Figure 2.

Three major liquid-based methods of culture of cancer cell spheroids are shown (a) Rotary wall vessel and spinner flask systems use rotary devices to constantly keep cells in suspension to aggregate into spheroids of random size. (b) Hanging drop array method uses gravitational-mediated aggregation of cells at the apex region of drops hanging from a plate containing through-holes and micro-rings to result in one spheroid per drop. (c) Aqueous two-phase system (ATPS) method uses two immiscible polymeric aqueous phases, where cancer cells are confined in the drop phase surrounded by the immiscible immersion phase. Cells spontaneously aggregate to form a compact spheroid of well-defined size. Panel a is reproduced from Molecular & Cancer Therapeutics 2007;6:2505–14. (A color version of this figure is available in the online journal.)