Organic Electrochemical Transistor-Based Immunosensor for Sars-Cov-2 Spike Protein Detection

With rapidly increasing transmissions of the severe respiratory syndrome coronavirus 2 (SARS-CoV-2), the World Health Organization (WHO) classified the SARS-CoV-2 outbreak as a global pandemic in March 2020.¹ Since then, SARS-CoV-2 has severely impacted society and health globally. To break the spread of such a virus, quick, reliable, easy to handle, point-of-care testing strategies with low detection limits are crucial. Currently, there are two standard tests, reverse transcription–quantitative polymerase chain reaction (RT–qPCR) and viral antigen test (rapid test). Both do not fulfill the demand completely: The first one provides high sensitivity but requires trained personal, high sample quality and specialized equipment. The second one provides a rapid result (~30 min) and is suited for point-of-care testing, but lacks sensitivity.² Hence, novel approaches and methodologies for low-cost and precocious-stage diagnosis are needed. Devices able to address these demands are electronic biosensor. A typical biosensor is composed of a bioreceptor that interacts with the analyte and a transducer that converts the resulting biological incident into a measurable signal.³ Organic electrochemical transistors (OECT) are excellent transducers for the conversion to electronic signals, since they operate well in aqueous (biologic) environments at low potentials (usually &lt; 1 V). Furthermore, they provide self-signal amplification.⁴ Here, we present an organic electrochemical transistor (OECT)-based biosensor that allows the detection of SARS-CoV-2 spike protein down to concentration levels of 10^-15 M (equivalent to 10⁻¹³ g*mL⁻¹). The OECTs are modified with SARS-CoV-2 immunoglobulin G (IgG) and the SARS-CoV-2 spike protein biorecognition results in a shift of the transfer curves. The proteins incubation time is 30 min, which is equivalent to the standard antigen tests. In summary, we have successfully developed a promising immunosensing platform based on OECTs with a highly sensitive diagnostic method for COVID-19, suitable for point-of-care testing.<br/>1. Cucinotta, D. & Vanelli, M. Acta Biomed 91, 157-160, (2020).<br/>2. Gong, F., Wei, H.-x., Li, Q., Liu, L. & Li, B. Frontiers in Molecular Biosciences, 8, (2021).<br/>3. Prabowo, B., et al. Chemosensors, 9(11), 299,(2021).<br/>4. Sun, H., et al. Journal of Materials Chemistry C, 6(44), 11778-11784, (2018).