Cells were passaged twice per week in 75 cm 3 flasks. MCF-7spheroids were produced following the hanging drop method [20] in 30 µLdroplets at a cell concentration of 2 × 10 6 cells mL −1 in DMEM. Thespheroids were cultured in the hanging droplets for 7 d before harvestand being encapsulated in the hydrogels in the devices.