Rapid and Sensitive Detection of Antigen from SARS-CoV‑2 Variants of Concern by a Multivalent Minibinder-Functionalized Nanomechanical Sensor

New
platforms for the rapid and sensitive detection of severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern
are urgently needed. Here we report the development of a nanomechanical
sensor based on the deflection of a microcantilever capable of detecting
the SARS-CoV-2 spike (S) glycoprotein antigen using computationally
designed multivalent minibinders immobilized on a microcantilever
surface. The sensor exhibits rapid (<5 min) detection of the target
antigens down to concentrations of 0.05 ng/mL (362 fM) and is more
than an order of magnitude more sensitive than an antibody-based cantilever
sensor. Validation of the sensor with clinical samples from 33 patients,
including 9 patients infected with the Omicron (BA.1) variant observed
detection of antigen from nasopharyngeal swabs with cycle threshold
(Ct) values as high as 39, suggesting a limit of detection similar
to that of the quantitative reverse transcription polymerase chain
reaction (RT-qPCR). Our findings demonstrate the use of minibinders
and nanomechanical sensors for the rapid and sensitive detection of
SARS-CoV-2 and potentially other disease markers.