Preparation,Interfacial Failure And Biological Performance Of Bioactive Glass Coating Materials On PEEK Substrate For Orthopedic Implant

Polyetheretherketone(PEEK)polymer is a promising orthopedic implant for its good mechanical properties and good biocompatibility.However,PEEK has low bioactivity that cannot generate osteoconduction and osteoproduction for bone repair.Bioactive glass(BG),a third-generation biomaterial,has outstanding bioactivity and can promote tissue repair for bone defect sites.Coating BG materials on PEEK is an effective way to improve the bioactivity of PEEK matrix and maintain its good mechanical properties.To clarify,there are two critical requirements for a bioactive coating used as orthopedic implants.The first is its good biological response,such as good biocompatibility,bioactivity as well as proper drug release.The second is its good interfacial bonding behavior to avoid coating failure and ensure robust service after implantation.The requirements mentioned above are in close relationship with the physical and chemical properties of BG materials and the interfacial properties of coatings.Thereby,the main contents and conclusions of the thesis are as follows:1.A hierarchically porous bioactive glass microsphere(ESBG)for coating materials was fabricated via electro spraying technique assisted with non-solvent induced phase inversion,where the biological response was controlled in view of structure and chemical composition of BG materials.(1)The crystalline phases of ESBG were dependent on sintering temperatures.Compared with the conventional 45S5(?)BG powders,the microspheres sintered over 800℃showed a different crystallinity-bioactivity correlation and the samples sintered at 1000℃had the fastest in vitro apatite formation rate.The best bioactivity was the combination of the porous structure and the formation of wollastonite phase.In addition,the cell viability and alkaline phosphate(ALP)activity of MC3T3-E1 cells cultured in the extracts of ESBG sintered at 1000℃ were higher than that in the BG powders.(2)The effects of hierarchically porous structure and Sr substitution on the biological response and drug delivery of ESBG were further investigated.The porous structure provided a faster ion release rate that enhanced the bioactivity of ESBG.After Sr substitution,the potential crystallinity of the glass increased and the ion release rate reduced,which modulated faster ion release of ESBG and maintained good in vitro behavior of MC3T3-E1 cells.The porous microspheres also displayed a three-stage drug release profile of gentamicin due to the hierarchy pore,providing a new insight into the design of a sustained and time-targeted drug release matrix.2.A bioactive BG-chitosan(CS)coating on PEEK substrate was fabricated by dip coating method,where the effects of susbtrate properties and drying stress of the binder CS coatings were investigated to avoid interfacial failure of the coatings.(1)After PEEK was pre-treated by sand blasting and acid etching,the bonding behavior of the BG-CS coating on PEEK was effectively enhanced.The maximum adhesion strength measured by pull off test was 5.73±0.86 MPa.Compared with the surface wettability of PEEK,surface roughness was more effective for improving the fracture resistance at the mixed stress mode applied in the four-point bending test.The results of the in vitro mineralization,cell adhesion,cell proliferation and ALP activity of MC3T3-E1 cells showed the enhanced bioactivity and cell behavior of the BG-CS coated PEEK.(2)Osmotic pressure was the dominant driving force for the drying stress of CS coatings.Unlike the previous studies,the shape of the stress history and the maximum stress of the CS coating were dependent on coating thickness.During the drying of the CS coatings,the evaporation rate of the solvent was much larger than the diffusion coefficient,which contributed to the vertical non-uniformity of solvent concentration and the formation of skin glassy layer.As the coating thickness increased,the thickness of the skin glassy layer increased.Therefore,the reduction of the evaporated solvent before and after solidification decreased and the stress decayed.