Decoration with electronegative 2D materials based on chemical transition layers on CFR-PEEK implants for promoting osteogenesis

Due to the unique lamellar structures, physicochemical and biological properties, electronegative two-dimensional (2D) materials have been explored for surface modification of carbon fibers reinforced polyetheretherketone (CFR-PEEK) composite. Deposition of electronegative 2D materials based on a porous surface created by concentrated H2SO4 has been studied to promote osteogenesis of CFR-PEEK. Generally, a porous layer will be pre-built on CFR-PEEK through severe corrosion of concentrated sulfuric acid to help the loading of 2D materials. However, the severe corrosion will greatly reduce surface mechanical strength, especially wear resistance and hardness, which increases the risk of collapse or even peeling of the bioactive coating by external force. Herein, instead of the severe corrosion, a mild corrosion by concentrated HNO3 was applied to modify the surface of CFR-PEEK to pre-create a dense transition layer for the further surface decoration of electronegative 2D materials (graphene oxide (GO) and black phosphorus (BP), representatively). The results indicated that hardness and wear resistance of the dense transition layer were markedly higher than those of the porous layer. Although GO and BP can be both loaded on these two transition layers, -SO3H on the porous transition layer showed moderate cytotoxicity, while -NO2 on the dense transition layer showed good cytocompatibility. The dense transition layer displayed higher mineralized deposition in vitro and new bone formation rate in vivo than the porous transition layer, moreover, GO and BP coatings improved osteogenesis. This work offers inspirations for the construction of electronegative 2D material coating on CFR-PEEK based on chemical transition layers.

Mechanical properties and osteogenesis of CFR-PEEK composite with interface strengthening by graphene oxide for implant application

In this work, 1 wt% of graphite oxide (GO) was used to strengthen the interface of carbon fibers (CF) reinforced polyetheretherketone (CFR-PEEK) composites, so as to obtain sufficiently high mechanical properties and bioactive surfaces which are two fundamental requirements for orthopedic/dental implants. Concretely, aminated GO was grafted onto oxidized CF in aqueous solution in a mild and non-toxic manner, subsequently, the CF grafted by GO was used for injection molding to prepare CFR-PEEK implant. The dispersibility of CF in the composites were remarkably boosted. Mechanical tests indicated that the flexural strength, compressive strength and hardness of CFR-PEEK were increased by 51%, 46%, and 30%, respectively. Furthermore, the flexural modulus increased to 11.67 ± 0.20 GPa and the compression modulus increased to 6.12 ± 0.11 GPa, which both meet the elastic modulus of human bone (6-30 GPa). The wear resistance was slightly improved. In the in vitro cell evaluation, CFR-PEEK with interface strengthening by GO showed no cytotoxicity and exhibited significantly enhanced adhesion and proliferation of Bone marrow mesenchymal stem cells (BMSCs) on the surface. More importantly, osteogenesis-related protein expression in vitro and osteogenetic evaluation in vivo all disclosed greatly accelerated osteo-differentiation of BMSCs on the composites due to the additive effect of GO at the interface. Based on this scheme, the CFR-PEEK composites with the dual functions of mechanical enhancement and osteointegration promotion holds great potential as implants in orthopedic/dental applications.