Review of magnesium-based biomaterials and their applications

In biomedical applications, the conventionally used metallic materials, including stainless steel, Co-based alloys and Ti alloys, often times exhibit unsatisfactory results such as stress shielding and metal ion releases. Secondary surgical operation(s) usually become inevitable to prevent long term exposure of body with the toxic implant contents. The metallic biomaterials are being revolutionized with the development of biodegradable materials including several metals, alloys, and metallic glasses. As such, the nature of metallic biomaterials are transformed from the bioinert to bioactive and multi-biofunctional (anti-bacterial, anti-proliferation, anti-cancer, etc.). Magnesium-based biomaterials are candidates to be used as new generation biodegradable metals. Magnesium (Mg) can dissolve in body fluid that means the implanted Mg can degrade during healing process, and if the degradation is controlled it would leave no debris after the completion of healing. Hence, the need for secondary surgical operation(s) for the implant removal could be eliminated. Besides its biocompatibility, the inherent mechanical properties of Mg are very similar to those of human bone. Researchers have been working on synthesis and characterization of Mg-based biomaterials with a variety of composition in order to control the degradation rate of Mg since uncontrolled degradation could result in loss of mechanical integrity, metal contamination in the body and intolerable hydrogen evolution by tissue. It was observed that the applied methods of synthesis and the choice of components affect the characteristics and performance of the Mg-based biomaterials. Researchers have synthesized many Mg-based materials through several synthesis routes and investigated their mechanical properties, biocompatibility and degradation behavior through in vitro, in vivo and in silico studies. This paper is a comprehensive review that compiles, analyses and critically discusses the recent literature on the important aspects of Mg-based biomaterials.