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For over two years, the world has endured a coronavirus pandemic resulting in over 470 million illnesses, 6 million deaths, and substantial supply chain disruptions. Prior to effective treatments, experts estimated that in the United States alone as many as 20 – 30 million tests should be conducted weekly to safely reopen, while highly effective vaccines took nearly a year to enter general distribution. This global event has highlighted the importance of developing and deploying rapid testing and treatment options for emerging pathogens. Currently, antibodies are the gold standard for biorecognition elements used in biosensors and may also be utilized to treat infection. Unfortunately, they can be challenging to mass produce and are sensitive to biological and temperature degradation, limiting broader distribution and equitable global access. Protein Catalyzed Capture agents (PCCs) present an alluring alternative as these small peptide macrocycles are comprised of unnatural amino acids and exhibit thermal and enzymatic stability. Their chemical synthesis enables scalable and reproducible production at diminished cost, while modular functionalities allow versatile applications in sensing and therapeutics, expanding the potential for more ubiquitous access to sensing & treatment options. This work sought to derive PCC receptors with high affinity and specificity for the SARS-CoV-2 spike protein from a one bead one compound peptide library. Chemically synthesized epitope fragments of the SARS-COV-2 spike protein were screened against the library and PCC receptor leads identified through entropically favored, un-catalyzed “click” reactions. Mass spectrometry and multiplex affinity assays then enabled down-selection of promising receptors. Modular chemical modifications were made to selected receptors to enable effective integration into a graphene field effect transistor (gFET) sensor which demonstrated a practical limit of detection of 103 pfu/mL inactivated SARS-CoV- 2 virus and the ability to discriminate between SARS-COV-2 and Influenza or Rhino viruses.
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