Diagnosing gastrointestinal diseases such as colitis and colorectal cancer often relies on colonoscopy, an invasive procedure that many patients avoid despite ongoing symptoms like bleeding, cramping, and diarrhoea. The lack of simple, noninvasive diagnostic tools means disease activity and progression can go undetected or monitored infrequently. Now, an ingestible sensor was able to travel through the gut in animal models and rapidly identify signs of intestinal bleeding after being recovered from stool.

The approach, developed by researchers from Zhejiang University of Technology (ZJUT, Hangzhou, China), revolves around engineered bacteria designed to sense heme, a component of red blood cells that signals gastrointestinal bleeding. To protect these bacteria from digestion and enable recovery, the researchers encapsulated them together with magnetic particles inside sodium alginate hydrogels. This process formed tiny microspheres that shielded the bacteria while still allowing blood-derived molecules to reach them.

Once swallowed, the microspheres pass through the gastrointestinal tract intact. If bleeding is present, heme interacts with the bacteria, triggering a light-producing signal. The magnetic particles allow the sensors to be easily retrieved from feces using a simple magnet, enabling fast analysis outside the body. The microsphere sensors were tested in mouse models of colitis ranging from healthy to severe disease.

After recovery from stool, cleanup and signal analysis took about 25 minutes, and light intensity increased consistently with disease severity. Importantly, the sensors showed strong biocompatibility, with healthy mice exhibiting no adverse effects. The hydrogel coating successfully protected the bacteria from digestive fluids while preserving their ability to detect heme.

The findings, published in ACS Sensors, suggest a promising noninvasive alternative for detecting gastrointestinal bleeding and monitoring inflammatory bowel disease. The platform could potentially reduce reliance on colonoscopy for initial screening and disease follow-up. Researchers note that the bacterial sensors could be adapted to detect other gut disease biomarkers, expanding their diagnostic scope. Future work will focus on validating the technology in human studies and exploring broader clinical applications.

“This technology provides a new paradigm for rapid and non-invasive detection of gastrointestinal diseases,” said Ying Zhou, a co-author of the study.

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