Characterizing the differentiation of osteoprogenitor cells on surface modified polyether-ether-ketone

The modified surface of polyether-ether-ketone (PEEK) was sequentially sulfonated, treated with silanization, fixed with glutaraldehyde, and grafted with type I collagen (COL I). Surface roughness and water contact angle measurements, scanning electron microscopy, and Fourier transform infrared spectroscopy were conducted. The viability of mouse fibroblast cells (NIH-3T3) on the modified PEEK was determined to study cytotoxicity, and bone-marrow-derived mouse pluripotent mesenchymal stem cells (D1) were cultured to evaluate the mineralization capability through cell adhesion, proliferation, and differentiation on the modified PEEK substrates. Sulfonated PEEK exhibited an evident rough surface, and the substrate was further silanized and grafted using COL I with spectroscopy absorption frequencies of carbonyl, sulfonyl hydroxide, and amide functional groups, which were incorporated to enhance the hydrophilic properties. Results showed that the substrate of PEEK modified by sulfonation, silanization, and further grafting with COL I generated a higher number of amide functional groups than all other functional groups. The D1 cell viability of each testing group increased with incubation time, but the difference was not significant. Conversely, D1 cell viability obviously decreased for a further prolonged culture period exceeding 14 days. The sulfonated PEEK substrate further treated with silanization and grafted with COL I exhibited the most remarkable performance of alkaline phosphatase (ALP) activity on the 10th day of incubation among all samples. In conclusion, we developed a sulfonated PEEK surface that was further treated with silanization, fixed with glutaraldehyde, and grafted with COL I. The modified surfaces can improve the bioinert property of PEEK through the rough and three-dimensional structures with evident hydrophilic properties for orthopedic implants.