An ultralight way to manipulate brain signals

Materials scientist Bozi Tian developed silicon-nanowire solar cells in 2007. Now, at the University of Chicago in Illinois, they have shown how similar nanoscale devices can be used to manipulate brain signals with light.

Describe what your team’s latest study has achieved.

We have shown that we can stimulate behavior in a mouse by placing a nanoscale silicon mesh on the part of the brain that converts nerve impulses into motion, and then shining a light onto the trap (Y. Jiang et al. Nature BioMed . Engg..; 2018). For example, we were able to control the animal’s left forearm by shining a beam to the right side of its brain.

Why is this approach game-changing

So far, there have been only two main methods of neurostimulation. The first involves implanting electrodes to produce nerve activity. The second, called optogenetics, requires cells to be genetically modified so that they can be controlled using light, but genetic modification is difficult and has ethical concerns. Our approach uses a noninvasive neurostimulation device that enables distant nerves to be stimulated with light. This can have a major impact on the treatment of pain and other disorders.

Has it steered your research in a new direction

Yes, we now plan to do research on non-human primates – for example, finding out how to restore grasping functions after paralysis.

Does the device have potential clinical applications

If we put a silicon mesh on the surface of the brain, we can do some activity inside the brain. And if you can stimulate the brain, you can cure some neurological diseases or help a person regain control of certain parts of their body. So it can be used to treat diseases like Parkinson’s or disorders like depression.

Describe one of your success moments

My graduate student Ramya Parameswaran has demonstrated how a silicon nanowire can excite single cells (R. Parameswaran et al. Nature Nanotech 13, 260–266; 2018). Some of the gold that catalyzes the growth of the silicon wire becomes the individual atoms covering the surface of the wire. When we extracted the atomic gold, some neurons could not activate. We later found that gold enhanced the electrochemical properties of silicon and made it a better neurostimulator.

You changed your research focus from energy to neurostimulation. What happened

I left China in 2004 to begin my PhD at Harvard University in Cambridge, Massachusetts, working on the use of single nanowires in photovoltaics. We showed that silicon nanowires can convert sunlight into electricity, just as conventional solar cells do. However, they are small enough that they can be integrated into nano devices. After that work was published (B. Tian et al. Nature 449, 885-889; 2007), I decided to completely change my research interest from energy to electrophysiology and bioscience.

Why did you make that change

Biology in particular offered a lot of opportunity and room for discovery in bringing nanowires and neuroscience together. And I like to explore the unknown. So, for the second half of my PhD, I worked on developing a transistor that is small enough to be delivered into a single cell to record electrical activities.

How was the transition

it was tough. I had no experience in cell culture, electrophysiology or working with animal tissues. I took a neuroscience course and learned a lot from it. Still, there were setbacks. For example, my cell cultures kept getting contaminated. But I told myself that if I persist, there will be good moments.

How did you find allies

When I started in Chicago, few biologists were interested in collaborating; The others were not. I gave a lecture to biophysics students, and was attended by Ana Correa, a biochemist and the wife of molecular biologist Francisco Bezzanilla. She introduced me to my husband later, and I and he have written grants and papers together since then. Sometimes all you need is that right moment and the right person.