Dopamine neurotransmitter determination using a graphite sheet–graphene nanosensor

What is Dopamine

Dopamine, a tiny chemical with an important role, is often referred to as the “feel-good” molecule, though it’s much more than that. It’s the cheerleader of your brain, cheering you on toward your interests, urging you to move, to focus. After finishing an activity or attaining a goal, dopamine provides a sensation of happiness and pleasure. Dopamine is a neurotransmitter and a hormone, but is a different in each context:

- Dopamine as a neurotransmitter:

In the brain, dopamine works as a neurotransmitter. This means it acts like a messenger, helping nerve cells (neurons) talk to each other.

 It helps with:

• Movement 

• Motivation and reward 

• Focus and learning

• Mood regulation

- Dopamine as a hormone:

Outside the brain, in your blood, dopamine acts as a hormone made by your adrenal glands (on top of your kidneys).

 It helps with:

• Controlling blood pressure

• Increasing heart rate in emergencies

• Helping kidneys work properly

The importance of Dopamine detection

Accurate quantification of dopamine levels in the body is crucial for the prevention, diagnosis, monitoring, and treatment of diseases such as Parkinson’s and  Alzheimer’s diseases. Consequently, the ability to accurately assess dopamine levels is a critical objective in medical diagnostics and therapeutic development.

How to detect dopamine

Indeed, a lot of the methods used to quantify dopamine are slow, costly or invasive. Now, imagine a device that can detect dopamine levels instantly, using droplets of blood or a sweat sensor. This is where the electrochemical sensors come into play. Every time dopamine interacts with the surface of  the sensor, it generates an electrical signal – it’s like saying “dopamine present”. These features make the electrochemical sensors low-cost and transportable for the detection of dopamine levels.

Electrocrochemical sensors 

Electrochemical sensors are exceptional instruments that quantify chemical compounds by converting the chemical reactions into electrical signals. These measurements are often conducted using a three-electrode system consisting of a working electrode, reference electrode, and auxiliary or counter electrode. The working electrode is where the reaction is performed while the reference electrode provides a constant and well-defined potential that allows precise measurement of the working electrode's potential (relative potential difference) . To complete the circuit, the current from the auxiliary or counter electrode is supplied. 

The interaction of the working electrode with the target substance like glucose or dopamine results in the former undergoing a redox reaction (losing or gaining an electron). Every transfer of electron is accompanied by a measurable value of electrical current. The amount of current that is produced is proportional to the concentration of the analyte.

Nanotechnology & dopamine sensing

Nanotechnology is the study and control of matter at the nanoscale, typically between 1- 100 nanometers which is the size of a few hundredth of a meter or less. At the nanoscale, matter can have strange physicochemical properties that are very different from those of bulk materials, due to its high surface-to-volume ratio. Nanostructured materials can be stronger, magnetically distinct, and more conductive than bulk materials.

Nanomaterials such as graphene and carbon nanotubes offer unparalleled speed, sensitivity, and accuracy, significantly enhancing dopamine sensing.

Why does our sensor matter?

In this  article, we fabricated a sensitive graphene-based sensor for dopamine detection. The electrode demonstrates a low detection limit, a wide linear range, and impressive stability, making it suitable for real sample analysis. This nanosensor benefits from simple, cost-effective, and rapid fabrication. It is worth mentioning that despite not using expensive materials in this work, the detection limit and linear range are highly comparable to those reported in the literature.

Conclusion

Due to dopamine’s involvement in several biological and neurological functions, exact measurement is vital in cases concerning Alzheimer’s and Parkinson’s diseases. A straightforward, low-cost sensor with high sensitivity and a simple fabrication process could significantly improve the diagnosis and treatment of these conditions. 

Read the paper: https://doi.org/10.1007/s41127-024-00075-9