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Nanoengineers at UC San Diego have developed the first drug-delivering micromotors for treating bacterial infection. (Credit: Laboratory for Nanobioelectronics at UC San Diego)

Nanoengineers have demonstrated for the first time the use of micromotors to treat a bacterial infection in the stomach. These tiny vehicles, each about half the width of a human hair, swim rapidly throughout the stomach while neutralizing gastric acid and then release their cargo of antibiotics at the desired pH. This micromotor-enabled delivery approach is a promising new method for treating stomach and gastrointestinal tract diseases with acid-sensitive drugs, researchers say.

Gastric acid can be destructive to orally administered drugs such as antibiotics and protein-based pharmaceuticals. Drugs used to treat bacterial infections, ulcers and other diseases in the stomach are normally taken with additional substances, called proton pump inhibitors, to suppress gastric acid production. The micromotors have a built-in mechanism to neutralize gastric acid and effectively deliver their drug payloads in the stomach — without the use of proton pump inhibitors.

Each micromotor consists of a spherical magnesium core coated with a protective layer of titanium dioxide, followed by a layer of the antibiotic clarithromycin, and an outer layer of a positively charged polymer called chitosan that enables the motors to stick to the stomach wall.

This binding is also enhanced by the propulsion of the micromotors, which is fueled by the stomach’s own acid. The magnesium cores react with gastric acid, generating a stream of hydrogen microbubbles that propel the motors around inside the stomach. This reaction also temporarily reduces the amount of acid in the stomach, increasing the pH level enough to allow the micromotors to release the drug and perform treatment. The normal stomach pH is restored within 24 hours.

The micromotors are mostly made of biodegradable materials. The magnesium cores and polymer layers are dissolved by gastric acid without producing harmful residues.

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