Antibacterial Properties Of TaN-Ag Composite Coatings On Medical Titanium Alloy Surface

BackgroundArtificial joint replacements have achieved great success in the treatment of end-stage joint diseases and greatly improved the quality of life of patients.With the growing number of patients undergoing joint replacement,the demand for artificial joint prosthesis is increasing.Medical titanium alloy?Ti6Al4V?is the most widely used artificial joint prosthesis material at present.Although titanium alloy has good biocompatibility,strong corrosion resistance and mechanical properties.However,titanium alloy has no antibacterial property,which is easy to cause prosthetic joint infection?PJI?.As one of the major complications of joint replacement,PJI can lead to delay the treatment cycle and increase the cost of treatment in patients,or even lead to amputation or death due to infections.Ideal artificial joint prosthesis should not only meet certain mechanical support,wear resistance and body fluid corrosion resistance,but also have antibacterial properties.Therefore,how to modify the surface of the prosthesis to enhance the antibacterial property is a hot topic.Currently,the transition metal nitride coatings have attracted much attention in the medical field due to their good wear resistance and biocompatibility.Among these materials,tantalum nitride?TaN?not only has good corrosion resistance and biocompatibility,but also can enhance cell adhesion and differentiation,makes it has a good application prospect in surface modified of orthopedic implants.However,TaN coatings still does not have antibacterial properties,so endow TaN coating with antibacterial properties through surface modification is necessary.Silver?Ag?has a broad spectrum of strong antimicrobial,no drug resistance characteristics,was widely used in the medical field.Meanwhile,a large number of studies have shown that the introduction of silver on the surface of materials can effectively improve the antimicrobial properties of materials.However,it is still necessary to study different existing form and content of Ag are required to exert the maximum antibacterial effect on the surface of the material.ObjectivesExploring the effects of different existing form and content of Ag on the antibacterial properties of TaN-Ag composite coatings,and the biocompatibility of the modified coatings were evaluated at the same time.MethodsFirstly,three different Ag content TaN-Ag composite coatings were deposited on the surface of medical titanium alloy by magnetron sputtering technology.Their structures,composition and surface topography were characterized by X-ray diffraction?XPS?,transmission electron microscopy?TEM?and atomic mechanics microscopy?AFM?.Then,two kinds of bacteria that often cause implant-related infections,Gram-positive S.aureus and Gram-negative E.coli,were selected to verify the antibacterial properties of the composite coatings by in vitro experiments.Finally,rabbit bone marrow mesenchymal stem cells?BMSCs?were isolated and used to evaluate the biocompatibility of the materials.BMSCs were co-cultured with the modified titanium substrate,and the effects of three TaN-Ag composite coatings on the bio-activity and proliferation of BMSCs were evaluated by in vitro tests.ResultsThrough the characterization of XPS,TEM and EDS,we successfully deposited TaN-Ag composite coatings with 0%,1.7%and 8.4%Ag content on the surface of titanium alloys,named as TaN,TaN-1.7%Ag and TaN-8.4.%Ag.TaN-1.7%Ag coating surface mainly exists in the form of Ag₂O,while TaN-8.4%Ag coating surface mainly exists in the form of Ag and Ag₂O mixture.The inhibition rates of TaN-1.7%Ag against S.aureus and E.coli were 52.4%and 38.6%,respectively.The inhibition rates of TaN-8.4%Ag coating on S.aureus and E.coli were 93.1%and 95.2%,respectively,and TaN-8.4%Ag coating could greatly induce the production of reactive oxygen species?ROS?,which was also the mechanism of its killing effect on bacteria.Cytotoxicity and cell proliferation results showed that,compared with the TaN coating,the silver coating group had a low toxicity,but there was no statistically significant difference,indicating that TaN-1.7%Ag and TaN-8.4%Ag coating did not significantly reduce the biocompatibility of the material.ConclusionsIn this study,it was proved that the TaN-Ag composite coatings completely covering the substrate could be successfully prepared on the surface of titanium alloy by magnetron sputtering technology.The coating was less cytotoxic and could effectively inhibit the growth of bacteria on the surface of the material.In conclusion,TaN-8.4%Ag coating is expected to be a new method for surface modification of orthopedic implants.