Smart self-healing coatings on biomedical magnesium alloys: A review

With promising mechanical property and biodegradability, magnesium (Mg) alloys are considered as the potential candidates in biomedical application. Rapid degradation of Mg alloys compromises the mechanical performance and interfacial bioactivity, hindering clinical adoption. Deposition of a surface coating is an effective technique to improve the corrosion protection and bio-efficacy of Mg biomedical implants. Because of the natural degradability and corrosion, the surface is inevitably damaged in the complex physiological environment. Therefore, it is essential to form a self-healing coating that can repair damage to restore the stable mechanical structure and functions of biomedical Mg alloys. This paper reviews the recent advances in coating technology and the related properties including biodegradation behavior, self-repairing activity, biocompatibility, and other biological effects, and the healing mechanism is discussed. Self-healing coatings suitable for Mg alloys include conversion coatings, encapsulation coatings, and multilayered coatings, and their properties in vitro and in vivo are reviewed by focusing on drug-controlled and prolonged release, sterilization, cytocompatibility, osteogenesis, hemocompatibility, and angiogenesis. This review aims at providing guidance for the future research and development of practical healing coatings for biomedical Mg implants.