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 Fe3O4 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 Fe3O4 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.