Effect of Gd-DTPA on cell morphology. MCF-7 cell morphologies in 0, 1, 10, 25, 50, 75, 100, and 125 mM Gd-DTPA (n=12) within 24 hours when incubated on (a) a ULA plate and (b) TCT plate. Within 6 hours, there are no apparent effects on cell morphology. At concentrations above 25 mM Gd-DTPA at 6 hours, the cell morphologies begins to differ from structures produced with 0 mM Gd-DTPA (control samples) for both ULA and TCT surfaces. In (a), as the concentration of Gd-DTPA ≥ 50 mM, the ability of cells to adhere together diminishes. Cell-cell adhesion is key for formation of a 3D structure. Similarly, in (b) concentrations of ≥ 50 mM limit intercellular attachment within 1-3 hours of exposure to Gd-DTPA. However, at 6 hours, intercellular adhesion overcomes the limiting influence of Gd-DTPA on cell-cell attachment. Therefore, to reduce harmful effects on cell morphology, exposure to Gd-DTPA should be limited to 25 mM for at most 6 hours. Scale bar = 50 μm.