For a doctor to be able to see exactly what’s going on inside your body, traditionally they would need to perform some kind of scan or laparoscopy, both are which costly and time-consuming procedures. However, thanks to researchers at MIT, the using of scans and cameras to diagnose stomach problems could all become a thing of the past.

Welcome to the bacteria-on-a-chip approach. This ingestible sensor is made using living cells combined with low-power electronics that have the ability to convert the bacterial response into a wireless signal. The new study was published last month in the online edition of Science, and in it, the researchers successfully demonstrated this approach working in pigs.





Over the past decade, there have been many a great achievement when it comes to engineering bacteria to fight environmental pollutants and disease. Often these bacteria are designed to produce light upon the detection of the target stimulus, but this usually requires the use of very costly, specialized lab equipment.

To get the best of both worlds, the researchers decided to combine these bacteria with an electronic chip so that it could convert the bacterial response into a wireless signal. “Our idea was to package bacteria cells inside a device,” says one of the study’s lead authors, Phillip Nadeau, former MIT postdoc. “The cells would be trapped and go along for the ride as the device passes through the stomach.”

To begin with, the researchers concentrated on bleeding that occurred within the GI tract. They first placed the bacteria onto their sensor, into four specially designed wells. These were covered by a semipermeable membrane which allows only the smallest of molecules to pass through. Underneath each well sits a phototransistor that measures how much light’s produced by the bacterial cells. This information then gets passed to a microprocessor which then transmits a wireless signal to a nearby smartphone or computer.





The sensor itself is only about 1.5 inches long and needs just 13 microwatts of power to run. Adding a 2.7-volt battery to the mix, the researchers are confident the device could run continuously for around one and a half months.

Upon testing of the sensor in pigs, the researchers found that it was able to correctly determine if there was any blood present in the pig’s stomach. They are hopeful that his kind of sensor can be used in the future either as a one-time use product or one that’s designed to stay in the digestive tract for a little longer.

“The goal with this sensor is that you would be able to circumvent an unnecessary procedure by just ingesting the capsule, and within a relatively short period of time you would know whether or not there was a bleeding event,” says the second lead author on the study, Mark Mimee.“ Moving forward the team is planning to reduce the size of the sensor and investigate just how long bacteria cells are able to survive inside the digestive tract. They would also like to develop sensors for other gastrointestinal conditions too.

As part of their study, the researchers adapted some other sensors which have not yet been tested on animals. The first sensor is one that detects thiosulfate, a sulfur-containing ion linked to inflammation. It could be used to monitor patients with inflammatory conditions such as Crohn’s disease. The second sensor is one that detects AHL, a bacterial signaling molecule that acts as a marker for gastrointestinal infections. “Most of the work we did in the paper was related to blood, but conceivably you could engineer bacteria to sense anything and produce light in response to that,” says Mimee.





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