Construction of nanofibrous scaffolds with interconnected perfusable microchannel networks for engineering of vascularized bone tissue

Vascularization and bone regeneration are two closely related processes during bone reconstruction. A three-dimensional (3D) scaffold with porous architecture provides a suitable microenvironment for vascular growth and bone formation. Here, we present a simple and general strategy to construct a nanofibrous poly(l-lactide)/poly(ε-caprolactone) (PLLA/PCL) scaffold with interconnected perfusable microchannel networks (IPMs) based on 3D printing technology by combining the phase separation and sacrificial template methods. The regular and customizable microchannel patterns within the scaffolds (spacings: 0.4 mm, 0.5 mm, and 0.6 mm; diameters: 0.8 mm, 1 mm, and 1.2 mm) were made to investigate the effect of microchannel structure on angiogenesis and osteogenesis. The results of subcutaneous embedding experiment showed that 0.5/0.8-IPMs (spacing/diameter = 0.5/0.8) and 0.5/1-IPMs (spacing/diameter = 0.5/1) scaffolds exhibited more vascular network formation as compared with other counterparts. After loading with vascular endothelial growth factor (VEGF), VEGF@IPMs-0.5/0.8 scaffold prompted better human umbilical vein endothelial cells (HUVECs) migration and neo-blood vessel formation, as determined by Transwell migration, scratch wound healing, and chorioallantoic membrane (CAM) assays. Furthermore, the microangiography and rat cranial bone defects experiments demonstrated that VEGF@IPMs-0.5/0.8 scaffold exhibited better performance in vascular network formation and new bone formation compared to VEGF@IPMs-0.5/1 scaffold. In summary, our results suggested that the microchannel structure within the scaffolds could be tailored by an adjustable caramel-based template strategy, and the combination of interconnected perfusion microchannel networks and angiogenic factors could significantly enhance vascularization and bone regeneration.