Page 89 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

STERILIZATION PROCEDURES IMPACT PURE MAGNESIUM MODIFIED BY PLASMA ELECTROLYTIC OXIDATION
the anodized samples could increase the oxygen concentrations and improve the resistance corrosion of the mate- rial. Our results corroborate findings of Park et al [30], that showed that surface-anodized Ti cleaned and sterilized with autoclave, gamma irradiation, oxygen plasma and ultraviolet light presented changes in the hydrophobicity and roughness which at the same time affected the biological performance of the surface. Samples sterilized by autoclaving showed an increment in the contact angle which was explained by the authors as a consequence of the temperature and pressure during process which affected the oxidation states and the oxide layer thickness on the treated surface. Similar results were found by Pegueroles et al [31] when grit-blasted titanium samples with differ- ent roughness, which were sterilized with steam autoclaving, presented a hydrophobization of the surface after this procedure. Also other authors explains the increment in the contact angle due to the contamination of the sample with organic impurities present in the environment during the process [22]. Finally, although further biological as- says will be required, such as cell viability and proliferation, the results from hemolysis presented here could be an indication that none of the methods evaluated here induced changes in the biological behavior of the surfaces.
4 Conclusions
Different options of sterilization were studied to know the impact of this process in the conservation of the anodic
films previous to its in vitro and in vivo evaluation. In general all sterilization methods did not affect the main com- 5 position of the material or cause degradation of the substrate. However dry-heat and formaldehyde techniques
showed modification on the surface morphology. In terms of surface energy, samples treated by autoclave and form-
aldehyde showed a decrement in wettability. Although the results of the present work did not provide any evidence
of sample passivation during the autoclave process, if this took place in some extension, it will be an advantage of
this sterilization procedure, as it will reduce its occurrence during in vitro assays.
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