Promotion Of Infectious Bone Defect Healing By Hydrogel Carrying Vancomycin Combined With 3D Printing Titanium Scaffold

Background:Bone infection(osteomyelitis)caused by bacteria has always been difficult to deal with.Debridement,systemic and local antibiotic therapy,necrotic bone fragments and the use of bone graft substitutes are the main treatment methods in clinic,which makes it inevitable to develop biomaterials with antibacterial and individualized bone regeneration.The ideal biomaterial should have individualized structure,bearing stress,biodegradability and good biocompatibility to prevent bacterial infection.3D printing technology is a potential engineering technology based on previous research and long-term development.Its advantage lies in that it can simulate the fine-scale network structure of natural bone tissue by computer,and it can prepare functional bone tissue engineering scaffold with functional nano-materials,drugs or cells and cytokines mixed into biomaterials.Biological multi-network structure is beneficial to nutrient transport and blood vessel growth.Bone tissue engineering scaffolds prepared from metal derivatives also have excellent mechanical properties.Objective:Hydrogel has high porosity and permeability,and good biocompatibility,which can establish sufficient local material environment for cell migration,expansion and differentiation,and at the same time absorb inflammatory exudate to reduce infection.Hydrogels can provide a good filling and drug release strategy for 3D printed bone tissue engineering materials.Polyamino acid temperature-sensitive hydrogel has good biocompatibility,which is liquid at 4℃ and solid at 25℃.This temperature-sensitive property enables it to be freely carried in 3D printed porous scaffolds.In this study,vancomycin was loaded into polyamino acid temperature-sensitive hydrogel and filled into 3D printed porous titanium scaffold.The composite scaffold was implanted into the infected bone defect,and vancomycin was gradually released through slow degradation of local hydrogel,thus ensuring a lasting antibacterial effect,thus meeting the requirements of anti-infection treatment for infected bone defect.This scheme will provide a new idea for the treatment of infectious bone defect in the future.Method:In this paper,a biodegradable polyamino acid hydrogel with the optimum concentration of 6wt% was prepared and loaded with vancomycin.It was added to porous titanium alloy scaffold(Ti6Al4V),and in vitro experiments were carried out with vancomycin with different concentrations(1%,2% and 3% respectively).The composite scaffold was co-cultured with bone marrow mesenchymal stem cells(BMSCs),and the cell compatibility was evaluated by cell proliferation inhibition experiment,cell living and dying staining experiment and ghost cycle peptide staining experiment.The optimal drug concentration was evaluated by in vitro antibacterial experiments(bacteriostatic circle experiment,bacterial proliferation inhibition experiment and in vitro bacterial smear experiment)for in vivo antibacterial experiments.In this study,according to the results of antibacterial experiments in vitro,vancomycin hydrogel composite scaffold loaded with 3% mass fraction was selected for in vivo experiments.To evaluate the effect of composite stent implantation in vivo on the repair of infected bone defect of femoral condyle in rabbits.Osteogenic characteristics were evaluated by Micro-CT scanning and tissue staining of rabbit femoral condyle samples after 4 weeks and 12 weeks of feeding.Results:1.In this study,polyamino acid hydrogel was prepared and its biocompatibility in vivo was tested by subcutaneous degradation experiment in rats.The results showed that the hydrogel could be degraded in vivo for about 50 days and had good biocompatibility.2.In order to increase the mechanical stress,in this study,polyamino acid hydrogel was loaded into the porous titanium alloy scaffold prepared by 3D printing technology,and vancomycin loading was increased to obtain antibacterial ability.We found that there was no difference in sample components through cell experiments,which confirmed that the composite scaffold had good biocompatibility.In vitro antibacterial experiments confirmed that the composite scaffold had good antibacterial effect on E.coli and S.aureus,and the addition of 3% vancomycin had better antibacterial effect.3.In order to verify the antibacterial effect and osteogenesis of the composite scaffold in vivo,we implanted the composite scaffold with 3%vancomycin into the animal model of infectious bone defect,and confirmed that the composite scaffold has good antibacterial and osteogenesis effect on infectious bone defect by Micro-CT and tissue staining.Conclusion:In this study,polyamino acid hydrogels were prepared and loaded into porous titanium alloy scaffolds prepared by 3D printing technology.Increasing the loading of vancomycin to obtain antibacterial ability,we confirmed that the composite scaffold has good biocompatibility and antibacterial ability to E.coli and S.aureus through cell experiments and in vitro antibacterial experiments.In vivo experiments,compared with the group without hydrogel and vancomycin,the results show that VH@TI scaffold has good biocompatibility,which can effectively release vancomycin locally and exert antibacterial effect in vivo,and make bone tissue regenerate and repair.