Osseointegration of nanohydroxyapatite- or nano-calcium silicate-incorporated polyetheretherketone bioactive composites in vivo

Polyetheretherketone (PEEK) exhibits appropriate biomechanical strength as well as good biocompatibility and stable chemical properties but lacks bioactivity and cannot achieve highly efficient osseointegration after implantation. Incorporating bioceramics into the PEEK matrix is a feasible approach for improving its bioactivity. In this study, nanohydroxyapatite (n-HA) and nano-calcium silicate (n-CS) were separately incorporated into PEEK to prepare n-HA/PEEK and n-CS/PEEK biocomposites, respectively, using a compounding and injection-molding technique, and the in vitro degradation characteristics were evaluated. Discs with a diameter of 8 mm were inserted in 8 mm full-thickness cranial defects in rabbits for 4 and 8 weeks, and implantation of pure PEEK was used as the control. Three-dimensional microcomputed tomography, histological analysis, fluorescence microscopy of new bone formation, and scanning electron microscopy were used to evaluate the osseointegration performance at the bone/implant interface. The results of the in vitro degradation study demonstrated that degradation of n-CS on the surface of n-CS/PEEK could release Ca and Si ions and form a porous structure. In vivo tests revealed that both n-CS/PEEK and n-HA/PEEK promoted osseointegration at the bone/implant interface compared to PEEK, and n-CS/PEEK exhibited higher bone contact ratio and more new bone formation compared with those of n-HA/PEEK, implying that n-CS/PEEK possessed a stronger ability to promote osseointegration. These two PEEK biocomposites are promising materials for the preparation of orthopedic or craniofacial implants.