Answers to Important Questions:
Q: What does this new biosensor detect?
A: It measures the concentration of BDNF (brain-derived neurotrophic factor), an important protein related to neurological health and mental well-being.
Q: Why is BDNF important for brain health?
A: Low levels of BDNF are linked to depression, schizophrenia, and cognitive impairment, while antidepressants can help restore them.
Q: How can this device improve the diagnosis of mental disorders?
A: By offering rapid, inexpensive, and non-invasive BDNF tests, early warning signs can be identified and progress in the treatment of psychiatric disorders can be monitored.
Summary: Scientists have developed a portable biosensor that can detect levels of BDNF, a protein linked to mental illnesses such as depression, schizophrenia, and bipolar disorder. This flexible and inexpensive device analyzes a single drop of saliva in less than three minutes, offering a rapid, affordable, and noninvasive diagnostic tool.
Because low levels of BDNF are associated with depression and cognitive decline, this test could help clinicians detect and monitor conditions earlier. With an estimated cost of just $2.19 per unit, the biosensor could transform mental health assessments, especially in resource-limited settings.
Key data
- Fast results: The saliva-based biosensor measures BDNF levels in less than three minutes.
- Affordable innovation: Each unit costs about $2.19, making it widely applicable.
- Clinical relevance: Low levels of BDNF are associated with depression, while increases may indicate recovery.
Source: FAPESP
Brazilian researchers have developed a portable, low-cost biosensor that can rapidly identify a protein whose altered levels are linked to psychiatric disorders, such as depression, schizophrenia, and bipolar disorder.
When it becomes commercially available in the future, it could aid in early detection, which is essential for treating and monitoring patients’ medical conditions.
The biosensor is the result of a collaboration between researchers at the University of São Paulo (USP) and Embrapa Instrumentação, a decentralized unit of the Brazilian Agricultural Research Corporation (Embrapa). The sensor consists of a flexible strip with electrodes that, when connected to a portable analyzer, analyzes droplets of human saliva.
In less than three minutes, the biosensor provides a concentration of BDNF (brain-derived neurotrophic factor), a protein important for the growth and maintenance of neurons and brain function, including learning and memory development.
Research published in ACS Polymers Au shows that the device can reliably measure extremely low concentrations of protein in a wide range of saliva (from 10⁻²⁰ to 10⁻¹⁰ grams per milliliter), down to low amounts that are still detectable (1.0² × 10 mg).
Each biosensor is estimated to cost US$2.19—less than R$12.00 at the current exchange rate—and offers long-term storage capacity. The next step, according to the scientists, is to obtain a patent.
Few sensors perform this type of analysis, and ours performed the best. It detected a wide range of concentrations, which is an excellent result from a medical point of view. When the protein level is too low, it can serve as a warning sign of diseases and psychiatric disorders.
On the other hand, the ability to detect increases in BDNF (Brain-Derived Neurotrophic Factor) makes this a useful tool for monitoring the patient’s progress in response to treatment, as explained by Paulo Augusto Raimundo Pereira, a researcher at the São Carlos Physics Institute (IFSC-USP) and the corresponding author, in an interview with Agência FAPESP.
Perera, with a background in chemistry and biotechnology, has worked with flexible sensors and electrochemical biosensors. Last year, he co-authored a paper in the Journal of Chemical Engineering that presented results from a portable urine self-analysis sensor designed to detect markers of diseases such as gout and Parkinson’s disease.
Link to disorders
Scientific literature suggests that low levels of BDNF are one of the factors involved in several neurological and psychiatric disorders associated with cognitive impairment.
Depression is one of these conditions. The protein’s effect is reversed with antidepressants. BDNF levels in healthy individuals are greater than 20 nanograms per milliliter (ng/mL), while those with major depressive disorder (MDD) are below 10 or 12 ng/mL.
According to data from the World Health Organization (WHO), more than one billion people are living with a mental disorder, with anxiety disorders and depression being the most common conditions.
According to the organization’s reports, including the Mental Health Atlas 2024 , these disorders are becoming increasingly common in all countries and affect people of all ages and income levels.
Between 2022 and 2024, work absences due to mental health problems in Brazil increased by 134%. According to the Occupational Safety and Health Observatory, this absence increased from 201,000 to 472,000 and was due to depression, anxiety disorders, and recurrent depression.
Pereira added that their motivation to work on this issue and find alternatives stemmed from the rise in mental illness cases and the resulting increased use of medications, particularly in the aftermath of the COVID-19 pandemic. (Pereira receives support from FAPESP grants 16/01919-6, 23/09685-8, and 22/02164-0.)
Device
The researchers developed a flexible strip printed on a polyester film substrate with three electrodes: an active working electrode, a pure carbon auxiliary electrode, and a silver reference electrode.
The working electrode was modified with carbon nanospheres. It was coated with two chemical compounds—polyethyleneimine and glutaraldehyde—to enhance sensitivity and serve as a matrix for immobilization of a BDNF-specific capture antibody (anti-BDNF). To prevent other interactions, a reactive ethanolamine layer was added.
BDNF detection is based on the formation of antigen-antibody immune complexes, which increase the resistance to electron transfer at the sensor surface. This increase is recorded using electrochemical impedance spectroscopy, a technique used to study the processes occurring at the interface between the electrode and the solution.
The results can be viewed in real time on a mobile device (smartphone) via wireless communication (Bluetooth).
Current methods for analyzing BDNF levels, which include techniques like ELISA, electrochemiluminescence, fluorescence, and high-performance liquid chromatography (HPLC), have drawbacks as they require time, large sample volumes, and must be conducted in specialized laboratories. The researcher stated that these efforts are propelling the field toward personalized medicine, where individual treatment plans are increasingly tailored, suggesting that the biosensors under development can be optimized for various patient profiles.
Funding: This research was provided by FAPESP through the thematic project “Towards the convergence of technologies: from sensors and biosensors to machine learning for information visualization and data analysis in medical diagnostics,” along with support from two additional projects (23/07686-7 and 20/09587-).
The research team comprises the following members: Nathalia Gómez, Marcelo Luiz Caligaro, Luiz Henrique Caprilli Matoso, Sergio Antonio Espinola Machado, and Osvaldo de Oliveira Jr.
About this mental health and neurotech research news
Author: Heloisa Reinert
Source: FAPESP
Contact: Heloisa Reinert – FAPESP
Image: The image is credited to StackZone Neuro
Original Research: Open access.
“Low-Cost, Disposable Biosensor for Detection of the Brain-Derived Neurotrophic Factor Biomarker in Noninvasively Collected Saliva toward Diagnosis of Mental Disorders” by Paulo Augusto Raymundo Pereira. ACS Polymers Au
Abstract
Disposable and low-cost biosensor for detecting brain-derived neurotrophic factor in non-invasively collected saliva samples for the diagnosis of brain disorders
The importance of early detection of biomarkers for neurodegenerative diseases has increased, as these biomarkers are essential for timely diagnosis, treatment, healthcare, and wellness applications.
We present a low-cost, disposable electrochemical immunosensor strip for the rapid and decentralized detection of brain-derived neurotrophic factor (BDNF) – one of the key neurotrophins (NT) associated with neurological and psychiatric disorders – in human saliva.
The salivary BDNF immunosensor strip is fabricated on a screen-printed carbon electrode functionalized with layers of carbon spheres (CSS), polyethyleneimine (PEI), and glutaraldehyde to improve sensitivity.
Through systematic optimization, the sensor achieved excellent analytical performance, with a wide dynamic detection range from 1.0 × 10–20 to 1.0 × 10–10 g mL–1, a fast response time of less than 3 min, and an extremely low detection limit of 1.0 × 10–10 D-10-10 D-10-10 DL-va.
The BDNF immunosensor exhibited excellent performance characteristics, including high selectivity, reproducibility, robustness, stability, and long-term storage capability.
At a price of less than $2.19 per unit, this disposable sensor also allows for rapid detection of BDNF in saliva samples from healthy volunteers, without other saliva components interfering with the system.
Environmental impacts were assessed using the Analytical Ecological Scale (AES), the Analytical Ecological Metrics Approach (AGREE), and the Blue Applicability Index (BAGI), which assesses the usability of the device (“blue aspect”). These assessments confirmed the durability of the BDNF disposable immunosensor strip.
This device offers a rapid, efficient, economical, and reliable method for decentralized and non-invasive saliva analysis of BDNF, enabling broader applications in healthcare, wellness monitoring, and clinical diagnostics related to the neurotrophin biomarker family.
