In addition to efficacious vaccines and antiviral therapeutics,
reliable and flexible in-home personal use diagnostics for the detection
of viral antigens are needed for effective control of the COVID-19
pandemic. Despite the approval of several PCR-based and affinity-based
in-home COVID-19 testing kits, many of them suffer from problems such
as a high false-negative rate, long waiting time, and short storage
period. Using the enabling one-bead-one-compound (OBOC) combinatorial
technology, several peptidic ligands with a nanomolar binding affinity
toward the SARS-CoV-2 spike protein (S-protein) were successfully
discovered. Taking advantage of the high surface area of porous nanofibers,
immobilization of these ligands on nanofibrous membranes allows the
development of personal use sensors that can achieve low nanomolar
sensitivity in the detection of the S-protein in saliva. This simple
biosensor employing naked-eye reading exhibits detection sensitivity
comparable to some of the current FDA-approved home detection kits.
Furthermore, the ligand used in the biosensor was found to detect
the S-protein derived from both the original strain and the Delta
variant. The workflow reported here may enable us to rapidly respond
to the development of home-based biosensors against future viral outbreaks.