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Microscopic ‘Submarines’ Could Treat Stomach Disease

Researchers have designed tiny micromotors that can independently navigate through the stomach neutralizing gastric acid before releasing drugs at a desired pH level.

Kristopher Sturgis

This graphic demonstrates how the tiny submarines work to neutralize gastric acid in the stomach.

Delivering drugs to the stomach could become a much easier task thanks to a new study out of the UC San Diego Jacobs School of Engineering where nanoengineering professors have designed a new microscopic "submarine" drug carrier that can navigate the harsh, acidic conditions of the stomach. The tiny micromotors were designed to speed independently through the stomach using gastric acid as fuel and neutralizing it, before releasing a drug payload once the desired pH is reached.

The micromotors are tiny magnesium spheres only 20 micrometers in size that are coated with a nanolayer of gold. Embedded in the micromotors is a pH sensitive polymer designed to release the drugs when a certain pH level activates the polymer.

In their most recent study, the group was able to embed the polymer coating with a dye known as rhodamine 6G as a model payload. The magnesium spheres were placed on a glass support during the coating process, where a tiny individual spot on the core of the sphere was left uncoated. In this uncoated spot, an electrochemical reaction occurs that consumes protons and forms magnesium ions that release tiny bubbles of hydrogen gas.

These bubbles are what propel the tiny submarines through the stomach, while at the same time neutralizing the gastric acid. After less than 20 minutes in the stomach, the surrounding environment reaches a neutral pH value, whereupon the polymer dissolves and releases the drug payload. The micromotors are entirely biocompatible so they can dissolve naturally into the body, and researchers say that normal pH value is re-established in the stomach within 24 hours.

We have seen something similar in the past when it comes to polymer materiasl designed to respond to pH levels in the stomach. In 2015 researchers from MIT designed a pH-responsive polymer gel that could be used to coat capsules and aid in drug deliveries to the stomach. The polymer gel was designed to be used in combination with drug delivery systems to enable orally-administered drugs with extended-release capabilities.

However this new method aims to not only provide a drug delivery system that can release drugs with more precision, but it also the first design that makes use of gastric acid rather than fighting against it. Gastric acid is produced in the stomach to protect from pathogens and promote digestion, but it can break down orally administered pH-sensitive drugs before they reach their desired destination. Some of these drugs can be coated with proton pump inhibitors that can block the production of gastric acid, but over time this can lead to headaches, diarrhea, and other harmful side effects.

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For years coating drugs with gastric-resistant substances has been used as a workaround for some of these issues, but it doesn't solve the problem for drugs that need to be activated in the stomach itself. These new microscopic submarines help address all of these issues by navigating to the stomach using gastric acid as fuel before releasing its payload.

As they move forward with their research, the nanoengineers from UC San Diego hope that this new technique can be used to address many of these longstanding issues in a simple-to-use drug delivery method. The group believes the method could soon be used to treat stomach ulcers, as well as a variety of different bacterial infections in the stomach. In time, the group aims to refine the method so that it can be used to treat virtually any stomach disease that responds to acid-sensitive drugs.

Kristopher Sturgis is a contributor to Qmed.

[image courtesy of WILEY ACADEMICS]

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