Making an electrically conducting soft polymer in a living tissue

Researchers have developed a way to make bioelectronics directly inside living tissues, an approach they tested by making electrodes in the brain, heart, and fin tissue of living zebrafish, as well as in isolated mammalian muscle tissues. According to the authors, the new method paves the way for in vivo fabrication of fully integrated electronic circuits within the nervous system and other living tissue. “Safety and stability analyses over long periods will be essential to determining whether such technology is useful for chronic implantations,” writes Sahika Inal in a related Perspective. “However, the strategy … suggests that any living tissue can turn into electronic matter and brings the field closer to generating seamless biotic-abiotic interfaces with a potentially long lifetime and minimum harm to tissues.” Implantable electronic devices that can interface with soft biological neural tissues offer a valuable approach to studying the complex electrical signaling of the nervous system and enable the therapeutic modulation of neural circuitry to prevent or treat various diseases and disorders. However, conventional bioelectronic implants often require the use of rigid electronic substrates that are incompatible with delicate living tissues and can provoke injury and inflammation that can affect a device’s electrical properties and long-term performance. Overcoming the incompatibility between static, solid-state electronic materials and dynamic, soft biological tissues has proven challenging. Here, Xenofon Strakosas and colleagues present a method to fabricate polymer-based, substrate-free electronic conducting materials directly inside a tissue. Strakosas et al. developed a complex molecular precursor cocktail that, when injected into a tissue, uses endogenous metabolites (glucose and lactate) to induce polymerization of organic precursors to form conducting polymer gels. To demonstrate the approach, the authors “grew” gel electrodes in the brain, heart, and fin tissue of living zebrafish, with no signs of tissue damage, and in isolated mammalian muscle tissues, including beef, pork and chicken. In medicinal leeches, they showed how the conducting gel could interface nervous tissue with electrodes on a tiny flexible probe.