Incorporation of BMP-2 nanoparticles on the surface of a 3D-printed hydroxyapatite scaffold using an ε-polycaprolactone polymer emulsion coating method for bone tissue engineering.

Hydroxyapatite (HAp)-based three-dimensional (3D) scaffolding is an excellent method for the fabrication of complex-shaped scaffolds to reconstruct bone defects. This study aimed at improving the osteoinductivity and compressive strength of the HAp-based 3D scaffold for bone regeneration. Bone morphogenetic protein-2-loaded nanoparticles (BMP-2/NPs) were prepared by a double emulsion-solvent evaporation method and incorporated onto the surface of 3D scaffolds using ε-polycaprolactone (PCL) and NPs emulsion solution. The surface morphology of the scaffold was characterized using scanning electron microscopy and its biocompatibility and osteogenic effects evaluated in vitro using human mesenchymal stem cells. The in vivo bone regeneration efficiency was determined using a rabbit calvarial bone defect model. We obtained 3D HAp scaffolds with NPs using PCL coating process. BMP-2/NPs were uniformly distributed on the scaffold surface and BMP-2 was gradually released. Furthermore, PCL coating improved the compressive strength of the scaffold. The cell proliferation, adhesion, and osteogenic differentiation properties were improved with PCL_BMP-2/NPs coated scaffold. In vivo experiments showed that the formation of new bone was significantly higher in the PCL_BMP-2/NPs group than in the uncoated scaffold-implanted group. The coating method using PCL and NPs emulsion solutions was useful not only to incorporate BMP-2/NPs onto the surface of the scaffold, but also to improve the compressive strength, which enhanced bone regeneration.