Online Resource Captions
Online Resource 1 Compositions of polyacrylamidegels with different Young’s moduli
Online Resource 2 The Young’s moduli of polyacrylamide (PAM) gels depends on the ratio of monomers in solution and the %volume total monomers. At least 3 experiments were run for each gel stiffness, error bars are standard deviations, as shown in Online Resource 1, and are too small to be visualized
Online Resource 3Total traction force and strain energies applied by single cells (each line is the time-dependence of a single cell) during the adhesion experiment, every one hour during 0.5-6.5 hours following seeding. The metastatic breast cancer cells (a, d) high metastatic potential cells, MDA-MB-231 and (b, e) low metastatic potential cells, MDA-MB-468 exhibit large biological variability in time and magnitude of force application. (c, f) The benign cells, MCF10A, apply more uniform and smaller forces and strain energies as compared to the metastatic cancer cells
Online Resource 4Local force maxima approach to normalize phenomenon occurring at different times in cells. (a) An example of single cells exhibiting 2 (green, bottom) and 3 (blue, top) local maxima of forces during the observation period of the cell adhesion experiment. (b) Normalized cell counts for every number of local force maxima. The local force maxima were counted within the experiment time-period for every cell line separately for high MP (MDA-MB-231, green), low MP (MDA-MB-468, red), and benign (MCF10A, blue) cells. The distribution of cell counts is independent of cell type and there is no significant difference in the number of cells for each number of local maxima, making it an independent parameter that can be used instead of time
Online Resource 5Schematic representation of the physical meaning of the eccentricity and the circularity as applied to describe cell morphology
Online Resource 6 Average of peak, strain energy applied at local energy maxima, correlated with time after seeding; low numbers are short times. The strain energy amplitudes on all gel stiffnesses decrease with time. Only cells that applied measurable strain energies during at least 5 time-points out of the total of 7 experimental time-points were included, and all cells exhibited 3 local strain energy maxima during the experiment time. (a) The cells apply the same amplitude of strain energies on the soft gel (2.4 kPa). (b, d) Low MP cells apply larger strain energies than high MP and both apply more strain energies than benign cells (c) high MP cells apply the highest strain energies. Error bars are standard errors
Online Resource 7The change in traction force is associated with cell area and time, as indicated through the local force maxima normalization; the numbers 1, 2, 3 indicate the corresponding local force maxima. (a) No significant difference between cells on the soft gel. (b) low MP (MDA-MB-468) cells apply higher forces and have the largest adhesion area on this gel. Both high and low MP cells apply less force as the area increases, while the benign cells do not change the force amplitude or their area. (c-d) All cells decrease the applied force when increasing their area. Benign cells apply significantly lower traction forces on all evaluated gels (p < 0.05). Error bars are standard errors
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