Preparation Of Tantalum/Magnesium Functional Coating On The Surface Of Titanium Implant And Investigation On Its Biological Properties

Objective:Titanium alloy is widely used in clinical bone repair due to its good biocompatibility and mechanical properties.However,titanium alloy is a biologically inert material and lacks osteoinductivity.When implanted in vivo,it cannot form an effective bone bond with surrounding tissues,which may cause implant loosening and shifting.Moreover,titanium alloys have poor corrosion resistance in the body,which easily leads to the release of toxic metal ions.Therefore,it is of great significance to modify the surface of titanium implants to enhance their osteogenic performance and corrosion resistance.Methods:(1)Tantalum/magnesium functional coating(Ti-Ta-Mg)was prepared on the surface of titanium sheets using sol-gel method(Sol-Gel).Meanwhile,tantalum coating(Ti-Ta),titanium sheet(Ti),tantalum sheet(Ta)were used as controls.Then,the coating morphology,composition were characterized using atomic force microscope(AFM),scanning electron microscope(SEM),energy spectrum analyzer(EDS)and X-ray photoelectron spectroscopy(XPS).Moreover,the hydrophilicity of the coating was measured using contact angle test system.The corrosion resistance of the coating was evaluated using electrochemical method.(2)The rabbit bone marrow mesenchymal stem cells(rBMSCs)were co-cultured with the samples,and the cell adhesion morphology,proliferation,osteogenic differentiation,matrix mineralization,and the expression of osteogenic genes were detected.(3)Porous titanium scaffold(PTi)with pore size of 600 ?m and porosity of 70%,was prepared using 3D printing.Then,tantalum/magnesium coating(PTi-Ta-Mg)was prepared using the same method.The surface morphology and composition of the porous scaffold were characterized using SEM and EDS.rBMSCs were co-culture with the porous scaffold.Cell morphology,proliferation,osteogenic differentiation,matrix mineralization and the expression of osteogenic genes were detected.(4)The femoral condyle defect model was constructed using New Zealand white rabbits,and the porous scaffold was implanted into the bone defect.The bone tissue repair was evaluated using radiography and histological examination.Results:(1)The results of AFM showed that the surface roughness of the titanium sheet had no significant change after the coating process(P>0.05).SEM indicated that a large number of nanoparticles were uniformly distributed on Ti-Ta-Mg and Ti-Ta surface and no crack formed.The contact angle test results suggested that the contact angle values of Ti-Ta-Mg and Ti-Ta coatings were similar(P>0.05),but significantly smaller than those on Ti and Ta surfaces(P<0.05).The results of electrochemical indicated that the Ti-Ta-Mg and Ti-Ta coatings enhanced the corrosion resistance of the titanium surface.(2)Compared with Ti-Ta,Ti and Ta surfaces,the early adhesion and spreading morphology of rBMSCs on Ti-Ta-Mg surfaces was much better,and the proliferation of rBMSCs was also faster(P<0.05);ALP staining and alizarin Red S staining showed that Ti-Ta-Mg could promote the differentiation of rBMSCs towards osteogenesis and matrix mineralization formation(P<0.05);The results of Fluorescence quantitative PCR(q-PCR)suggested that Runx2,ALP,OCN,OPN had the highest expression on Ti-Ta-Mg surface(P<0.05),followed by Ti-Ta surface(P<0.05).(3)SEM results indicated that the surface morphologies of the three porous scaffolds of PTi-Ta-Mg,PTi-Ta and PTi were similar;EDS detected the existence of Ta and Mg on the surface of the PTi-Ta-Mg scaffold,and Ta on the surface of the PTi-Ta scaffold.The results of Phalloidin staining suggested that the adhesion and spreading morphology of rBMSCs on the surface of PTi-Ta-Mg scaffolds were better than those on the surfaces of PTi-Ta and PTi scaffolds.Live/dead cell staining indicated that the three porous scaffolds had good biological properties compatibility.Compared with PTi-Ta and PTi scaffolds,PTi-Ta-Mg scaffolds enhanced rBMSCs proliferation,osteogenic differentiation and the gene expressions related with osteogenesis(P<0.05).(4)The animals recovered well after the operation,and no animals died within 3 months.The implanted scaffold was fixed in place and no shedding was found.Also,no inflammatory reaction was observed in the tissues surrounding the scaffold.X-ray examination showed that there was no fracture and bone resorption occurence.With the increase of implantation time,the internal light transmittance of the scaffold gradually decreased,especially for PTi-Ta-Mg scaffold.The micro-CT scan showed that the new bone tissue extended from the periphery of the scaffold to the center.The quantitative results of bone tissue volume showed that the bone volume in PTi-Ta-Mg scaffold at 4,8,and 12 weeks was greater than those in PTi-Ta and PTi scaffolds(P<0.05).The fluorescent labeling and histological examination showed that at week 4,8,and 12,new bone tissue formed in the PTi-Ta-Mg scaffold were also larger than those in PTi-Ta and PTi scaffolds(P<0.05).Also,the new bone tissue was mainly concentrated in the intersection area between the scaffold and surrounding tissues.Conclusion:In this study,the tantalum/magnesium functional coating was successfully prepared on the surface of titanium using sol-gel method.The coating was tightly bonded to the titanium substrate without cracks.In vitro and in vivo results showed that the addition of tantalum/magnesium elements enhanced the bone-forming properties of the titanium implant,and also improved the corrosion resistance of the titanium implant.The coating preparation method used in this study is simple and easy to operate,which has good potential in clinical application.