Severed nerves in the body can lead to the loss of muscle function and muscle atrophy, unless the severed nerve endings get reconnected. One possible new solution devised by Chinese researchers uses liquid metal to create an electrical conduit capable of transmitting signals between the severed nerve ends.
The liquid metal solution consists of a gallium-indium-tin (GaInSn) alloy that has successfully bridged severed sciatic nerves taken from the calf muscles of bullfrogs, according to Technology Review. A team at Tsinghua University in Beijing showed that the metal alloy—capable of remaining liquid at body temperature and thought to be benign—could transmit nerve signals much more effectively than the commonly-used Ringer's solution meant to mimic the salt mixture in body fluids.
Such a solution could keep the affected muscles active by continuing to transmit nerve signals and prevent muscle loss. That would buy plenty of time for the severed nerve endings to slowly grew back together at the snail's pace of one millimeter per day. The liquid metal idea also presents an alternative to usual methods of suturing together the cut nerve endings if they're close enough together, or as a tool for even more complex nerve transplants.
Caption: Photographs of x-ray images showing a bullfrog's lower body both with the injected liquid metal and without. Images: Tsinghua University
The Chinese team ran its experiments by snipping the sciatic nerve and the connected muscles from bullfrogs, placing the severed nerve ends and their respective muscles in separate petri dishes, and then testing connecting conduits consisting of either the liquid metal or Ringer's solution. In the liquid metal case, the electroneurographic signal was "virtually similar" to the signal transmitted by an intact sciatic nerve, according to the paper published on 7 April in the arXiv database.
As a bonus, the Chinese researchers found that the liquid metal injected into a bullfrog's calf muscles shows up clearly under x-rays. That would make it easy to locate and remove the liquid metal using a micro-syringe if it no longer became necessary.
A future step might involve using the liquid metal alongside growth factors that encourage nerve regeneration. Tiny microchannels or concentric tubes could contain the liquid metal and growth factors in a complete package for helping to repair severed nerves. But many questions remain about whether the liquid metal solution really does help preserve muscle function in the long term, as well as whether it's truly safe to use inside human bodies.
Jeremy Hsu has been working as a science and technology journalist in New York City since 2008. He has written on subjects as diverse as supercomputing and wearable electronics for IEEE Spectrum. When he’s not trying to wrap his head around the latest quantum computing news for Spectrum, he also contributes to a variety of publications such as Scientific American, Discover, Popular Science, and others. He is a graduate of New York University’s Science, Health & Environmental Reporting Program.