Preparation And In Vitro Biological Performance Of Sulfonated Carbon Fiber Reinforced PEEK With Sr/Mg Co-doped Hydroxyapatite Coating

Objective:Carbon fiber reinforced polyether ether ketone(CF/PEEK)composite is a novel bone implant material,but its inert surface limits its development in oral implant field.In order to enhance the surface bioactivity and further improve its osseointegration of CF/PEEK composite,we used a novel strontium and magnesium co-doped hydroxyapatite(HA)coating to modify it.Moreover,the three-dimensional pore structure was prepared on the CF/PEEK surface by sulfonation with concentrated sulfuric acid to improve the bonding strength between HA coating and CF/PEEK composite.Therefore,Sr/Mg co-doped hydroxyapatite coating on sulfonated CF/PEEK was prepared in this study,and its surface properties,biocompatibility and bioactivity were evaluated to provide a new idea for the development of oral bone implant materials.Methods:The Sr/Mg co-doped HA coating was prepared on sulfonated CF/PEEK composite by a method of deposition assisted with microwave.The surface properties of samples were observed and characterized by scanning electron microscope(SEM)and contact Angle measuring instrument.The bioactivity was evaluated by soaking it in simulated body fluid(SBF)for 14 days.Mouse fibroblasts L929 were inoculated on the surface of the samples and cultured for 1d,4d and 7d,respectively.To evaluate the biosafety,the cytotoxicity was detected by CCK-8 kit and the cell morphology was observed under an inverted microscope.Rat bone marrow mesenchymal stem cells(BMSCs)were inoculated on the surface of the sample.The cell adhesion morphology was observed under inverted fluorescence microscope,and cell proliferation was detected by CCK-8 kit.The activity of alkaline phosphatase(ALP)was measured at 7d and 14 d,and the mineralization ability of cell matrix was measured with alizarin red solution at 14 d.The expressions of related osteogenesis genes ALP,Runx-2,OC and Col-Ⅰ were detected by real-time fluorescence quantitative PCR(RT-q PCR)to evaluate the in vitro osteogenic ability.Results:1.The result of SEM have shown that the surface of sulfonated CF/PEEK(SCF/PEEK)presents a uniform 3D porous network structure with different pore sizes.Sr/Mg co-doped HA coating are typical pinprick and strip distributed on the SCF/PEEK surface.After soaking in SBF for 14 d,the surface of the sample was covered with spherical apatite particles.The contact angles of Sr/HA and Mg-Sr/HA were 66.86±6.592 and 64.57±3.226,respectively,which were smaller(82.11±2.576)compared with SCF/PEEK(P < 0.05).2.SCF/PEEK,Sr/HA and Mg-Sr /HA had no obvious toxicity to cells on day 1 and day 7.However,on day 4,the toxicity of SCF/PEEK group was in level 2,indicating that sulfonation brought mild adverse effects on cells in a short period.The cell morphology was normal at all time.3.The cell adhesion density of BMSCs on the surface of SCF/PEEK,Sr/HA and Mg-Sr/HA increased successively,and the cytoskeleton was more obviously observed by inverted fluorescence microscope.The proliferation activity of the three groups increased successively on day 1,day 4 and day 7,and Mg-Sr/HA group was the strongest especially,which was consistent with the cytotoxicity results.The ALP activity and matrix mineralization of BMSCs on Sr/HA and Mg-Sr/HA surface were higher than those of SCF/PEEK at each time,which was consistent with the expression of ALP,Runx-2,OC and Col-Ⅰ genes.In particular,Mg-Sr/HA showed the best ability of in vitro osteogenic induction.Conclusion:In this study,CF/PEEK composite was surface modified by sulfonation treatment and Sr/Mg co-doped HA coating.After surface modification,the hydrophilicity of the material increases,which can induce the formation of spherical apatite particles,showing good biological activity.Cell adhesion,proliferation,the level of ALP activity,matrix mineralization and osteogenic gene expression were enhanced,which reflected that the material had better in vitro osteogenic properties.Moreover,the Sr/Mg doped HA coating showed reliable biological safety as a result of avoiding toxic damage to cells brought by sulfonation treatment.In conclusion,the sulfonated CF/PEEK composite covering with Sr/Mg co-doped HA coating show good cytocompatibility,bioactivity and osteogenic properties.