Researchers may have found a way to beat the stomach’s harsh environment – strong, grinding muscles and acid – so that clinicians can monitor what’s going on inside, diagnose and deliver treatment without having to take invasive steps. A medical device developed by a team of engineers led by Dr. Xuanhe Zhao of the Massachusetts Institute of Technology might be the answer: A hydrogel device that could be swallowed, swell to a large soft sphere and then deswell to a floppy membrane and exit the body.
After swallowing the soft but strong device it would quickly expand in the stomach to become too large to pass into the intestine, which is what happens after food is broken down. The device would also be designed in such a way that it wouldn’t get stuck in the valve that leads to the large intestine. Inspired by pufferfish, which can quickly inflate and then later deflate their spherical body, the team wanted their device to also shrink on demand. After shrinking, the tiny device would be small enough to pass out of the body through the intestine.
The engineers fabricated a sphere from two kinds of hydrogels. The outer hydrogel membrane consisted of polyvinyl alcohol. Their method of freeze-drying the polyvinyl alcohol made the membrane soft and porous but strong. Inside this spherical membrane were particles of polyacrylic acid, which can quickly absorb fluids.
The effort was supported in part by NIH’s National Institute of Biomedical Imaging and Bioengineering (NIBIB). A paper about the strong hydrogel material was published in Science Advances in January. Results from lab and animal testing of the device made from two hydrogels also appeared in Nature Communications in January.
When the team dropped their 3-cubic-centimeter hydrogel test device into water or stomach fluid, the volume expanded by about 25 times in 10 minutes. A concentrated dose of calcium could shrink the resulting sphere in 15 minutes. The calcium dose would be about 20 times what’s in a glass of milk. Other tests showed that the device could withstand nearly 27,000 compressions.
The research team added a wireless temperature sensor and tested the device in six Yorkshire pigs. It stood up to both the harsh stomach acid and the grinding muscles for up to 29 days. While in the stomach, the sensor captured data every 10 minutes.
“The dream is to have a Jell-O-like smart pill, that once swallowed stays in the stomach and monitors the patient’s health for a long time such as a month,” Zhao says.
Lab tests showed that, in addition to sensors for monitoring conditions in the stomach, the device could carry substances like caffeine for slow release into the belly. The device might also be used to restrict meal sizes by taking up space inside the stomach. However, further development will be needed before testing the device in people.