Recreating the in vivo FeCl₃ model in a microfluidic platform. (A) Schematic of FeCl₃ application (not to scale) in which a saturated 1 M FeCl₃ patch is placed on the vessel adventitia. As the FeCl₃ diffuses through the layers of the vessel wall, apparent concentration decreases, and at the luminal surface of the endothelial cells, the FeCl₃ concentration is ≥50 mM. The dashed box at the luminal surface of the endothelial cells represents the location of interface of the solutions. (B) Endothelial cells are seeded in the large channel (250 μm) of a T-shaped microfluidic to recapitulate a blood vessel. FeCl₃ is infused in the side channel (50 μm) and the blood/FeCl₃ interface is visualized; shear stress 4 dyne/cm². (C) Left to right, Bare microfluidic channel, endothelialized channel, and an example of fluid interface using fluorescent dyes and infusion rates of 2.7 μL per minute in large channel and 0.4 μL per minute in side channel. The dashed box represents the fluid interface that would be seen at the vessel wall in vivo. All scale bars represent 50 μm.