Published on January 31, 2016
Researchers have successfully demonstrated how it is possible to
interface graphene - a two-dimensional form of carbon - with neurons, or nerve
cells, while maintaining the integrity of these vital cells. The work may be
used to build graphene-based electrodes that can safely be implanted in the
brain, offering promise for the restoration of sensory functions for amputee or
paralysed patients, or for individuals with motor disorders such as epilepsy or
Parkinson's disease.
The research, published in the journal ACS Nano, was an
interdisciplinary collaboration coordinated by the University of Trieste in
Italy and the Cambridge Graphene Centre.
Previously, other groups had shown that it is possible to use
treated graphene to interact with neurons. However the signal to noise ratio
from this interface was very low. By developing methods of working with
untreated graphene, the researchers retained the material's electrical
conductivity, making it a significantly better electrode.
"For the first time we interfaced graphene to neurons
directly," said Professor Laura Ballerini of the University of Trieste in
Italy. "We then tested the ability of neurons to generate electrical
signals known to represent brain activities, and found that the neurons
retained their neuronal signalling properties unaltered. This is the first
functional study of neuronal synaptic activity using uncoated graphene based
materials."
Our understanding of the brain has increased to such a degree
that by interfacing directly between the brain and the outside world we can now
harness and control some of its functions. For instance, by measuring the
brain's electrical impulses, sensory functions can be recovered. This can be
used to control robotic arms for amputee patients or any number of basic
processes for paralysed patients - from speech to movement of objects in the
world around them. Alternatively, by interfering with these electrical
impulses, motor disorders (such as epilepsy or Parkinson's) can start to be
controlled.
Scientists have made this possible by developing electrodes that
can be placed deep within the brain. These electrodes connect directly to
neurons and transmit their electrical signals away from the body, allowing
their meaning to be decoded.
However, the interface between neurons and electrodes has often
been problematic: not only do the electrodes need to be highly sensitive to
electrical impulses, but they need to be stable in the body without altering
the tissue they measure.
Too often the modern electrodes used for this interface (based
on tungsten or silicon) suffer from partial or complete loss of signal over
time. This is often caused by the formation of scar tissue from the electrode
insertion, which prevents the electrode from moving with the natural movements
of the brain due to its rigid nature.
Graphene has been shown to be a promising material to solve
these problems, because of its excellent conductivity, flexibility,
biocompatibility and stability within the body.
Based on experiments conducted in rat brain cell cultures, the
researchers found that untreated graphene electrodes interfaced well with
neurons. By studying the neurons with electron microscopy and
immunofluorescence the researchers found that they remained healthy,
transmitting normal electric impulses and, importantly, none of the adverse
reactions which lead to the damaging scar tissue were seen.
According to the researchers, this is the first step towards
using pristine graphene-based materials as an electrode for a neuro-interface.
In future, the researchers will investigate how different forms of graphene,
from multiple layers to monolayers, are able to affect neurons, and whether
tuning the material properties of graphene might alter the synapses and
neuronal excitability in new and unique ways. "Hopefully this will pave
the way for better deep brain implants to both harness and control the brain,
with higher sensitivity and fewer unwanted side effects," said Ballerini.
"We are currently involved in frontline research in
graphene technology towards biomedical applications," said Professor
Maurizio Prato from the University of Trieste. "In this scenario, the
development and translation in neurology of graphene-based high-performance
biodevices requires the exploration of the interactions between graphene nano-
and micro-sheets with the sophisticated signalling machinery of nerve cells.
Our work is only a first step in that direction."
"These initial results show how we are just scratching the
tip of an iceberg when it comes to the potential of graphene and related
materials in bio-applications and medicine," said Professor Andrea
Ferrari, Director of the Cambridge Graphene Centre. "The expertise
developed at the Cambridge Graphene Centre allows us to produce large
quantities of pristine material in solution, and this study proves the
compatibility of our process with neuro-interfaces."
Source:
University of Cambridge
http://www.news-medical.net/news/20160131/Graphene-based-electrodes-could-be-safely-implanted-in-the-brain.aspx
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