Label-free ultrarapid spheroid formation in microfluidic chip using magneto-Archimedes effect

This paper demonstrates formation of a spheroid array in a microfluidic chip with neither cell labeling nor a specific microchannel pattern. Label-free ultrarapid magnetic cell manipulation is made possible by adding a paramagnetic salt to the culture medium to enhance the diamagnetic property of the cells. The cells in the paramagnetic medium aggregate ultrarapidly on an array within a microchannel by applying a magnetic field and the cell aggregates become spheroids after one day of culture. The results suggest that this cell manipulation method is a promising approach to construct micro 3D tissues in a closed small space.