INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Surface modification by glass ceramic coatings of magnesium alloys: surface and electrochemical performance in vitro
Autor/es:
OMAR, SHEILA; BALLARRE, JOSEFINA; ENRIQUE MARTINEZ-CAMPOS; CERE, SILVIA; DURAN, ALICIA
Lugar:
Bertinoro
Reunión:
Simposio; 9ª BioMetal. Symmposium on biodegradable metals for biomedical applications.; 2017
Resumen:
INTRODUCTION: Surface modification of metallic materials is the approach for developing functional properties to assure good biocompatibility, enhance tissue acceptance, and/ or inhibit corrosion rate. In this work, surface modification of two commercial magnesium alloys is presented. The alloys were coated with 58S glass coating by sol-gel, with organic precursors such as silicon and phosphate alcoxydes and calcium lactate with the aim of inducing new bone formation by the bioactive glass together with the deceleration of the corrosion rate and hence the hydrogen evolution. METHODS: AZ31B (Al 3%, Zn 1%, Mn 0.2%) and AZ91D (Al 9%, Zn 1%, Fe 0.005%, Mn 0.33%, Ni 0.002%) were used as substrates. Plane samples were polished until 2500 grit SiC paper and cleaned prior to coat. 58S glass (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) was prepared by sol-gel method using tetramethyl orthosilicate, methyltriethoxysilane, triethyl phosphite and calcium L-lactate hydrate as precursors, HNO3 1N was used as catalyser, ethylene glycol to improve the alkoxide condensation degree and methanol dissolve the calcium lactate. Micro-Raman assays were performed to analyze deposits composition (Invia Reflex Confocal, Renishaw RM 2000, UK) with a 785 nm wavelength laser. Electrochemical assays were performed to determine degree of degradation of the coating and the Mg alloy. Hank Buffered Salt Solution (HBSS) at 37 ºC was used as electrolyte. Coated samples were seeded with C2C12-GFP mouse autofluorescent pre-myoblast cell line. Cells were incubated at 37 °C with 5% CO2 and the medium was refreshed every 2 or 3 days. C2C12-GFP cells were seeded on the materials with a density of 3 × 104 cells per cm2. This cell line was evaluated by fluorescence microscopy (FITC filter λex/λem = 490/525 nm) at 72 and 196 h (h) to determine cell adhesion and growing on the material.RESULTS: coatings thickness were 1.2 ±0.1 and 0.9 ±0.2 µm for AZ31 and AZ91 respectively. EIS results show that the coatings applied onto AZ31 although are thicker than the ones applied on AZ91 present more defects since the total impedance of the former is lower than for the AZ91. This fact is observed in the very early stages of immersion and also after 17 days of immersion. By Raman spectroscopy, magnesium hydroxide, Mg-Al hydrocalcites (Mg and Al hydroxy-carbonate), apatite and hydroxyl-carbonate apatite can be detected on the surface after 72 h immersion1. Cell culture show that AZ31 alloys both blank and coated showed preliminary good adhesion but then a possible cytotoxic effect is observed. Both AZ91 blank and coated samples showed good cytocompatibility, cell adhesion and proliferation.DISCUSSION & CONCLUSIONS: Coatings applied onto the Mg alloys shown to be biocompatible in vitro (in the sense of apatite like deposit) but cytocompatibility only proceed for the samples using AZ91 as substrate. This is probably associated to the higher corrosion rate that the AZ31 experiments both coated and bare and the control of the local alkalinisation that the media experiments2. REFERENCES:1I.Notingher, A.R. Boccaccini, J.Jones, V. Maquet, L.L. Hench (2002) Materials Characterization; 49:255-60, 2 L.G.Bland, A.DKing, N.Birbilis, J.R.Scully (2015) Corrosion 71, 128?145.