Tracking Cell-Induced Pillar Displacements

Cells were spreading on pillar arrays coated with fibronectin (10 μg/ml, Roche). Time lapse imaging of pillars was performed with bright-field microscopy using an Orca-flash 2.8 camera (Hamamatsu) attached to an inverted microscope (Olympus IX81) maintained at 37°C running MicroManager software (Edelstein et al., 2010 (link)). Images were recorded at 1 Hz using a ×100 objective (1.4 NA oil immersion, Olympus). Videos were processed with ImageJ (National Institutes of Health) using the Nano Tracking plugin to track the position of pillars. The time-series positions of all pillars in contact with the cell were fed into a MatLab program (MathWorks) to generate displacement maps as explained previously (Wolfenson et al., 2016 (link); Saxena et al., 2017a (link)).