Plasma Surface Functionalized Polyetheretherketone for Enhanced Osseo-Integration at Bone-Implant Interface.

This study aims at improving osseo-integration at the bone-implant interface of polyetheretherketone (PEEK) by water (H2O) and ammonia (NH3) plasma immersion ion implantation (PIII). The pertinent surface characteristics including surface energy, roughness, morphology, and chemical composition are investigated systematically and the in vitro biological performance is evaluated by cell adhesion and proliferation, alkaline phosphatase (ALP) activity, real-time RT-PCR evaluation, and mineralization tests. In vivo osseo-integration is examined via implanting samples into the distal femur of the rats. The hydrophilicity, surface roughness, cell adhesion, and proliferation, ALP activity, and osteogenic differentiation after H2O PIII or NH3 PIII are improved significantly. Furthermore, substantially enhanced osseo-integration is achieved in vivo. Nonline-of-sight plasma surface functionalization, which is particularly suitable for biomedical implants with an irregular geometry, does not alter the bulk compressive yield strength and elastic modulus of the materials. Consequently, the favorable bulk attributes of PEEK are preserved while the surface biological properties are enhanced thus boding well for wider orthopedic application of the biopolymer.

Cytocompatibility, osseointegration, and bioactivity of three-dimensional porous and nanostructured network on polyetheretherketone.

Porous biomaterials with the proper three-dimensional (3D) surface network can enhance biological functionalities especially in tissue engineering, but it has been difficult to accomplish this on an important biopolymer, polyetheretherketone (PEEK), due to its inherent chemical inertness. In this study, a 3D porous and nanostructured network with bio-functional groups is produced on PEEK by sulfonation and subsequent water immersion. Two kinds of sulfonation-treated PEEK (SPEEK) samples, SPEEK-W (water immersion and rinsing after sulfonation) and SPEEK-WA (SPEEK-W with further acetone rinsing) are prepared. The surface characteristics, in vitro cellular behavior, in vivo osseointegration, and apatite-forming ability are systematically investigated by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, cell adhesion and cell proliferation assay, real-time RT-PCR analysis, micro-CT evaluation, push-out tests, and immersion tests. SPEEK-WA induces pre-osteoblast functions including initial cell adhesion, proliferation, and osteogenic differentiation in vitro as well as substantially enhanced osseointegration and bone-implant bonding strength in vivo and apatite-forming ability. Although SPEEK-W has a similar surface morphology and chemical composition as SPEEK-WA, its cytocompatibility is inferior due to residual sulfuric acid. Our results reveal that the pre-osteoblast functions, bone growth, and apatite formation on the SPEEK surfaces are affected by many factors, including positive effects introduced by the 3D porous structure and SO3H groups as well as negative ones due to the low pH environment. Surface functionalization broadens the use of PEEK in orthopedic implants.