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

Why Easier, Noninvasive Gut Diagnostics Are Needed

In the U.S., millions of people live with colorectal cancer or inflammatory bowel disease, including colitis, which can lead to intestinal bleeding, diarrhea and abdominal pain. Colonoscopy remains the gold-standard diagnostic tool. It relies on an endoscope, a camera-tipped flexible device that is carefully guided through the large intestine. Although it provides valuable medical insight, many individuals hesitate to undergo the procedure because it requires extensive preparation and can feel invasive. To develop an alternative, Zhou, Bang-Ce Ye, Zhen-Ping Zou and colleagues are exploring the use of bacteria that detect biomarkers such as heme, a component of red blood cells that signals bleeding inside the gut.

Building Bacterial Sensors That Survive Digestion

The team previously designed bacteria that emit light when they encounter heme, but the early versions broke down during digestion and were difficult to retrieve afterward. In the new study, the researchers protected the bacteria by enclosing them, along with magnetic particles, inside small droplets of sodium alginate, a thickening ingredient commonly found in foods. This produced sturdy hydrogel microspheres that travel through the digestive tract and can be removed from stool with a magnet. Initial laboratory tests confirmed that the hydrogel shield allowed the bacteria to survive simulated digestive conditions while still letting heme reach the sensor and trigger a glow.

Testing the Microspheres in Mouse Models of Colitis

The researchers then gave the microspheres orally to mice with varying levels of colitis, ranging from no disease activity to severe inflammation. After the spheres moved through the gastrointestinal tract, the team retrieved them using a magnet and reported three key findings:

• Microsphere cleanup and signal analysis required about 25 minutes.
• The sensors produced stronger light signals as disease severity increased, indicating higher levels of heme in animals with more advanced colitis.
• Tests in healthy mice showed that the microspheres were biocompatible and safe.

Future Potential for Human Testing and Disease Monitoring

Although the technology has not yet been evaluated in humans, the researchers suggest that encapsulated bacterial sensors could one day help diagnose gastrointestinal diseases, monitor treatment responses and track changes in disease over time.

The authors acknowledge funding from the National Natural Science Foundation of China, the National Key Research and Development Program of China, and the China Postdoctoral Science Foundation.