Technique for the control of spheroid diameter using microfabricated chips

This paper describes a new technique for the control of spheroid diameter in liver-derived cell lines using microfabricated chips that were prepared by combining microfabrication with chemical surface modification. The chip possesses multicavities in a triangular arrangement in the central region (10 mm x 10 mm) of a polymethylmethacrylate (PMMA) plate (24 mm x 24 mm), and the surface of the chip was modified with polyethylene glycol, thereby producing a surface that is non-adhesive to cells. HepG2 cells, a model liver-derived cell line, inoculated onto the chip were trapped within each cavity and proliferated to gradually form spheroids with smooth surfaces and high circularity. Although the spheroid diameters increased with cell proliferation during the initial 10 days of culture, they remained constant thereafter. The spheroid diameters were dependent on the scales of the multicavities on the chip, and the spheroid configuration with uniform diameter was maintained for at least 1 month. In particular, it was demonstrated using chips of various designs that the cavity diameter and the pitch between cavities were effective factors in controlling the spheroid diameter. Furthermore, the protein secretion activities of the spheroid formed on the chip were higher than those of the monolayers for at least 1 month of culture. These results indicate that this chip is a useful technique for the control of spheroid diameter and for the mass preparation of uniform spheroids.