For the first time ever, scientists can control human brain cells using quantum dots

What if you could treat conditions ranging from Alzheimer's to blindness, all with a flash of light? Researchers think it's possible — and they plan on using tiny particles called quantum dots to do it.

Brain stimulation can be incredibly tricky. Performing it from outside the head is effective, but doesn't give you very much specificity when it comes to turning on a specific brain region; sticking electrodes on the brain itself offers you precision, but it's also incredibly invasive.

Recently, researchers have sought out solutions to these problems with methods that rely on light, in hopes that they can be used to stimulate brain activity with a high level of precision without having to crack your skull open. Right now, the buzz-word in light-mediated brain stimulation is optogenetics, which looks incredibly promising, but relies on genetic modifications that are still considered too risky to test in humans.

But quantum dots — which also rely on light, but not genetic tinkering — may provide a way around some of optogenetics' limitations. In a paper published in the latest issue of Biomedical Optics Express, researcher Lih Lin and her colleagues have demonstrated for the first time that quantum dots can be used to control the activity of brain cells. New Scientist's Catherine de Lange summarizes the researchers' experiment:

[Lin's team] cultivated prostate cancer cells on a film covered with quantum dots. The cell membranes of the cancer cells were positioned next to the dots. The team then shone light onto the nanoparticles.

For the first time ever, scientists can control human brain cells using quantum dotsEnergy from the light excites electrons within the quantum dot which causes the surrounding area to become negatively charged [see diagram featured here]. This caused some of the cancer cells' ion channels, which are mediated by a voltage, to open, allowing ions to rush in or out of the cells.

In nerve cells, opening ion channels is a crucial step in generating action potentials – the signals by which the cells communicate in the brain. If the voltage change is large enough, an action potential is generated.

When Lin's team repeated their experiment with nerve cells, they found that stimulating the quantum dots caused ion channels to open and the nerve cell to fire.

For quantum dots to work in the treatment of diseases like Alzheimer's, they would have to first be delivered to the brain. Believe it or not, this is a process that can actually be performed intravenously, and wouldn't pose much of a technical problem (at least in theory). The major hurdle faced by cortical quantum dots is actually the light source; i.e. how does one expose these nanoparticles to light once they're tucked away inside your brain tissue?

This challenge means that brain-based quantum dots may still be a ways off — but other parts of your body are significantly easier for light to access. Your retinas, for example, absorb light naturally. What's more, ion channels — which, you'll recall, the quantum dots act on — play a pivotal role in regulating eye sight. If quantum dots prove capable of reactivating damaged retinal cells, says de Lange, they could even be used to treat blindness.

The researchers' findings are published in the latest issue of Biomedical Optics Express (No subscription required).
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Top image via Shutterstock; Quantum dot diagram via New Scientist