Gel injected into living animals turns into an electrode

The researchers injected the leeches with a gel that turned into soft electrodes, allowing them to control muscle contractions. This gel could eventually be used in the brain to treat neurological conditions without surgery.

To Carmela Padavich-Callaghan

An injectable gel that transforms into a conductive substance in the body has been shown not to interfere with the swimming ability of zebrafish, and was also used to control dead leech muscles. It can be injected into the human brain to treat neurological conditions without implanting electrodes, a tissue-damaging process.

Magnus Berggren and his colleagues at Linköping University in Sweden have developed an injectable gel made of many molecules of a type of chemical called monomers and enzymes that trigger reactions in breaking down sugars. The enzyme produces hydrogen peroxide, which reacts with the monomer and attaches to polymers in the body, forming soft, flexible electrodes.

The researchers tailored the gel to work with sugars such as glucose already present in animal tissues. The anatomy of these animals is well understood, so they tested it on zebrafish and medical leeches.

The researchers injected the gel into the fins, brains, or hearts of nine zebrafish. The zebrafish successfully self-assembled into electrodes and turned black inside the nearly transparent fish. After injection, the fish continued to swim normally. After dissecting the fish, Berggren and his colleagues applied a voltage to a slice of brain tissue filled with the transformed gel, causing the electricity to energize them, much as if conventional electrodes were inserted into the fish’s brain. was found to pass through

To test whether the soft electrodes conduct well enough to affect the animal’s body, the researchers added gel on top of standard metal electrodes, deformed the gel, and applied the coated electrodes to three electrodes. It was inserted through a small incision into the central nerve of two dead leeches.

Making soft electrodes inside the brain, rather than inserting them from the outside, would alleviate some of the so-called “fork and jelly” problems, says David Martin. at the University of Delaware.

Claudia Tortiglione of the Italian National Research Council says gels may not work with all types of tissue unless the chemical composition is adjusted. She says that if the sugars needed for physiotherapy aren’t present in the tissue, the gel won’t deform.

“We’ve already created a new version of the gel with fine-tuned chemistries that form electrodes only in specific tissues,” said Berggen. “Ultimately, we want to target plaque-like tissue in the brain that causes disease.” Such electrodes are already being used to reduce tremor in conditions such as Parkinson’s disease. May be part of electrostimulation therapy.