Preparation Of Three-dimensional Porous Composite PEEK Scaffold And The Experimental Study On Bone Repair Performance

Background:Bone defects are generally caused by trauma,infection,bone tumor resection or metabolic bone disease,which usually require bone grafts for reconstruction when the length of bone defect exceeds the critical size and bone tissue could not heal itself.At present,the main clinical treatment methods are autogenous or allogeneic bone graft.Autologous bone graft is considered as the gold standard in the treatment of bone defects.It has good osteogenic properties and does not lead to immune rejection,but the supply of grafts is limited and there are risks of secondary injuries and infections during donor site surgery.Allogeneic bone graft is considered an alternative,which is widely available and does not require additional donor site surgery.However,immune rejection and the potential risk of epidemic transmission limit the widespread use.Due to these disadvantages of autologous bone graft or allogeneic bone graft,bone tissue engineering(BTE)has gradually attracted the attention of researchers,and they have been devoted to developing bone graft substitutes made of various biocompatible materials in the past decade.Bone tissue engineering scaffolds play a crucial role in the application of bone tissue engineering.Ideal scaffolds for BTE should have the following excellent properties:(1)good biocompatibility which could avoid inflammation and rejection reactions in vivo;(2)good mechanical properties,which could provide certain support;(3)appropriate pore size and porosity which could provide good growth conditions for osteocytes,increase host cell migration and enhance osteogenic differentiation;(4)suitable degradation rate and non-toxic metabolites.At present,scaffolds widely studied for bone tissue engineering mainly include metal,ceramic and polymer scaffolds.Polyetheretherketone(PEEK)is a thermoplastic aromatic semi-crystalline synthetic polymer with good biocompatibility,chemical stability,elastic modulus similar to cortical bone and natural radiolucency.It has been gradually developed into bone implants in orthopedic fields and is expected to be used for large bone defects repair.However,PEEK has a biologically inert surface,which results in poor osteogenic ability and osseointegration with surrounding bone tissue.Meanwhile,the high melting point of PEEK makes it difficult for traditional processing methods to produce implants with customized shapes and precise porous structure.These shortcomings limit the further application of PEEK in clinic.Therefore,the design and preparation of composite PEEK scaffolds with threedimensional porous structure and bioactive surface is the key to meet the clinical needs of bone defect treatment.Recently,3D printing technology has become a transformative tool in the field of biomedical applications,especially in the direction of bone tissue engineering.Through this technique,different biomaterials can be prepared into porous scaffolds with customized shapes,pore size,porosity and interpore connectivity,providing the most favorable conditions for cell adhesion and proliferation.Meanwhile,it is conductive to the formation of bone tissue and microvessels.Bone tissue could grow into the internal structure of the porous scaffold,resulting in satisfactory osseointegration.At present,innovations in Fusion Deposition Modeling(FDM)have allowed the printing of high-temperature polymers,which means that PEEK scaffolds with custom shapes and precise porous structure can be created using 3D printing technology.In order to improve the surface properties of polyetheretherketone implants for better biological activity,the surface morphology and chemical properties of PEEK were modified through physicochemical methods,coating deposition or biological functionalization.A variety of different modification techniques can be used together to achieve the desired surface properties.Sulfonation is a commonly used method,which could produce pores with a diameter of less than 5 ?m on the surface of PEEK,increasing the surface roughness.This is conducive to the further coating of bioactive materials.Ultraviolet(UV)grafting is also a common physicochemical modification method which could generate reactive functional groups on PEEK.Thus,the biological activity of PEEK surface could be enhanced to achieve better osteogenic ability and osseointegration.Purpose:The purpose of this study is to fabricate composite PEEK scaffolds with threedimensional porous structure and bioactive surface by combining 3D printing technology and surface modification methods,as bone graft substitutes for the treatment of bone defects,in order to solve the problem of clinical bone defect treatment.The composite PEEK scaffold has a three-dimensional porous structure combining macropores and micropores,which is beneficial to cell adhesion and proliferation,as well as the growth of new bone and microvessels.Meanwhile,bioactive surface can enhance the surface biological activity of composite PEEK scaffold.By characterizing its physical and chemical properties and conducting in vitro and in vivo experiments,the relationship between the three-dimensional porous structural and biological active surface of the composite PEEK scaffolds and bone defect repair was analyzed,and the mechanism of promoting bone regeneration and osseointegration was explored.So as to provide new ideas and methods for the development of PEEK bone graft materials for bone defect repair.Methods:1.Porous PEEK scaffolds with different sizes were fabricated by 3D printing technology,and the scaffolds were sulfonated.Then the morphology,mechanical properties and hydrophilicity of the scaffolds were evaluated.2.The porous PEEK scaffolds were coated with CSMA/POSS nanocomposite through UV-initiated graft polymerization.The morphology,chemical composition,surface hydrophilicity,protein adsorption capacity and in vitro mineralization capacity of the composite PEEK scaffolds were evaluated.3.The composite PEEK scaffolds was co-cultured with rBMSCs,and the biocompatibility of the composite scaffold was evaluated by cell proliferation assay and living/dead cell staining.The morphology of cells on the composite scaffold was observed by scanning electron microscope and confocal laser microscope.Osteogenic differentiation and calcium deposition of cells on the composite scaffolds were observed by alkaline phosphatase staining and alizarin red staining.The expression of osteogenic genes and proteins on the composite scaffold were evaluated by RT-PCR and Western Blot.4.The rat cranial defect repair model was established and the composite PEEK scaffolds were implanted into the bone defect.Micro-CT analysis and histological staining were performed on the cranial specimens at 4 and 8 weeks after surgery.The bone repair capacity and osseointegration property of the composite PEEK scaffolds were further evaluated through an in vivo bone defect repair experiment.Results:1.In this study,porous PEEK scaffolds with different sizes were successfully fabricated by 3D printing technology.The scaffolds show a relatively smooth surface,uniform pore size,good connectivity between pores and certain compressive performance.The microporous network formed on the surface of the scaffold after sulfonation treatment.2.The three-dimensional porous composite PEEK scaffolds coated with CSMA/POSS nanocomposites were successfully prepared through UV-initiated graft polymerization.The grafting of CSMA/POSS on the surface of PEEK scaffolds was confirmed by FTIR and XPS tests.The surface and sectional morphology of the composite PEEK scaffolds were observed by scanning electron microscope.The nanocomposite gel formed on the surface and in the unit pore of the PEEK scaffolds indicating that the three-dimensional porous PEEK composite scaffold was successfully constructed in this study.After modification,the hydrophilicity,protein adsorption capacity and mineralization capacity of the scaffold surface were improved compared with those of the unmodified group.3.The good biocompatibility of the composite scaffolds was verified by CCK-8and living/dead cell staining experiments.Scanning electron microscopy and confocal laser microscopy proved that the composite scaffolds were suitable for cell adhesion and migration.The results of alkaline phosphatase staining and alizarin red staining proved that the composite scaffolds could promote osteogenic differentiation and calcium nodular deposition of rBMSCs.The results of RT-PCR and Western Blot showed that the composite scaffolds could induce osteogenic differentiation at the gene and protein expression levels.4.The composite PEEK scaffolds were implanted into the rat cranial defect repair model,and the results of micro-CT analysis and histological staining confirmed that the composite PEEK scaffolds had a better ability of osteogenesis induction and osseointegration.Conclusion:The three-dimensional porous composite PEEK scaffolds coated with CSMA/POSS nanocomposite can be successfully fabricated by combining 3D printing technology and surface modification.The composite PEEK scaffold has a three-dimensional porous structure combining macropores and micropores and CSMA/POSS bioactive surface,which can enhance the ability of osseointegration and osteogenesis induction in vivo,providing a new idea and method for the development of PEEK bone graft material for repairing bone defects.