Preparation Of Hybrid Coating And Corrosion Properties Of Biomedical Magnesium Implants

Titanium,stainless steel and chromium-based alloy,as a biological hard tissue implant materials have been used clinically.When these metal biomaterials implanted in the human body,the corrosion maybe due to the release of the toxic ions,which can cause inflammation and reduce the biocompatibility,resulting in tissue damage.In addition,the elastic modulus of the metal-based biomaterials are very different from those of human bone,which will produce stress shielding effect.It is not conducive to new bone growth and remodeling,and easily lead to secondary fractures.With the deepening research of biomedical implant materials,the development of good mechanical properties and biocompatibility,but also the in vivo secure degradation of new implant material is of great significance.In comparison of the above metal-based implants,magnesium and magnesium alloy have been widely used in biomedical implant materials because of its good mechanical properties such as high strength,light weight,excellent biocompatibility and good biodegradability.However,the uncontrollably rapid corrosion rate of magnesium alloy may cause high local alkalinity,a large amount of hydrogen evolution,and collapse of tissue scaffold,which can greatly affect its application in clinical.So in recent years,scientists have been working to control the corrosion rate of magnesium and its alloys.In this paper,AZ31 and Mg-Sr alloys are choosed to be as the based material.And various functionally hybrid coatings were prepared on the surface of the samples to control the degradation rate.A functional hybrid coating composed of DCPD/PLGA is prepared on the AZ31 magnesium alloy through electrochemical deposition and spin coating.The corrosion behaviours of untreated,DCPD-coated and DCPD/PLGA coated magnesium alloy in SBF and 0.9%NaCl are studied.The thickness and size of DCPD coating became larger with the increase of deposition time.120 min deposition obtained a coating with best compaction.When the deposition time reached 240 min,cracks became more.The electrochemical tests showed that the corrosion resistance of magnesium alloy became better with the increase of the deposition time.PLGA coverage can further enhance the corrosion resistance of DCPD by tilling the cracks and pores.The hybrid coating not only regulates the degradation rate.For corrosion resistance of magnesium alloy,a hybrid coating of ZrO2/PLGA were prepared on AZ31 magnesium alloy.After atomic layer deposition,a thin film of ZrO2 was obtained on the substrate,and the ZrO2 coating with different cycle both can develop the corrosion resistance.A hybrid coating,which is uniform and compact,was prepared after spin coating,but also had some cracks.Electrochemical tests revealed that Zr02/PLGA coated magnesium alloy can better control the corrosion rate compared to the untreated and ZrO2 substrate.In addition,the paper also studied the corrosion behaviour and antibacterial properties of Mg-Sr alloy with good biocompatibility and degradability.ZrO2 film was first compared on the substrate through atomic layer deposition,and then PLGA and PLGA/Ag coatings are respectively prepared by spin coating.The results showed that Zr02,Zr02/PLGA,ZrO2/PLGA/Ag coating could improve the corrosion resistance.Meanwhile,the ZrO2/PLGA/Ag coating can enhance the antibacterial properties of substrate.