Modelling a Human Blood-Brain Barrier Co-Culture Using an Ultrathin Silicon Nitride Membrane-Based Microfluidic Device

Abstract: Understanding the vesicular trafficking of receptors and receptor ligands in the brain
capillary endothelium is essential for the development of the next generations of biologics targeting
neurodegenerative diseases. Such complex biological questions are often approached by in vitro
models in combination with various techniques. Here, we present the development of a stem
cell-based human in vitro blood-brain barrier model composed of induced brain microvascular
endothelial cells (iBMECs) on the modular SiM (a microdevice featuring a silicon nitride membrane)
platform. The SiM was equipped with a 100 nm thick nanoporous silicon nitride membrane
with glass-like imaging quality that allowed the use of high-resolution in situ imaging to study
the intracellular trafficking. As a proof-of-concept experiment, we investigated the trafficking of
two monoclonal antibodies (mAb): an anti-human transferrin receptor mAb (15G11) and an antibasigin
mAb (#52) using the SiM-iBMEC-human astrocyte model. Our results demonstrated effective
endothelial uptake of the selected antibodies; however, no significant transcytosis was observed
when the barrier was tight. In contrast, when the iBMECs did not form a confluent barrier on the
SiM, the antibodies accumulated inside both the iBMECs and astrocytes, demonstrating that the
cells have an active endocytic and subcellular sorting machinery and that the SiM itself does not
hinder antibody transport. In conclusion, our SiM-iBMEC-human astrocyte model provides a tight
barrier with endothelial-like cells, which can be used for high-resolution in situ imaging and for
studying receptor-mediated transport and transcytosis in a physiological barrier.