Figure 4.

Paper-based invasion assays. (A) Photograph of a single-zone scaffold (left), which fits directly into a commercial 96-well plate. Schematics of a paper-based version of the Transwell assay in which invasive and nonmotile cells are separated in the presence of chemokines (top) or cocultures (bottom). Part A was adapted with permission from ref 54. Copyright 2019 The Royal Society of Chemistry. (B) Schematic of an invasion stack in which cells were separated by the distance they travel in the presence of an oxygen gradient (left). Representative data set of cell distribution throughout the stack after 48 h, quantified with a qPCR assay. Part B was adapted with permission from ref 43. Copyright 2015 American Chemical Society. (C) Schematic of channel-based invasion assay in which cellular movement along in an oxygen gradient was tracked in situ with an inverted fluorescence microscope (left). Representative image of cellular distribution in the channel (top, right) and data sets summarizing movement after 48 h (bottom, right). Part C was adapted with permission from ref 53. Copyright 2016 The Royal Society of Chemistry.