Highly Sensitive and Ultra-Rapid Antigen-based Detection of SARS-CoV-2 using Nanomechanical Sensor Platform

Agarwal, Dilip Kumar; Nandwana, Vikas; Henrich, Stephen E.; Josyula, Vara Prasad V.N.; Thaxton, C. Shad; Qi, Chao; Simons, Lacy M.; Hultquist, Judd F.; Ozer, Egon A.; Shekhawat, Gajendra S.; Dravid, Vinayak P.

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 the 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 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(-1) (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 minutes (swab to signal ≤ 5 min) and exhibit high selectivity and analytical sensitivity (LoD: 100 copies mL(-1); 0.71 ng mL(-1) of N protein). These finding demonstrate potential for nanomechanical signal transduction towards rapid antigen detection for early screening of SARS-CoV-2 and its related mutants.