Fig 1.
a) Collagen fibers aligned via microfluidic flow in a channel with 400 μm height. Insert: magnification of image marked with orange box. b) Orientation distribution of fibers in 33 gels aligned with microfluidics (mean values blue; standard error light blue) and in non-aligned gels prepared in a well (mean values red; standard error light red). Scale bars = 200 μm.
Fig 2.
Characterization of shear flow and fiber alignment around the spheroid, while the main flow direction is from top to bottom.
a) Spheroid (magenta) and aligned collagen fibers (cyan) with vectors in alignment direction (white) around the spheroid after polymerization. b) Flow trajectory of beads around a spheroid embedded in collagen during polymerization. The trajectory is the minimum projection of a time series of brightfield images. c) Velocity magnitude (color code) calculated from a particle image velocimetry measurement. d) Simulated velocity field (color code represents velocity magnitude) of the collagen mixture and the trajectory of a single collagen fiber (white bar) around the cell aggregate in the microfluidic channel. Scale bars = 200 μm.
Fig 3.
a) Microscopy images of spheroids invading into the surrounding aligned matrix over the course of 3 days. Note: the spheroid remains filled with cells, the void in the center of the spheroid is a result of image editing for better contrast in the composite with the matrix. For original images see S4 Fig. b) Mean relative invasion distance of 10 outmost cells in each direction (color-coded directions). The markers are averages of 20 aggregates. For error bars see supplementary information. c) Mean invasion distance of 10 outmost cells for different directions. The distance travelled per day in each direction is color coded in blue. Scale bars = 200 μm.
Fig 4.
Invasion and fiber alignment on upstream and downstream front.
a) Collagen fibers (cyan) and spheroid (magenta) at the upstream (red) and downstream (blue) side of the spheroid at day 0. b) Collagen fibers (cyan) and cells (magenta) at the upstream (orange) and downstream (purple) side of the spheroid at day 1. c) Position of invasion front with respect to initial spheroid surface (day 0) after 1 day and after 3 days on downstream and upstream side of 10 aggregates (*p < 0.05). d) Degree of alignment of the collagen fibers on downstream and upstream side of 10 aggregates at day 0 and day 1 (°p > 0.05, *p < 0.005). Scale bars = 200 μm.
Fig 5.
a) Overlayed images of cell invasion in the collagen gel (cyan) during the experiment (magenta) and the simulated migration of cells (white) in a similar environment over the course of 3 days. b) Invasion distance of 10 outmost cells in each direction (color-coded directions) obtained in the simulations. For error bars see supplementary information. c) Invasion distance of 10 outmost cells in different directions obtained in the simulations. The distance travelled per day in each direction is color coded in blue. Scale bars = 200 μm.