Construction Of Surface Functional Coatings For Medical Metal Materials And Study On Their Biological Properties

Medical titanium(Ti)has broad application prospects in the field of heart valves due to its low density and good biocompatibility.Medical magnesium alloy(Mg)has also been extensively studied in the field of cardiovascular stents due to its biodegradability.However,they do not have anti-thrombosis and anti-bacterial ability.They are prone to form thrombus when they are in contact with blood.At the same time,bacteria are easily adhered to the surface,which leads to infection.The application(such as cardiovascular stents,heart valves,biosensors,etc.)in some areas of blood-contacting is limited.In order to solve these problems,anti-coagulation and anti-bacterial functional coatings were prepared on Ti and Mg substrates by layer-by-layer self-assembly technology.The surface morphology and roughness of the sample surface were measured by field emission scanning electron microscopy(SEM)and atomic force microscopy(AFM);the valence of elements was measured by X-ray photoelectron spectroscopy(XPS);and the wettability of the sample surface was characterized by water contact angle(WCA).The biological properties and corrosion resistance of the coating were characterized by in vitro coagulation,platelet adhesion,antimicrobial test,cell static culture and electrochemical test.The main contents of this paper are as follows:(1)Heparin(Hep)/chitosan(Chi)coatings were prepared on Ti surface by covalent immobilization and electrostatic bonding.A large number of hydroxyl groups were formed on the surface of Ti after alkali treatment,which could covalently bind with Hep and fix Hep on the surface of Ti.Chi and Hep had opposite charges and could be fixed on the surface of heparinized Ti by electrostatic bonding to form anticoagulant and antimicrobial Hep/Chi coatings.The results of SEM,AFM,WAC and XPS showed that Hep and Chi were successfully fixed on the surface of Ti matrix.In vitro coagulation test,platelet adhesion test and protein adhesion test showed that Hep treatment increased blood loss and hemoglobin absorbance on the surface of the sample,inhibited the adhesion of platelets and proteins on its surface,reduced the activation degree and improved the blood compatibility on the surface of the sample.The results of antimicrobial experiments showed that the samples immobilized with Chi could effectively kill E.coli and Staphylococcus aureus,thus showing good antimicrobial properties.(2)Hep/Chi coatings were prepared on Mg surface by similar preparation methods.The results of coagulation test in vitro showed that the weight loss of blood and the absorbance of hemoglobin on the surface of Hep-treated samples increased significantly,showing good blood compatibility.The results of electrochemical experiments show that the corrosion resistance of the samples increases gradually with the progress of the process.The results of bacterial coating and SEM morphology showed that the number of Escherichia coli and Staphylococcus aureus on the surface of the samples decreased significantly after immobilization of Chi and Mg matrix,and the bacteria appeared deformation,rupture and dissolution to a certain extent,showing good antimicrobial properties.(3)Dopamine(PDA)/hyaluronic acid(HA)coatings were prepared on Mg surface by electrostatic bonding.PDA/HA coatings with anticoagulation and corrosion resistance were prepared by electrostatic bonding of PDA and HA with aggregated-OH on Mg surface after alkali treatment.The results of coagulation test in vitro showed that the weight loss of blood and the absorbance of hemoglobin increased significantly after fixing HA,and the high concentration of HA showed better blood compatibility.The results of electrochemical experiments and in vitro degradation experiments show that the corrosion resistance of the modified coating is significantly improved compared with that of Mg matrix.