Design, microfabrication and testing of brain-on-A-chip (boc) platform using neural organoids (spheroids)

Three-dimensional (3D) organoid engineering aims to steer cell aggregates toward physiological mimicking of human tissue and organ systems at the cellular level, essentially serving as tissue and organ proxies that recapitulate biological parameters (e.g., spatial organization of heterogenous tissue-specific cells, cell-cell interactions, etc.). Currently, attempts at generation of brain organoids do not mature beyond the prenatal brain equivalent, the major obstacle being the lack of vascularization in the initial embryoid bodies that ultimately limit the growth and maturation of the organoids. Thus, attention is turned toward generation of a brain-on-A-chip model that can serve as a relevant model of the human brain in its recapitulation of the neuronal circuit (i.e., organoid-on-chip or "OOC"; brain-on-chip or "BOC"). In this study, soft lithography techniques using polydimethylsiloxane (PDMS) elastomers were implemented to fabricate a microfluidic chip to serve as a BOC/ OOC. A mold was fabricated using 3D printing for performing soft lithography of the BOC (followed by bonding on to a glass slide). Neural organoids (spheroids) were dispensed into the BOC using a pipette. The BOC was designed for the organoids to be captured at specific locations using micro-pillars that are located strategically within the microchannel network. Copper microelectrodes were manually inserted into the device through specially designed ports to serve as probes (as electrical sensors) and were mounted strategically for detection of electrical response from the organoids. Experiments were conducted to acquire and analyze the electrical response of the organoids when subjected to a variety of conditions (and stimuli). Two sets of organoids were tested in these experiments: organoids that are light responsive (LR) and organoids that are not light responsive (NLR). The set of experiments performed in this study include: control experiments using pure media (exposed to light), control experiments performed using media decanted from organoid suspensions (with and without exposure to light for both LR and NLR), baseline tests using organoids not exposed to light (control experiments for both LR and NLR), and experiments involving organoids exposed to variety of stimuli (light exposure, saline solution, etc. for both LR and NLR).