Conductive Hydrogel Acts as an Artificial Nerve

Peripheral nerves transmit signals from the brain to the rest of the body. Injuries in which a peripheral nerve has been completely severed are difficult to treat. Autologous nerve transplantation is a commonly used treatment that involves removing part of a nerve from somewhere else in the body and sewing it onto the ends of the severed one. However, this surgery does not always restore function, and multiple follow-up surgeries are sometimes needed. Artificial nerve grafts, in combination with supporting cells, can also be used, but it often takes a long time for the nerves to fully recover. An effective, fast-acting treatment that could replace autologous nerve transplantation would, thus, be useful.

Chang-Chun Wang, Nanjing Institute of Technology and Jiangsu Key Laboratory of Advanced Structural Materials & Application Technology, Nanjing, China, Ze-Zhang Zhu, Qun-Dong Shen, Nanjing University, China, and colleagues have used conducting hydrogels as an artificial nerve replacement. These hydrogels are water-swollen, biocompatible polymers that can transmit bioelectrical signals. The team used a tough but stretchable conductive hydrogel containing polyaniline and polyacrylamide. First, the team synthesized a polyacrylamide hydrogel by reacting an aqueous solution of acrylamide with N,N’-methylene bis(acrylamide) as a cross-linker and ammonium sulfate as an initiator. The polyacrylamide was then immersed in an aqueous hydrochloric acid solution of aniline to give the desired polyacrylamide/polyaniline hydrogel.

The crosslinked polymer has a microporous network that allows nerve cells to adhere well to the material. The team first showed that the hydrogel can conduct bioelectrical signals through a damaged sciatic nerve removed from a toad. Then, they implanted the hydrogel into rats with sciatic nerve injuries that affect the use of the legs. The results of this in vivo test indicate that rats’ nerve function was restored, which suggests the hydrogel could be used to replace damaged nerve. The electricity-conducting properties of the material improve upon irradiation with near-infrared (NIR) light, which can penetrate tissues. This might make it possible to further enhance nerve conduction and recovery.