Research on biodegradable stents is mainly focused on coronary stents. However, there is a demand for degradable stents in the field of pediatric cardiology as they have the potential to allow growth of vessels and preserve all treatment options. Potential applications include aortic coarctation, stenosis of the pulmonary artery and branches, and other. Vessel diameters range from about 6 to 25 mm, thus stents larger than coronary are required.
Recently our group reported a tensile test method for magnesium wires together with a new concept for fast in vivo screening of possible stent materials [1, 2]. Initial results revealed a mismatch between microstructural and tensile properties. The present work focusses on the surface treatment process.
Machine-drawn Mg10Gd-wires were annealed (400°C or 450°C; 30, 60 or 90 min), cut to 30 mm length and etched in a mild acidic solution followed by intensive washing in 100% ethanol.
Surface morphology was analysed using SEM. After plastic embedding of the wires, tensile tests were performed.
Results & Discussion
Although microstructure analysis showed smaller grains for 400°C (8-10 µm) compared to 450°C annealed wires (15-19 µm), the initial experiments did not show a pronounced difference in mechanical behaviour. Surface roughness was identified as a possible reason for this mismatch. The new applied finishing process revealed the importance of a smooth surface yielding higher elongation at fracture compared to the rough wires from the first study.
 M. Bartosch, H. Peters, D. O h-Ici et al. “Different approaches for in vivo testing of absorbable metals in blood vessels,” Eur. Cell. Mater., vol. 28, no. S03, p. 45, 2014.
 M. Bartosch, H. Peters, B. Schmitt et al. “Tensile and microstructural properties of annealed Mg10Gd-alloy wires,” Eur. Cells Mater., vol. 30, no. page 30, p. 2262, 2015.
The authors thank Gert Wiese (Helmholtz-Zentrum Geesthacht) and Dag Wulsten (Julius Wolff Institut, Charité).
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