Jiahui Dong (1), Nazlı Tümer (1), Marius Leeflang (1), Peyman Taheri (2), Lidy E. Fratila-Apachitei (1), Arjan Mol (2), Amir. A. Zadpoor (1), Jie Zhou (1)
Journal of Magnesium and Alloys, December 2021. DOI: 10.1016/j.jma.2021.11.018

Keywords

Additive manufacturing; Material extrusion; Magnesium-zinc alloy; Porous scaffold; Biodegradation

Abstract

Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes. The recent progress in additive manufacturing (AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures. Extrusion-based AM, followed by debinding and sintering, has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds, which can avoid some crucial problems encountered when applying powder bed fusion AM techniques. However, such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation. In the present research, alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously. The in vitro biodegradation behavior, mechanical properties, and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated. Moreover, the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds. The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2 second phase particles. The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1, as compared to pure Mg scaffolds. Over 28 days of static immersion in modified simulated body fluid, the corrosion rate of the Mg-Zn scaffolds decreased from 2.3 ± 0.9 mm/y to 0.7 ± 0.1 mm/y. The yield strength and Young's modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests. Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility. In direct cell culture, some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds. Overall, this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting biomaterials.

How Our Software Was Used

Dragonfly was used for the segmentation of corrosion products in DICOM images.

Author Affiliation

(1) Department of Biomechanical Engineering, Delft University of Technology, Delft 2628 CD, the Netherlands.
(2)Department of Materials Science and Engineering, Delft University of Technology, Delft 2628 CD, the Netherlands.