Study On The Synthesis Of Silver Loaded TiO₂ Nanotubes Film On Medical Titanium And Its Antibacterial Property

The medical devices using the medical titanium as the substrate are widely used in clinic.However,bacteria adhered to the surface of such medical devices seriously affect the success rate of implanting operation and even result in patient death.Enhancing the antibacterial property of the medical titanium through surface modification is a focus of the current research field.There are a great variety of traditional antibiotics.Different bacteria should be treated by different antibiotics.Moreover,the bacteria are easily resistant to a certain antibiotic after long-term use.Therefore,antibiotics are not suitable for the antibacterial coating of the medical titanium.As a broad-spectrum,inorganic,antibacterial agent,the Ag nanoparticles have been widely used in daily necessities and some drugs for external use since the bacteria will not develop any resistance to it.It is important to deeply investigate the mechanism of action of Ag/titanium dioxide nanotubes(TiO2 NTs)nano-composite film,develop efficient and safe surface modification techniques,and realize good antibacterial property and biocompatibility of the medical titanium surface.In thiswork,the coating of TiO2 NTs was formed on the surface of medical titanium substrate through physical and chemical methods.Different methods were adopted to load nano-Ag particles to the TiO2 NTs surface,so as to enhance its antibacterial property.Firstly,the supercritical carbon dioxide(SCCO2)and the pulse electrodeposition were utilized to load different sized nano-Ag particles to the TiO2 NTs surface,so as to systematically investigate the influence of different experiment parameters and the antibacterial property of Ag-loaded TiO2 NTs.Secondly,the polydopamine(PDA)coating was prepared on the TiO2 NTs surface with the solution method under room temperature.Different specifications of PDA-Ag-TiO2 NTs were obtained through the green reduction reaction of the silver nitrate solution.PDA-Ag-TiO2 NTs were combined with chitosan-zinc and chitosan-gentamicin,respectively to form different composite coatings.Meanwhile,the biological properties of various composite coatings were investigated.Then,the traditional solution method under room temperature was optimized to significantly reduce the time of PDA formation.Different metal ions were chelated to the PDA coating,to investigate the TiO2 NTs Ag-loading effect of different PDA coatings.The biological properties of different PDA-Ag composite coatings were compared through the inhibition zone test,the cell adhesion and spreading test and the WST-1 cytotoxicity test.Finally,the pulse and constant current electrodeposition methods were used to prepare different morphologies of calcium phosphate coatings on the TiO2 NTs surface.The PDA-Zn composite coating was applied to the calcium phosphate coating.The rapid preparation of antibacterial calcium phosphate coating was realized.The main research contents are as follows:(1).Electrochemically anodic oxidation method was used to fabricate TiO2 NTs film on the surface of Ti foil.The silver nanoparticles were loaded on the surface of TiO2 NTs by pulse electrodeposition technology,and the influence of experimental parameters on the size and the distribution of it was investigated.After that,the ScCO2 fluid system was combined with pulse electrodepositon to investigate the influence on the silver nanoparticle products.It is confirmed by inhibition method that the product from ScCO2 and pulse electrodeposition had better antibacterial activity than the product from pulse electrodepositon.(2).After formation of PDA coating on the surface of TiO2 NTs,a green reduction reaction was used to load silver nanoparticles on the TiO2 NTs.The influence of experimental parameters on this PDA-Ag-TiO2 NTs was studied systematically.After that,chitosan-zinc mix solution was used to react with PDA-Ag-TiO2 NTs to form CS-Zn-PDA-Ag-TiO2 NTs.The antibacterial ability and biocompatibility of this composite coating was investigated.At last,the chitosan-gentamicin mix solution was also used for synthesis ofCS-Gen-PDA-Ag-TiO2 NTs.This composite coating had a good sustained-release and antibacterial performances.(3).Rapid polymerization of DAto form PDA film on the surface of TiO2 NTs was achieved by performing the reaction in a water bath at 90?(PDA-H).Furthermore,the reduction of Ag+ ions was markedly accelerated by the PDA-Zn film that was formed on the surface of TiO2 NTs from a solution of dopamine and zinc nitrate under the same heating conditions.The reaction between the PDA-Zn film and silver nitrate was dramatically reduced to 10 min,and the silver nanoparticles deposited on the PDA-Zn film were more uniform than those by PDA-H film.This PDA-Zn-Ag/TiO2 NTs material exhibited good antibacterial activity,as evidenced by the inhibition zone observed in a culture of E.coli and S.aurues.The WST-1 assay also indicated that the PDA-Zn-Ag film possessed a lower cell cytotoxicity and better biocompatibility than other films.In addition,the structure of the PDA-Zn film was stable;after leaving the film in the air for a week,it was still reactive with silver nitrate.Cu ions were also chelated to DA to form PDA-Cu film on the surface of TiO2 NTs.The difference of PDA-Cu with PDA-Zn was systematically investigated,and it is found tha such film did not have better biological performance.(4).CaP coating was fabricated on the surface of TiO2 NTs by combining pulse electrodeposition with a constant current electrodeposition.The different morphologies of CaP coating were obtained by adjusting the experimental parameter of constant current electrodeposition.The morphology of CaP without cracks was chose to test under ASTM-D3359 standard.The result indicated that it had good mechanical bonding performance.The traditional method of doping zinc ions into the structure of CaP was too complicated,and the doping amount was limited.PDA-Zn film was used on the surface of CaP,and then reacted with silver nitrate to fabricate PDA-Zn-Ag composite film.It was a facile method to exceed the limit amount of zinc,and has antibacterial effect to E.coli.