In vivo and in vitro study of resorbable magnesium wires for medical implants: Mg purity, surface quality, Zn alloying and polymer coating

TL;DR

This study investigates the microstructure, mechanical properties, and biocompatibility of various magnesium wires with zinc alloying and polymer coatings, aiming to improve their performance for medical implants and bone support.

Contribution

It provides comprehensive in vitro and in vivo analysis of ultra-pure and alloyed magnesium wires with coatings, highlighting their potential for biodegradable bone-support applications.

Findings

Polymer-coated Mg-Zn wires promote osteogenesis in vivo.

Low-alloyed Mg-Zn wires reduce hydrogen evolution and improve mechanical properties.

Coatings effectively slow in vivo degradation of magnesium wires.

Abstract

Magnesium is an excellent material in terms of biocompatibility and its corrosion products can serve as an active source for new bone formation. However, localized corrosion and H2 generation limit the potential of Mg-based implants. Utilizing low-alloyed Mg-Zn wires can strongly reduce problems with large H2 bubbles and improve the mechanical properties considerably while maintaining excellent long-term biocompatibility. Acidic pickling and a polymer coating can be effectively used to lower the rate of in vivo degradation. In this work, microstructural, mechanical, and in vitro characterization of 250 um and 300 um extruded wires made from ultra-pure Mg, commercially pure Mg, Mg-0.15Zn, Mg-0.4Zn and Mg-1Zn was performed. Additionally, Mg-0.4Zn wires together with a variant coated with a copolymer of L-lactide and {\epsilon}-caprolactone were tested in vivo on artificially damaged Wistar rat femurs. Based on the observed Mg-induced osteogenesis, polymer-coated Mg wires with a small addition of Zn are a perspective material for bone-support applications, such as cerclage and fixation wires.