Signal Amplification Study for Gold-Coated Tilted Fiber Bragg Grating With Avidin-Biotin Sandwich Assay in the Detection of SARS-CoV-2

This study presents a method for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This investigation involves a multilayer sandwich immunoassay utilizing a monoclonal antibody-functionalized gold-coated tilted fiber Bragg grating (Au-TFBG), in combination with a polyclonal antibody-based avidin-biotin complex (ABC). The Au-TFBG undergoes a sequential process of surface functionalization, encompassing monoclonal antibodies (MAbs) immobilization onto the biosensor surface, viral particle captured by the immobilized MAbs, polyclonal antibodies (PAbs) binding to the captured virus, and subsequent interactions between PAbs and ABCs. Following each procedural step, the biosensor is rinsed thoroughly with a new and clean phosphate-buffered saline (PBS) solution to eliminate any residual substances. Integration of the polyclonal antibody-based ABC enhances the sensitivity which is depicted by the signal amplification of the biosensor and reduces the limit of detection (LOD) by ~70%, from 100.05 to 29.97 copies
$\cdot \text {mL}^{-{1}}$
. This enhancement is attributed to the larger molecular mass of biotinylated PAbs specific to captured viruses. Specificity tests involving non-SARS-CoV-2 and various SARS-CoV-2 strains have been conducted to demonstrate robust performance of the biosensor whereas control tests have been implemented to confirm the biosensor’s reliability under different conditions for practical applications.