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How sensors are giving us another way to peek inside our bodies

Scientists have engineered sensors that can be swallowed and sensors that disappear

This ingestible sensor has bacteria inside that is programmed to sense blood in the gut, and then wirelessly deliver that information.
Photo: Lillie Paquette, MIT

The bacteria, molecules, and chemicals in our bodies hold important clues about our health, and scientists are creating sensors that can tap into this information in the easiest way possible. These are sensors that can be swallowed to warn of gut trouble, implanted to monitor how well an injury is recovering, or just sit on teeth to track the state of your mouth.

The gut sensor is about the size of a pen cap, and it’s filled with bacteria that scientists genetically engineered to detect a compound in blood called heme, and then glow if heme is present. The sensor can pick up the glow of the bacteria, and then ping a smartphone app. (In the future, it could pick up other compounds, too.)

The sensor has only been tested in pigs so far, according to the study published in the journal Science this week, but it has the potential to be a less invasive way to peek inside the body and check for gastrointestinal and stomach issues. “If you’re over 50, you’re supposed to go to the doctor and get a colonoscopy, but what if you could swallow a pill that tells you early signs of infection?” says study co-author Timothy Lu, a bioengineer at the Massachusetts Institute of Technology.

This isn’t the only such sensor. Last year, the US Food and Drug Administration approved a “digital pill” that can keep tabs of whether patients have taken their medication, and there have been early human trials on a pill that tracks, well, gas. The MIT team wants to test their sensor in humans, too, but they need to make a few improvements first. It needs to be about a third smaller, and doctors would be also able to track exactly where the sensor is in the gut, researchers told Stat News.

Stomach troubles aside, another new sensor could one day help you deal with physical injury. In a study published in Nature Electronics last week, scientists engineered an implantable sensor that can help with physical therapy. It then decomposes so there’s no need for another surgery to take it out. This sensor is made of rubbery materials, less than a third of an inch long, and it’s designed especially for tendon injuries, says study co-author Paige Fox, a professor of reconstructive surgery at Stanford University.

A tendon injury can be tricky to fix. Tendons don’t have much blood supply, they heal slowly, and they scar instead of generating a brand-new, healthy tendon. A serious tendon injury usually requires surgery to sew everything back up anyway, and that’s when the sensor would be implanted. It measures strain and pressure, and it can help patients with their rehabilitation programs, says Fox. Being told to “use your hand at half-strength” or “bend your tendon 30 degrees” can seem subjective and confusing. A sensor that collects this info and sends it to a smartphone could give more useful feedback — like “use more strength” — that speeds the recovery process.

Again, though, this tech hasn’t been tested in humans. For their study, the scientists implanted the sensor in the back of a rat. The rat didn’t have any side effects and the device decomposed on it own. (By packaging the sensor in more or less material, researchers can also control exactly how long it takes to degrade.) Next, they’re seeing if this can be used for different kinds of injuries and hope to do tests that clear it for people.

Tooth-mounted sensors could become available sooner than sensors deep in our bodies. Created by bioengineers at Tufts University, they look like tiny gold stickers. They have three different layers that work together to pick up chemicals in saliva. The information is then sent to a mobile phone. When the scientists tested it in humans, the sensor successfully detected glucose, alcohol, and salt, according to a study recently published in the journal Advanced Materials Technologies.

A tooth-mounted sensor that can monitor glucose, alcohol, and salt.
Photo by Fiorenzo Omenetto

Though this device has gotten a lot of hype for its potential to help people diet, it’s not sensitive enough to determine calorie count, according to study author and Tufts bioengineer Fiorenzo Omenetto. His team is more interested in using the sensor to treat disease. Saliva contains plenty of hormones that can provide real-time health information or be used to diagnose diseases from oral cancer to diabetes. The next challenge is to make the materials better so the sensor can accurately pick up this wider variety of signals, Omenetto says.

All this research is early, but it means we’re one step closer to using technology to get data from inside our bodies to the outside, where we can take a closer look.