Scientists Grow Electrodes Inside The Body

Researchers at Linköping University in Sweden have developed a method whereby the body can ‘grow its own’ electrodes. The minimally invasive technique involves injecting a hydrogel that is laden with enzymes into target tissues. The enzymes interact with molecules that are present in the tissue to change the structure of the gel and allow it to become electrically conductive. The approach could facilitate a variety of advanced medical systems, from pacemakers to brain-computer interfaces. Excitingly, the technology avoids the need for invasive surgery or conventional stiff electrical components that are not well matched to native tissues and can provoke unwanted immune reactions. So far, the researchers have shown that they can grow electrodes in the brain, heart, and tail fins of zebrafish and near the neural system in leeches.

Integration of the body with electrical components for medical benefit is well underway, with current versions of brain-computer interface systems allowing paralyzed patients to write text or control an electric wheelchair. However, the point of interface between the body and external machines is typically an implanted electrode, and current versions of such devices can come with multiple drawbacks.

Most electrodes are largely rigid, which does not allow them to blend well with soft tissues, potentially resulting in tissue irritation or damage, immune responses, and eventual electrode malfunction or complete failure. Moreover, implanting such electrodes will typically require some type of surgical procedure, increasing expense and patient inconvenience and discomfort.    

To address these limitations, the Linköping University researchers have developed an injectable material that turns into a conductive bolus in the body. The injectable hydrogel contains a cocktail of enzymes that interact with molecules present in the body to create a conductive structure.

Here are some lines from the study abstract that detail some of these constituents and how they work: “a complex precursor system including an oxidase to generate hydrogen peroxide in situ, a peroxidase to catalyze oxidative polymerization, a water-soluble conjugated monomer, a polyelectrolyte with counterions for covalent cross linking, and a surfactant for stabilization. With this cocktail, the authors were able to induce polymerization and subsequent gelation in different tissue environments.”

So far, the researchers have shown that the material can create electrically conductive structures in animals, including zebrafish and leeches without causing any obvious adverse effects. “By making smart changes to the chemistry, we were able to develop electrodes that were accepted by the brain tissue and immune system. The zebrafish is an excellent model for the study of organic electrodes in brains,” said Professor Roger Olsson, a researcher involved in the study.      

Study in journal Science: Metabolite-induced in vivo fabrication of substrate-free organic bioelectronics

Via: Linköping University