Page 87 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

STERILIZATION PROCEDURES IMPACT PURE MAGNESIUM MODIFIED BY PLASMA ELECTROLYTIC OXIDATION
served with an average size of the pores of 1.02±0.1μm. The thickness of the anodic film was about 2μm. he im- ages of the surface of the anodic film samples treated with steam autoclaving and UV irradiation did not show any changes on morphology. On the other hand, samples sterilized by dry-heat showed random cracks on the surfaces which can be product of internal stresses induced in the coating by the heating of the samples. Additionally, for samples treated by steam formaldehyde sterilization, changes in the morphology of the coating surface was evident, both porosity and topography appears to have been modified by the sterilization treatment. However, cross-section images for all the treatments showed no major effects on the internal structure and thickness of the anodic films. In similar manner, it was not observed any effect on the substrate material, in all cases the interface coating/substrate appears to be unaltered.
As an additional evaluation, contact angle was measured and the corresponding surface energy was calculated. In
Table.1 these results are summarized showing that samples treated by autoclaving and in a lesser amount by steam formaldehyde sterilization, showed an increment for the contact angle values and consequently these samples also presented a decrease in surface energy compared to the other treatments and the untreated sample.
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Finally, as an approach to the biological performance of the samples, evaluation of the hemocompatibility was carried out. Results showed that none of the evaluated samples presented hemolysis after contact with human blood (Fig.5).
Fig.5 Hemocompatibility of Mg samples sterilized by different methods. Samples showed no hemoly-
4. Discussion
sis after being in contact with human blood.
The high reactivity of Mg makes this material complicated in its manipulation as an implant. Some considerations must be taken into account to be sure that the product obtained after anodization is the same to be evaluated in vitro or to be implanted in a living organism. Within the proposed sterilization techniques, irradiation by UV light is the method that could produce least modification on the material at structural level, however a rise in the oxygen content at this sample surface was observed by EDS analysis. This result is consistent with the reports of Ito et al[19], who stated that the process of adsorption of oxygen are promoted by the exposition of MgO to UV irradiation where oxygen species (ozonide and superoxide) are formed. Additionally and according to studies from Att et al [20][21] on
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