The bioactive polyetheretherketone (PEEK) was fabricated by the combination of PEEK and CaO-SiO2 particles, which formed hydroxyapatite on its surfaces in simulated body fluid and showed good mechanical propeties. The study revealed osteoblast-like cell proliferation and gene expression on the bioactive PEEK. Peek and bioactive PEEK discs (24 mm in diameter and 2 mm in thickness) were prepared. Bioactive PEEk was produced by the combination of 80 vol% Peek powder and 20 vol% CaO-SiO2 particles (30CaO · 70SiO2). Discs were sterilized with ethylene oxide gas. The study was approved by the ethics committee in Chiba University. Human osteoblast-like cells were used in the study. The cells at passage 3–5 were used in the experiments. 2 × 105cells /disc were culture at 37°C in a humidified atmosphere with 5% CO2, and the media was replaced every 3 days. At days 3, 7, 21, the culture media, cells and discs were collected respectively. Cell attachment assay was performed. Cells were seeded at a density of 4 × 105 cells /well and incubated for 2 hours at 37 C in a humidified atmosphere with 5% CO2. The cells on the discs were evaluated by DNA content. The real-time PCR was performed with regard to type I collagen (COLI), osteocalcin (OC), osteonectin (ON), osteopontin (OPN), and GAPDH. The alkaline phosphatase activity (ALP) was measeured at 3, 7, and 21 days, which samples as used in the DNA-content assay. Alizalin Red Staining was performed at day 21 to quantify calcification deposits in discs. Results were analyzed using Student's The content of DNA showed similar increases on PEEK and bioactive PEEK in the course of day 3, 7, 21. The cell attachment of bioactive PEEK was two times larger than that of PEEK. Real-time PCR results of human osteoblast-like cells cultured on PEEK and bioactive PEEK discs were shown in Fig. 1. There were no significant differences between cells on PEEK and bioactive PEEK with respect to COL I and ON mRNA expression. However, human osteoblast-like cells on bioactive PEEK presented higher expression of OPN and OCN mRNA at day 21. No significant differences were found in ALP activity of both discs. Calcification deposits were observed only on bioactive PEEK at day 21Materials and Methods
Results
The osteoconductivity is the most desirable characteristic to achieve early fixation of the cementless-type artificial joints with bone. Apatite deposition on the surface of materials can induce the osteoconductivity in bony defect. In previous studies, various surface treatments have been proposed to provide titanium-based artificial joints with the osteoconductivity. The most popular surface treatment for commercial artificial joints is plasma-spray coating with apatite. Although the technique has been widely used for commercial artificial joints in the world, it remains some disadvantages attributed to high temperature during the process, such as fracture at the interface between metal and apatite, changes in the composition, crystallinity and structure of plasma-sprayed apatite. The chemical surface treatment with NaOH and H2O2 solution to provide spontaneous apatite-forming ability in the body could overcome the problems of plasma-spray process, since the treatments could be expected to not only continually express the apatite-forming ability in the body but also deposit the bone-like apatite having the similar crystal structure, crystallinity and composition of bone apatite. Therefore, surface treatments provided the spontaneous apatite-forming ability would be effective for titanium-based artificial joints with osteoconductivity. Recently, our research group developed the extremely simple technique for providing the spontaneous apatite-forming ability to titanium by both spatial design and thermal oxidation, denoted as “GRAPE technology”. Pure titanium with machined micro-groove of less than 800 μm in depth and 1000 μm in width and thermally oxidized at 400°C in air induced apatite deposition in the internal space of micro-grooves during exposure to simulated body fluid. In this study, the application possibility of GRAPE technology was examined by using Ti-6Al-4V and Ti-15Zr-4Ta-4Nb. Apatite formed on the thermally oxidized Ti-15Zr-4Ta-4Nb at 500 and 600°C with micro-groove 500 μm wide and depth in the simulated body fluid for 7 days. In contrast, no apatite formation was observed on the thermally oxidized Ti-6Al-4V at 400, 500 and 600°C with micro-groove 500 μm wide and depth in the simulated body fluid for 7 days. Okazaki et al. reported that Ti-15Zr-4Ta-4Nb shows higher corrosion resistance, mechanical properties and cytocompatibility than Ti-6Al-4V. Hence, it is expected that the Ti-15Zr-4Ta-4Nb with GRAPE technology could be innovative cement-less artificial joints to achieve early fixation through its osteoconductivity and excellent performances.
