Bioactive Copper-Doped Natural Hydroxyapatite Quantum Dots/Graphene Oxide Nanocomposites in 3D-Printed PCL Scaffolds for Superior Osteogenic and Angiogenic Performance in Bone Tissue Engineering

This study introduces a sustainable scaffold designed by integrating copper-doped natural hydroxyapatite quantum-dots (Cu-HA QDs) and graphene oxide (GO) into a polycaprolactone (PCL) matrix using 3D printing technology, to address the dual requirements of osteogenesis and angiogenesis in large bone defects. HR-TEM and synchrotron SAXS/WAXS investigations of the Cu-HA QDs exhibited a highly crystalline hexagonal structure with distinct QD architecture, and core-level HR-XPS analysis confirmed Cu²⁺ substitution for Ca²⁺ within the HA lattice. Incorporating Cu-HA–GO nanocomposites significantly improved the physicochemical properties of the PCL scaffolds, including enhanced wettability, accelerated hydrolytic degradation, and enhanced mechanical stiffness. Under basal culture conditions, the PCL/Cu-HA–GO scaffolds significantly promoted mesenchymal stem cell proliferation, extracellular matrix mineralization, and differentiation. Furthermore, robust expression of key osteogenic genes ALP, RUNX2, and OCN increased by 28-, 33-, and 21-fold, respectively, and angiogenic genes HIF-1α and Ang1 increased by 45- and 18-fold, respectively. Immunofluorescence staining demonstrated strong osteocalcin signals and widespread formation of CD31-positive capillary-like structures throughout the scaffold, highlighting its unique potential to enhance bone regeneration and vascularization concurrently. These results present the 3D-printed PCL/Cu-HA–GO scaffolds as a promising, sustainable, and superior dual-functional osteogenic and angiogenic performances, offering an effective alternative for large/critical-size bone defect regeneration.