An ingestible pill was developed that, upon reaching the stomach, quickly swells to the size of a soft, squishy ping-pong ball big enough to stay in the stomach for an extended period of time. The inflatable pill is embedded with a sensor that continuously tracks the stomach's temperature for up to 30 days. If the pill needs to be removed from the stomach, a patient can drink a solution of calcium that triggers the pill to quickly shrink to its original size and pass safely out of the body.
The new pill is made from two types of hydrogels — mixtures of polymers and water that resemble the consistency of Jell-O®. The combination enables the pill to quickly swell in the stomach while remaining impervious to the stomach's churning acidic environment. The hydrogel-based design is softer, more biocompatible, and longer-lasting than current ingestible sensors that either can remain in the stomach for a few days or are made from hard plastics or metals that are stiffer than the gastrointestinal (GI) tract.
The design resembles a small, Jell-O-like capsule made from two hydrogel materials. The inner material contains sodium polyacrylate — super-absorbent particles used in commercial products such as diapers for their ability to rapidly soak up liquid and inflate. If the pill were made only from these particles, however, it would immediately break apart and pass out of the stomach as individual beads. A second, protective hydrogel layer was designed to encapsulate the fast-swelling particles. This outer membrane is made from nanoscopic crystalline chains, each folded over another, in a nearly impenetrable, gridlock pattern — an “anti-fatigue” feature.
When dunked in various solutions of water and fluid resembling gastric juices, the pill inflated to 100 times its original size in about 15 minutes — much faster than existing swellable hydrogels. Once inflated, the pill is about the softness of tofu or Jell-O, yet surprisingly strong. The pill also was mechanically squeezed thousands of times, at forces even greater than what the pill would experience from regular contractions in the stomach. It was found that a solution of calcium ions, at a concentration higher than what's in milk, can shrink the swollen particles. This triggers the pill to deflate and pass out of the stomach.
The pill may safely deliver a number of different sensors to the stomach to monitor, for instance, pH levels or signs of certain bacteria or viruses. Tiny cameras may also be embedded into the pills to image the progress of tumors or ulcers over the course of several weeks.