The Preparation Of Magnesium Alloy Materials For Bone Tissue Repair With MGF And Investigation Of Degradation

Magnesium alloys exhibit an attractive combination of biocompatibility, ultimate loading capacity and biodegradability. These properties make them ideal candidates in biomedical fields, which apply in nails, blade plates and vascular stents. But magnesium alloys are characterized by low corrosion resistance. So it is important to exploit novel biomedical magnesium alloys in orthopedic implant fields, making the degradation rate matching with the bone healing rate. In recent years, research on the corrosion resistance and the surface modification is the key point, which promotes the magnesium alloy applied in clinic.In this study, ZEK100 magnesium alloy was selected for tests. The samples were immersed in PBS for different intervals. Then the corrosion mechanism and the corrosion mechanical properties were studied. It is found that the corrosion behaviors are characterized by pitting corrosion. The depth of corrosion pits grows with immersion time. The corrosion rate decreases a lot in the initial 7 days, and then almost stays unchanged. Moreover, after 28 days' immersion, the elastic modulus almost keeps stable, while the yield strength and the ultimate strength decreases a lot, which indicates that corrosion has important effects on the tensile mechanical properties. The fatigue life of the samples under the same stress conditions decreases with increasing immersion time under the asymmetric stress-controlled cyclic loading. Considering the effect of corrosion on the material failure, a modified fatigue life model is proposed for magnesium alloy under corrosion.Surface modification on the magnesium alloys were obtained via layer by layer technique. Then the mechano-growth factor was loaded on the magnesium alloy matrix. The degradation properties, the corrosion mechanical properties were studied. The modified magnesium alloys are characterized by scanning electron microscopy(SEM), atomic force microscopy(AFM), Fourier transform infrared(FTIR). The results show that surface modification on the magnesium alloys can be obtained by the layer by layer method. The degradation form and the trend of corrosion rate of magnesium alloys after modified are the same as before. But the corrosion rate is a little lower after modification, which can solve the problem of the fast degradation of the magnesium alloy. And the surface modification will not affect the strength of the magnesium alloys, which can still maintain their good mechanical performance.The magnesium alloy substrates were set as control group. And the modified magnesium alloys by mechano-growth factor were set as experimental group. The two groups were implanted into the female Wistar rats, respectively. In vivo degradation of two groups was compared. And we also compared the in vivo and in vitro degradation. The in vivo corrosion rate of the magnesium alloys after modification is lower, which demonstrate that surface modification can inhibit the rapid degradation of magnesium alloys. According to the contrast between in vivo and in vitro experiment, we find that under the same corrosion time, in vivo corrosion rate is far lower than in vitro corrosion rate. It is obvious that in vitro experiment is different from in vivo, and it can accelerate the corrosion of magnesium alloys.