Degradation Analysis of Thin Mg-xAg Wires Using X-ray Near-Field Holotomography

Sebastian Meyer,Stefan Bruns,Berit Zeller-Plumhoff,Silja Flenner,Imke Greving,Regine Willumeit-Römer,Kamila Iskhakova,Hanna Ćwieka,Björn Wiese,Andreas Wolf,Daniela Sanders,Johannes Hagemann

doi:10.3390/met11091422

Sebastian Meyer, Stefan Bruns + Show 10 more

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https://doi.org/10.3390/met11091422

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Abstract

Magnesium–silver alloys are of high interest for the use as temporary bone implants due to their antibacterial properties in addition to biocompatibility and biodegradability. Thin wires in particular can be used for scaffolding, but the determination of their degradation rate and homogeneity using traditional methods is difficult. Therefore, we have employed 3D imaging using X-ray near-field holotomography with sub-micrometer resolution to study the degradation of thin (250 μm diameter) Mg-2Ag and Mg-6Ag wires. The wires were studied in two states, recrystallized and solution annealed to assess the influence of Ag content and precipitates on the degradation. Imaging was employed after degradation in Dulbecco’s modified Eagle’s medium and 10% fetal bovine serum after 1 to 7 days. At 3 days of immersion the degradation rates of both alloys in both states were similar, but at 7 days higher silver content and solution annealing lead to decreased degradation rates. The opposite was observed for the pitting factor. Overall, the standard deviation of the determined parameters was high, owing to the relatively small field of view during imaging and high degradation inhomogeneity of the samples. Nevertheless, Mg-6Ag in the solution annealed state emerges as a potential material for thin wire manufacturing for implants.

Highlights

Magnesium (Mg) is of high interest for the application as temporary implant material, due to its high biocompatibility and biodegradability [1]
The binary phase diagram of Mg and a>]. Utilizing silver (Ag) simulated by PandatTM
The observed trends are in part contrary to the results presented in the literature, which showed that higher Ag content leads to an increase in the degradation rate [9,12,14]

Summary

Introduction

Magnesium (Mg) is of high interest for the application as temporary implant material, due to its high biocompatibility and biodegradability [1]. Mg alloy implants are already in use for clinical applications in the form of bone screws or stents [2,3]. Their use as suture or splinting material is has been envisioned since the end of the 19th century [4,5]. In order to achieve higher deformability of Mg wires, appropriate heat treatments and recrystallization with drawing steps are necessary. Using these techniques wire diameters close to human hair or 50 μm have been produced [11]

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