Diamond quantum sensors and magnetic fields improve insight into how brain cells function

Tech Science 1. feb 2024 2 min Associate Professor Alexander Huck Written by Kristian Sjøgren

Researchers have developed a new method of studying brain cells and to determine whether the brain cells are functioning properly. One researcher says that the method may enable the brain to be studied in a new way, improving knowledge of brain disease.

Learning about brain disease requires reliable methods to investigate whether the brain cells are functioning well.

Today, however, researchers are limited to studying the brain cells under a microscope or implanting electrodes in the brain cells to examine their electrical conductivity.

Both methods have shortcomings, but now researchers have developed a new method to study the activity of brain cells using diamonds and measuring the magnetic fields created by active brain cells.

A researcher behind the development of the method says that it could revolutionise studies of brain cell activity.

“The method enables us to study activity in nerve cells without electrodes. We can study regions of the brain without touching and also study the communication between nerve cells in living tissue better,” explains Alexander Huck, Associate Professor, Quantum Physics and Information Technology, Department of Physics, Technical University of Denmark, Kongens Lyngby.

The research has been published in Scientific Reports.

Difficult to measure activity between brain cells

Before developing the method, the researchers aimed to find ways to investigate the activity in nerve cells without electrodes.

The idea behind the method was therefore to measure the weak magnetic field nerve cells produce when they communicate with each other.

Measuring magnetic fields in the body is not a revolutionary idea; researchers have been doing this for many years. However, this often requires large and bulky devices that are not suitable for small, living pieces of brain tissue.

The researchers therefore developed a new method using microscopic defects in synthetic diamonds in which a nitrogen atom replaces a carbon atom.

This creates a nitrogen-vacancy centre in the diamonds that can absorb light and release it again and enables diamonds to respond to magnetic fields.

“These nitrogen-vacancy centres have a spin, and in a magnetic field, the spin oscillates around this field. If the magnetic field increases or decreases, the spin will oscillate a bit faster or slower, and we can measure this through changes in the emission of light in the nitrogen-vacancy centre,” says Alexander Huck.

Diamond sensors record magnetic field from brain cells

In practice, the researchers first place a brain tissue slice on an insulating layer of aluminium foil in a 3D plastic chamber.

The diamond is placed in a hole at the bottom of the chamber under the insulating layer.

The researchers then direct green laser light into the diamond and record the changes in the light emitted by the diamond.

When the nerve cells send signals to each other, the resulting magnetic field affects the electron in the nitrogen-vacancy centre and thus the intensity of the light the diamond emits – all of which happens without either laser light or anything else touching the tissue sample.

“Our study shows that the activity in brain tissue can be determined by measuring the magnetic field that active brain cells create, using nitrogen-vacancy centres in diamonds,” explains Alexander Huck.

The researchers validated the method by comparing the measurements with those obtained by implanting electrodes in the tissue, which is a very effective method of measuring activity in brain cells but also might damage the cells over time.

Creating a unique map of communication between brain cells

Although the new method for studying activity in and between nerve cells is in the relatively early stages of development, Alexander Huck thinks that the method has potential beyond existing methods.

For example, the activity of a single brain cell can easily be measured by inserting an electrode into the brain cell.

However, in determining the activity of several brain cells communicating with each other, inserting an electrode in all of them to study how communication between brain cells is distributed over time and place is not possible in practice – because this will damage the tissue.

Using the new method, the researchers can probably much more easily visualise the communication between brain cells in a living slice of tissue.

“We cannot yet do this using the current method, but the future perspective is to study how information is disseminated in the brain and what differentiates healthy tissue and tissue from a disordered brain, such as in Parkinson’s disease, Alzheimer’s disease or other neurodegenerative diseases,” says Alexander Huck.

In further developing the method, the researchers will try to develop more suitable diamonds and investigate using improved optical techniques to collect the signals from the diamond and the cells.

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