An in vitro and in vivo characterization of fine WE43B magnesium wire with varied thermomechanical processing conditions

• Published in: Journal of biomedical materials research. Part B, Applied biomaterials Applied biomaterials, 2018-07, Vol.106 (5), p.1987-1997
• Main Authors: Griebel, Adam J, Schaffer, Jeremy E, Hopkins, Tracy M, Alghalayini, Alaa, Mkorombindo, Tinomudaishe, Ojo, Kolade O, Xu, Zhigang, Little, Kevin J, Pixley, Sarah K
• Format: Article
• Language: English
• Subjects: Alloys; Biomedical materials; Cell culture; Cold working; Corrosion; Corrosion cell; Corrosion effects; Corrosion rate; Corrosion tests; Grain; Heat treatments; Histology; Implantation; In vivo methods and tests; Localized corrosion; Magnesium; Magnesium base alloys; Materials research; Materials science; Mechanical properties; Metallurgy; Morphology; Organic chemistry; Surgery; Surgical implants; Thermomechanical treatment; Transplants & implants; Wire
• ISSN: 1552-4973; 1552-4981
• DOI: 10.1002/jbm.b.34008

Absorbable implants made of magnesium alloys may revolutionize surgical intervention, and fine magnesium wire will be critical to many applications. Functionally, the wires must have sufficient mechanical properties to withstand implantation and in-service loading, have excellent tissue tolerance, and exhibit an appropriate degradation rate for the application. Alloy chemistry and thermomechanical processing conditions will significantly impact the material's functional performance, but the exact translation of these parameters to implant performance is unclear. With this in mind, fine (127 µm) WE43B magnesium alloy wires in five thermomechanical process (TMP) conditions (90% cold work [CW], and 250, 375, 400, and 450°C heat treatments) were investigated for their effect on mechanical and corrosion behavior. The TMP conditions gave clear metallurgical differences: transverse grain dimensions ranged from 200 nm (CW) to 3 µm (450°C), UTS varied from 324 MPa (450°C) to 608 MPa (250°C), and surgical knotting showed some were suitable (CW, 400°C, 450°C) while others were not (250°C, 350°C). In vitro and in vivo corrosion testing yielded interesting and in some cases conflicting results. After 1 month immersion in cell culture medium, wire corrosion was extensive, and TMP conditions altered the macrocorrosion morphology but not the rate or total release of magnesium ions. After 1 month subdermal implantation in mice, all wires were well tolerated and showed very little corrosion (per µCT and histology), but differences in localized corrosion were detected between conditions. This study indicates that WE43B wires treated at 450°C may be most suitable for surgical knotting procedures. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1987-1997, 2018.