Imagine a future where your doctor can inject a gel into your tissue and the gel forms a soft, current-conducting electrode. This can then be used to treat your nervous system disease. After a while, the electrode has dissolved and disappeared. Swedish researchers have already developed the gel and eventually want to be able to connect electronic components to biological tissues, such as the brain.
The conductivity of the injectable gel is tested on a microfabricated circuit. Image credit: Thor Balkhed/Linköping University
Electronic medicine is a field of research that does not fit neatly into any existing field.
“Right now you’re talking to a physicist, a chemist and myself, who have a background in biomedicine. We’re working with materials scientists and electrical engineers to integrate knowledge from our different fields. For this to work, you need to understand the brain and understand chemistry and physics,” says Hanne Biesmans, a PhD student at the Laboratory of Organic Electronics, LOE, at Linköping University.
The research she is referring to is in so-called organic electronics that can be connected to living tissue. The long-term goal is to be able to treat various diseases of the nervous system and brain. Her colleague Tobias Abrahamsson is a chemist.
“The interdisciplinary nature of our research, where we combine different aspects and areas of knowledge, is very exciting. You could also say that I have a more personal motivation, because in my family there are diseases that affect the nervous system,” he says.
Translated between biology and electronics
But what is organic electronics? And how could it be used to treat diseases – such as epilepsy, depression, or Alzheimer’s and Parkinson’s – that are difficult to treat today?
“In the body, communication takes place via a large number of small molecules, such as neurotransmitters and ions. Neuronal signaling, for example, is also a wave of ions that gives rise to an electrical impulse. So we want something that can take all this information and act as a translator between ions and electrons,” says Xenofon Strakosas, an assistant professor with a background in physics.
In 2023, they succeeded, together with other researchers from Linköping University, Lund University and the University of Gothenburg, in growing gel electrodes in living tissue.
“Instead of using metals and other inorganic materials to conduct current, electronics can be created from different materials based on carbon and hydrogen atoms – in other words, organic materials – that are conductive. These are more compatible with biological tissues and therefore better suited for integration, for example, into the body,” explains Tobias Abrahamsson.
Organic electronic materials are very useful for conducting biological signals because they can conduct ions as well as electrons. In addition, they are soft, unlike metals. Electrical brain stimulation is already used to treat some diseases. Electrodes are implanted in the brain, for example, to treat Parkinson’s disease.
“But the implants used in clinics today are quite rudimentary; they are made of hard or rigid materials such as metals. And our body is soft. So there is friction that can lead to inflammation and the formation of scar tissue. Our materials are softer and more compatible with the body,” says Hanne Biesmans.
Electrodes inside plants
About ten years ago, their colleagues at the LOE showed that they could make plants suck up a water-soluble substance that formed an electrically conductive structure inside the plant stem. A kind of electrode, in other words, inside a plant.
The substance in question is something called a polymer – a substance made up of many small, similar units that can form long chains together through a process called polymerization. This time, roses were used, and the researchers were able to show that they had created organic electrodes. This opened the door to a new field of research.
“But there was a piece missing. We didn’t know how to form polymers inside mammals and in the brain, for example. But then we realized that we could contain enzymes in the gel and use the body’s own substances to start the polymerization,” says Xenofon Strakosas.
The idea allowed the researchers to now be able to inject the slightly viscous gel-like solution into the tissue. When it comes into contact with substances in the body, such as glucose, the properties of the gel change. And the Swedish researchers were the first in the world to succeed with the method used to activate the formation of electrodes in tissue.
“The gel self-polymerizes in the tissues and becomes electrically conductive. We let biology do the work for us,” explains Xenofon Strakosas.
Also, it stays where it was injected. This is important because the researchers want to be able to control where the gel is in the tissue. The research team has shown that they can grow electrodes in the brains of zebrafish and around the nervous systems of leeches. They are now investigating whether this also works in mice.
But there is still a long way to go before treating diseases with the gel becomes a reality. First, the research team will explore the stability of the gel inside the tissue. Does it break down after a while and what happens next? Another important question is how the conductive gel can be connected to electronics outside the body.
“It’s not the easiest thing to do, but I hope that in time this method can be used to monitor what’s happening inside the body, down to the cellular level. Then we might be able to better understand what triggers or leads to different diseases of the nervous system,” says Tobias Abrahamsson.
“There is still a lot to solve, but we are making progress,” says Xenofon Strakosas. It would be great if we could eventually use the electrodes to read signals inside the body and use them for research or in health care.
Written by Karin Söderlund Leifler
Source: Linköping University
Originally published in The European Times.
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