Surface modification of biodegradable magnesium and its alloys for biomedical applications

P Tian,X Liu

doi:10.1093/rb/rbu013

Abstract

Magnesium and its alloys are being paid much attention recently as temporary implants, such as orthopedic implants and cardiovascular stents. However, the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date, which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal. Moreover, rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment, such as local gas cavity around the implant, local alkalization and magnesium ion enrichment, which will reduce the integration between implant and tissue. So, in order to obtain better performance of magnesium-based implants in clinical trials, special alloy designs and surface modifications are prerequisite. Actually, when a magnesium-based implant is inserted in vivo, corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface. So the surface properties, such as corrosion resistance, hemocompatibility and cytocompatibility of the implant, are critical for their in vivo performance. Compared with alloy designs, surface modification is less costly, flexible to construct multi-functional surface and can prevent addition of toxic alloying elements. In this review, we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application. The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization.

Highlights

Metallic biomaterials have played an important role in implant applications in loading bearing conditions, such as orthopedic implants and cardiovascular stents, where their high mechanical strength and fracture toughness make them to be superior to ceramics, polymers and polymer/ceramic composites
The X-ray photoelectron spectroscopy (XPS) results revealed that a thin Zn rich surface layer with Zn existing in the metallic state was formed by ion implantation, which attributed to the decrease of corrosion resistance due to the galvanic effect (Fig. 6b) [116]
Surface modification plays an important role in practical applications of magnesium-based materials evaluated by in vitro and in vivo tests, especially at the initial degradation stage of their service

Summary

Introduction

Metallic biomaterials have played an important role in implant applications in loading bearing conditions, such as orthopedic implants and cardiovascular stents, where their high mechanical strength and fracture toughness make them to be superior to ceramics, polymers and polymer/ceramic composites. For magnesium-based implants, proper surface corrosion resistance and good biocompatibility for surrounding tissues integration with the implants are critical for their applications. The fluoride-treated magnesium alloy maintained better mechanical strength evaluated by three-point bending test, presenting a promise for application as biodegradable implants [71].

Results

Conclusion