Preparation And Properties Of Ion-Doped HA/Chitosan Composite Coating On Magnesium Alloys

Magnesium and magnesium alloys,as a representative of degradable medical metals,have good biocompatibility and mechanical compatibility.They have broad application prospects as bone repair materials,but also face the challenges of corrosion resistance,osteogenic and antibacterial properties,which limit clinical application.In view of this,this thesis adopted biomimicry concept,with the unique micro/nano topography in bone reconstruction process,and the composition of bone tissue as imitation objects,prepared a series of chitosan（CS）coatings and ion doped hydroxyapatite（HA）/CS composite coatings on magnesium alloy with a combination of sol gel-dip-coating method and microwave liquid phase method.Moreover,structural characterization and corrosion resistance,osteogenic and antibacterial property tests were conducted.The regulatory mechanism of CS coating structure and antibacterial mechanism of ion-doped HA/CS composite coating were basically clarified.The main research contents are described as follows:（1）CS coatings and fluorine-doped HA（FHA）/CS composite coatings were prepared on the surface of magnesium alloy by adjusting CS molecular weight and solution mass concentration.CS coatings act as the middle layer of FHA coating and magnesium alloy;CS molecular weight and solution concentration improved the surface density of CS coating;FHA nanoneedle coating has biomimetic micro/nano topography to some extent.Cell experiment results showed that FHA/CS composite coating could inhibit the rapid degradation of magnesium alloy,maintain normal cell viability,and improve the m RNA level of osteogenic markers,indicating that FHA/CS composite coating improved the osteogenic property of magnesium alloy compared with CS coating.（2）Further,the doping amounts of Cu²⁺,Ag⁺and Si O₄^4-in FHA coating were optimized;it is found that the surface morphology of ion-doped HA/CS composite coatings was affected by the type and content of doped ions.Ag⁺doping promoted HA growth along the c axis,forming Ag Cu HA nanocone polycrystalline clusters.The biological test results showed that Ag Cu HA/CS composite coating has the strongest antibacterial property in all samples.In addition,the antibacterial properties of the samples not only depend on the content of antibacterial active ions,but also was affected by the dissolution capacity of ions and CS molecules in the coating.Ag Cu HA/CS composite coating has the highest cell viability,indicating that the coating not only inhibited the rapid degradation of magnesium alloy,but also promoted BMSC proliferation.In conclusion,Ag Cu HA/CS composite coating has unique micro/nano topography and excellent corrosion resistance,simultaneously realized the topographical biomimicry of bone resorption surface and compositional biomimicry of bone tissue.The corrosion resistance,antibacterial properties and BMSC viability of magnesium alloy bone repair material were enhanced simultaneously.This study provides some new ideas for the biomimicry design for ion-doped HA/natural bioactive polysaccharide composite coatings of medical magnesium and magnesium alloys.