Three-dimensional reflectance traction microscopy reveals the traction field of breast cancer cells in 3D collagen matrix.

<p>(A-D) The strain magnitude <i>ε</i> and deformation field <b>D</b> measured around four isolated MDA-MB-231 cells before and after the cells are treated with cytochalsin-D. <i>ε</i> of orthogonal cross-sections are shown as color maps. <b>D</b> projected on to these cross-sections are shown as arrows. The cell surfaces (illuminated red surfaces) are reconstructed from isosurface rendering of fluorescently labeled cytoplasms. The arrows are color coded by the magnitude of the projected deformation fields. (A) and (B) demonstrate deformation and strain fields around cells with rounded morphology. (C) and (D) show the results around cells with larger aspect ratios.