Graphene is a two-dimensional form of carbon, and successful demonstrations have been carried out by researchers to prove the possibility of interfacing graphene with nerve cells, or neurons, without affecting their integrity.
The demonstrations could help to develop graphene-based electrodes, which could be safely implanted into the brain. This study shows potential in restoring the sensory functions for individuals with Parkinson's disease, epilepsy, amputees or paralyzed patients.
The Cambridge Graphene Centre and the University of Trieste in Italy together worked on this research, which was published in ACS Nano.
Other research teams have earlier demonstrated the possibility of using treated graphene to work with neurons. However very low signal to noise ratio was obtained from this interface. In this work, techniques were developed that allow the use of untreated graphene, and as a result they were able to retain the electrical conductivity of the material. This enables the graphene to function as a better electrode.
For the first time we interfaced graphene to neurons directly. We then tested the ability of neurons to generate electrical signals known to represent brain activities, and found that the neurons retained their neuronal signaling properties unaltered. This is the first functional study of neuronal synaptic activity using uncoated graphene based materials.
Professor Laura Ballerini, University of Trieste
It is possible to control some of the functions of the brain, by directly interfacing between the brain and the outside environment. For instance, it is possible to retrieve the sensory organs by evaluating the electrical impulses of the brain. This could help to control an amputee patient’s robotic arms or basic processes for paralyzed individuals, such as helping them with their speech and movement of objects surrounding them. It is also possible to control motor disorders like Parkinson's disease or epilepsy when these electrical impulses are interfered with.
To make this possible, scientists have created electrodes that can be inserted deep into the human brain. These electrodes come into direct contact with the neurons and then send out electrical signals from the body to decode their meaning.
The issue that exists in the interface between neurons and electrodes is that the electrodes are not only expected to be extremely sensitive to electrical impulses, but they are also expected to be firm in the body without making changes in the tissue that is measured.
Often modern electrodes used for the tungsten-based or silicon-based interface suffer from complete or partial loss of signal over time. This occurs when scar tissues are created when the electrode is inserted, stopping the movement of the electrode with the natural movements of the brain due to its firm nature.
These issues can be solved using graphene due to its efficient stability, flexibility, conductivity, and biocompatibility within the body.
The researchers carried out experiments in the brain cell cultures of rats and concluded that interfacing with neurons was efficient in the case of untreated graphene electrodes. Based on the studies conducted on the neurons with electron microscopy and immunofluorescence, the researchers highlighted that the neurons continued to be healthy and transmitted normal electric impulses. Negative reactions that cause damage to the scar tissue were also not seen.
The research team considered this to be the first step in using pristine graphene-based materials instead of electrodes for a neuro-interface. The team plan to examine how different types of graphene, ranging from multiple layers to monolayers, are capable of affecting neurons. The researchers also plan to analyze whether changes made to the material properties of graphene can alter the neuronal excitability and synapses in 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.
Professor Laura Ballerini, University of Trieste
"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 signaling 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. 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.
Professor Andrea Ferrari, Director of the Cambridge Graphene Centre
The research was financially supported by the European initiative, Graphene Flagship.