Construction of a nanofiber network within 3D printed scaffolds for vascularized bone regeneration

Three-dimensional (3D) printed scaffolds provide a promising prospective for application in bone tissue engineering. 3D printed scaffolds with micro- and nano-fibrous structures that facilitate cell adhesion and migration, and combined vascularization and osteoinduction bioactivity will be ideal implants for bone defect repair. Here, we fabricated a 3D printed biodegradable poly (glycerol-co-sebacic acid-co-l-lactic acid-co-polyethylene glycol) (PGSLP)-based scaffold that was internally filled with gelatin nanofibers and allowed the local release of deferoxamine (DFO), which is essential for angiogenesis and osteogenesis in bone regeneration. The nanofibrous structured gelatin/PGSLP (NGP) scaffold was fabricated using a thermally induced phase separation (TIPS) technique, and the macroporous structured gelatin/PGSLP (MGP) scaffold was prepared by directly freeze-drying. The in vitro experiments demonstrated that both DFO-loaded NGP and DFO-loaded MGP scaffolds can promote the migration and tubular formation of human umbilical vein endothelial cells (HUVECs), and enhance the mineralized nodule formation and osteogenic-related gene expression during osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). In a rat critical-sized calvarial defect model, the results suggested that the scaffolds with DFO loading significantly promote the vascular formation and accelerate bone regeneration, while the enhancement of vascularization and osteogenesis in vivo in DFO-loaded NGP scaffold was better than that in DFO-loaded MGP scaffold. Therefore, the constructed PGLSP-based scaffolds with micro- and nano-fibrous structures would be promising candidates to match the structural and functional requirements for vascularized bone regeneration.