Development of Nanobody-Displayed Whole-Cell Biosensors for the Colorimetric Detection of SARS-CoV-2

The accurate and effective detectionof severe acute respiratorysyndrome coronavirus 2 (SARS-CoV-2) is essential to preventing thespread of infectious diseases and ensuring human health. Herein, ananobody-displayed whole-cell biosensor was developed for colorimetricdetection of SARS-CoV-2 spike proteins. Serving as bioreceptors, yeastsurfaces were genetically engineered to display SARS-CoV-2 bindingof llama-derived single-domain antibodies (nanobodies) with high captureefficiency, facilitating the concentration and purification of SARS-CoV-2.Gold nanoparticles (AuNPs) employed as signal transductions were functionalizedwith horseradish peroxidase (HRP) and anti-SARS monoclonal antibodiesto enhance the detection sensitivity. In the presence of SARS-CoV-2spike proteins, the sandwiched binding will be formed by linking engineeredyeast, SARS-CoV-2 spike proteins, and reporter AuNPs. The colorimetricsignal was generated by the enzymatic reaction of HRP and its correspondingcolorimetric substrate/chromogen system. At the optimal conditions,the developed whole-cell biosensor enables the sensitive detectionof SARS-CoV-2 spike proteins in a linear range from 0.01 to 1 & mu;g/mLwith a limit of detection (LOD) of 0.037 & mu;g/mL (about 4 x10(8) virion particles/mL). Furthermore, the whole-cell biosensorwas demonstrated to detect the spike protein of different SARS-CoV-2variants in human serum, providing new possibilities for the detectionof future SARS-CoV-2 variants.