Solving neurological disorders by using electrodes grown in the brain!

The boundaries between biology and technology are becoming blurred. Researchers have successfully grown electrodes in living tissue using the body's molecules as triggers. The result, published in the journal Science, paves the way for the formation of fully integrated electronic circuits in living organisms.

For several decades, we have tried to create electronics that mimic biology. Now we let biology create the electronics for us!

Linking electronics to biological tissue is important to understanding complex biological functions, combating diseases in the brain, and developing future interfaces between man and machine. However, conventional bioelectronics, developed in parallel with the semiconductor industry, have a fixed and static design that is difficult, if not impossible, to combine with living biological signal systems.

To bridge this gap between biology and technology, researchers have developed a method for creating soft, substrate-free, electronically conductive materials in living tissue. By injecting a gel containing enzymes as the "assembly molecules," the researchers were able to grow electrodes in the tissue of zebrafish and medicinal leeches.

Contact with the body's substances changes the structure of the gel and makes it electrically conductive, which it isn't before injection. Depending on the tissue, we can also adjust the composition of the gel to get the electrical process going.

The body's endogenous molecules are enough to trigger the formation of electrodes. There is no need for genetic modification or external signals, such as light or electrical energy, which has been necessary in previous experiments. This is  the first successful work in the field.

The injectable gel being tested on a microfabricated circuit. Credit: Thor Balkhed

This study paves the way for a new paradigm in bioelectronics. Where it previously took implanted physical objects to start electronic processes in the body, injection of a viscous gel will be enough in the future.

In their study, the researchers further show that the method can target the electronically conducting material to specific biological substructures and thereby create suitable interfaces for nerve stimulation. In the long term, the fabrication of fully integrated electronic circuits in living organisms may be possible.

 The researchers successfully achieved electrode formation in the brain, heart, and tail fins of zebrafish and around the nervous tissue of medicinal leeches. The animals were not harmed by the injected gel and were otherwise not affected by the electrode formation. One of the many challenges in these trials was to take the animals' immune system into account.

By making smart changes to the chemistry, they were able to develop electrodes that were accepted by the brain tissue and immune system.

 Xenofon Strakosas et al, Metabolite-induced in vivo fabrication of substrate-free organic bioelectronics, Science (2023). DOI: 10.1126/science.adc9998. www.science.org/doi/10.1126/science.adc9998