Brazilian scientists have created a low-cost, portable sensor that can quickly detect a brain protein linked to mental health conditions like depression, schizophrenia, and bipolar disorder.
This new tool may help doctors find and treat these problems earlier, which could lead to better care for patients.
The sensor was made through a partnership between the University of São Paulo (USP) and Embrapa Instrumentação, a division of the Brazilian Agricultural Research Corporation. It is a small, flexible strip with electrodes that can read a drop of saliva in less than three minutes.
The test looks for a protein called BDNF—short for brain-derived neurotrophic factor. BDNF plays a key role in helping brain cells grow and stay healthy. It also supports learning and memory.
Changes in BDNF levels have been linked to mental disorders. For example, people with depression often have low BDNF levels.
Normally, healthy people have more than 20 nanograms per milliliter (ng/mL) of this protein, but in those with major depression, levels can drop below 10–12 ng/mL. Scientists believe that by tracking BDNF, doctors can spot early signs of mental health issues or check if a treatment is working.
The sensor is both affordable and powerful. It can detect extremely low levels of BDNF in saliva—down to one part in ten billion billion grams per milliliter (1.0 × 10⁻²⁰ g/mL). Each test strip costs just $2.19 to produce and has a long shelf life. The results are sent to a smartphone in real time using Bluetooth.
This new device could replace more complex tests that are expensive, take longer, and need special labs. These current methods include ELISA, electrochemiluminescence, fluorescence, and high-performance liquid chromatography (HPLC). All of them require skilled technicians and a lot of time.
The sensor uses electrochemical technology. It has three types of electrodes printed on a flexible film. One electrode is specially treated to detect BDNF. It’s coated with chemicals that help trap the protein when it’s present in saliva.
When BDNF binds to the electrode, it creates a small electrical signal that can be measured. This change tells the sensor how much of the protein is in the saliva.
Lead researcher Paulo Augusto Raymundo Pereira, a chemistry and biotechnology expert, says that this test may help doctors not only detect mental illness early but also track how well treatments are working. Pereira was also involved in earlier research that developed a sensor to detect signs of diseases like Parkinson’s and gout through urine tests.
This breakthrough comes at an important time. Mental health disorders like depression and anxiety are on the rise globally. According to the World Health Organization, more than 1 billion people live with mental health problems. In Brazil, sick leave due to mental illness rose by 134% from 2022 to 2024.
The COVID-19 pandemic has made mental health challenges even more common. Pereira says this increase in cases and the growing use of medications encouraged his team to find a new way to help.
The next step for the team is to get a patent for the biosensor and eventually make it available for doctors and clinics to use. Because it is fast, cheap, and easy to use, this tool could make a big difference—especially in places where mental health services are limited.
In conclusion, this simple saliva test could offer a smarter way to detect and monitor mental illness. It could help doctors take action earlier, adjust treatments more quickly, and improve care for millions of people around the world.
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The study is published in ACS Polymers Au.
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