Miniaturized Capsule System Toward Real-Time Electrochemical Detection of H 2 S in the Gastrointestinal Tract.

Hydrogen sulfide (H ₂ S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H ₂ S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H ₂ S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas-sensing ingestible capsule is developed to enable real-time, wireless amperometric measurement of H ₂ S in GI conditions. A gold (Au) three-electrode sensor is modified with a Nafion solid-polymer electrolyte (Nafion-Au) to enhance selectivity toward H ₂ S in humid environments. The Nafion-Au sensor-integrated capsule shows a linear current response in H ₂ S concentration ranging from 0.21 to 4.5 ppm (R ² = 0.954) with a normalized sensitivity of 12.4% ppm ^-1 when evaluated in a benchtop setting. The sensor proves highly selective toward H ₂ S in the presence of known interferent gases, such as hydrogen (H ₂ ), with a selectivity ratio of H ₂ S:H ₂ = 1340, as well as toward methane (CH ₄ ) and carbon dioxide (CO ₂ ). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold-based notification is investigated, showing potential for in vivo application. Thus, the developed H ₂ S capsule platform provides an analytical tool to uncover the complex biology-modulating effects of intraluminal H ₂ S.
(© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)