Fiber Optic Plasmonic Sandwich Immunosensor: Influence of AuNP Label Size and Concentration

This study demonstrates the effect of size and concentration of the gold nanoparticles (AuNP) labels on the sensitivity of evanescent wave absorbance (EWA) based fiber optic sandwich immunobiosensor. A plasmonic sandwich immunoassay using human Immunoglobulin G (HIgG) and goat anti-HIgG (GaHIgG) was performed on a U-bent polymethyl methacrylate (PMMA) based plastic optical fiber (POF) probe (core diameter 500 μm and bend diameter 1.4 mm). Enhanced EWA response was observed with 60 nm AuNP labels for the analyte concentration 1 μg/ml in comparison to 20, 40 and 80 nm AuNP labels. Furthermore, on optimizing the GAbs concentration the sensitivity of the sensor enhanced significantly with 20× 60 nm labels with a LOD of 100 fg/ml. The advantages such as ease in fiber probe handling and simple instrumentation are highly promising for development of fiberoptic biosensors for various applications.