Ultrasensitive voltammetric detection of SARS-CoV-2 in clinical samples

In every pandemic, it is critical to test as many people as possible and keep track of the number of new cases of infection. Therefore, there is a need for novel, fast and unambiguous testing methods. In this study, we designed a sandwich-type voltammetric immunosensor based on unlabeled- and labeled with a redox probe antibodies against virus spike protein for fast and ultrasensitive detection of SARS-CoV-2. The process of the preparation of the sensor layer included chemisorption of cysteamine layer and covalent anchoring of antibody specific for the S1 subunit of the S protein. The source of the voltametric signal was the antibody labeled with the redox probe, which was introduced onto biosensor surface only after the recognition of the virus. This easy-to-handle immunosensor was characterized by a wide analytical range (2.0·10^-7 to 0.20 mg·L^-1) and low detection limit (8.0·10^-8 mg·L^-1 ≡ 0.08 pg·mL^-1 ≡ 4 virions·μL^-1). The utility of the designed device was also evidenced by the detection of SARS-CoV-2 in the clinical samples. Moreover, the main advantage and a huge novelty of the developed device, compared to those already existing, is the moment of generating the analytical signal of the redox probe that appears only after the virus recognition. Thus, our diagnostic innovation may considerably contribute to controlling the COVID-19 pandemic. The as-developed immunosensor may well offer a novel alternative approach for viral detection that could complement or even replace the existing methods.