Recombinant human BMP-7 grafted poly(lactide-co-glycolide)/hydroxyapatite scaffolds via polydopamine for enhanced calvarial repair

Poly(lactic-co-glycolic acid) (PLGA) and hydroxyapatite (HA) are considered potential osteoinductive materials because of their biodegradability and mineralization features. However, the hydrophobicity of scaffold surfaces is less supportive of cell attachment and proliferation because of poor wettability. The mode of binding of growth factors to the scaffold also affects cell differentiation into osteoblasts. The half-life of a growth factor in vivo can be increased by binding the factor to the scaffold surface. In this work, we prepared a porous PLGA/HA scaffold grafted with recombinant human bone morphogenic protein-7 (rhBMP-7) attached via polydopamine (pDA) for bone repair. The pDA coated PLGA/HA (pDA-PLGA/HA) scaffolds were characterized by energy dispersive X-ray analysis and Fourier-transform infrared spectroscopy. The microstructure and porosity of PLGA/HA scaffolds were analyzed by scanning electron microscopy and micro-computed tomography. The release profile of rhBMP-7 grafted onto the pDA-PLGA/HA (pDA-PLGA/HA/BMP-7) scaffolds was examined for 21 days. The attachment efficiency, cell proliferation rate, alkaline phosphatase activity, calcium deposition, and osteoblast-related gene expression of bone marrow-derived stem cells to PLGA/HA, pDA-PLGA/HA, and pDA-PLGA/HA/BMP-7 scaffolds were evaluated. To assess the ability of bone repair in vivo, scaffolds were implanted into critical-sized calvarial defects created in mice, and the in vivo tissue-engineered bone was monitored by micro-computed tomography and histology. In vivo experiments revealed rapid healing of the defects treated with the pDA-PLGA/HA/BMP-7 scaffolds compared with pDA-PLGA/HA and PLGA/HA scaffolds at week 8 post-surgery. These results collectively demonstrate that the rhBMP-7-immobilized PLGA/HA scaffold via pDA is a promising candidate for calvarial repair.