of Mg can be controlled by PEO technique. Modification acts as a double-edged sword: it reduces the degradation rate, while it improves biocompatibility, in particular under hemodynamic conditions. PEO is a technique that allow the control of the structure on the layer produced in Mg by the modification of some variables.

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