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

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.

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.

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.

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