Control normalized percent viability. 2D cell populations of monotypic MDA-MB-231, fibroblast, and coculture populations are exposed to 25 mM Gd-DTPA for 3 and 24 hours. A 25 mM Gd-DTPA concentration does not influence the cell viability of (a) monotypic MDA-MB-231 and coculture cell populations composed of (b) 12.5%, (c) 25%, and (d) 50% fibroblast cells at 3 and 24 hours and (e) monotypic fibroblast cell populations at 3 hours. However, at 24 hours of exposure to 25 mM Gd-DTPA, the control percent viability for monotypic fibroblast cell populations decreases (∗).