Studies On Surface Modification And Biocompatibility Of Polyetheretherketone(PEEK) For Orthopedic Implants

Polyetheretherketone(PEEK) is one of the most potential candidates of biomaterials with good biocompatibility and biosecurity in orthopedic implant applications. However, its bio-inert limits the biofunction including osteoconduction and osseointegration, which severely hampers its outcome after implantation. Currently, some surface modification methods have been developed as the important research trend to improve the biofunction and bone-implant interfaces of PEEK.The research progress of the surface modification methods of PEEK was reviewed briefly. The evaluation method of biosecurity was also described in detail.Two surface modified PEEK materials including collagen-coated PEEK(CCPEEK) and bone morphogenetic protein-2 modified PEEK(BIPEEK) were prepared by the surface modification of recombinant type-I collagen-coated PEEK and human bone morphogenetic protein-2(rh BMP-2) on the surface of PEEK. After adsorbed onto the PEEK surface by hydrophobic interaction, type-I collagen was cross-linked and then rh BMP-2 was immobilized by covalent amide bond. The surface modified PEEK materials were further characterizated by the water contact angle tests, XPS, SEM and ELISA tests. The results clearly confirmed the surface modification of PEEK by type-I collagen and human bone morphogenetic protein-2(rh BMP-2).PEEK and two surface modified CCPEEK and BIPEEK materials were tested by the cell experiments including the cholecystokinin-8(CCK-8), activity assay of ALP and alizarin red S dying assay in vitro. The results indicated that all PEEK, CCPEEK and BIPEEK possessed the low cell cytotoxicities. Compared with pure PEEK, CCPEEK and BIPEEK showed the higher osteogenesis differentiation rates of MC3T3-E1 cells when MC3T3-E1 cells were cultured on modified PEEK materials. Meanwhile, type-I collagen and rh BMP-2 coatings also improved the proliferation of MC3T3-E1 cells.The lumbar vertebrae implanting models were prepared of PEEK and two surface modified CCPEEK and BIPEEK materials and then were implanted in the New Zealand rabbits. The lumbar vertebrae implanting models were further measured by the Micro CT and biomechanical analysis. No obvious acute toxic effects or acute toxic effects were induced by PEEK and two surface modified CCPEEK and BIPEEK materials in vivo. In comparison to pure PEEK, CCPEEK and BIPEEK resulted in the positive changes in implanted position near the vertebrae after 8 weeks of implantation. All major parameters including BMD, BV/TV, BS/BV and Tb. Th were improved and Tb. Sp. Pull-out tests also demonstrated the firmer interfaces were formed between bone and modified PEEK. Therefore, the surface modification of type-I collagen and human bone morphogenetic protein-2(rh BMP-2) can efficiently improve the biocompatibility and biofunction of PEEK.