Edible batteries could make ingestible medical devices and targeted drug delivery safer

A taste of the future of medicine.
A taste of the future of medicine.
Image: Bettinger lab
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Batteries, at least the type you buy at the drugstore, are toxic and absolutely not meant to be ingested. But researchers at Carnegie Mellon University are creating batteries that are not only safe if they’re swallowed—they’re meant to end up inside your body.

A team led by Christopher Bettinger, an assistant professor in the school’s Department of Materials Science and Engineering, believe that digestible batteries could to be used to power “edible electronics” that serve a variety of medical purposes, from diagnosis to treatment.

To make batteries that are safe to ingest, the researchers “replaced the potentially toxic components of the battery with that of benign, endogenous materials of the human body,”said Bettinger at a press conference organized by American Chemical Society Tuesday (Aug. 22). The key ingredient is melanin, a pigment that naturally occurs in human skin, hair, and eyes, to create the electrodes. According to a press release, “melanins absorb ultraviolet light to quench free radicals and protect us from damage. They also happen to bind and unbind metallic ions.”

“We thought, this is basically a battery,” Bettinger said.

Their biodegradable battery is encapsulated in a digestible 3D-printed shell made of a gelatin material, like the type used in some vitamins. The capsule “could deliver controlled-release therapies to fight disease with previously impossible precision and safety,” Bloomberg reports. After the pill is swallowed, the battery comes into contact with ions (atoms or molecule with a positive or negative electrical charge) in the stomach, activating current flow in the device. Targeted drug-delivery methods use this electrical field to trigger the release of the chemicals into the body.

The melanin-based battery doesn’t last long, but it doesn’t have to. It’s designed to power up to 10 milliWatt devices for 10 to 20 hours—a time frame in which it could effectively facilitate drug delivery or power sensing devices, such as those used to monitor blood-sugar levels.

Lots of medical devices used in diagnosis and treatment are battery driven, but toxicity remains an issue. For instance, ingestible cameras, that are meant to be excreted after one use (or at most a handful of uses), typically contain “off-the-shelf” battery materials that can pose a threat when they get lodged in the body and burst.

But if the gelatin shell bursts before the new edible batteries can fulfill their purpose, there’s little danger. ”The same kind of pigments that we use are actually the same kind of pigments that you find in a squid ink pasta actually, so if you’ve ever had squid ink pasta then you’ve already consumed more melanin than are in the batteries,” Bettinger said at the conference. As a result, repeated use of the batteries pose little risk.

“We have to think about biologically-derived materials that could replace some of these things you might find in a RadioShack,” Bettinger said. In 2013, Bettinger used cuttlefish ink to make edible, dissolvable power sources and by 2015, he was already working on swallowable medical devices. Next, the team will experiment with a combination of an edible polymer, pectin, and benign metals like magnesium and iron, to create different types of ingestible batteries. Bettinger said that the team is also looking for partners that could help engineer specific applications for the technology.