Microwave-Assisted Calcium Phosphate Coatings on Carbon Fibre-Reinforced PEEK Scaffolds for Orthopaedic Implant Applications

Abstract

Carbon fibre-reinforced polyetheretherketone (CF-PEEK) is a promising biomaterial due to its high strength, stiffness, radiolucency, and wear resistance; however, its bioinert nature limits osteointegration in orthopaedic applications. In this study, porous CF-PEEK scaffolds with controlled porosities (45–70%) were fabricated using compression moulding and the NaCl particle leaching technique. To enhance bioactivity, the scaffolds were surface-activated, and a microwave-assisted calcium phosphate (Ca-P) coating was applied in a biomimetic medium. Morphological evaluation using field emission scanning electron microscopy (SEM) revealed a uniform, interconnected porous architecture in uncoated scaffolds, while Ca-P-coated scaffolds exhibited a continuous apatite layer, which was confirmed by cross-sectional SEM micrographs. The X-ray diffraction analysis identified characteristic semi-crystalline PEEK peaks, along with additional Ca-P phases, after coating of the scaffolds. All coatings demonstrated strong adhesion to the scaffolds, as indicated by the 5B ratings for P60C and P70C in the cross-cut adhesion test. The measured porosity closely matched the initial porogen content. Water absorption increased with porosity, reaching 69.02% for the scaffold with the highest porosity (P70). Mechanical testing showed a compressive strength of ≈ 132.48 MPa for P70, which is suitable for load-bearing orthopaedic implants. Biological assessments demonstrated enhanced protein adsorption, haemocompatibility (haemolysis < 5%), and optimal in vitro bioactivity in Ca-P-coated scaffolds. Cell culture studies with MG-63 osteoblast-like cells demonstrated superior cell viability and adhesion, particularly with the highly porous P70C scaffold. Therefore, the developed Ca-P-coated CF-PEEK scaffold exhibited an optimal balance of mechanical integrity, bioactivity, and cytocompatibility, making it a strong candidate for orthopaedic applications.