Microfabricated Brain Organ-On-A-Chip Systems for Neurophysiological Studies

Neurological diseases are a major challenge to reach new therapies. However, physiological signals that regulate neurodegeneration in the central nervous system (CNS) are still little known since there is no suitable in vitro model for studying the basis of localized cells and molecules. Here this dissertation presents the development of biomimetic microsystems that reconstitute neurophysiologically important functional brain and neurovascular interface in the CNS. The brain organs-on-chips can recapitulate pharmacological responses and complex interactions between different types of cells that are mediated by the extracellular matrix and intercellular junctions within the organ model. Since the developed microsystems have a biomimetic tissue structure, it is possible to more accurately function and simulate the delivery and penetration of the drug compound in vivo than the 2D cell monolayer in the conventional culture model or the prior microfluidics. The developed brain chip is composed of four culture chambers with 10 aggregate traps and multi-electrode arrays enable electrical stimulation for 40 neuronal aggregates as well as drug stimulation. Uniform 150 μm aggregates from the microwell can be cultured for 4 weeks. This system developed for the study of CNS myelin formation showed that the 10Hz of electrical stimulation for the promotion of myelination was successfully confirmed with 500 nM retinoic acid treatment results in the automatic image analysis. iii The other developed blood-brain barrier (BBB) chip consists of 4 × 4 microfluidic channel arrays and 16 channel multi-electrode arrays, able to electrically analyze 16 sites. Co-culture BBB-on-a-chip contains neurovascular endothelium separated from primary astrocyte by a porous membrane that allows cell-cell interactions through the membrane. In this platform, the effects of astrocyte-coculture, extracellular matrix, and in vivo shear stress level on barrier permeability were characterized through TEER measurements and dextran permeability assays. Also, despite the presence of BBB, monocyte infiltration into the CNS was observed by monocyte chemotactic protein (CCL2), which corresponds to the early event of brain injury. Finally, the system developed to address these pharmacological problems for drug development showed how drugs work in brain vessels (histamine) and brain tissues (tetrodotoxin), as well as delivering drugs from brain vessels to brain tissue (atenolol)