Cellular ATP of monotypic and coculture 3D cellular structures. Measurements are made from the time of formation until 336 hours for monotypic and cocultured 3D cellular structures (a) printed with magnetic assistance and (b) formed through gravitational settling. For monotypic and cocultured 3D structures (a) printed with magnetic assistance, cellular ATP does not change significantly within experimental error. Monotypic MDA-MB-231 and cocultures for structures (b) formed under the influence of gravity alone have a minimum cellular ATP level at 72 hours and monotypic fibroblast cellular structures at 216 hours. The legend in (a) applies to panel (b).