Self-Powered Ingestible “Smart Pill” Monitors the Small Intestine

Researchers from the University of California San Diego (UCSD) have created a battery-free ingestible biosensor that can continuously monitor the intestinal environment. Their work is published in Nature Communications.

The burden of gastrointestinal disorders

Gastrointestinal (GI) disorders pose a significant health burden across the globe, affecting approximately 4 in 10 people. GI disorders can include diabetes, inflammatory bowel disease (IBD) and obesity. The common thread across these disorders is a dysfunction of the intestinal processes required to absorb or digest gut metabolites.

Diagnosing GI disorders is far from a simple task, and methods for monitoring the small intestine of patients can be uncomfortable or even painful. “Currently, the way to sample fluid inside the stomach and intestines is to do an endoscopy, where a catheter is inserted down your throat and into your GI tract by a doctor,” says Patrick Mercier, professor of electrical and computer engineering at UCSD.

Creating a “smart pill” to track intestinal metabolites

Mercier and colleagues, including Joseph Wang, distinguished professor in the department of engineering at UCSD, looked to engineering principles for a solution. Together, they have created an ingestible “smart pill”, measuring 2.6cm in length and 0.9cm in diameter that runs on glucose, a ubiquitous source of energy. "By combining the ultra-low-power circuit and wireless technologies from my lab with a glucose-powered fuel cell and cutting-edge electrochemical sensing from the lab of UC San Diego nanoengineering professor Joseph Wang, we have an opportunity to create new modalities for understanding what is happening in the small intestine," says Mercier.

"It has proven difficult to create an ingestible device equipped with the necessary sensors and electronics to perform wireless readout that doesn’t need batteries," Wang adds. The smart pill is integrated into a circuit capable of performing energy harvesting, biosensing and wireless telemetry, which is powered by a power-to-frequency conversion scheme that harnesses magnetic body communication. “It uses glucose present in the intestines as a biofuel to power the device,” explains Mercier. “Making this all work with ultra-low-power electronics and with a stable yet small glucose biofuel cell were major technical challenges that were addressed here.”

Promising results from pig studies

In a proof-of-concept study, the researchers tested the smart pill in pigs. “In our experiments, the battery-free biosensor technology continuously monitored glucose levels in the small intestines of pigs 14 hours after ingestion, yielding measurements every 5 seconds for 2–5 hours,” says Ernesto De La Paz Andres, a nanoengineering graduate student at UCSD and one of the co-first authors on the paper.

As for next steps, the team plan to increase the number of sensors that are available in the pills, which could enable monitoring of more chemical parameters in the intestines. “Given that the gastrointestinal tract possesses dynamic changes of pH, temperature and oxygen concentrations, future work envisions the integration of additional sensing modalities to account for these differences,” says De La Paz Andres. They also intend to reduce the size of the pills for human testing so that they are easier to swallow.

Reference: De la Paz E, Maganti NH, Trifonov A, et al. A self-powered ingestible wireless biosensing system for real-time in situ monitoring of gastrointestinal tract metabolites. Nat Comms. 2022;13(1):7405. doi: 10.1038/s41467-022-35074-y.

This article is a rework of a press release issued by the University of California San Diego. Material has been edited for length and content.