Magnetically Controlled Growth-Factor-Immobilized Multilayer Cell Sheets for Complex Tissue Regeneration.

The scaffold-free cell-sheet technique plays a significant role in stem-cell-based regeneration. Furthermore, growth factors are known to direct stem cell differentiation and enhance tissue regeneration. However, the absence of an effective means to incorporate growth factors into the cell sheets hinders further optimization of the regeneration efficiency. Here, a novel design of magnetically controlled "growth-factor-immobilized cell sheets" is reported. A new Fe3 O4 magnetic nanoparticle (MNP) coated with nanoscale graphene oxide (nGO@Fe3 O4 ) is developed to label stem cells and deliver growth factors. First, the nGO@Fe3 O4 MNPs can be easily swallowed by dental-pulp stem cells (DPSCs) and have no influence on cell viability. Thus, the MNP-labeled cells can be organized via magnetic force to form multilayered cell sheets in different patterns. Second, compared to traditional Fe3 O4 nanoparticles, the graphene oxide coating provides plenty of carboxyl groups to bind and deliver growth factors. Therefore, with these nGO@Fe3 O4 MNPs, bone-morphogenetic-protein-2 (BMP2) is successfully incorporated into the DPSCs sheets to induce more bone formation. Furthermore, an integrated osteochondral complex is also constructed using a combination of DPSCs/TGFβ3 and DPSCs/BMP2. All these results demonstrate that the new cell-sheet tissue-engineering approach exhibits promising potential for future use in regenerative medicine.