Multiplexed Blood-Brain Barrier Organ-on-Chip

Organ-on-chip devices are thoroughly studied in academia and industry due to their high potential in pharmaceutical and biomedical applications. However, most of the existing organ-on-chip models focus on proof of concept of individual functional units without the possibility of testing multiple experimental stimuli in parallel. Here we developed a multiplexed chip with eight parallel channels branching from a common access port via which, all eight channels can be addressed simultaneously without the need for extra pipetting steps thus increasing the reproducibility of the experimental results. At the same time, eight outlets provide individual entry to each channel with the opportunity to create eight different experimental conditions. A multiplexed chip can be assembled as a one-layer device for studying monocultures or as a two-layer device with two compartments for studying barrier tissue functions. For a two-layer device, a ~2 µm thick transparent PDMS membrane with 5 µm through-hole size was fabricated in-house using a soft lithography technique, thereby allowing visual inspection of the cell-culture in real-time. The functionality of the chip was studied by recapitulating the blood-brain barrier function. Brain endothelial cells were cultured in mono- or coculture with human astrocytes. Immunostaining revealed ZO-1 and VE-cadherin expression in endothelial cells as well as GFAP expression in astrocytes. Furthermore, multiplexed permeability studies through the cellular barrier showed expected higher permeability coefficients for smaller molecules (4 kDa FITC-Dextran) whereas larger molecules (20 kDa) crossed the barrier at a lower rate. With these results, we show that it can be used as an organ-on-chip model for future multiplexed drug testing.