Reconnecting Severed Nerves with Liquid Metal

Chinese biomedical engineers used liquid metal (alloy gallium-indium-selenium) to pass electrical signals across the gap in severed dysfunctional nerves.

Three kinds of nerve conduits to repair the injured peripheral nerve. (a) Nerve conduit  with microchannels. (b) Nerve conduit with a shape of thin slice. (c) Nerve conduit with concentric  tubes

Three kinds of nerve conduits to repair the injured peripheral nerve. (a) Nerve conduit
with microchannels. (b) Nerve conduit with a shape of thin slice. (c) Nerve conduit with concentric
tubes

Jing Liu at Tsinghua University in Beijing and her team have reconnected severed nerves using liquid metal for the first time. They even say that the metal’s conductivity in transmitting the signals greatly outperforms the standard saline electrolyte used to preserve the electrical properties of living tissue.

Once a peripheral nerve is severed, it’s loss of function can bring on atrophy of the attached muscles and a dramatic change in the quality of life.

After decades of work, there have been no effective methods for reconnecting severed nerves. There are procedures that sew the ends back together, or to graft nerves into the gap that is created between both severed ends. Dependent upon the ability of the nerve ends to grow and mend back together, these techniques are unsuccessful because nerves grow at a rate of one mm per day. During this kind of time, the muscles can atrophy and degrade beyond repair.

The point of this area of research is to find a way to keep these muscles active while the nerves regrow.

This team of Chinese biomedical engineers have now run a study illustrating a viable technique using this liquid metal’s electrical properties.

Connecting sciatic nerves to a calf muscle taken from bullfrogs, they applied a pulse to one end of the nerve and measured the signal that reached the calf muscle as it contracted with each pulse. They then cut the sciatic nerve (the longest and widest single nerve in our body) and placed each of the severed ends in a solution filled with either the liquid metal or with a solution of salts meant to mimic the properties of body fluids. They then reapplied the pulses and measured how they propagated across the new gap.

While the pulses that passed through the salt solution degraded severely, “the measured  electroneurographic signal from the transected bullfrog’s sciatic nerve reconnected by the liquid metal after the electrical stimulation was close to that from the intact sciatic nerve,” says Jing and her team.

Also, since the metal is a liquid at body temperatures and shows up in x-rays, it can be cleanly removed via microsyringe after therapy.

Jing and others hope to test how much muscle function can be preserved using liquid metal as well as its safety inside in the body if it were to leak with animal models then maybe human ones. “This new generation nerve connecting material is expected to be important for the functional recovery during regeneration of the injured peripheral nerve and the optimization of neurosurgery in the near future,” they say.

 

 

 

Alec Schwartz
Biochemistry and Molecular Biology Major
Dickinson College
Class of 2016

 

 

Ref: http://arxiv.org/abs/1404.5931: Liquid Metal as Connecting or Functional Recovery Channel for the Transected Sciatic Nerve

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