Fig. 3

a Schematic illustration of bridging deferoxamine (DFO) on the surface of 3D printed polycaprolactone (PCL) scaffold and its biological function for bone regeneration. i) Upper panel: Diagram showing the preparation process of PCL-DFO scaffolds including surface aminolysis and layer-by-layer assembly with oppositely charged carboxymethyl chitosan (CCS). Lower panel: Four scaffolds were used in animal study including the pure PCL, their intermediate product PCL-NH₂, and the final product PCL-DFO. ii) The chemical molecular structure of DFO (left) and CCS (right). iii) Schematic illustration showing the effect of PCL-DFO scaffold on angiogenesis and osteogenesis at the bone defect site. iv) The cellular mechanism of promoting bone regeneration by DFO in mesenchymal stem cells (MSCs) and in vascular endothelia cells (ECs). b Micro-CT analysis of the effect of scaffolds on bone repair in vivo. The identified scaffolds (polycaprolactone (PCL), aminated PCL (PCH) and deferoxamine-loaded PCL (PCD) were implanted into the femur defect of rats, and rats without scaffolds were used as control (CON). c Representative two-dimensional micro-CT images (i) and three-dimensional reconstructed micro-CT images (ii) showing the effect of different scaffolds on the new bone tissue formation inside the defect site. The bone defect area was circled by dot line (red).