[Catalyst 2017]

Graphene
Nanoribbons &
Spinal Cord Repair
TINY TECHNOLOGY, HUGE IMPACT
RUCHI GUPTA
The same technology that has been used
to strengthen polymers 1 , de-ice helicopter
wings 2 , and create more efficient batteries 3
may one day help those with damaged or even
severed spinal cords walk again. The Tour
Lab at Rice University, headed by Dr. James
Tour, is harnessing the power of graphene
nanoribbons to create a special new material
called Texas-PEG that may revolutionize the
way we treat spinal cord injuries; one day,
it may even make whole body transplants a
reality.
Dr. Tour, the T.T. and W.F. Chao Professor of
Chemistry, Professor of Materials Science and
NanoEngineering, and Professor of Computer
Science at Rice University, is a synthetic
organic chemist who mainly focuses on
nanotechnology. He currently holds over 120
patents and has published over 600 papers,
and was inducted into the National Academy
of Inventors in 2015. 4 His lab is currently
working on several different projects, such as
investigating various applications of graphene,
creating and testing nanomachines, and
the synthesizing and imaging of nanocars.
The Tour Lab first discovered graphene
nanoribbons while working with graphene
back in 2009. 5 Their team found a way to
“unzip” graphene nanotubes into smaller
strips called graphene nanoribbons by
injecting sodium and potassium atoms
between nanotube layers in a nanotube stack
until the tube split open. “We fell upon the
graphene nanoribbons,” says Dr. Tour. “I had
seen it a few years ago in my lab but I didn’t
believe it could be done because there wasn’t
enough evidence. When I realized what we
had, I knew it was enormous.”
This discovery was monumental: graphene
nanoribbons have been used in a variety of
different applications because of their novel
characteristics. Less than 50 nm wide (which
is about the width of a virus), graphene
nanoribbons are 200 times stronger than
steel and are great conductors of heat and
electricity. They can be used to make materials
56 | CATALYST
significantly stronger or electrically conductive
without adding much additional weight. It
wasn’t until many years after their initial
discovery, however, that the lab discovered
that graphene nanoribbons could be used to
heal severed spinal cords.
The idea began after one of Dr. Tour’s
students read about European research on
head and whole body transplants on Reddit.
This research was focused on taking a brain
dead patient with a healthy body and pairing
them with someone who has brain activity but
has lost bodily function. The biggest challenge,
however, was melding the spine together.
The neurons in the two separated parts of
the spinal cord could not communicate with
one another, and as a result, the animals
involved with whole body and head transplant
experiments only regained about 10% of their
original motor function. The post-graduate
student contacted the European researchers,
who then proposed using the Tour lab’s
graphene nanoribbons in their research,
as Dr. Tour’s team had already proven that
neurons grew very well along graphene.
“When a spinal cord is severed, the neurons
grow from the bottom up and the top down,
but they pass like ships in the night; they
never connect. But if they connect, they will
be fused together and start working again. So
the idea was to put very thin nanoribbons in
the gap between the two parts of the spinal
cord to get them to align,” explains Dr. Tour.
Nanoribbons are extremely conductive,
so when their edges are activated with
polyethylene glycol, or PEG, they form an
active network that allows the spinal cord to
reconnect. This material is called Texas-PEG,
and although it is only about 1% graphene
nanoribbons, this is still enough to create an
electric network through which the neurons in
the spinal cord can connect and communicate
with one another.
The Tour lab tested this material on rats by
severing their spinal cords and then using
Texas-PEG to see how much of their mobility
was recovered. The rats scored about 19/21
on a mobility scale after only 3 weeks, a
remarkable advancement from the 10%
recovery in previous European trials. “It was
just phenomenal. There were rats running
away after 3 weeks with a totally severed
spinal cord! We knew immediately that
something was happening because one day
they would touch their foot and their brain
was detecting it,” says Dr. Tour. The first
human trials will begin in 2017 overseas. Due
to FDA regulations, it may be awhile before
we see trials in the United States, but the FDA
will accept data from successful trials in other
countries. Graphene nanoribbons may one
day become a viable treatment option for
spinal injuries.
This isn’t the end of Dr. Tour’s research with
graphene nanoribbons. “We’ve combined
our research with neurons and graphene
nanoribbons with antioxidants: we inject
antioxidants into the bloodstream to minimize
swelling. All of this is being tested in Korea
on animals. We will decide on an optimal
formulation this year, and it will be tried on a
human this year,” Dr. Tour explained. Most of
all, Dr. Tour and his lab would like to see their
research with graphene nanoribbons used in
the United States to help quadriplegics who
suffer from limited mobility due to spinal cord
damage. What began as a lucky discovery
now has the potential to change the lives of
thousands.
WORKS CITED
[1] Wijeratne, Sithara S., et al. Sci. Rep. 2016, 6.
[2] Raji, Abdul-Rahman O., et al. ACS Appl. Mater.
Interfaces. 2016, 8 (5), 3551-3556.
[3] Salvatierra, Rodrigo V., et al. Adv. Energy Mater. 2016,
6 (24).
[4] National Academy of Inventors. http://www.
academyofinventors.org/ (accessed Feb. 1, 2017).
[5] Zehtab Yazdi, Alireza, et al. ACS Nano. 2015, 9 (6),
5833-5845
Image courtesy of Tour Group
DESIGN BY Monika Karki, Vidya Giri
EDITED BY Jeff Michel