Minimalist Design for a Hand-Held SARS-Cov-2 Sensor: Peptide-Induced Covalent Assembly of Hydrogel Enabling Facile Fiber-Optic Detection of a Virus Marker Protein.

The rampaging COVID-19 needs bioassaying methods of low cost and high robustness for those living in the poorly developed regions. Here, we propose such a method that does not need expensive and complicated equipment. Only a set of hand-held small devices is sufficient. A section along an optic fiber cable is stripped, so that laser light travelling through it will leak outside, while biosensing process taken place on this stripped section can form a new cladding layer of hydrogel, restoring the laser output of the fiber. A short peptide probe immobilized on the stripped section of the fiber can covalently capture a biomarker protein of SARS-Cov-2 from the serum sample. Through the cross-linking of the target protein with the interfering proteins in the serum sample, a hydrogel is covalently immobilized around the stripped section, highly resistant to detergent rinsing that is indispensable for removing nonspecific interference from the clinical sample. Using this "covalent biosensing" strategy, only one peptide probe is sufficient to simultaneously achieve ultrahigh affinity toward the biomarker protein of SARS-Cov-2 and effective signal amplification.