A multicellular spheroid formation and extraction chip using removable cell trapping barriers

This paper presents a multicellular spheroid chip capable of forming and extracting three-dimensional (3D) spheroids using removable cell trapping barriers. Compared to the conventional macro-scale spheroid formation methods, including spinning, hanging-drop, and liquid-overlay methods, the recent micro-scale spheroid chips have the advantage of forming smaller spheroids with better uniformity. The recent micro spheroid chips, however, have difficulties in extracting the spheroids due to fixed cell trapping barriers. The present spheroid chip, having two PDMS layers, uses removable cell trapping barriers, thereby making it easy to form and extract uniform and small-sized spheroids. We have designed, fabricated and characterized a 4 x 1 spheroid chip, where membrane cell trapping barriers are inflated at a pressure of 50 kPa for spheroid formation and are deflated at zero gauge pressure for simple and safe extraction of the spheroids formed. In this experimental study, the cell suspension of non-small lung cancer cells, H1650, is supplied to the fabricated spheroid chip in the pressure range 145-155 Pa. The fabricated spheroid chips collect the cancer cells in the cell trapping regions from the cell suspension at a concentration of 2 x 10(6) ml(-1), thus forming uniform 3D spheroids with a diameter of 197.2 +/- 11.7 mu m, after 24 h incubation at 5% CO2 and 37 degrees C environment. After the removal of the cell trapping barriers, the spheroids formed were extracted through the outlet ports at a cell inlet pressure of 5 kPa. The cells in the extracted spheroids showed a viability of 80.3 +/- 7.7%. The present spheroid chip offers a simple and effective method of obtaining uniform and small-sized 3D spheroids for the next stage of cell-based biomedical research, such as gene expression analysis and spheroid inoculation in animal models.