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Expanding Gel Pill Designed for Long-Term Diagnostics

Expanding ingestible get

Ingestible hydrogel device swells in water. (Xinyue Liu, MIT)

31 Jan. 2019. An ingestible gel capsule is shown in tests with animals to expand and reside in the stomach for as long as a month for delivering drugs or monitoring bodily functions. A team from Massachusetts Institute of Technology and Chinese University of Hong Kong describes their device in yesterday’s issue of the journal Nature Communications.

Researchers from the labs of MIT mechanical engineering professor Xuanhe Zhao and Giovanni Traverso, a gastroenterologist at Brigham and Women’s Hospital in Boston expected to join the MIT faculty later this year, are seeking safer alternatives to implants for long-term drug delivery and monitoring processes in the body. Most implants up to now use metals, silicon, ceramics, and plastics, which while safe, usually require invasive procedures. Ingestible hydrogels, soft water-based biocompatible polymers taken like a pill, offer an alternative to implants, but up to now are not able to swell quickly or withstand the rigors of gastric acids and mechanical strains in the stomach.

Zhao’s lab of materials scientists and engineers studies hydrogels interacting with electronics for medical and other uses, including robotics. In this case, the team designed a hydrogel material that starts out in a small, compact size, but can quickly expand to about the size of a ping-pong ball, to keep from passing out of the stomach. The researchers based their solution on the pufferfish, a slow-moving species that quickly blows-up in size to discourage predators. By adding sodium polyacrylate, a superabsorbent material used in disposable diapers, to its mix, the expandable hydrogel takes in water to quickly expand in size in much the same way as a pufferfish.

Lab tests show the hydrogel capsules are soft enough to keep from damaging internal organs, yet strong enough to withstand stomach acids and mechanical forces in the digestive system. The researchers also show that a calcium chloride solution can quickly and safely reduce the size of the expanded gel to let it pass through the digestive system when no longer needed.

Earlier work by Traverso shows the feasibility of ingestible capsules that can monitor functions in the body. As reported by Science & Enterprise last month, Traverso and colleagues developed an ingestible capsule containing a Bluetooth transmitter that can send wireless signals for weeks. To prove the concept in this case, the team outfitted their ingestible hydrogel capsules with temperature monitors and drug-delivery depots, both shown to be feasible in lab simulations.

The researchers then tested the hydrogel capsules in pigs, which have digestive systems similar to humans. The tests show the expandable hydrogels could be ingested as capsules, quickly swell in size, and remain in the pigs stomachs for as long as 29 days. Similar capsules without the absorbent materials allowing them to expand lasted no more than 6 days. Further tests with temperature sensors added to the capsules show the sensors could monitor temperatures in the stomach also for 29 days. After the capsules were retrieved, the temperature measurements corresponded with dietary changes in the pigs, showing the feasibility of the devices.

The researchers believe the soft expandable hydrogels could offer an alternative to more rigid balloons for dietary control that require invasive endoscopes to thread through the esophagus into the stomach. “With our design, you wouldn’t need to go through a painful process to implant a rigid balloon,” says Zhao in an MIT statement. “Maybe you can take a few of these pills instead, to help fill out your stomach, and lose weight. We see many possibilities for this hydrogel device.”

Several authors, including Zhao, are listed as inventors on a provisional patent application for the expandable hydrogel technology. Traverso is co-founder and a board member of Lyndra Therapeutics Inc. in Watertown, Massachusetts developing long-term drug delivery technologies for Alzheimer’s disease and psychiatric disorders. The company announced on Tuesday it raised $55 million in its second venture funding round.

The following video tells more about and demonstrates the expandable gel capsules.

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