Jellyfish in the stomach
MIT has created a swelling pill that will control the stomach for a month
Dmitry Mazalevsky, Naked Science
With this device, it will be possible to deliver various sensors to the stomach – for example, to monitor the pH level, search for bacteria and viruses, deliver tiny cameras, and also as a more convenient alternative to a diet.
Engineers from MIT have developed a swallowing tablet similar to jelly, which, after reaching the stomach, quickly swells to the size of a ping-pong ball. A tablet large enough to stay in the stomach for a long time has a built-in sensor that continuously monitors the temperature of the stomach for 30 days. If necessary, the device can be removed from the stomach: to do this, the patient must drink a calcium solution that will compress the tablet to its original size, which will allow it to safely exit the body. This invention is reported on the university's website (Ingest, expanding pill monitors the stomach for up to a month).
The tablet is made of two types of hydrogels – a mixture of polymers and water – which resemble jelly in consistency. This combination allows the tablets to swell quickly in the stomach without being threatened in an acidic environment. The hydrogel-based drug is much softer and more durable than modern powered sensors, which can either stay in the stomach for only a few days, or are made of hard plastics or metals that are much rougher than the gastrointestinal tract.
Today, when scientists try to develop rapidly swelling gels, they usually resort to diffusion, allowing water to gradually diffuse into the hydrogel network. But it takes hours or even days to inflate to the right size – this is more than the time of emptying the stomach. Instead, MIT researchers were looking for ways to create a hydrogel pill that could inflate much faster–at a speed comparable to that of frightened blowfish.
As a result, scientists came up with a design that resembles a small, jelly-like capsule made of two hydrogel materials. The inner material contains sodium polyacrylate – superadsorbent particles that are used, for example, in diapers – because of their ability to quickly absorb liquid and inflate.
The researchers, however, understood that if a pill were made only from these particles, it would immediately disintegrate and come out of the stomach. Therefore, they developed a second, protective layer of hydrogel to encapsulate rapidly swelling particles. This outer membrane is made of many nanoscopic crystal chains, each of which is stacked on top of the other.
In the laboratory, the researchers dipped the tablet into various solutions of water and liquids similar in composition to gastric juice, and found that the tablet swelled 100 times compared to the original size in about 15 minutes – much faster than existing swelling hydrogels. To test the strength of the pill, the researchers mechanically squeezed it thousands of times, with efforts even exceeding those that the pill can experience from regular contractions in the stomach.
Finally, they built in small temperature sensors and tested them on pigs whose gastrointestinal tract is very similar to a human one. Later, the team extracted a temperature sensor from pig excrement, and after studying it, found that the sensor is able to accurately track the daily activity of animals for up to 30 days.
In the future, researchers suggest that tablets can safely deliver several different sensors to the stomach – for example, to monitor pH levels or signs of certain bacteria or viruses.
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