Highly sensitive and ultra-rapid antigen-based detection of SARS-CoV-2 using nanomechanical sensor platform.

The rapid spread of COVID-19 including recent emergence of new variants with its extreme range of pathologies create an urgent need to develop a versatile sensor for a rapid, precise, and highly sensitive detection of SARS-CoV-2. Herein, we report a microcantilever-based optical detection of SARS-CoV-2 antigenic proteins in just few minutes with high specificity by employing fluidic-atomic force microscopy (f-AFM) mediated nanomechanical deflection method. The corresponding antibodies against the target antigens were first grafted on the gold-coated microcantilever surface pre-functionalized with EDC-NHS chemistry for a suitable antibody-antigen interaction. Rapid detection of SARS-CoV-2 nucleocapsid (N) and spike (S1) receptor binding domain (RBD) proteins was first demonstrated at a clinically relevant concentration down to 1 ng/mL (33 pM) by real-time monitoring of nanomechanical signal induced by antibody-antigen interaction. More importantly, we further show high specific detection of antigens with nasopharyngeal swab specimens from patients pre-determined with qRT-PCR. The results take less than 5 min (swab to signal ≤5 min) and exhibit high selectivity and analytical sensitivity (LoD: 100 copies/ ml; 0.71 ng/ml of N protein). These findings demonstrate potential for nanomechanical signal transduction towards rapid antigen detection for early screening of SARS-CoV-2 and its related mutants.