Figure 2.

Antibody diffusion. MCF7 cells were labeled with cell tracker green and grown as 1000 cells/spheroids. MCF7 spheroids were embedded in a collagen hydrogel within the microdevices. After 24 hours in culture, a fluorescent antibody (anti-EpCAM) was perfused through one of the lateral lumens to study antibody penetration. (a) In the absence of the MCF7 sphere, the antibody penetrated through the matrix and after 4 hours the diffusion profile exhibited an evident linear gradient. (b) When the MCF7 spheroid was present, the antibody attached to the spheroid periphery. (c) the presence of endothelial cells coating the lumen wall delayed the antibody penetration. (d) Higher magnification of the condition shown in (b). Penetration of the antibody within the spheroid was much slower compared with its diffusion through the hydrogel. After 1 day, the antibody remained at the periphery of the sphere and even after 3 days the core was not labeled. MCF7 cells in the spheroid were stained with cell tracker green to discard light scattering was completely blocking the light coming from the spheroid core. (e) Graphs show the diffusion profile across the delimited region (yellow rectangle). (f) MCF7 spheroids were stained with the fluorescent lipid DiD and labelled with the antibody (anti-EpCAM in red) for 3 days. Confocal images at higher magnification revealed after 3 days some cells had internalized the antibody in intracellular vesicles.