Flexural Properties of Polyetheretherketone Composites Containing Hydroxyapatite, Graphene Oxide, and Carbon Fiber for Spinal Implant Materials

Because of its good biocompatibility and low elastic modulus, polyetheretherketone (PEEK) is gaining increasing attention as an alternative to metallic spinal implants; however, its applications are limited due to its bioinertness, hydrophobicity, and poor mechanical properties compared to those of human cortical bone. The aim of this study was to develop a PEEK composite with improved bioactivity and flexural properties by incorporating hydroxyapatite (HA), graphene oxide (GO), and carbon fiber (CF) as fillers. In this study, we have attempted to minimize the CF content and maximize the HA content to ensure high bioactivity and hydrophilicity. HA and GO were modified with a silane coupling agent to enhance their dispersion in and interfacial adhesion with the PEEK matrix. The filler content was optimized with 0.5 wt% of modified GO (m-GO), 30 wt% of modified HA (m-HA), and 10 wt% of CF to yield a PEEK composite with flexural properties comparable to those of the human cortical bone. The in vitro bioactivity test and the water contact angle measurement confirmed that the composite was bioactive and had a hydrophilic surface, respectively. This unique PEEK/m-GO/m-HA/CF composite could potentially yield an effective design strategy for the development of high-performance PEEK biocomposites.