The Optimization Of Sliver Antibacterial Coatings On Titanium-base Biomaterials And Their Biological Properties

Objective A biofilm is a key factor in the pathogenesis of periprosthetic joint infection(PJI).It exists not only on the surface of the implant,but also in the articular cavity and the tissues around the implant.Polysaccharide intercellular adhesion(PIA)-dependent and PIA-independent biofilm mechanisms both play an important role in staphylococcal biofilm development.It has been demonstrated that silver(Ag)element has good antibacterial properties,and silver ion(Ag~+)can be released or not be released from the Ag modified implant surface.Herein,the aim of our study was to optimize the surface of pure titanium by virtue of different surface modification techniques to maximize its antimicrobial property and overcome some adverse effects,and then we carried out a series of material characterization and biological evaluation.Materials and methods 1.For the Ag~+releasable coating,we first fabricated titanium dioxide coating on the titanium foil by the micro-arc oxidation method,and then different contents of Ag nanoparticles were incorporated on such a surface through the hydrothermal chemical method.For the Ag~+non-releasable coating,we first prepared the titanium dioxide nanotubes(NTs)arrays in situ through anodic oxidation on the titanium surface,and then embedded Ag nanoparticles on the surface by plasma immersion silver ion implantation technique.Lastly,the vancomycin was loaded into nanotubes by lyophilization and vacuum drying.2.We characterized theses samples by means of field emission scanning electron microscopy,X-ray diffractometer,X-ray photoelectron spectroscopy,field emission transmission electron microscopy and other instruments.The cytotoxicity of the specimens was analyzed using the Cell Counting Kit-8(CCK-8)assay.The in vitro antibacterial effects were evaluated through the spread plate method,scanning electron microscopy and confocal laser scanning microscope.In order to better simulate the clinical practice,we established a in vitro biomaterials-bacteria-cells co-culture system to observe the growth of cells on the bacteria-contaminated surface.In addition,we also analyzed the effect of the silver releasable coating on the expressions of related genes for two types of biofilms.Furthermore,we established a new rabbit PJI model and evaluated the in vivo antibacterial effect of the silver non-releasable coating using X-ray,scanning electron microscopy,bacterial count and tissue sections.Results 1.The release of silver ions in the Ag~+releasable surfaces exhibited a sustained release in the medium,and the release amount was proportional to the doped amount.However,Ag nanoparticles were immobilized in the Ag~+non-releasable coatings and Ag~+release was rarely detected in the solution,but the release of vancomycin in the nanotubes exhibited initial explosive release and subsequent slow release.2.The in vitro results suggested that the coatings Ag-0.01(Ag~+releasable surface)and NT-Ag-V(Ag~+non-releasable coating)without cytotoxicity were both resistant to planktonic and sessile bacteria,thereby inhibiting the formation of biofilms.In the co-culture study,the cell coverage of the aforementioned two coatings was the highest.However,with respect to the cytocompatibility,Ag-0.1 coating could produce cytotoxicity unless the release of Ag~+was properly controlled.In addition,the Ag-0.01 coating could affect the expression of PIA-dependent and PIA-independent biofilm-forming genes.The in vivo results of NT-Ag-V coating demonstrated that it possessed good antibacterial effect and early tissue integration property.Conclusion With the aid of different surface modification techniques,we build the silver-containing coatings that have good biocompatibility and excellent antibacterial effects on the titanium surface,and find that they can both kill the planktonic and adherent bacteria and promote cell adhesion and growth,which will better prevent PJI.