Preparation Of Antibacterial Coatings And Antibacterial Properties Of Biomedical Titanium Implants

With the acceleration of global population aging,the number of patients who suffer from osteoporosis and fractures increased significantly.In addition,bone tissue damage caused by various accidents such as industrial injury,traffic accidents etc.making the growing demand for medical implant materials.For instance,about 69.4 million people over the age of 50 suffer from osteoporosis in China and there are more than 687 000 hip fracture and 1.8 million vertebral fracture incidents per year.Since the use of pure titanium in bone implants in vivo in the 1930s,different Ti-based alloys including first-generation pure titanium products and newgeneration Al-and V-free titanium alloys have been developed to repair or substitute for damaged hard tissues.Ti-based materials offer advantages such as good biocompatibility,corrosion resistance,and wear resistance,suitable Young's modulus,as well as high strength compared to other metals.Therefore,the biomedical titanium implant materials are widely used as hard tissue replacement materials,such as artificial joints,dental implants etc.Unfortunately,bacterial infection is a serious complication during and after surgery jeopardizing long-term fixation of the metallic implants and causing premature failure.To prevent infection,it is essential to endow metallic implants with the self-antibacterial ability.In addition,if this material can not form a close bone combination with hard tissue in organism after the implanting of the biologically inert titanium implant,the thrombosis will form,then the failure of implant arise.Therefore,the preparation of implants with both biological activity and anti-bacterial properties is an important issue need to be solved urgently.Based on the above problems,the present paper intends to prepare a layer of ZnO nanorods on titanium surface,and explores the best experimental parameters.Although the ZnO nanorods have good antibacterial activity,it also possess a greater cytotoxicity,which can be solved through the addition of PLGA/Ag coatings.To obtain functionalized surfaces,the surface of ZnO nanorods was treated with a silane coupling agent or dopamine which can be good for the following grafting of functional biological macromolecular.The basic contents of the thesis are as follows:1.The hydrothermal growth of ZnO nanorods on titanium surfaceIn this study,the ZnO nanorods on titanium surface were prepared using hydrothermal growth method.The composition,structure and morphology of ZnO nanorods were analyzed.The effect of various parameters,such as the seed concentration,reaction temperature,reaction time et al.,on the morphology of ZnO nanorods was also studied.In addition,the possible reaction mechanisms of hydrothermal growth of ZnO nanorods were put forward in this article,which played an important role in the future related research.2.Synthesis of antibacterial PLGA/Ag/ZnO composite coatings on titanium surfaceTo prevent the attachment of bacteria to implant surfaces,PLGA/Ag/ZnO composite coatings were fabricated on titanium substrates through two procedure,namely the hydrothermal growth of ZnO nanorods and the spin-coating of PLGA/Ag layer.The incorporation of silver nanoparticles(AgNPs)in PLGA was carried out in different concentrations(0,1,3,6 wt/v%).The results showed that ZnO nanorods were grown on substrates and PLGA/Ag was coated uniform on the surface of ZnO nanorods.The release of Zn2+ and Ag+ can be controlled by the degradation of PLGA,evidencing a prolonged integrated antibacterial effect.The antimicrobial activity was evaluated using two different strains of S.aureus and S.epidermidis.Proliferation of mouse calvarial cells(MC3T3-E1)exhibited minimal cytotoxicity on implants containing 1 wt%and 3 wt%of AgNPs,while 6 wt%of AgNPs inhibited cell proliferation.Results of the antimicrobial evaluation and MC3T3-E1 proliferation revealed that the composite coating consist of PLGA,doping with 3 wt%AgNPs,and ZnO nanorods can function as a good implant materials for orthopedic application.3.Synthesis of antibacterial PDA/ZnO composite coatings on titanium surfaceTo obtain functionalized surfaces,the surface of ZnO nanorods was treated with dopamine and then a thin film of polydopamine(PDA)was formed through the self-assembly,which can be good for the following grafting of functional biological macromolecular.In addition,the introduction of the PDA coating can improve the wettability and the possible cytotoxicity while the dopamine-treated samples have worthy antibacterial properties,so it is a promising orthopedic implant material.