Surface modification of PEEK for improving osteocompatibility

Abstract

Event Abstract Back to Event Surface modification of PEEK for improving osteocompatibility Shun Kunomura1* and Yasuhiko Iwasaki2, 3* 1 Kansai university, Graduate School of Science and Engineering, Japan 2 Kansai university, Faculty of Chemistry, Materials and Bioengineering, Japan 3 Kansai university, ORDIST, Japan Introduction: Currently, metallic implants such as titanium alloys and cobalt-chromium alloy are used in cementless total hip arthroplasty. Metallic implants have excellent strength and toughness and are effective as osteocompatibility materials. However, they have been known to cause complications such as transient osteoporosis of the hip results from stress shielding, metal allergy and fatigue fracture. To prevent them, polyetheretherketone (PEEK) is employed, which has excellent mechanical properties and durability. Although bone fixation devices of PEEK showed high performance, osteocompatibility of the surface is not sufficient. In order to apply PEEK for the stem of an artificial hip joint, osteocompatibility should be added. We have clarified that poly (ethylene sodium phosphate) shows the high affinity to calcium deposits generated from osteoblasts [1]. Moreover, Yang et al. reported that functions of osteoblasts were promoted on polyphosphoesters [2]. In this study, we modified the poly (ethylene sodium phosphate) on PEEK surface by self-initiated graft polymerization to improve osteocompatibility of the surface. Materials and Methods: Poly (ethylene sodium phosphate) macromonomers (PEPMA·Na) were synthesized according to a previously described method [1]. PEEK specimens were soaked in PEPMA·Na solution, kept 40°C over night to evaporate the solvent, and irradiated UV-light for several periods. PEPMA·Na immobilized PEEK (PEP-PEEK) was performed by water contact angle measurements and X-ray photoelectron spectroscopy. MC3T3-E1 cells were used to investigate the interaction between cells and the PEP-PEEK. Moreover, the specimens were soaked in the simulated body fluid (SBF) to evaluate apatite-forming ability on the surface [3]. Results: Fig. 1 shows the XPS data for PEP-PEEK surfaces and the phosphorus composition increased with an increase in the UV-irradiation time. The surface wettability of PEEK is also significantly improved by the surface modification. Although the cell adhesion of the PEP-PEEK surface was lower than the original PEEK surface, the proliferation of the adherent cells was observed. The calcium deposition on PEP-PEEK surface was preferentially occurred compare with that on the original PEEK surface as shown in Fig .2. Discussion: The enhancement of surface wettability and phosphorus composition suggests immobilization of PEPMA·Na on PEEK surface. The low cell adhesion of PEP-PEEK surface would be due to the high wettability of PEPMA·Na reduced cell adhesion. The previous literature reported that apatite-forming ability correlated with osseointegration [3]. Therefore, PEP-PEEK surface which induces calcium deposition may have osteocompatibility. Conclusion: PEPMA·Na was synthesized, and modified on the surface of PEEK by UV-irradiation. Although cell adhesion of the PEP-PEEK surface was reduced, proliferation of the adherent cells was observed. And the surface modification could significantly enhance the calcium deposition. Therefore, the PEPMA·Na-immobilization on PEEK would be useful way for improving osteocompatibility. A part of this work was supported by AMED Strategic Promotion of Innovative Research and Development