Crying out loud: How tears can reveal the brain’s secrets

Tears can help diagnose neurological disorders, suggests a new study. (shutterstock.com / Zdorov Kirill Vladimirovich)

Tears may be a key to understanding people’s brain health, a new study says.

A new sensor technology can detect chemicals in human tears, and could potentially help scientists detect neurological conditions, according to a new study published by the American Chemical Society on Wednesday.

“We aim to facilitate the ultra-early detection of neurological disorders, creating opportunities for clinical interventions before major symptoms manifest,” author Neftali Lenin Villarreal Carreno says in a press release accompanying the study.

The low-cost sensor can detect dopamine, a chemical partially responsible for happiness but also important to movement, emotional regulation, and motivation, according to the press release.

However, the research took place using synthetic rather than organic human tears, but the results demonstrate that there is a reasonable potential for the technology to help in diagnoses using real human tears.

Changes in dopamine levels, lower or higher than regular, can help diagnose psychiatric conditions, like depression, Parkinson’s disease or schizophrenia. Right now, dopamine monitoring methods include sampling blood or urine, and sometimes even implanted devices.

In contrast, the tear collection can be done quickly and painlessly, even operating successfully despite interfering factors in the synthetic tears, the press release says.

“Our sensor can detect dopamine from levels well below the healthy baseline and up to three times higher,” study co-author Lucas Minghini Goncalves says in the press release. “This capability ensures that a person’s initial dopamine drop can be identified early on, which is crucial to enabling timely, proactive therapeutic interventions.”

The sensors are about the size of a stamp, and feature a conductive layer of graphene that will generate an electrical signal when dopamine interacts with it. Graphene is a sheet of carbon that is only a single atom thick, while graphite is a common mineral is made up of many layers of graphene. The material works well due to its “high conductivity, large surface area, and chemical stability,” the researchers found.

“As a promising and yet noncommercialized alternative, electrochemical sensors have emerged as a promising alternative for the detection of (dopamine) in biological fluids due to their high sensitivity, selectivity, and possibility of miniaturization,” the study says.

The study highlights the ease of manufacturing the material and its low cost. Nickel can further enhance graphene’s sensitivity towards specific molecules like dopamine. The researchers’ device primarily relies on graphene but features nickel as a compliment material.

With further research and development neuroscientists and psychiatrists could simply use a tear sample to help diagnose neuro-conditions and diseases without needing costly or invasive procedures.