Characterization And In Vitro Antibacterial Ability Of TC4/Ag Composite Modified Via FSP

Purpose: A variety of antimicrobial implant materials have been developed at this stage,but most of them have poor biocompatibility and coating stripping problem.In order to make the antibacterial implant materials exhibt good biocompatibility and to ensure that the antibacterial components do not peel off during the implantation process,friction stir processing(FSP)technology is utilized to integrate the nano silver particles(Ag NPs)into Ti-6Al-4V(TC4)substrate to attempt to modify the surface of the implant materials.The intrinsic relationship between surface topography and material composition and antimicrobial properties is highlighted.Methods: 1.The fabrication and characterization of TC4/Ag MMNC.The control group was a TC4 without FSP.The experimental groups were grouped by different groove depths.The samples were characterized: the surface microstructure of the samples was observed by scanning electron microscopy(SEM);the elemental analysis was performed by X-ray diffraction(XRD);the ultrastructure of the materials was observed by transmission electron microscopy(TEM);through atomic force microscope(AFM)and following calculation,threedimensional topographic images and roughness of the surfaces were obtained;3D atomic probe tomography(3DAPT)was carried out to gain three-dimensional maps of different atoms at the nanoscale.2.Corrosion resistance test of TC4/Ag MMNC.In the ion precipitation experiment,each group of specimens was immersed in artificial simulated body fluid(SBF)for 14 days,and inductively coupled plasma mass spectrometry(ICP-MS)was used to measure the concentration of titanium and silver ions in solution.For electrochemical test,all samples’ corrosion resistance was measured by electrochemical impedance spectroscopy(EIS).3.Biological performance detection of TC4/Ag MMNC.Antibacterial experiment: Each group of specimens was co-cultured with bacterial and plate counting method,fluorescence microscope and SEM was used to test the antibacterial ability of the test piece;Cytotoxicity assay: The effects of specimens’ leaching solution on the metabolism and proliferation of rat bone marrow mesenchymal stem cells(BMSCs)were investigated by CCK-8 method.Results: It was found that the silver-rich nanoparticles were more homogeneously distributed on the surface of TC4 and their content increased as the groove depth growed.TEM detection showed that the diameter of the silverrich nanoparticles was about 10-20 nm,and the interface between silver-rich nanoparticles and TC4 matrix was indistinct,indicating the diffusion transition of the elements between these two phases.It was found that silver also existed in the TC4 matrix where silver content is 4.3-5.6%,indicating the construction of an integrated functional surface.The surface stirred with Ag was nanometer-scale.As the addition of silver increased,the surface grain size and surface roughness decreased.EIS showed that the corrosion resistance was the strongest in the deepest-groove group and TC4 had the weakest corrosion resistance.The results of antibacterial experiments indicated that fewer strains adhered on the surface processed by FSP than that of TC4.Only several bacteria were found on the surface in the deepest-groove group suggesting that the TC4/Ag composite nano surface can effectively inhibit bacteria;the in vitro cytotoxicity test results showed that the leaching solution of each group exhibted no obvious cytotoxicity to rat’s BMSCs.Conclusion: Ag NPs can be uniformly integrated onto the surface of TC4 by FSP to achieve an integrated TC4 / Ag metal matrix composite(TC4/Ag MMC)with nano-scale surface.TC4/Ag MMC can effectively exert antibacterial effect,and the antibacterial effect is not related to the released Ag ions,but may be more related to the amount of Ag NPs embedded on the surface,which directly contacts the bacterial cell wall and destroys the cell membrane to exhibit antibacterial property.In addition,TC4/Ag MMC shows better biocompatibility and potentially is a valuable antimicrobial implant material,yet further experiments need to be performed to explore the application prospects of this material.