Preparation Of Hydroxyapatite/Graphene/Graphene Oxide Modified Magnesium Alloy And Study On Its Drug Loading Properties

Magnesium and its alloys have attracted more and more attention as promising implant materials due to their excellent properties such as good biocompatibility and comparable mechanical properties with natural bone.They can be gradually degraded and absorbed so as to avoid the second surgery for implants removal after the tissues are healed completely.Unfortunately,the high corrosion rate which causes early mechanical failure of the implants in physiological environment limits the widespread use of magnesium alloys for clinical application in biology.Therefore,the corrosion resistance of magnesium alloys must be improved in order to expand their clinical application.In this study,ZK60 magnesium alloy with good biocompatibility was used to fabricate hydroxyapitite(HA)coating on the surface of magnesium alloy by hydrothermal method,and the preparation conditions were optimized.The results show that the p H of the coating solution is 9,the hydrothermal temperature is105 °C and the hydrothermal time is 18 h,which can greatly improve the corrosion resistance of magnesium alloy substrate(9.77 times).At the same time,the experiments also confirm that the microstructure of the coating is mainly affected by the p H value of the coating solution.The hydrothermal treatment temperature and time mainly affect the growth rate of HA crystals and do not change the morphology and growth direction of HA crystals.Based on the optimized HA coating,graphene/graphene oxide(G/GO)was used to further improve the corrosion resistance of magnesium alloy,and the composite coatings were characterized by SEM,XRD,FTIR and Raman spectrometer,etc.The results show that when G or GO is added to the hydrothermal coating solution,G changes the growth orientation of HA crystals,and GO refines the grain,both can improve the corrosion resistance of the composite coating modified magnesium alloy(HA/05G: 1.65 times,HA/05GO: 1.77 times).Then,both G and GO(G:GO=3:2,1:1)are added to the hydrothermal coating solution,the corrosion resistance of the composite coating is better than that of G or GO alone.The interface bonding strength of HA/05 G,HA/05 GO and HA/3G/2GO composite coatings is improved by 3,1 and 3 grades compared to HA coating,respectively.The drug loading properties of icariin on HA,HA/05 GO and HA/3G/2GO coating modified magnesium alloy samples were studied.The results show that these coatings can effectively load the drug of icariin,but the main role of drug loading in the composite coatings is HA.After adding GO,the drug loading of HA/05 GO composite coating has only increased by 8.98% compared with HA coating.But the loading of icariin on HA/3G/2GO composite coating has decreased by 24.22% compared with HA coating.