Polyetheretherketone-Metal Composites for Biomedical Applications

Abstract

Polyetheretherketone (PEEK) implants are widely accepted and adopted in the orthopaedic field. However, PEEK is relatively bioinert and results in limited fixation with bone. In order to improve the initial cell responses and the fixation of the PEEK implants, PEEK-metal composites were investigated using titanium (Ti) and magnesium (Mg). PEEK-Ti and PEEK-Mg composites with up to 60 vol% metal contents were successfully prepared by compression molding the mixed metal and PEEK powders and were analysed for potential use in the medical field.

Ti has excellent biocompatibility and mechanical properties. With the incorporation of Ti in PEEK, the composite materials showed that in vitro cell attachment, proliferation and differentiation were enhanced and the mechanical properties of the composites can be tailored to mimic the bone more closely. With the incorporation of 60 vol% of Ti to PEEK, the compressive strength increased from 132 MPa to 247 MPa and the elastic modulus increased from 3.7 GPa to 7.1 GPa. The significant improvements in biological and mechanical properties suggest that PEEK-Ti composites can be tailored to be used as potential load-bearing implant material.

With biodegradable Mg used as fillers, PEEK- Mg composites were fabricated to enhance the biocompatibility and to provide stronger interlocking of the implant once the Mg is degraded in physiological environment. Hydroxyapatite, a bioactive substance, was coated on the exposed Mg surfaces to enhance the early stage cellular activities and to reduce the corrosion rate of Mg. The post-corrosion morphologies, mechanical properties and preliminary cellular tests were performed to evaluate the potential of PEEK-Mg as a novel implant material. The compressive strength composites were not significantly different from the pure PEEK samples. However, the elastic modulus of 60 vol% PEEK-Mg increased to 5.4 GPa from 3.1 GPa of the pure PEEK. These results show that hydroxyapatite layer on the exposed Mg surfaces can enhance the cellular properties on the surface of the implants, and the pores formed by the degradation of Mg particles can be used to improve the bone-to-PEEK fixation through the mechanical interlock of the implant with the adjacent bones.

This study investigated PEEK-Ti and PEEK-Mg as potential orthopaedic implant materials. By incorporating biocompatible metal particles into PEEK, the mechanical and the biological properties were enhanced. These results show that PEEK-metal composites are promising materials for use as biomaterials.