Three-dimensional spheroid-forming lab-on-a-chip using micro-rotational flow

We propose a spheroid-forming lab-on-a-chip that uses micro-rotational flow to control the size of three-dimensional hepatocyte spheroids. The developed device consists of a microchamber made of polydimethylsiloxane produced by soft lithography and a perfusion system consisting of a reservoir, a dampener, a chamber, a shredder channel, and a peristaltic pump to constantly circulate cell culture medium containing human hepatocellular liver carcinoma cells. Cells are attracted to the center of the chamber, where they aggregate and form spheroids. The size of the spheroids produced by this device can be controlled by varying the cell density and the flow conditions. Thus, spheroids of various sizes can be formed without altering the chamber design. The developed perfusion system permits cultures to be stored for a long time by suppressing sudden changes in the micro-rotation flow; this ability was verified by performing a live/dead assay. Hepatic spheroids with average diameters in the range 130-430 μm and with a standard deviation of less than 17.2% were successfully produced. Their sizes were found to depend on the chamber diameter and the cell density. The standard deviation of spheroids with average diameters between 150 and 200 μm was as low as 16.0%. Micro particle image velocimetry revealed a spheroid-forming region in the chamber. It also enabled the number of cells that form a spheroid to be estimated. Crown