3D-printed dual-ion chronological release functional platform reconstructs neuro-vascularization network for critical-sized bone defect regeneration

Critical-sized bone defects remain an unsolved challenge because of the failure to induce early reconstruction of the neuro-vascularization network. Nerve and vascular regeneration begin immediately after the occurrence of bone defect and play a key role in the subsequent osteogenic differentiation. In this study, a 3D-printed alpha-tricalcium phosphate scaffolds with dual-ion chronological release functional platform consisted of magnesium containing gelatin microspheres and zinc-doped bioglass was designed to reconstruct neuro-vascularization network for critical-sized bone defect regeneration. Our results demonstrated that magnesium containing gelatin microspheres could regulate the release rate of Mg2+ and achieve early complete release of Mg2+. The controlled release of Mg2+ can effectively enhance the vascularization of human umbilical vein endothelial cells and the ability of nerve regeneration of PC12 cells in vitro and also avoid the potential inhibition of high con-centration of Mg2+ on bone formation in late osteogenesis. Moreover, zinc-doped bioglass ensured the long-term release of Zn2+, thereby promoting the activity and osteogenic differentiation of bone marrow mesenchymal stem cells. In rat calvarial critical-sized defect models, 3D-printed alpha-tricalcium phosphate scaffolds with dual-ion chronological release functional platform could significantly enhance neuro-vascularization network density and exhibited excellent performance in promoting new bone formation. Consequently, the 3D-printed alpha-tricalcium phosphate scaffolds with dual-ion chronological release functional platform has the potential to be used as bone grafts for repairing critical-sized bone defects and provides guidance for the design of repair materials.