RESUMEN
This work provides a comparative study on the corrosion protection efficiency of Ce, La films as well as Ce/La and La/Ce oxide bilayered coatings deposited onto AA7075 and AA6061 substrates by the radio frequency (RF) magnetron sputtering technique. The coating thickness ranged approximately from 12 to 835 nm, which changed with the deposition parameters and substrate composition. The relationship between microstructure, roughness and electrochemical performance is examined. The reactivity and crystallinity of rare earth (RE) films can be tailored by adjusting the sputtering parameters. Sputtered La films with thickness ca. 390 nm and average roughness of 66 nm showed the best corrosion protection properties in chloride medium as determined by potentiodynamic curves and electrochemical impedance spectroscopy (EIS). The method to obtain RE bilayered coatings, i.e., La/Ce or Ce/La as well as the substrate composition and applied power conditioned their inhibition properties. The RE bilayered coatings displayed better barrier properties than Ce films, which were poorer than those featured by La films.
RESUMEN
The present work evaluates the biocompatibility of a fluoride surface-modified AZ31 magnesium alloy (AZ31HF) with different cell lines that coexist in the implant environment to test its potential use as a biodegradable and absorbable biomaterial for bone repair. A clear stimulation of cell proliferation and an enhancement of the mitochondrial respiratory activity were observed when mouse osteoblasts (MC3T3-E1), fibroblasts (L929), and macrophages (J774) cell lines were cultured with the modified alloy. No significant change in apoptosis or viability rates was observed when osteoblasts and fibroblasts cultures were grown in the presence of this alloy. A proteomic analysis of the MC3T3-E1 cell extracts cultured in the presence of AZ31HF showed an overexpression of proteins related with the mineralization process, which is a necessary step for bone repair. An increase in the lactate dehydrogenase activity was observed in the MC3T3-E1 and J774 cell cultures that could be a response of the oxidative stress produced by the presence of the material. This stress could be related to the increase observed in the respiratory mitochondrial activity or respiratory burst measured in theses cultures that indicate damage in the cell membranes and subsequently some cell death. Results reported here, for and against AZ31HF, should be taken into account when considering the potential use of this modified alloy in bone repair applications.