Biotribological properties of nano zirconium dioxide and hydroxyapatite-reinforced polyetheretherketone (HA/ZrO2/PEEK) biocomposites

Polyetheretherketone (PEEK) has been considered as an excellent orthopedic implant material due to its similar elastic modulus to that of human bones. However, many obstacles including the bio-inertness nature and inferior osteoconduction of PEEK limit its wide applications in clinics. Nano hydroxyapatite (HA) and zirconium dioxide (ZrO2) were incorporated into PEEK to fabricate HA/ZrO2/PEEK biocomposites. The result of wettability of these biocomposites showed that the introduction of the ZrO2 and HA nanoparticles in PEEK could enhance its hydrophilic property at 1–2% HA and 1–5% ZrO2 concentrations. The biotribological properties and bioactivity of PEEK and HA/ZrO2/PEEK biocomposites were investigated in detail. The friction coefficient of these biocomposites increased with the increase of frequency and their wear width increased obviously with the increase of load. Biological and tribological experiments indicated that bovine serum possessed the best lubrication performance, and the 1%HA–1%ZrO2 and 2%HA–5%ZrO2 samples exhibited the lowest friction coefficient and wear rate. Then, the in vitro tests demonstrated that the HA/ZrO2/PEEK biocomposites exhibited improved cell activity and alkaline phosphatase activity than pure PEEK, and both 1%HA/1%ZrO2/PEEK and 2%HA/5%ZrO2/PEEK biocomposite samples could better promote bone calcification. The PEEK biocomposite with 2 wt% HA and 5 wt% ZrO2 nanoparticles exhibited the best tribological properties and bioactivity, which could be expected to develop a kind of potential medical material for practical clinical applications.