The accuracy of infectious disease tests is one of the most critical aspects of diagnosing a person's health condition. Immunosensors are used to ensure these tests fulfill their function, with results determined by certain signals generated during processes. However, sometimes these signals are disrupted, which can hinder an accurate diagnosis.

Dr. Antanas Zinovicius, an alumnus of the Faculty of mechanics at Vilnius Gediminas Technical University (VILNIUS TECH), addressed this in his doctoral studies and aimed to develop immunosensors with much more precise signal transmission.

Utilising nanoparticles

One of the most advanced recognition systems in nature is our immune system. Immunosensors are created by using its components, antigens, and antibodies, highly sensitive and selective.

"Almost every one of us has tried immunosensors in some form over the past five years, one of them being instant COVID-19 tests. However, these immunosensors are qualitative—they only provide a 'yes' or 'no' answer when diagnosing an infection. The immunosensors we are developing are quantitative—they can precisely determine the concentration of an antigen or antibody," explains Dr. Zinovicius.

However, the scientist notes that when developing quantitative immunosensors, they often face situations where the signal is too weak or blocked. To address these issues, antibodies are modified with an enzyme that, while helping to amplify the signal, may lose its properties and the signal is weakened when environmental conditions change. Additionally, in complex media like blood, this enzyme can be blocked, reducing signal strength. To solve these problems, Dr. Zinovicius incorporated nanomaterials such as gold and platinum nanoparticles and reduced graphene oxide into the next-generation quantitative immunosensors. These materials have enzyme-like properties but cannot be denatured, making their signals more reliable. The resulting signal is measured using a combined scanning electrochemical microscopy and electrochemical impedance spectroscopy method.

"We first created a prototype. After testing it, we found that the sensor can detect antigen concentrations ranging from 1 picogram (one trillionth of a gram) to 10 micrograms. Compared to current immunosensors, this detection range is 10 times broader. Additionally, the immunosensor response is obtained within 20 minutes. These results confirm that the developed prototype could be used in diagnostics," explains the scientist.

These results also expand the possibilities of creating more sustainable electrochemical immunosensors. Dr. Zinovicius further explains that since this method simplifies sample preparation and antibody attachment to inexpensive surfaces, it enables the development of low-cost disposable immunosensors as equipment could be reused. "Consideration should also be given to reducing the size of the sensor, further lowering the cost. This would make quantitative immunosensors more accessible to consumers, allowing us to monitor our health effectively from home."

The article was prepared by Milda Mockunaite-Vitkiene, project manager for Internal communication projects at the Public communication directorate of VILNIUS TECH.