Strategy to improve endogenous bone regeneration of 3D-printed PCL/nano-HA composite scaffold: Collagen designs with BMP-2 and FGF-2

In bone tissue engineering, the endogenous regeneration of bone defects still represents a clinical challenge despite the development of intervention therapy to achieve bone regeneration via autologous grafts, allogeneic grafts, bone morphogenetic protein (BMP)-2, etc. To overcome the limitation of endogenous bone regeneration, we assumed that the 3D-printed collagen pattern with BMP-2 and fibroblast growth factor (FGF)-2 in the 3D-printed polycaprolactone/nano-hydroxyapatite scaffold could guide the endogenous regeneration of bone defects. Therefore, to test our hypothesis, polycaprolactone/nano-hydroxyapatite/collagen scaffolds with dual growth factors (BMP-2 and FGF-2) and various hydrogel patterns (positive, edge, and radial patterns) were fabricated at the same ratio and concentration of dual growth factors. Consequently, we revealed that the in vitro released concentrations of BMP-2 and FGF-2 were not affected by collagen patterns in the polycaprolactone/nano-hydroxyapatite scaffold. Furthermore, endogenous bone regeneration and angiogenesis in the polycaprolactone/nano-hydroxyapatite/collagen scaffold with a radial pattern were promoted compared with those in the polycaprolactone/nano-hydroxyapatite/collagen scaffolds with positive and edge patterns. Therefore, we demonstrated that a collagen design loaded with dual growth factors in the 3D-printed scaffold could affect endogenous bone regeneration and angiogenesis.