Pill-shaped biosensor keeps track of gut metabolites in real time

Engineering researchers have developed a battery-free, pill-shaped ingestible biosensor that provides continuous monitoring in the intestines, allowing scientists to monitor gut metabolites in real time.

UC San Diego researchers develop a self-powered ingestible sensor system designed to monitor metabolites in the small intestine over time
UC San Diego researchers develop a self-powered ingestible sensor system designed to monitor metabolites in the small intestine over time - Photo by David Ballot for the Jacobs School of Engineering, UC San Diego

The ingestible, biofuel-driven sensor facilitates in-situ access to the small intestine, making glucose monitoring easier while generating continuous results. These measurements provide a critical component of tracking overall gastrointestinal health, a major factor in studying nutrition, diagnosing and treating various diseases, and preventing obesity. The work was led by engineers at the University of California San Diego and appears in the December issue of Nature Communications.

“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 five seconds for two to five hours,” said Ernesto De La Paz Andres, a nanoengineering graduate student at UC San Diego and one of the co-first authors on the paper.

Gastrointestinal disorders include inflammatory bowel disease (IBD), diabetes or obesity, all caused, in part, by the dysfunction of the intestinal processes involving the absorption or digestion of gut metabolites. Developing ingestible sensors, such as the new smart pill system from UC San Diego, comes with significant challenges.

"It has proven difficult to create an ingestible device equipped with the necessary sensors and electronics to perform wireless readout and doesn’t need batteries," said nanoengineering professor Joseph Wang, co-director of the UC San Diego Center for Wearable Sensors. 


To address these specifications, the team decided on a self-powered glucose biofuel biosensor integrated into a circuit that performs energy harvesting, biosensing and wireless telemetry using a power-to-frequency conversion scheme utilising magnetic human body communication.

The battery-free operation is made possible by the team's glucose biofuel cell (BFC) for obtaining power during operation while simultaneously measuring changing glucose concentrations. Its energy-efficient magnetic human body communication (mHBC) scheme operates in the 40-200MHz range to receive the time-resolved transmitted signals.

“It uses glucose present in the intestines as a biofuel to power the device,” said 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.”

The proof-of-concept smart pill measures 2.6 cm in length and 0.9 cm in diameter. So far, small intestine data recording has been performed in pigs, which have a similar size GI tract to humans. 

The researchers now plan to increase the number of sensors available in the pills, which will enable monitoring of more chemical parameters in the intestines. They also plan to further miniaturise the sensors and electronic circuitry to match what is currently available in the smart-pill market.