3D printed scaffolds with multistage osteogenic activity for bone defect repair.

The bone defect repair is a complex process including immune regulation, stem cell osteogenic differentiation and extracellular matrix mineralization. Current bone tissue engineering approaches often fail to adapt throughout the above osteogenic process, resulting in suboptimal repair outcomes. To address this problem, a 3D-printed scaffold with multistage osteogenic activity based on shape-memory elastomer and electroactive material is developed. The scaffold exhibits excellent shape memory performance and can trigger shape recovery by physiological temperature. The physiological temperature-triggered shape-memory behavior makes the scaffold promising for minimally invasive implantation. After electric field polarization, the scaffold's surface carries the negative charge, which can activate the PI3K/Akt signaling pathway to promote the polarization of macrophages to M2 phenotype and activate the FAK/ERK signaling pathway to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), indicating that the scaffold can effectively participate in immune microenvironment regulation and stem cell osteogenic differentiation. Additionally, the negative charge on the scaffold's surface can attract calcium and phosphate ions, forming a mineralized matrix and promoting late-stage extracellular matrix mineralization by continuously supplying mineralizing ions such as calcium and phosphate. Overall, this study introduces a 3D-printed scaffold with multistage osteogenic activity, offering a promising strategy for bone defect repair.