Injectable Hydrogel Allows Scientists to Grow Electrodes inside Body

By HospiMedica International staff writers
Posted on 21 Mar 2023

Understanding complex biological functions, combating brain diseases, and developing interfaces between humans and machines all depend on linking electronics to biological tissue. Conventional bioelectronics, developed in parallel with the semiconductor industry, have a fixed and static design that is challenging, if not impossible, to combine with living biological signal systems. To address this issue, researchers have devised a method for creating soft and substrate-free electronically conductive materials in living tissue. Using a gel containing enzymes as "assembly molecules," researchers were able to grow electrodes in the tissue of zebrafish and medicinal leeches, bridging the gap between biology and technology.

In a groundbreaking study, researchers at Linköping University (Linköping, Sweden), Lund University (Lund, Sweden), and University of Gothenburg (Gothenburg, Sweden) have shown that electrodes can be triggered by the body's endogenous molecules without the need for genetic modification or external signals like light or electrical energy - a requirement in previous experiments. The researchers' achievement marks the first time that a successful formation of electrodes has been observed without resorting to such interventions. The study establishes a new paradigm in bioelectronics, where future injection of a viscous gel instead of implanted physical objects will suffice to stimulate electronic processes in the body.

Image: Using the injectable gel, the researchers were able to grow electrodes in living tissue (Photo courtesy of Linköping University)

The researchers' study also demonstrated that the method is capable of targeting the electronically conducting material to specific biological substructures to create appropriate interfaces for nerve stimulation. In the long run, fully integrated electronic circuits may be developed in living organisms using this method. The team from Lund University successfully created electrodes in the brain, heart, and tail fins of zebrafish and around the nervous tissue of medicinal leeches without causing harm to the animals during the injection of the gel that formed the electrodes. Their experiment was not without its challenges, however, and it took the researchers many years to figure out the ideal combination of substances and gel structure needed to form electrodes in these areas.

“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,” said Xenofon Strakosas, researcher at LOE and Lund University and one of the study's main authors.

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