Magnetically actuated bone scaffold: Microstructure, cell response and osteogenesis

Most of the existing scaffolds do not provide physical stimulation to cells in scaffold-guided bone regeneration. In this work, a superparamagnetic scaffold was fabricated using selective laser sintering with polyglycolic acid as matrix and Fe 3 O 4 nanoparticles as internal magnetic source. Additionally, a self-developed external static magnetic field (SMF) was used to provide external magnetic source. In this case, the magnetic moment of the Fe 3 O 4 nanoparticles rearranged along the direction of SMF, thereby generating a locally enhanced magnetic field. The enhanced magnetic field might directly stimulate cell surface receptors and activate downstream signaling pathways. As a consequence, the human umbilical cord-derived mesenchymal stem cells cultivated in the scaffold exhibited significantly enhanced gene expression of alkaline phosphatase , osteocalcin, type I collagen and runt-related transcription factor-2. In vivo tests revealed that the bone regeneration was accelerated with bone mineral density (with SMF: 515 ± 50 mg/cc, without SMF: 326 ± 15 mg/cc), percentage of bone volume/tissue volume (with SMF: 92 ± 3.5%, without SMF: 73 ± 5.2%) and new bone area fraction (with SMF: 86 ± 2.2%, without SMF: 70 ± 1.6%) after 8 weeks' implantation. The biodistribution and serum biochemistry analysis demonstrated that superparamagnetic scaffold possessed favorable biosafety.