Preparation And Surface Modification Of Biomedical Carbon Fiber/Peek Composites

BackgroundAs a semi-crystalline thermoplastic engineering plastics,polyether ether ketone(PEEK)has attracted much attention due to its excellent mechanical properties,thermal properties,chemical stability and biocompatibility.As a hot biomedical polymer material,PEEK is considered to be a new medical implant material instead of traditional titanium alloy.However,in terms of mechanical strength,PEEK can not meet the needs of human skeleton very well.Therefore,in this study,carbon fibers(CF)were used as fiber fillers to strengthen PEEK,in order to obtain a new composite to meet the mechanical strength of human implant materials.In addition,as an implant material,whether the elastic modulus matches the elastic modulus of human skeleton is directly related to the success of implantation surgery.Therefore,by changing the content and length of carbon fibers,the effects of these two factors on the mechanical strength and elastic modulus of PEEK composites were explored.On the other hand,as a biomedical material,PEEK must have good biological activity,and PEEK is a kind of inert material,which greatly limits the application of PEEK as a biomaterial.In order to change the surface morphology of CF/PEEK composites,surface sulfonation treatment and graphene oxide treatment were carried out on the prepared composites.At the same time,new bioactive functional groups were introduced into CF/PEEK composites to improve the surface bioactivity of CF/PEEK composites.In addition,as a biomedical material,it should have good biocompatibility.Therefore,this project had carried out cell toxicity,cell proliferation,cell adhesion and other in vitro experiments and in vivo implantation test was carried out on the prepared and surface-treated materials in order to evaluate the biocompatibility of the prepared and surface-treated composite materials to provide theoretical basis for further research.Objectives1.The CF/PEEK composites were prepared.The effects of carbon fiber content and size on the mechanical properties of the composites were characterized by mechanical experiments and fracture morphology.The cytotoxicity,cell adhesion and proliferation experiments in vitro were used to explore the effects of content and length for different carbon fibers on compatibility and biosafety.2.The surface of the composite was subjected to sulfonation treatment and its surface morphology was observed by scanning electron microscopy(SEM).The effects of surface sulfonation on the biological activity of CF/PEEK composites were investigated by cytotoxicity,cell adhesion and proliferation experiments in vitro.3.The graphene oxide was coated on the surface of the composite.The surface morphology was characterized by scanning electron microscopy.The effects of GO surface modification on the bioactivity of the composite were investigated by cytotoxicity,cell adhesion,proliferation experiments and in vivo implantation test.Methods1.Prepare standard specimens of CF/PEEK composites by injection molding CF with different contents and sizes and PEEK at 380 °C according to national standards,test the tensile and flexural strength and modulus with compressive strength of composites according to the mechanical test standard;impact strength was measured by JJ-20 free support beam impact tester;hardness value was measured by micro-micro hardness tester FM-700e;and fracture morphology of curved samples was observed by scanning electron microscopy(SEM).2.S-CF/PEEK sample was obtained by sulfonation of the surface of the composite by soaking concentrated sulfuric acid for 5 min;then the sulfonated sample was immersed in the graphene oxide solution by the impregnation method to cover the surface with the graphene.GO-S-CF/PEEK samples were obtained.The surface morphology of the sulfonated samples S-CF/PEEK and GO-S-CF/PEEK samples was observed by scanning electron microscopy(SEM).3.In vitro cell experiments: The in vitro cytotoxicity test was performed on each group of materials by CCK-8 method.The third generation mouse fibroblast L-929 was cultured with different material extracts,and the cell morphology was observed on the first,fourth and seventh days.The OD value was measured at 450 nm,and the relative growth rate(RGR)was calculated to evaluate whether the materials in each group were toxic.SD rat bone marrow mesenchymal stem cells(BMSCs)were inoculated on the surface of the material for cell adhesion experiments,and fixed after 48 hours.Permeabilization,immunofluorescence staining with TRITC Phalloidin Rhodamine labeled phalloidin working solution and DAPI staining solution,observed under laser confocal microscopy;SD rat bone marrow mesenchymal stem cells(BMSCs)were inoculated on the surface of the material,After 1、4 and 7 days,the absorbance value was measured at 450 nm using a microplate reader to evaluate the cell proliferation ability.4.In vivo implantation experiment: SD rats were selected to establish rat skull defect model.Composite materials were implanted into mouse skull.The mice were executed 4 weeks after operation.After execution,micro-CT was taken to observe the osseointegration of bone defect areas at different time points.The specimens were decalcified and the osteogenesis was observed under optical microscope after HE staining.Results1.CF/PEEK composites with different content of carbon fibers(0%,25%,30%,35%,40%)were successfully prepared by injection molding.The addition of carbon fibers could effectively improve the tensile strength,flexural strength,compressive strength and hardness of the composites,but reduce the impact strength.The elastic modulus of PEEK increased to a suitable range for human cortical bone with the addition of carbon fibers.At the same time,the addition of carbon fibers did not lead to significant increase in cytotoxicity,and 25 CF has the lowest cytotoxicity in composite materials.2.Long CF/PEEK composites had higher tensile strength,flexural strength and compressive strength than short CF/PEEK composites,which could effectively enhance the mechanical strength of materials,but also improve the elastic modulus of materials.Moreover,neither 25 CF nor L-25 CF had obvious hemolysis,no acute systemic toxicity and good biocompatibility.3.Both PEEK and CF/PEEK after sulfonation showed porous structures,and the addition of carbon fibers would increase the pore size of PEEK after sulfonation.This porous structure was conducive to cell adhesion and proliferation.Cytotoxicity test showed that the sulfonated composites had a grade 1 cytotoxicity after full cleaning,and had no obvious cytotoxicity.4.The GO-treated CF/PEEK were covered by the GO layer structure outside the porous sulfonated layer,and the sulfonated layer was no longer exposed.At the same time,a large number of hydrophilic groups on the surface of GO layer were successfully introduced into CF/PEEK with GO layers,which was conducive to cell adhesion.BMSCs cells had large spreading area on the surface of GO-S-25 CF,obvious cytoskeleton,stretching morphology and clear nucleus.The cytotoxicity of GO-treated materials was at level 1,and there was no obvious cytotoxicity.GO-treated CF/PEEK could be used as medical implant materials.Conclusions1.Carbon fibers/polyether ether ketone(CF/PEEK)composites with different contents were successfully prepared.The addition of carbon fibers can effectively improve the mechanical strength of the composites without significantly increasing the cytotoxicity.2.Long carbon fibers can effectively enhance the mechanical strength of the material,but also improve the elastic modulus of the material.Long and short carbon fibers/polyether ether ketone composites have good biocompatibility.3.Porous structure will be formed on the surface of CF/PEEK composites after sulfonation with sulfuric acid,and the addition of carbon fibers will increase the pore size on the surface of PEEK after sulfonation.This porous structure is conducive to cell adhesion and proliferation without obvious cytotoxicity.4.GO treatment will cover the GO layer structure outside the porous sulfonated layer of the composites.At the same time,GO layer is conducive to cell adhesion,without obvious cytotoxicity,and can be used as medical implant materials.5.The results of implantation experiments in vivo show that both sulfonation and GO treatments can improve the bone bonding strength of the materials.GO-modified composite after sulfonation has a good interface with surrounding bone tissue,which can effectively promote the growth of osteoblasts.