Chinese biomedical engineers have used a liquid metal to transmit electrical signals through the space between some severed sciatic nerves. According to the researchers, the work could lead to a new treatment for nerve injuries.
When peripheral nerves are divided, the loss of function leads to atrophy of the affected muscles, in addition to leading to a considerable change in quality of life and, in many cases, a shorter life expectancy.
Despite decades of researching this, no one has discovered an effective way to reconnect severed nerves. There are various techniques for sewing the ends back together or grafting nerves into the gap created between the severed ends, but since nerves grow at a rate of 1mm per day, it can take a long time, even years, to reconnect . Meanwhile, muscles can be irretrievably degraded, leading to long-term disability.
Now, Jing Liu of Beijing Tsinghua University and some friends claim to have reconnected severed nerves using liquid metal for the first time. And, according to them, in conducting electrical signals between the severed ends of a nerve, metal radically outperforms the standard saline electrolyte used to preserve the electrical properties of living tissue.
Biomedical engineers have been monitoring the gallium-indium-selenium liquid metal alloy for some time. This material is liquid at body temperature and is believed to be totally benign.
Now, the team of Chinese biomedical engineers says the metal's electrical properties could help preserve the function of nerves while they regenerate. And they have carried out the first experiments to show that the technique is viable.
Jing and his colleagues used bullfrog sciatic nerves connected to a calf muscle. They applied an electrical pulse to one end of the nerve and measured the signal reaching the calf muscle, which contracted with each pulse.
They then cut the sciatic nerve and placed each of the severed ends into a capillary filled with either liquid metal or Ringer's solution, a multi-salt solution designed to mimic the properties of bodily fluids. They then reapplied the pulses and measured how they propagated through the space between the two ends.
The results have been interesting. According to Jing and his colleagues, the pulses that passed through Ringer's solution tended to seriously degrade. Rather, the pulses easily passed through the liquid metal. According to Jing and his colleagues: "The electroneurographic signal measured from the severed sciatic nerve of the bullfrog reconnected by the liquid metal after electrical stimulation was similar to that of the intact sciatic nerve."
What's more, since liquid metal shows up clearly on X-rays, it can be easily removed from the body when it is no longer needed, using a microsyringe.