Figure 4. Scaffold-free tissue construction with 3D sphere architecture. (A).

Schematic illustrations of sphere-shaped scaffold-free tissue culturing using ring shaped magnets. Following a temperature change in the cultured cells, the ring shaped magnet was placed above the cell-sheet. 10 minutes after temperature reduction, the cells on TNFS began to detach and magnetically levitated before gathering at the center of the ring shaped magnet. (B) Simulation results by COMSOL Multiphysics®. When the distance between the ring shaped magnet and the work plane (cell sheet) was less than 6 mm, the magnetic field on the work plane had a central minimum and was maximized surround the ring hole. However, when the magnet was far enough from the work plane (greater than 6 mm above), the central maximum of the magnetic field was produced promoting the formation of sphere shaped tissues. (C) Picture of C2C12 cells in levitation with ring-shaped magnet for 0 and 72 hours. (D) Confocal image of C2C12 sphere after 5 days in levitation. White arrow denotes direction of cell alignment within the cell sheet. Scale bars: 200 μm in (C) and 100 μm (left) and 50 μm (right) in (D).