Enhanced bioactivity and osseointegration of PEEK with accelerated neutral atom beam technology

Abstract

Polyetheretherketone (PEEK) is growing in popularity for orthopedic, spinal, and trauma applications but has potential significant limitations in use. PEEK is biocompatible, similar in elasticity to bone, and radiolucent, but is inert and therefore does not integrate well with bone. Current efforts are focusing on increasing the bioactivity of PEEK with surface modifications to improve the bone-implant interface. We used a novel Accelerated Neutral Atom Beam (ANAB) technology to enhance the bioactivity of PEEK. Human osteoblast-like cells seeded on ANAB-treated PEEK result in significantly enhanced proliferation compared with control PEEK. Cells grown on ANAB-treated PEEK increase osteogenic expression of ALPL (1.98-fold, p < 0.002), RUNX2 (3.20-fold, p < 0.002), COL1A (1.94-fold, p < 0.015), IBSP (2.78-fold, p < 0.003), and BMP2 (1.89-fold, p < 0.004). Cells grown on these treated surfaces also lead to an increased mineralization (6.4-fold at 21 days, p < 0.0005). In an ovine study, ANAB-treated PEEK implants resulted in enhanced bone-in-contact by 3.09-fold (p < 0.014), increased push-out strength (control 1959 ± 1445 kPa; ANAB 4068 ± 1197 kPa, p < 0.05), and evidence of bone ingrowth at both the early (4 weeks) and later (12 weeks) time points. Taken together, these data suggest that ANAB treatment of PEEK has the potential to enhance its bioactivity, leading to bone formation and significantly decreasing osseointegration time of orthopedic and spinal implants. ANAB treatment, therefore, may significantly enhance the performance of PEEK medical implants and lead to improved clinical outcomes. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 531-543, 2017.

Surface phosphonation treatment shows dose-dependent enhancement of the bioactivity of polyetheretherketone

“…Additionally, its radiolucency facilitates the monitoring of bony fusion during the postoperative follow-up period. 3 However, PEEK presents inferior osteogenic activity and bone-implant integration capability because of its bioinertness, 4,5 and thus its clinical applications as orthopedic and dental implants are limited.…”

Surface Modification Strategies to Improve the Osseointegration of Poly(etheretherketone) and Its Composites

“…The increase in nanoscale roughness from 1.1 to 2.0 nm and the addition of hydroxyl and carboxylic acid groups on the ANAB‐treated surfaces led to 95% and 108% increases in pull‐out strength after 4 and 12 weeks, respectively, in the tibia and femur of Dorset sheep . Bone ingrowth was also enhanced for the ANAB‐treated surfaces after 4 weeks in the Dorset sheep, and the BIC for cortical bone increased 3.1‐fold after 12 weeks compared to untreated PEEK . Similarly, in another study, H 2 O plasma‐treated PEEK with increased carbonyl groups, ripple‐like surface features, and roughness less than 20 nm resulted in enhanced osteogenic differentiation of murine pre‐OBs and bone formation around PEEK after 1 and 2 weeks in a rat femur .…”

“…All charged species are deflected with an electrostatic field before they near the surface so only neutral species can contact the surface . ANAB modifications have been used to create nanotextured PEEK surfaces with altered surface chemistry, and the depth of the treatment is limited to the top 5 nm because only neutral atoms reach the surface . ANAB can alter the surface chemistry, roughness, and wettability of PEEK.…”

“…Oxygen‐containing functional groups have also been attached to roughened PEEK to improve osseointegration. Carboxylic acid and hydroxyl groups created on nanotextured PEEK surfaces with ANAB treatment ( R a = 2 nm) caused human MSCs to significantly increase ALP activity, mineralization, and expression of osteogenic genes including Runx2, bone morphogenic protein‐2 (BMP‐2), Col1A1, and IBSP . The increase in nanoscale roughness from 1.1 to 2.0 nm and the addition of hydroxyl and carboxylic acid groups on the ANAB‐treated surfaces led to 95% and 108% increases in pull‐out strength after 4 and 12 weeks, respectively, in the tibia and femur of Dorset sheep .…”

“…Carboxylic acid and hydroxyl groups created on nanotextured PEEK surfaces with ANAB treatment ( R a = 2 nm) caused human MSCs to significantly increase ALP activity, mineralization, and expression of osteogenic genes including Runx2, bone morphogenic protein‐2 (BMP‐2), Col1A1, and IBSP . The increase in nanoscale roughness from 1.1 to 2.0 nm and the addition of hydroxyl and carboxylic acid groups on the ANAB‐treated surfaces led to 95% and 108% increases in pull‐out strength after 4 and 12 weeks, respectively, in the tibia and femur of Dorset sheep . Bone ingrowth was also enhanced for the ANAB‐treated surfaces after 4 weeks in the Dorset sheep, and the BIC for cortical bone increased 3.1‐fold after 12 weeks compared to untreated PEEK .…”