MIT-designed biosensor capsule uses genetically engineered light-emitting bacteria (right) to detect molecules that identify bleeding or other gastrointestinal problems. Ultra-low-power electronics (left) sense the light and send diagnostic information wirelessly to a cellphone. (credit: Lillie Paquette/MIT)

MIT engineers have designed and built a tiny ingestible biosensor* capsule that can diagnose gastrointestinal problems, and the engineers demonstrated its ability to detect bleeding in pigs.

Currently, if patients are suspected to be bleeding from a gastric ulcer, for example, they have to undergo an endoscopy to diagnose the problem, which often requires the patient to be sedated.

If the engineers can shrink the sensor capsule and detect a variety of other conditions, the research could potentially transform the diagnosis of gastrointestinal diseases and conditions, according to the researchers.

Diagnosing gastrointestinal diseases in real time

To detect diseases or conditions, the genetically engineered bacteria (green) are placed into multiple wells (blue), covered by a semipermeable membrane (white) that allows small molecules (red) from the surrounding environment to diffuse through. The bacteria luminesce (glow) when they sense the specific type of molecule they are designed for. (In the experiment with pigs, heme — part of the red hemoglobin blood pigment — indicated bleeding.) A phototransistor (brown) measures the amount of light produced by the bacterial cells and relays that information to a microprocessor in the capsule, which then sends a wireless signal to a nearby computer or smartphone. (credit: Mark Mimee et al./Science)

The researchers showed that the ingestible biosensor could correctly determine whether any blood was present in the pig’s stomach. They anticipate that this type of sensor could be deployed for either one-time use or to remain in the digestive tract for several days or weeks, sending continuous signals. The sensors could also be designed to carry multiple strains of bacteria, allowing for diagnosing multiple diseases and conditions.

The researchers plan to reduce the size of the sensor capsule (currently 10 millimeters wide by 30 millimeters long) and to study how long the bacteria cells can survive in the digestive tract. They also hope to develop sensors for gastrointestinal conditions other than bleeding.**

Reference: Science. Source: MIT.

* The sensor requires only 13 microwatts of power. The researchers equipped the sensor with a 2.7-volt battery, which they estimate could power the device for about 1.5 months of continuous use. They say it could also be powered by a voltaic cell sustained by acidic fluids in the stomach, using previously developed MIT technology.

** For example, one of the sensors they designed detects a sulfur-containing ion called thiosulfate, which is linked to inflammation and could be used to monitor patients with Crohn’s disease or other inflammatory conditions. Another one detects a bacterial signaling molecule called AHL, which can serve as a marker for gastrointestinal infections because different types of bacteria produce slightly different versions of the molecule.