4. Conclusion
To the best of our knowledge, only few GBA-on-a-chip models have been reported to date. Herein, a prototypic GBA-on-a-chip was suggested, where gut and BBB were co-cultured. Responses of cells to microbial substrates correlated with in vivo models. We also assessed transport of exosomes in the GBA chip, suggesting the fluidic environment caused changes in the transport of exosomes. There should exist multiple direct/indirect pathways where microbial products and exosomes in the gut affect the brain. To uncover these pathways, inclusion of microbiome, gut cells, immune cells, BBB and neurons in our GBA chip is desirable for future studies.