Figure 1.

Schematic representation of the tumor-on-a-chip device (top (a) and side (b) views) consisting of a large cell culture chamber in which collagen supplemented with tumor cells is introduced. To confine the cell-laden hydrogel in the center of the device, removable filaments (cotton threads, here) were first introduced in the device, and pulled out of the device before gelation of the collagen (a & b). Culture medium with 21% O₂ was added in the two side channels during the experiments. The device was fabricated from PDMS and bonded to a glass substrate; the PDMS layer comprised a 175-μm thick PMMA film to prevent O₂ from freely diffusing into the cell culture chamber so as to be able to establish gradients of O₂ in the tumor-on-a-chip model between the perfusion channels and the center of the 3D cellular model. (c) Pictures of the fabricated device loaded with dyes (blue: Trypan blue; red: dextran labeled with fluorescein and TAMRA) before (top) or 5 min after (bottom) removing the cotton threads. On these pictures, all reservoirs have a 1.5-mm diameter.