Preparation Of Micro And Nano Composite Surface On Ti-6Al-4V Based On Laser Processing And Its Osteogenic And Antibacterial Properties

Titanium alloys(Ti-6Al-4V)are widely used in clinical orthopedic implants because of its excellent mechanical strength,corrosion resistance and low elastic modulus.However,the Ti-6Al-4V itself is biological inertness with no antibacterial ability,which is prone to problems such as loosening,abscission of implants and bacterial infection after implantation in the body.Therefore,it is necessary to modify its surface to improve the biocompatibility of titanium implant.Currently,sandblasting and acid etching is still one of the most widely used methods in the industry,but it still cannot improve the biological properties significantly.In this study,micro-nano composite structure coated with ZnO were prepared on the surface of Ti-6Al-4V implants by two-step laser processing combined with solution-assisting method to enhance their osteogenic and antibacterial properties.Firstly,the optimal processing parameters of nanosecond laser processing were explored,and the solution-assisting method was used to construct micro grooves coated with ZnO.Then the synergistic effect of micro grooves and ZnO coating on osteoblast behavior were studied by in vitro experiment of MC3T3-E1.The results showed that the micro grooves coated with ZnO were successfully prepared using processing parameters of f=50kHz,V=250mm/s,and P=5W.The synergistic effect of them promoted the biocompatibility significantly without generating cytotoxicity.Secondly,the optimal processing parameters for femtosecond laser processing were explored,the periodic nanostructures were fabricated on the basis of micro-grooves,with a ZnO coating was added on the surface.Then the effects of the modified surface on cell response and gene expression were investigated by in vitro experiment of MC3T3-E1.The results showed that the dual-scale composite structure coated with ZnO was constructed using the parameters of f=800kHz,V=400mm/s,P=18W,which was more conducive to the proliferation,adhesion and differentiation of MC3T3-E1,and enhanced the gene expression of cells.Then,the antibacterial properties of the micro-nano composite structure coated with ZnO coating were explored.The detection experiments of bacterial activity such as spread plate method,bacterial morphology observation and live&dead bacterial staining were used to study the effect of the modified surface on S.aureus and E.coli.The results showed that the early anti-adhesion of the micro-nano composite structure and the long-acting antibacterial effect of ZnO significantly improved the antibacterial properties of Ti-6Al-4V implant.Finally,the in vivo osteogenic properties of the modified titanium implants were investigated.The surface modification of Ti-6Al-4V rod-shaped implants was carried out as above mentioned method.The micro-CT analysis and Mimics 3D model reconstruction were conducted after implantation in the proximal femur of rats for 2 and 4 weeks to investigate the new bone formation around the implant.The interface bonding strength between implant and bone was evaluated by histological staining experiments.The results showed that the titanium rods with micro-nano composite structure coated with ZnO had the best osteogenic ability.