Fig. 2.

Breast tumor ECM mimetic stiffness array. (a) 96 well PA hydrogel stiffness arrays encumbering the mechanical profile of primary tumor ECM. Here, stiffness is systematically increased across the plate, with untreated glass included as a rigid control (moduli ≈10⁵ MPa). To prepare the multi-well array, glass bottom plates are chemically treated (red) to covalently attach PA gels formed in each well (purple). Functionalization of the gel surface with fibronectin (orange) allows for attachment of seeded cells. (b) Stiffness array gels were prepared with elastic moduli values that matched the rigidity profile of primary mammary tumor ECM (5 to 60 kPa) by controlling the weight percent of bis-acrylamide (bis) crosslinker added to the polymer solution (n = 3). (c) Representative immnofluorescent image demonstrating homogenous display of covalently linked fibronectin (red) on the gel surface (scale bar = 400 m). Associated z-stacks confirm protein coating is limited to the top of the gels. (d) Proliferation of primary mammary tumor cells isolated from MMTV-PYMT mice on 5 to 30 kPa PA gels, as measured by cell nuclei counting (n = 3). (e) Cell spreading as a function of substrate stiffness for primary tumor cells (1° tumor) or the human breast cancer cell li ne MCF-7 (n = 30). Error bars represent one standard deviation