Soft pill to track the insides of the stomach developed

By Dr. Ananya Mandal, MDFeb 3 2019

Engineers from MIT have successfully developed a soft pill that is indigestible. Once ingested it swells within the stomach and becomes a soft ping pong ball that can stay within the stomach for a long period of time.

The ingestible hydrogel device swells in water with high speed and high ratio. Image: Xinyue Liu

This inflatable soft pill can then acts as a sensor and transmit the information from within the stomach to the computer outside. The study results were published in the journal Nature Communications.

The sensors within the ball can detect the temperatures from within the stomach for up to 30 days. For removal of the pill the patient needs to have a solution of calcium that can shrink the size of the pill to its original. This is then passed out of the body normally and safely.

The team says that the pill is made up of two types of hydrogels. These are polymers and water mixture that make it the consistence of a jell-o. This makes the process of swelling of the pill within the stomach in acidic environment. This new design makes it more biocompatible and softer and longer lasting. This makes the sensor longer-lasting than present sensors which are ingestible.

Xuanhe Zhao, associate professor of mechanical engineering at MIT said in a statement, “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.” The study was conducted by a team including Xinyue Liu, Christoph Steiger, and Shaoting Lin. They explain that the idea for the pill came from the defence mechanism of the pufferfish, or blowfish. The pufferfish blows up into a ball with spikes by swiftly sucking up large amounts of water. Its body is tough and fast inflating says Zhao and they replicated this phenomenon with the hydrogel pills. The pill is made to carry the sensors within the stomach to assess the disease states within the stomach, he explained.

Liu said in a statement, “Currently, when people try to design these highly swellable gels, they usually use diffusion, letting water gradually diffuse into the hydrogel network. But to swell to the size of a ping-pong ball takes hours, or even days. It’s longer than the emptying time of the stomach.” The outer layer of the pill is made up of a hydrogel layer nanoscopic, crystalline chains that protects the fast-swelling particles within. “You would have to crack through many crystalline domains to break this membrane. That’s what makes this hydrogel extremely robust, and at the same time, soft,” said Liu.

The team tested the pill in lab conditions. They put it in solutions of water and fluid similar to stomach contents. Within 15 minutes the pill swelled to about 100 times its original size. Then the team squeezed the pill like the stomach walls would. Lin explained, “The stomach applies thousands to millions of cycles of load to grind food down. And we found that even when we make a small cut in the membrane, and then stretch and squeeze it thousands of times, the cut does not grow larger. Our design is very robust.”

A new hydrogel device swells to more than twice its size in just a few minutes in water.

They then noted that a solution of calcium ions with concentrations more than that of milk can shrink the pill to bring it back to its original size. This can allow it to pass out safely from the body, they explain. The team tested the sensor containing pills in pigs. The sensors could accurately relate the animals’ daily activity patterns and the stomach temperatures for up to 30 days.

This research was supported by the National Science Foundation, National Institutes of Health, and the Bill and Melinda Gates Foundation.