Rapid single-molecule detection of COVID-19 and MERS antigens via nanobody-functionalized organic electrochemical transistors

The COVID-19 pandemic has highlighted
the need for rapid and sensitive protein detection and quantification in simple
and robust formats for widespread point-of-care applications. Here, we report nanobody-functionalized
organic electrochemical transistors with a modular architecture for the rapid
quantification of single-molecule-to-nanomolar levels of specific antigens in
complex bodily fluids. The sensors combine a solution-processable conjugated
polymer in the transistor channel and the high-density and
orientation-controlled bioconjugation of nanobody–SpyCatcher fusion proteins on
disposable gate electrodes. They provide results after 10-min of exposure to 5
μL of unprocessed
samples, maintain high specificity and single-molecule sensitivity in human
saliva and serum, and can be reprogrammed to detect any protein antigen if a
corresponding specific nanobody is available. We used the sensors to detect
green fluorescent protein,
SARS-CoV-2 and MERS-CoV spike proteins, and for the COVID-19 screening of
unprocessed clinical nasopharyngeal swab and saliva samples with a wide range
of viral loads.