Immobilization via polydopamine of dual growth factors on polyetheretherketone: improvement of cell adhesion, proliferation, and osteo-differentiation

Polyetheretherketone (PEEK) is a promising biomedical material for orthopedic and dental applications owing to its excellent mechanical properties, near absence of immune toxicity, and X-radiolucency but suffers from bioinertness and inferior osteo-conduction. Surface modification of PEEK can effectively overcome these problems, while retaining most of its advantageous properties. In this study, the dual growth factors IGF-1 and BMP-2 were immobilized onto the porous surface of PEEK materials using polydopamine (pDA) coating to construct a bioactive interface. The surface characteristics of modified PEEK were evaluated by scanning electron microscopy and X-ray photoelectron spectroscopy. The pore size, generally distributed between 0.24 and 0.74 µm, was evaluated using ImageJ software. Hydrophilicity and BSA protein adsorption capacity were significantly enhanced after pDA coating. IGF-1 and BMP-2 were successfully immobilized onto the porous surface via pDA coating, and the immobilization efficiency was determined by ELISA. In vitro, samples treated with 50 ng/ml IGF-1 and 50 ng/ml BMP-2 showed better cytocompatibility for cell proliferation. The in vitro studies revealed that PEEK immobilized with dual growth factors could significantly improve cell attachment, spreading, proliferation, extracellular matrix secretion, alkaline phosphatase activity, and mineralization of MC3T3-E1 cells.