Using graphene to test for ALS and other neurodegenerative diseases

Using graphene to detect ALS
By adding patients’ cerebrospinal fluid to graphene, we can tell whether they have ALS or multiple sclerosis. (Image: adapted from today.uic.edu)

In the near future, we may be using graphene to test for ALS and other neurodegenerative diseases, says a team of researchers. Scientists have found numerous uses for graphene, which many describe as a ‘supermaterial.’ It can enhance solar cell capacity, revolutionize batteries, and filter the finest subatomic particles. It can also enable electronic components and is a component of super-strong and longer lasting hiking boots.

ALS stands for amyotrophic lateral sclerosis, a progressive, neurodegenerative disease that affects nerve cells in the spinal cord and brain. Stephen Hawking (1942-2018), the British theoretical physicist, cosmologist, and author, had ALS. We also call it Lou Gehrig’s disease and motor neurone disease.

The researchers, from the University of Illinois at Chicago, the Cedars-Sinai Medical Center, and the Rosalind Franklin University of Medicine and Science, wrote about their study and findings in the journal ACS Applied Materials & Interfaces (citation below). The authors were Bijentimala Keisham, Akop Seksenyan, Steven Denyer, Pouyan Kheirkhah, Gregory D. Arnone, Pablo Avalos, Abhiraj D. Bhimani, Clive Svendsen, Vikas Berry, and Ankit I. Mehta.

Adding ALS patients’ cerebrospinal fluid to graphene

The researchers added ALS patients’ cerebrospinal fluid to graphene. They detected a different and distinct change in the vibrational characteristics of the graphene compared to other people’s cerebrospinal fluid. The other people were individuals with multiple sclerosis (a type of neurodegenerative disease) and ‘healthy’ people. ‘Healthy,’ in this context, means without neurodegenerative disease.

With the help of these distinct changes, the researchers could accurately predict who the fluid came from. Specifically, people with MS (multiple sclerosis), ALS, or healthy individuals.

Graphene, which is made up of carbon, is the world’s strongest and thinnest substance. It is only one-atom thick. Each carbon atom binds to other carbon atoms by chemical bonds. These bonds’ elasticity produces phonons, i.e., resonant vibrations. We can measure phonons very accurately.

When molecules interact with graphene, their phonons change in a specific and quantifiable way. The molecules in the cerebrospinal fluid of people with ALS, for example, change in their own unique way. Hence, we can tell whether the fluid came from an ALS patient, thanks to graphene.

Measuring changes in graphene’s phonon energy

Co-author, Vikas Berry, an Associate Professor and Head of Chemical Engineering at the University of Illinois’ College of Engineering, explained:

“Graphene is just one atom thick, so a molecule on its surface in comparison is enormous and can produce a specific change in graphene’s phonon energy, which we can measure. Changes in graphene’s vibrational characteristics depend on the unique electronic characteristics of the added molecule, known as its “dipole moment.'”

“We can determine the dipole moment of the molecule added to graphene by measuring changes in graphene’s phonon energy caused by the molecule.”

Testing ALS and MS patients’ fluid

The researchers used graphene to determine whether the fluid came from a person with ALS, MS, or a healthy individual.

There is no definitive test for ALS. Doctors reach a diagnosis mostly by a process of elimination. In other words, they gradually rule out other disorders. Therefore, an objective test would help patients begin treatment sooner. Current treatment helps slow down the progression of the disease.

The researchers obtained the fluid from the Human Brain and Spinal Fluid Resource Center. The Center banks cerebrospinal fluid and tissue from deceased patients.

The researchers tested the fluid from 13 ALS patients, three with MS, and seven healthy individuals. They also tested the fluid of three patients with an unknown neurodegenerative disease.

Distinct changes in graphene’s phonon energies

Prof. Berry said:

“We saw unique and distinct changes in graphene’s phonon energies depending on whether the fluid was from someone with ALS, multiple sclerosis or someone without neurodegenerative disease.”

“We were also able to determine whether the fluid was from someone over age 55 or younger than 55 when we tested cerebrospinal fluid from ALS patients.”

“We think the difference we see between older and younger ALS patients is driven by unique biochemical signatures we are picking up that correlate to inherited ALS, which usually produces symptoms before age 55, and what’s known as sporadic ALS which occurs later in life.”

The authors believe that the graphene is picking up on the unique combinations of proteins and other biomolecules – biosignature – present in the fluid of patients with different diseases.

Prof. Berry said:

“The electronic properties of graphene have been extensively studied, but only recently have we begun to examine its phononic properties as a way to detect diseases.”

“And it turns out that graphene is an extremely versatile and accurate detector of biosignatures of diseases found both in cerebrospinal fluids and whole cells.”

Citation

Quantum Capacitance Based Amplified Graphene Phononics for Studying Neurodegenerative Diseases,” Bijentimala Keisham, Akop Seksenyan, Steven Denyer, Pouyan Kheirkhah, Gregory D. Arnone, Pablo Avalos, Abhiraj D. Bhimani, Clive Svendsen, Vikas Berry, and Ankit I. Mehta. ACS Applied Materials & Interfaces 2019, 11 (1), pp 169–175. DOI: 10.1021/acsami.8b15893.

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