Biodegredable and Bioactive Orthopaedic Magnesium Implants with Multilayered Protective Coating

Biocompatible and biodegradable magnesium (Mg) and its alloys are excellent biomaterials as orthopaedic implant, but they corrode too quickly in vivo to perform such functions as supporting and fixation. In this study, we have successfully prepared a multilayered coating on the surface of Mg, which contains a chemical conversion layer of fluoride or phosphating, an adhesion layer, and a layer of biodegradable polylactide (PLA). The recorded weight loss and the ionic magnesium (Mg2+) releasing in the simulated body fluid (SBF) demonstrate that the corrosion rate of the protected Mg has been reduced to one tenth as compared to that of the unprotected bare Mg. The corrosion rate of the protected Mg can be adjusted with either the chemical conversion type or the thickness of the PLA layer. The bare and the protected Mg have been manufactured and implanted in the tibia defect of Sprague Dawley rats, the X-ray and micro-CT images show an improved anti-corrosion of the protected Mg in vivo, and the histological ...