Neural implants are of great value in neuroscience research as they enable a connection between nervous tissue and the ex vivo environment. Because of this, they also provide therapy for patients oppressed with a horde of neuronal disorders such as PD, spinal cord injury, stroke and aid in restoring sensory functions for paralyzed patients and amputees.
Implantable electrodes are designed to seize signals from individual neurons in the brain over a long period of time. For this, the electrodes should be:
1. Biofriendly, i.e, shouldn’t cause any significant damage to the brain tissue
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2. Flexible in relation to the brain tissue as the brain floats in a fluid inside the skull and moves around while breathing and head movements.
The challenge with earlier developed flexible electrodes was that they couldn’t maintain their shape when implanted. When fixated on a solid chip, they showed limited flexibility. Using stiffer electrodes resulted in irritation of brain tissue and damage of the surrounding nerve cells.
Since then, figuring out a way to allow electrodes to directly interface with neurons without harming their integrity is one of the most pressing tasks for neuroscientists.
Researchers from Italy’s University of Trieste and the Cambridge Graphene Center recently made a significant advancement in this direction by demonstrating that untreated graphene can be used to interface with neurons without damaging their integrity. Before this, implants of treated graphene (coated with peptides, amino acids) were used with an aim to favor neuronal cohesion, however, this produced a relatively low signal to noise ratio when compared with untreated graphene. This is, hence, the first functional study of neuronal synaptic activity using uncoated graphene-based materials.
Why Graphene
Graphene consists of carbon atoms arranged in a structure of honeycomb lattice and is 100 times stronger than steel. When compared to tungsten and silicon, frequently used materials to make electrodes for brain implants, graphene electrodes have several pluses.
Insertion of silicon and tungsten electrodes resulted in the form of scar tissue which blocked the electric impulses propagating through gray matter, leading to partial or total loss of signal over time. So the need is to implant an electrode without damaging neurons.
Graphene, with its excellent conductivity and plasticity, is an ideal material for producing electrodes which could be implanted without encouraging the growth of scar tissue.
The team studied the interaction of graphene with neuron cultures using electron microscopy and immunofluorescence and found that the neurons remained healthy and functional without any adverse reactions.
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