Abstract

Increasing Complexity of a Brain-on-a-Chip Device and Associated Neuronal Cultures

David Soscia, Postdoctoral Researcher, Lawrence Livermore National Laboratory

An in vitro brain-on-a-chip platform utilizing multi-electrode arrays (MEA) holds promise as a noninvasive experimental approach for evaluating toxicity of chemicals, validating new pharmaceutical drugs, and understanding neurological disease in humans.  Often, these devices contain a monolayer of a single purified primary neuronal cell type.  While these primary cultures can provide key insights into neuronal response and function, they fail to recapitulate in vivo cellular and molecular complexity as they lack representation and organization from multiple brain regions, as well as supporting glia.  Here, we present developments toward a more intricate in vitro system through advanced engineering and increased biological complexity.  A novel, removable cell seeding insert was developed to deposit neurons from different brain regions into separate regions of a substrate without the use of permanent physical barriers or chemical surface modifications.  Using the insert, we deposited primary rat cortical and hippocampal neurons into distinct regions of a custom 60-channel MEA.  Electrophysiology measurements were compared between the two systems over several weeks in vitro.  For the regionalized cell cultures, electrophysiology measurements demonstrated that while key firing characteristics were preserved for each neuronal type, some burst features were altered when the cells were co-cultured and able to form direct connections.  Separately, we evaluated the cellular activity of primary rat neuronal cultures cultured on the MEA containing additional supporting glial cell types (e.g., astrocytes and oligodendrocytes). For cultures containing glial cells, significant differences in electrophysiology responses were observed as cell culture complexity increased, including an earlier firing response and increased burst rate. Immunocytochemistry was used to identify each cell type, evaluate cell morphology, and assess the phenotypic state of supporting oligodendrocytes and astrocytes. These results suggest that a more complex brain-on-a-chip platform may provide additional insight and relevance to the in vitro brain model and will be validated using chemical challenges. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 through LDRD award 17-SI-002.