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Superficially modified Mg-based alloy for biomedical applications: interaction with cells in culture


Development of new biodegradable materials for fracture repair implants is required in order to avoid a second surgery for their removal. Magnesium (Mg) and Mg-based alloys are promising candidates for this application given their good biocompatibility and osteoinductive properties. However, the degradation rate of Mg in aqueous media is high and releases hydrogen gas, which causes pain and local swelling. Superficial treatments, such as anodization, emerge as a potential solution to this limitation.

Objetivos - Metodologia - Resultados - Discussão dos Resultados/Objectives - Methodology - Results - Discussion of Results/Objetivos - Metodología - Resultados - Discusión de los resultados

Objective. To evaluate the influence of surface modification achieved by anodization at low voltage on Mg-based implants on mammalian fibroblasts adhesion and growth.
Metodology. AZ91 pieces were polished and anodized at low voltage for 40 min in potassium hydroxide solution, and sterilized by dry heat. As control material, non-treated AZ91 pieces were polished and sterilized in the same way. First, the evaluation of superficial microstructure of materials was carried on by scanning electron microscopy (SEM) and rugosimetry. Then, bovine fibroblasts were seeded on the materials (anodized AZ91 or control) for 24 h; as cellular control, cells were cultured without material (on plastic). Cellular adhesion and proliferation were evaluated after 24 h by Hoechst staining. Culture medium pH and osmolarity were also recorded. Surface roughness and weight of materials was assessed before and after cell culture.
Results. The surface of AZ91 anodized pieces showed a homogeneously distributed oxide layer with cracks and rough (average roughness: Ra = 0.88 ± 0.005 µm; Rz = 1.23 ± 0 µm). AZ91 control surface was homogeneous and smooth, with scratches associated with polishing (Ra = 0.2 ± 0.05 µm; Rz = 1.43 ± 0.27 µm). Number of cells adhered and grown on the anodized AZ91 was significantly higher than those adhered on the AZ91 control and also to those grown without the material (on the dish surface; one way ANOVA, F = 118, p < 0.001). pH and osmolarity of culture medium were similarly increased for anodized AZ91 and AZ91 control, in relation with values from cell culture without material. Ra of anodized AZ91 and AZ91 control did not change after cell culture (RaAZ91 anodized = 0.81 ± 0.07 µm; RaAZ91 control = 0.22 ± 0.03 µm), but the depth of valleys on the surface increased markedly for anodized AZ91 (Rz = 5.16 ± 0.47 µm) and lightly for AZ91 control (Rz = 1.92 ± 0.27 µm). Weight loss of both materials was despicable after cell culture.
Discussion. Anodization of Mg-based alloy at low voltage generated a homogeneous oxide layer on the material surface. This treatment increased the adhesion of bovine fibroblasts, probably due to a lower release of hydrogen gas from the surface or the topography of the oxide layer. At the time of evaluation, differences in the level of degradation (release of osmolytes, changes in pH and weight loss) were not detected between anodized AZ91 and AZ91control.

Considerações Finais/Final considerations/Consideraciones finales

Conclussions. Anodization of Mg-based AZ91 alloys at low voltage improves cellular surface adhesion. Therefore, this treated material is a promising candidate for future in vitro –e.g. in contact with osteoblasts and macrophages- and in vivo assessment.

Palavras-chave/Key words/Palabras clave

anodization ,fibroblasts ,cellular adhesion and proliferation ,anodization of Mg-based AZ91 alloys , osteoblasts and macrophages




MARIA ROSA KATUNAR, Julieta Leticia Merlo, Jesica Canizo, Andrea Gomez Sanchez, Silvia Marcela Cere