The tiny micromotors – each about half the width of a human hair – propel themselves through the stomach while neutralizing gastric acid and releasing antibiotics at the desired pH. Such a micromotor-enabled delivery approach, say the researchers, offers a promising new method for treating stomach and gastrointestinal tract diseases.
Delivering orally administered drugs for such infections is complicated by the stomach’s normally occurring gastric acid, which can be destructive to drugs like antibiotics. As a result, these drugs are normally taken with additional substances – called proton pump inhibitors – designed to suppress gastric acid production, but not without the risk of adverse side effects, especially if taken in high doses or over longer periods.
According to the researchers, their micromotors have a built-in mechanism to neutralize gastric acid and effectively deliver drug payloads into the stomach without the use of such proton pump inhibitors.
“It’s a one-step treatment with these micromotors, combining acid neutralization with therapeutic action,” says Berta Esteban-Fernández de Ávila, a postdoctoral scholar at UC San Diego and a co-first author of a paper on the research.
The micromotors are described as consisting of a spherical magnesium core coated with a protective layer of titanium dioxide, followed by a layer of the antibiotic clarithromycin. An outer layer of a positively-charged polymer called chitosan enables the motors to stick to the stomach wall.
The micromotors’ magnesium cores react with the stomach’s gastric acid, which generates hydrogen microbubbles that propel the motors around inside the stomach while at the same time temporarily reducing the amount of stomach acid and allowing the micromotors to release the drug and perform treatment. 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.
The researchers tested the micromotors in mice with a specific bacterial infection. They found that treatment with the micromotors was slightly more effective than when the same dose of antibiotic was given in combination with proton pump inhibitors.
The researchers are planning further studies aimed at evaluating the therapeutic performance of the micromotors in vivo and compare it with other standard therapies against stomach diseases. They also plan to test different drug combinations with the micromotors to treat multiple diseases in the stomach, or in different sections of the gastrointestinal tract.
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