Serotonin Sensing Technologies to Promote Understanding of the Gut–Brain Axis

The gut–brain axis (GBA) is the bidirectional biochemical signaling pathway between the gastrointestinal (GI) tract and the central nervous system (CNS). Although the GBA is recognized as an important signaling network, its specific mechanics are not fully understood. The monoamine neurotransmitter serotonin [5-hydroxytryptamine (5-HT)] is identified as an important signaling molecule in the CNS and GI tract. 5-HT's concurrent and widespread role in both neurological and GI physiology implicates it as a biomarker in the GBA, motivating the development of sensing technologies to study its dynamics, and subsequently lending to a fuller understanding of the GBA. To simultaneously understand the contribution of 5-HT to underlying signaling pathways and its downstream physiological effects, we have concurrently developed micro-nano-bio devices and systems to measure 5-HT dynamics in vitro, ex vivo, and in vivo. Our in vitro platforms measure 5-HT release events in response to stimuli in a simplified gut model, our ex vivo sensing technology measures 5-HT concentrations in the CNS of dissected crayfish, and our in vivo platforms measure 5-HT dynamics and aim to help elucidate the physiological role of 5-HT. Together, these sensing technologies provide engineering approaches for monitoring 5-HT dynamics and promote understanding of GBA pathways.