Fig. 1: Griddient operation.

a Image of the Griddient platform, black outlines show the 32 individual microfluidic chambers underneath the platform. b, c Picture of the bottom of the Griddient platform showing the microfluidic chambers filled with food dye for visualization purposes. d Experimental protocol for the Griddient operation. 1. Cells were mixed with a type 1 rat tail collagen solution and injected into the main chamber through one of the diffusion ports. 2. Collagen polymerized for 10–15 min at room temperature. 3. When the collagen is fully polymerized, endothelial cells are seeded on top of the hydrogel interface as a monolayer. 4. After endothelial cells have been attached, media or PBS, were added to the reservoir wells. 5. The media/PBS of each well can be modified to generate or revert the desired gradients. E-G. 40 kDa FITC-Dextran and 70 kDa TR-dextran diffusion in the Griddient after 24 h in lineal (e), radial (f), or periodic (g) configuration.