Mg ZX10 alloy for biomedical applications: Surface characterization and comparative corrosion studies under simulated biological conditions

Abstract

Biodegradable magnesium (Mg)-based alloys emerge as potential intracorporeal implants for clinical application in bone tissue, the cardiovascular and the nervous systems. The surfaces of control (non-sterilized) and sterilized (180 °C 1 h) Mg ZX10 alloy were studied. The alloy evolution in SBF (simulated saline solution) and in DMEM (Dulbecco´s Modified Eagle Medium) with fetal calf serum (FCS) was investigated using: Raman spectroscopy, FTIR-ATR, electrochemical assays and scanning electron microscopy (SEM). The Mg ZX10 microstructure analysis revealed an average grain size of 23.4 ± 11.02 and 31.6 ± 13.07 μm, considering the minor and major axis, respectively. In addition, the Mg ZX10 microstructure exhibited a homogeneous grain distribution. The contact angle formed between the water and the surface of control Mg ZX10 and sterilized were 32.24° ± 1.53 and 46.76° ± 0.83, respectively. Consequently, both groups of samples exhibited hydrophilic surfaces. Furthermore, the free surface energy of control Mg ZX10 was 63.23 ± 0.72 mN/m and sterilized Mg ZX10 was 52.31 mN/m ± 1.25, those energy values were in agreement with previous reports. Upon immersion in SBF, Raman spectroscopy detected the presence of magnesium oxides-hydroxides, phosphates and carbonates compounds in both groups of samples without significant differences. FTIR spectra of the sterilized alloys, after immersion in DMEM + FCS, showed the presence of amide and carbon-carbon bonds, magnesium-oxides, as well as phosphates and carbonates groups. These findings suggested the deposition of organic and inorganic compounds on the alloy surface. Electrochemical assays carried out in SBF demonstrated a slight reduction in the degradation of the sterilized alloy compared to control Mg ZX10. Moreover, a substantial decrease in the corrosion behavior of the sterilized alloy immersed in DMEM + FCS with respect to the same alloy immersed in SBF was observed. SEM images showed that the alloy, previously immersed in SBF, exhibited degradation cracks. Contrary, the sterilized alloy surface immersed in DMEM + FCS was more homogenous with deposits of structures similar to hybrid nanoflowers. Based on these results, this sterilization process does not alter the chemistry of Mg ZX10 alloy surface and, even, its application exhibits an advantage since the high corrosion rate of Mg in physiological media. Furthermore, the organic-inorganic structures adsorbed, after alloy immersion in DMEM + FCS, could decrease corrosion behavior.