There are challenges in making materials that are soft enough to come into contact with living tissue, but firm enough to be inserted into the body. Researchers from the Universities of Linköping, Lund and Gothenburg in Sweden have successfully grown electrodes in living tissue using body molecules as triggers. Their findings could lead to the formation of fully integrated electronic circuits in living organisms.

Understanding complicated biological processes, fighting brain diseases and creating future machine-human interactions depend on linking electronics to biological tissue. Conventional bioelectronics, on the other hand, has a fixed and static design that makes it challenging to integrate with living biological signaling systems when possible. These devices were created simultaneously with the semiconductor industry.

Researchers developed a method to dynamically create soft, substrate-free conductive materials in the biological environment to address this incompatibility. The method makes it possible to create soft, substrate-free, electronically conductive materials in living tissue.

Researchers injected a gel made up of enzymes as the “assembly molecules” to grow electrodes into the tissue of zebrafish and medicinal leeches.

Xenofon Strakosas, a researcher at LOE and Lund University and one of the study’s lead authors, said: “Contact with endogenous substances changes the structure of the gel and makes it electrically conductive, which was not the case before injection. Depending on the tissue, we can also adjust the composition of the gel to initiate the electrical process.”

Endogenous chemicals produced by the body are enough to trigger the development of electrodes. Contrary to other research, there is no need for genetic change or external signals such as light or electrical energy. The Swedish researchers are the first in the world to have achieved this.

Scientists have further shown that the method can target the electronically conductive material to specific biological substructures, creating appropriate nerve stimulation interfaces. In the future, it might be possible to create fully integrated electronic circuits in biological things.

During experiments at Lund University, the researchers successfully formed electrodes in the brains, hearts and tail fins of zebrafish and around the nervous tissue of medicinal leeches. The formation of the electrodes had no effect on the animals, nor did the gel that was injected. One of the many challenges in these trials was to take the animals’ immune systems into account.

Professor Roger Olsson from Lund University Medical School said: “By making smart changes to the chemistry, we were able to develop electrodes that are accepted by brain tissue and the immune system. The zebrafish is an excellent model to study organic electrodes in the brain.”

Hanne Biesmans, a Ph.D. student at LOE and one of the main authors, said: “Our results open up entirely new ways of thinking about biology and electronics. We still have many problems to solve, but this study is a good starting point for future research.”

Magazine reference:

Xenofon Strakosas, Hanne Biesmans, Tobias Abrahamsson, et al. Metabolite-induced in vivo fabrication of substrate-free organic bioelectronics. Science 2023. DOI: 10.1126/science.adc9998