Page 86 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 5
Results from XRD (Fig 3) showed the crystalline composition of all samples. All diffractograms showed peaks corre- sponding to MgO besides to signals from the Mg substrate. The diffuse background observed at approximately 45° in the untreated sample (Fig. 3 A), revealed the presence of amorphous compounds, which was clearly reduced for the sterilized surfaces. As the temperatures employed in all the sterilizing treatments are relatively low, there is not pos- sibility of occurrence of phase transformation. Therefore, the reduction in the presence of amorphous material on the treated surfaces, indicates the cleaning effect of the various procedures, which resulted in decrease of the amount of anodization by-products. There was not a clear indication of existence of crystalline phases containing Si such as Mg2SiO4, which could be related with the amorphous nature of these species, the low content of those compounds in the oxide film and/or the concealing effect of the huge Mg peaks; both structures diffract at similar angles.
Fig.4. Top-view SEM image of the surface and cross-section for anodized samples of Mg before and after different sterilization procedures.
On the other hand, analysis of the surfaces and the cross-section was carried out to determine the integrity of the coatings after the different sterilization processes. In Fig.4 it is possible to observe at different magnification (1,000x and 3,000x) the general appearance of the surfaces. A homogeneous distribution of interconnected pores was ob-
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