SARS-CoV-2 and its variants detection by palladium nano-thin-film impedance-based biosensor*

SARS-CoV-2 is identified at the end of 2019. This is a highly contagious, and global spreading virus. Furthermore, a lot of variants of this virus have been identified in different areas. Unfortunately, the spreading of these variants, especially the delta variant, is much faster than that of wildtype. Some breakthrough infections are also observed in the fully vaccinated people. Therefore, a rapid, sensitive and accurate sensing platform for the detection of SARS CoV-2 is important for better controlling the spread of this newly emerging infectious disease. In this study we have synthesized and refolded these key proteins, spike protein receptor binding domain (spike RBD) and angiotensin converting enzyme II (ACE2), into functional forms by over-critical refolding process. The ACE2 which can directly immobilize on the palladium nano thin film (Pd-NTF) via Pd-thiol linkage. The functionalized Pd-NTF can be used as electrode probe of electrochemical impedance spectrometer to analyze the interaction between ACE2 and wildtype or mutants spike RBD. We found that the delta variant has higher affinity than wildtype. This biosensing system can be used not only in viruses detection but also anti-virus infection drugs screen.