Scientists Just ‘Grew’ Electrodes in Leeches. Can It Be Done in Humans, Too?

This method could lead to a safer treatment for neurological conditions like Parkinson’s.

Written by Joanna Thompson
Originally Published: 
Medical leeches for hirudotherapy on leech farm or laboratory

Brain cells communicate via chemical signals and short electrical impulses, a phenomenon doctors have long aimed to harness in medicine. But delivering jolts to the nervous system, also known as electrical stimulation, has proved challenging (and, not to mention, risky). Now, scientists are working to make electrical stimulation in the brain much easier and safer.

In a paper published last week in Science, a team of Swedish researchers laid out their vision of gel-based biocompatible electrodes in the brains of live animals. This method could eventually lead to life-saving treatments for people with conditions like Parkinson’s and epilepsy.

Scientists have created an injectable gel that can organize itself into electrodes within the brain.

Thor Balkhed

It’s electric

Humans have been tinkering with electricity’s medical applications for thousands of years. As early as AD 46, the Roman emperor Claudius’s personal physician recommended he hold an electric fish to his forehead to cure headaches.

Scientists didn’t harness zapping power until several centuries later — but as soon as they did, they began by experimenting with the brain.

A series of experiments spanning the early- and mid-19th century suggested that stimulating certain areas of the cortical cortex with electrodes could produce specific reactions, such facial tics, in dogs. Researchers also discovered that this method could potentially alleviate some neurological conditions. But it proved tricky to deliver the electricity.

“For a long time, we have wanted to make electrodes [that] we won’t have to implant into the brain,” Martin Hjort, a materials scientist at Lund University in Sweden and one of the co-authors of the paper, tells Inverse.

Doctors have used implanted electrodes to attempt to treat conditions such as epilepsy and Parkinson’s, which causes tremors and balance difficulties, for just over thirty years. This procedure is called deep brain stimulation, or DBS. Essentially, patients have thin electrodes implanted deep inside the brain that generate electrical impulses to help “stimulate” neural activity.

This method may help control involuntary muscle movements by regulating the impulses that the brain sends to nerves throughout the body. To date, over 150,000 people have received DBS treatment.

This type of therapy can come with hazards. The electrodes tend to be stiff and inflexible — not ideal for delicate tissues. “You typically get a lot of damage at the insertion site,” Hjort says.

Such damage can lead to post-op complications, including migraines, numbness and increased risk of seizure. But a new type of electrode could sidestep these complications entirely.

Deep brain stimulation can be risky and cause side effects — the new injectable gel could offer a safer alternative.

Andriy Onufriyenko/Moment/Getty Images

The brain as an electronics factory

In the new study, the researchers describe their new injectable, gel-based polymer that organizes itself into electrodes within living tissues. “We let biology create the electronics for us,” Magnus Berggren, an organic electronics researcher at Linköping University in Sweden and senior author of the study, said in a press release.

When the molecules inside the gel meet enzymes inside an animal’s body, they become electrically conductive. This reaction could allow scientists to stimulate various areas inside the body with an externally applied voltage.

The researchers successfully coaxed gel-based electrodes to grow inside the bodies of live zebrafish and leeches. The electrodes organized themselves inside the tissue of each organ the gel was injected into, including the brain and heart.

Ultimately, the procedure didn’t appear to cause pain or discomfort in the zebrafish (the same was presumably true for the leeches, though it was harder to tell).

When zebrafish are in pain, they respond “in a lot of different ways, such as firing off swimming very fast, or they can roll around,” Hjort says. “We didn’t see any of these negative effects. So I think that’s a very good sign.”

Hjort and his co-authors caution that while their results are exciting, this technology is still a long way from any human applications. They still need to show that the gel electrodes work in fish and leeches when stimulated externally, for example — but demonstrating that they can form safely marks an encouraging first step.

In the future, this method could show major promise for people. In addition to safer deep brain stimulation therapy, the tech could allow for more sophisticated brain scans or even motorized prosthetics that react to nerve signals.

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