Strength and bioactivity of PEEK composites containing multiwalled carbon nanotubes and bioactive glass

Abstract

Polyetheretherketone (PEEK) polymer is a widely accepted implantable biomaterial in the biomedical field. However, PEEK has a low elastic modulus (E-modulus) as well as a bio-inert nature which is not conductive to rapid bone cell attachment, hence, producing delayed or weak bone-implant integration. Multiwalled carbon nanotubes (MWCNTs) represent one of the strongest known materials that could be added to a polymer to improve its mechanical properties. Bioactive glasses (BGs) can form hydroxyapatite deposits on their surfaces and form a tight bond with the bone, thus, their incorporation into the PEEK matrix may improve its bioactivity.

Methods: Eight groups were formulated according to the type and percentage of modification of PEEK by MWCNTs and BGs. Group 1: Pure PEEK (P), Group 2: P + 3% MWCNTs (PC₃), Group 3: P + 5% MWCNTs (PC₅), Group 4: P + 5% BGs (PG₅), Group 5: P + 10% BGs (PG₁₀), Group 6: P + 3% MWCNTs + 5% BGs (PC₃G₅), Group 7: P + 3% MWCNTs + 10% BGs (PC₃G₁₀), and Group 8: P + 5% MWCNTs + 5% BGs (PC₅G₅). Characterization of the vacuum-pressed PEEK and PEEK composite specimens was done using FE-SEM, EDS, FT-IR and TF-XRD. Three-point load test was done to obtain the flexural strength (F.S) and the E-modulus of the specimens. Wettability was determined by measuring the contact angle with distilled water. In-vitro bioactivity was determined after immersion of specimens in simulated body fluid (SBF). Moreover, the effect of the specimens on osteoblastic cell viability was evaluated.

Results: Three-point load test results have shown an improvement in both F.S. and E-modulus for groups PC₅, PC₃G₅ and PC₅G₅. The lowest contact angle was obtained for group PC₅G₅ followed by the PC₃G₁₀ group. All specimens containing BGs showed the formation of hydroxyapatite-like deposits after their immersion in SBF, as well as an improvement in osteoblastic cell viability compared to PEEK.

Conclusion: PC₃G_10, PC₃G₅ and PG₁₀, groups are promising for the fabrication of patient-specific implants that can be used in low-stress-bearing areas.

Keywords: Composite; Hydroxyapatite; Mechanical properties; Nano bioactive glass; Patient-specific implant; Polyetheretherketone.