The nervous system of mammals is poorly regenerative at best. The use of implantable scaffold materials is one of the strategies under development in the tissue engineering community to encourage greater degrees of regrowth following nerve damage. Such materials can be infused with chemical cues to guide cell activity, or provided with other useful properties such as conductivity. The work noted here is an example of this field of research and development, quite similar to many other studies conducted over the past decade or more. As for all medical research in this heavily regulated environment, it is slow to make it to the clinic in any meaningful way.
Injuries in which a peripheral nerve has been completely severed, such as a deep cut from an accident, are difficult to treat. A common strategy, called autologous nerve transplantation, involves removing a section of peripheral nerve from elsewhere in the body and sewing it onto the ends of the severed one. However, the surgery does not always restore function, and multiple follow-up surgeries are sometimes needed. Artificial nerve grafts, in combination with supporting cells, have also been used, but it often takes a long time for nerves to fully recover. Researchers wanted to develop an effective, fast-acting treatment that could replace autologous nerve transplantation. For this purpose, they decided to explore conducting hydrogels – water-swollen, biocompatible polymers that can transmit bioelectrical signals.
The researchers prepared a tough but stretchable conductive hydrogel containing polyaniline and polyacrylamide. The crosslinked polymer had a 3D microporous network that, once implanted, allowed nerve cells to enter and adhere, helping restore lost tissue. The team showed that the material could conduct bioelectrical signals through a damaged sciatic nerve removed from a toad. Then, they implanted the hydrogel into rats with sciatic nerve injuries. Two weeks later, the rats’ nerves recovered their bioelectrical properties, and their walking improved compared with untreated rats. Because the electricity-conducting properties of the material improve with irradiation by near-infrared light, which can penetrate tissues, it could be possible to further enhance nerve conduction and recovery in this way.