Nanobioelectronics to treat bacterial infection in the stomach

By Dr. Ananya Mandal, MDAug 16 2017

Nanotechnology has made another breakthrough at the University of California San Diego. For the first time the researchers have shown that micromotors or microscopic robots could be used to treat a bacterial infection in the stomach in mice models win the laboratory.

The micromotors are each about half the thickness of a human hair and are capable of swimming fast throughout the stomach and help to neutralize the highly acidic medium within the stomach. Then they release their cargo of the antibiotics at the pH that is set from before and help cure the infection. The study report was published in the journal Nature Communications.

The team of researchers included nanoengineering professors Joseph Wang and Liangfang Zhang at the UC San Diego Jacobs School of Engineering. These professors have earlier developed the movement of these micromotors within the body. This effort makes these micromotors as excellent drug delivery options they said.

According to the team of researchers, this new method could be the breakthrough that was being anticipated. It could treat stomach and gastrointestinal tract diseases with acid-sensitive drugs now.

Earlier most of these acid-sensitive agents got destroyed in the stomach acid as soon as they came in contact with the acid within the stomach. Notably antibiotics and protein based drugs got easily damaged with the acid in the stomach.

To prevent damage to the drug before it can act, the patient had to be asked to take agents such as proton pump inhibitors, to suppress gastric acid production. Drugs were also being developed with an acid-resistant coating to protect them from the acids.

However none of these were foolproof and the overall effect of the acid-sensitive drug remained low. Proton pump inhibitors further caused other side effects especially when used over a long period of time.

With this new technology the micromotors are built with a mechanism that can neutralize gastric acid to bring the pH to a desired level. Once the optimum pH is achieved in the stomach, the micromotors can safely deliver the antibiotics they are carrying.

These antibiotics can act without fear of getting denatured by the acid. Berta Esteban-Fernández de Ávila, a postdoctoral scholar in Wang's research group at UC San Diego and a author of the paper explained that now there is no need for a two step process – neutralization of the acid and then administration of the drug. Now a one step process that combines “acid neutralization with therapeutic action” can be achieved.

The authors explain that each of these tiny robots or micromotors carry a spherical magnesium core. This gets a coating of a protective layer of titanium dioxide. Over this coat is a layer of the antibiotic clarithromycin.

On top of these layers is another layer of a positively-charged polymer called chitosan. Chitosan would help these micromotors adhere to the stomach wall while they are inside the stomach. Once this bidning or adherence takes place the magnesium cores react with gastric acid. This leads to formation of hydrogen microbubbles.

These microbubbles help to propel the motors around inside the stomach. Also this reaction reduces the gastric acid and raises the pH by reducing the gastric acid. Once the desired pH is achieved the micromotors release the drug. Normal acidic pH comes back within 24 hours of the treatment write researchers.

The micromotors are made up of biodegradable materials and do not pose a threat to the patient. The magnesium cores as well as the polymer layers are dissolved by gastric acid.

As an initial step the team of researchers used these micromotors in mice with Helicobacter pylori infections.

The micromotors carried clinical dose of the antibiotic clarithromycin and were given to the mice orally once a day for five consecutive days.

After the study the counts of the bacteria within the mouse stomach was assessed to check the effectiveness of the drug. Two groups of mice were tested. One with the micromotors carrying the antibiotic and another with traditional oral clarithromycin along with a gastric acid suppressor proton pump inhibitor.

The micromotors were found to be more effective compared to the traditional approach in reducing the bacterial load write researchers.

This is still an early stage and further studies are needed to prove the efficacy and safety of these nano technology marvels. Other diseases and drug combinations would also be included in the studies to check if this system works.