Reliable diagnostic tests are key to fight the ongoing COVID-19 pandemic, with new Sars-CoV-2 variants spreading quickly. Molecular tests are highly reliable and sensitive, but are not user-friendly or portable. Nasal swabs provide results in a few minutes, but involve multiple delicate manual operations and are prone to error.
An Italian research team, including Luisa Torsi and Fabrizio Torricelli, from the University of Bari, in collaboration with researchers from the University of Brescia, wanted to develop a test with a performance similar to molecular tests, through a low-cost device that can be operated by a patient. Scientists tested the device performance on 240 assays recording a specificity and sensitivity higher than 99%1.
The new test, called BioScreen, consists of a digital cartridge on which the user can place a saliva sample. Inside there is a microscopic molecular foil covered in antibodies that can bind even a single Sars-CoV-2 virus protein. The binding causes the electrostatic properties of the sheet to change, triggering a domino effect that leaves an electric signature on the whole surface. This signal is amplified and digitized by the transistors integrated in the cartridge, and then sent via Bluetooth to a smartphone for analysis and results.
“The electrostatic domino-like phenomenon essential to our device can be found in the sensory mechanisms of cells so, in a sense, we took inspiration from nature” says Torsi. “Since the detector specificity comes from antibodies, we can modify it to recognize different targets and develop similar devices other diagnostic applications”. According to the authors, for example, such a device could also help in cancer diagnosis and against the Xylella fastidiosa tree epidemic.
“This device merges comparable performance to molecular test and ease of manufacture” says Maria Chiara Carrozza, a biomedical engineer and current president of the National Research Council. “It has great potential in improving early diagnosis of many progressive diseases”.