A new University of Chicago study shows how tiny, light-powered wires fashioned out of silicon could produce electrical signals between neurons in the brain.
The study offers a unique insight into the brain’s poorly-understood network of fast-moving electrical signals. It is largely unknown how these signals turn into thought, movement or disease but as they are electrical the researchers believe they could use them to essentially ‘hack’ the human brain for this information. The study also sheds light on certain brain disorders which the nanowires developed by the researchers could one day be used to treat.
Ramya Parameswaran, graduate student and first author of the study, said: “We hope that this technology can eventually be used for both fundamental bioelectric studies of not just neuronal circuits but also other cell types that rely on electrical signalling to function. We also hope to use our nanowires for clinical therapeutics to restore cellular function in the context of disease.
“We hope to target any disorders that are characterised by aberrant electrical signalling in cells. In the brain, we can target Parkinson’s disease or psychiatric disorders such as major depressive disorder. Additionally, we hope to target diseases that involve peripheral nerve damage, such as diabetic peripheral neuropathy.”
Optogenetics is a technique that was discovered ten years ago for manipulating neural activity with light. This technique has only ever been done with genetics and requires the difficulty of inserting a gene into a target cell to make it respond to light. A perfect alternative to this remains elusive.
However, the University of Chicago researchers aimed to provide a solution. They built minuscule wires previously designed for solar cells. The nanowires are so small that hundreds of them could sit side by side on the edge of a sheet of paper, putting them on the same scale as the parts of cells they are trying to communicate with. The team tested the approach with rat neurons grown in a lab and saw they could trigger neurons to fire electrical signals.
Parameswaran said: “Our technology is exciting because it explores a concept from energy research – photoelectrochemical reactions – and uses it for neuromodulation. Importantly, we demonstrate that our nanowires can achieve neuromodulation in a non-genetic and non-invasive manner, using light as a stimulus. Additionally, our nanowires are free-standing and can be dispersed in a drug-like fashion.”
The nanowires combine two types of silicon to create a small electrical current when struck by light. Gold, diffused by a special process onto the surface of the wire, acts as a catalyst to promote electrochemical reactions.
Assistant Professor Bozhi Tian, leader of the research team, said: “When the wire is in place and illuminated, the voltage difference between the inside and outside of the cell is slightly reduced. This lowers the barrier for the neuron to fire an electrical signal to its neighbouring cells.”
Parameswaran said: “The nice thing about it is that both gold and silicon are biologically compatible materials. After they’re injected into the body, structures of this size would degrade naturally within a couple of months.”
Tian added: “It’s a fundamental but very promising approach.”
Next, the researchers plan to test the system in animals. They hope this will aid the further understanding of how electrical signals work in the brain and take them a step closer to finding solutions to brain disorders.