Construction Of Biodegradable Antibacterial Coating On ZA6-1 Zinc Alloy Surface And Study Of Its Biomedical Propertie

Due to the excellent mechanical properties and good biodegradability,zinc and its alloy have been a research hotspot in the field of bone replacement and repair materials.According to literature,ZA6-1 zinc alloy has shown suitable degradation rate and good biocompatibility for the requirement of orthopaedic implants,indicating it is a potential metallic implant material.Orthopaedic surgery is often accompanied with infection caused by bacteria,which can lead to serious consequences such as infectious bone nonunion.pathological fracture and so on.The conventional clinical treatment for such problem is to use antibiotics or surgical debridement.However,antibiotics can enhance bacterial resistance and damage liver and kidney function,while debridement is expensive and causes additional pain to patients.Zinc alloys can kill bacteria by releasing Zn²⁺,but the rapid degradation will lead to the early corruption of the implant and then shorten its service time,leading to a mismatch of recovery and reconstruction of human bones.Therefore,it is of great scientific significance and research value to deposit antibacterial coatings on the surface of ZA6-1 zinc alloy to gain good antibacterial property,appropriate degradation rate and good biocompatibility.The main research contents of this dissertation are as follows:1.Fabrication of retarded-releasing type antibacterial PTH/LYS-PDA coating:as inspired by the adhesive activity of marine mussel adhesion protein,PTH/LYS-PDA coating was obtained by depositing lysozyme（LYS）and parathyroid hormone（PTH）at different concentrations on the surface of zinc alloy through the self-polymerization and adhesion of polydopamine under weakly alkaline（p H=8.5）.The microstructure,chemical composition and chemical state were characterized by scanning electron microscope（SEM）and X-ray photoelectron spectrometer（XPS）.The antibacterial property of the coating was evaluated by antibacterial circle test and bacterial surface adhesion test.The corrosion behavior and Zn²⁺release ability of zinc alloy after coating deposition were investigated by electrochemical experiment and inductively coupled plasma mass spectrometry.The influences of coating deposition on the hydrophilicity,the cell viability,morphology and differentiation of MC3T3-E1 mouse osteoblasts were studied by contact angle tester,MTT method,fluorescence staining and alkaline phosphatase test.The results showed that PTH/LYS-PDA coating exhibited good antibacterial performance against staphylococcus aureus,slightly reduced the degradation rate of zinc alloy substrate,controlled the excessive release of Zn²⁺,and promoted the proliferation,growth and differentiation of osteoblasts.2.Fabrication of retarded-releasing type antibacterial SDS/LA-PLGA-APTES coating:the surface of zinc alloy was functionalized by 3-aminopropyltriethoxysilane（APTES）through dry/wet chemical reaction,and the polylactic acid glycolic acid copolymer（PLGA）containing sodium dodecyl sulfate（SDS）and levulinic acid（LA）was immobilized on as functionlized surface by electrostastic interaction between protonated amino group and carboxyl group to construct SDS/LA-PLGA-APTES coating.The microstructure,chemical composition and chemical state were characterized by SEM,AFM,Raman,FTIR and XPS.The corrosion behavior and Zn²⁺release ability of zinc alloy after coating deposition were investigated by electrochemical experiment and inductively coupled plasma mass spectrometry.The antibacterial property of the coating was evaluated by antibacterial circle test and bacterial surface adhesion test.The influences of coating deposition on the hydrophilicity,the toxicity,morphology and differentiation of MC3T3-E1 mouse osteoblasts were studied by contact angle tester,MTT method,fluorescence staining and alkaline phosphatase test.The results showed that SDS/LA-PLGA-APTES coating exhibited excellent antibacterial performance against Gram-negative and Gram-positive bacteria,greatly reduced the degradation rate of zinc alloy substrate,controlled the excessive release of Zn²⁺,and promoted the proliferation,growth and differentiation of osteoblasts.With the increase of SDS/LA deposited on the surface of zinc alloy substrate,its antibacterial property gradually increased and other properties gradually weakened and showed certain cytotoxicity.3.Fabrication of Au NPs@Zn O micro/nano array coating on the surface of zinc alloy substrate:as inspired by the semiconductor photocatalysis which could produce active oxygen groups to disinfect,Zn O micro nano arrays with different structures were in situ grown on the surface of zinc alloy in an autoclave using ammonia lye.And then gold nanoparticles（Au NPs）were loaded on the surface of Zn O micro/nano arrays by UV reduction method to construct Au NPs@Zn O coating.The microstructure,crystal structure,chemical composition and chemical state were characterized by SEM,XRD and XPS.The antibacterial property of the coating was evaluated by antibacterial circle test and spread plate method.The corrosion behavior and Zn²⁺release ability of zinc alloy after coating deposition were investigated by electrochemical experiment and inductively coupled plasma mass spectrometry.The light absorption capacity of the coating were analyzed by UV-Vis.The influences of coating deposition on the hydrophilicity,the toxicity,morphology and differentiation of MC3T3-E1 mouse osteoblasts were studied by contact angle tester,MTT method,fluorescence staining and alkaline phosphatase test.The results showed that Zn O micro/nano array exhibited good antibacterial performance in the darkness and good biocompatibility.Otherwise,it could effectively reduce the degradation rate of zinc alloy substrate and regulate the above properties by adjusting the coating structure.Heterojunction was formed by loading Au NPs on the Zn O micro/nano array,leading to an optimization of the energy band structure of Zn O and the absorption and utilization of visible light.Au NPs@Zn O coating exhibited good antibacterial performance in the darkness and lightness,and its antibacterial properties were significantly enhanced in the lightness.With the increase of Au content in the coating,the Au NPs@Zn O coating showed certain cytotoxicity.