Preparation And Optimization Of Coating On Magnesium Alloy Surface

Vascular stents are essential equipment for interventional treatment of patients with cardiovascular diseases.An ideal degradable stent can provide the necessary mechanical strength to maintain vascular patency and vascular tissue reconstruction at the early stage of implantation and in the absorption process,and can also promote the rehabilitation of the human body by local release of drugs through drug loading.Otherwise,the drug can reduce the possibility of thrombosis and inflammation in later stage.Magnesium alloy scaffolds have good biocompatibility and biodegradability,the mechanical properties and machinability of magnesium alloy are much better than polymer scaffolds.Magnesium is the basic nutrient element of human body.Magnesium ions generated by magnesium alloy degradation can be absorbed by human body and participate in human metabolic cycle.However,the rapid corrosion rate and uneven corrosion process of magnesium alloy in human physiological environment limit its clinical application as biological materials.Therefore,improving the corrosion resistance and functionality of magnesium alloys by surface modification has become an important means to optimize the current medical magnesium alloys.PHB(poly-β-hydroxybutyrate)has good biocompatibility and biodegradability,and PHB is often used in clinical wound sutures and dressings.In human body,the ester bond of PHB was broken passively after being infiltrated by body fluid.In addition,a small amount of esterase and macrophages also promoted the degradation of PHB.Therefore,the combination of PHB and magnesium alloy matrix can reduce the degradation rate of magnesium alloy scaffolds.LBL(Layer-by-layer self-assembly)method is a kind of nano-scale controllable intermolecular assembly method.LBL can attract heparin drug molecules with negative charges and VEGF(vascular endothelial growth factor)with positive charges to the surface of PHB substrate with positive charges after amination by positive and negative charges,forming a drug-active coating to improve the biocompatibility of the material.The follows are main research contents and results of this paper:1.Preparation,characterization and corrosion resistance test of coating magnesium alloy.By observing the surface morphology,corrosion potential and solution changes in the degradation process,it can be found that the drug loading process does not destroy the integrity and corrosion resistance of the PHB substrate structure on the surface of magnesium alloy.In the static degradation cycle,the degradation behavior of the PHB substrate does not change significantly due to the drug loading.2.Biocompatibility of drug-loaded coating magnesium alloy.The hemolysis rate and platelet adhesion number of magnesium alloy coated with blood compatibility drug loading coating were much lower than those of other coatings,and the dynamic coagulation time,PT(prothrombin time)and APTT(activated partial thromboplastin time)of the material surface were significantly longer.In cell compatibility test,the extract of drug-coated magnesium alloy can promote cell growth,improve cell migration rate,reduce cell damage,inhibit cell apoptosis and improve cell adhesion ability.3.Structure optimization between magnesium alloy and PHB by anodic oxidation and copper plating,as well as electrochemical properties and biocompatibility of the material.The AO-Cu/Cu O structure between magnesium alloy and PHB substrate significantly improves the binding force between magnesium alloy and PHB.The electrochemical impedance and corrosion potential results show that the structure has higher impedance and lower current density.In the antibacterial experiment,the extract of MACP inhibited the growth and reproduction of E.coli.In terms of biocompatibility,MACP extract had no significant effect on hemolysis rate,coagulation function,LDH release | cell activity and cell growth morphology,while the number of blood cell adhesion on the surface of MACP material did not increase.