By Mariam Malik ‘22

Hydrogels are known for absorbing significant amounts of water and having a high biocompatibility, while also possessing a high level of mechanical conformity and the ability to self-heal. Devices that physiologically monitor the body are usually made from materials with a high biocompatibility, including certain metals, silicon, and ceramics. But installing these devices require intrusive procedures. However, researchers at the Massachusetts Institute of Technology (MIT) used these unique characteristics of the hydrogel to create a jelly-like pill that simply needs to be taken orally and achieves gastric residency once inside. Xuanhe Zhao, associate professor of mechanical engineering at MIT, adds that with the pill, people would have a painless alternative to the otherwise quite painful process of implanting medical devices.

Despite the many pros of hydrogels, long-term strength is not one of them. Also, in order for hydrogels to achieve gastric residency, the hydrogels need to swell quickly and endure gastric mechanical forces. Thus, the pill’s design was highly specific, being made of highly-absorbent hydrogel particles, surrounded by an anti-fatigue porous hydrogel membrane. The pills were then tested for their gastric retention on pigs. The team of researchers found that the pill floated openly, and there was no clinical or radiographic evidence of bowel destruction. Radiographic evidence did also show that the pill maintained its swollen, spherical shape in the contracting movements of the stomach, showing that it can withstand the stomach’s natural environment.

The team also recorded gastric temperatures for a period of time, which were later used to characterize the subject’s dietary behavior. Eight am to eight pm was the most active time of consumption for all pigs, and ingestion times varied. One limitation that faces the team is that the gastric emptying in pigs is slower than it is in humans. Pigs also have a lower gastric compression force than humans, so further testing will be needed.

References

1. X. Liu, et. al., Ingestible hydrogel device. Nature Communications 10, (2019). doi: 10.1038/s41467-019-08355-2.
   
2. Image retrieved from: https://commons.wikimedia.org/wiki/File:Prozac_pills.jpg