Mechanism Research On 3D Printing Titanium Alloy Microporous Scaffold Loaded With PRP And Simvastatin To Promote Osseointegration

BackgroundIn clinical practice,it is common to have large bone defects caused by trauma or tumor resection,as well as a large amount of bone graft between vertebral bodies after discectomy.The most commonly used bone transplant is autologous bone,but autologous bone transplantation is limited by additional surgical trauma,donor site complications,and insufficient autologous bone supply,so it is necessary to find alternative materials with good osteogenic performance.In recent years,3D printing scaffolds and related systems have been the research focus of bone tissue engineering.By using biocompatible materials to design and prepare porous scaffolds,and carrying gel that can promote cell proliferation and osteogenesis related inducers,local good osteointegration can be achieved.Titanium alloy(Ti6Al4V)has the characteristics of good biocompatibility and high mechanical strength,making it the most commonly used implant material in dentistry and orthopedics.In the early stage of bone healing,local angiogenesis is of great significance for local nutrition supply and bone tissue repair.The lack of local blood vessels can also lead to problems such as ischemic bone necrosis and poor bone healing.In addition,the release and induction of local growth factors are important influencing factors for local bone tissue generation.Platelet rich plasma(PRP)is a platelet concentrate rich in growth factors obtained from autologous whole blood after centrifugation,including platelet derived growth factor(PDGF),insulin like growth factor(IGF),and transforming growth factor(TGF).Research shows that PRP can promote bone regeneration and significantly promote the repair of bone defects.However,local injection will reduce the osteogenic effect due to the explosive release of local growth factors.At present,PRP gel can be used to solve this problem.Simvastatin is a drug used to reduce cholesterol and the risk of heart disease,and experiments have found that local application of simvastatin has a good effect on early bone formation.In conclusion,the application of PRP gel with simvastatin combined with titanium alloy porous scaffold may be a better strategy for bone defect repair.PurposeIn this study,the PRP gel loaded with simvastatin combined with porous titanium alloy scaffold system was established to build a bioactive interface to promote local vascular and bone regeneration,and verify its bone integration performance.MethodsWe used 3D printer(EBM type)to print titanium alloy porous support with a diameter of 500 μm.The porosity is 78%.Added PRP on the surface,added Ca Cl2 to activate PRP,and then added thrombin solution containing simvastatin to obtain 3D printed porous titanium scaffold composite PRP gel loaded with simvastatin system.The experiment was divided into three groups: pure Ti stent(Ti),Ti stent composite PRP gel(Ti/PRP),Ti stent composite PRP gel and simvastatin(Ti/PRP/Simv).Through cell viability verification,including cell live/dead staining,CCK-8,angiogenesis capability verification,including tubule formation experiment,scratch repair experiment,cell migration experiment and RT-q PCR experiment,osteogenesis capability verification,including ALP staining,ALP quantitative detection and RT-q PCR experiment,and in vivo verification of the osteogenesis and angiogenesis capability of the system,including Micro-CT experiment.ResultsThe results of live/dead cell staining and CCK-8 experiments showed that the Ti/PRP/Simv group had good biocompatibility;Tubular formation experiment,scratch repair experiment,cell migration experiment and Image-J quantitative analysis showed that the ability to induce angiogenesis in Ti/PRP/Simv group was significantly stronger than that in Ti and Ti/PRP groups;The RT q PCR experiment found a significant increase in the expression of angiogenic related genes in the Ti/PRP/Simv group,with consistent and comparable results.Through qualitative ALP staining,quantitative ALP detection,and RT q PCR experiments,it was found that the bone promoting ability of the Ti/PRP/Simv group was significantly improved compared to the Ti and Ti/PRP groups.Animal experiments found that the Ti/PRP/Simv group had significant bone ingrowth inside the scaffold,and the number and volume of new bone trabeculae increased significantly.Conclusion3D printed porous titanium stent combined with PRP gel and simvastatin system have good biocompatibility,osteogenic ability and angiogenic ability,providing a new treatment idea for the repair of bone defects.