RhBMP-2 immobilized on poly(phthalazinone ether nitrile ketone) via chemical and physical modification for promoting in vitro osteogenic differentiation

[Display omitted] •Poly(phthalazinone ether nitrile ketone) is first used as biomaterials.•RhBMP-2 increases the surface energy of Poly(phthalazinone ether nitrile ketone).•RhBMP-2 loading efficiency improved by covalent immobilization.•The osteogenic activity of the specimens enhanced by rhBMP-2 immobilization.•The biocompatibility improved by rhBMP-2 immobilization via heparin binding. Poly(ether ether ketone) (PEEK) is a polyaryletherketone commonly used for bone implants, but it is difficult to modify the PEEK surface. Conversely, poly(phthalazinone ether nitrile ketone) (PPENK) is a polyaryletherketone whose surface can be modified by using chemical reactions owing to its cyano group. In this paper, two types of materials, P-BMP-2 and PH-BMP-2, were prepared by covalent immobilization and heparin binding of rhBMP-2 respectively to enhance the osteogenic activity of PPENK. X-ray photoelectron spectroscopy and water contact-angle measurement were used to demonstrate the hydrolysis of the cyano groups on PPENK, amine group grafting and immobilization of rhBMP-2. Immunohistochemical staining and evaluation of loading and release behaviour were used to demonstrate the existence of rhBMP-2 on PPENK surfaces. The biological activity of MC3T3-E1 preosteoblast cells on the samples were evaluated using cell adhesion, viability and proliferation tests. The genetic expression of genes associated with osteogenic activity was assessed by reverse transcription polymerase chain reaction. Based on the obtained in vitro experimental results, both P-BMP-2 and PH-BMP-2 exhibit good cytocompatibility and promote differentiation of MC3T3-E1 preosteoblast cells. In particular, the favourable biocompatibility can be obtained using the heparin-binding method.