U-bent fiberoptic evanescent wave absorbance plasmonic sandwich biosensor: Silver based signal enhancement

In this study, silver enhanced labelling method was employed in evanescent wave absorbance based fiber optic immunosensor for improving the sensitivity of biomolecular detection. A multi-dimensional sensitive and specific detection of Human Immunoglobulin G (HIgG) is illustrated by exploiting: (i) U-bent optical probe with enhanced evanescent absorbance sensitivity, (ii) Highly specific sandwich immunoassay format, (iii) Plasmonic particles (AuNP) having high extinction properties as labels and (iv) Enhanced extinction due to silver deposition on catalytic labels. A detection sensitivity of 0.02 A530nm/log (ng/ml) was obtained using sandwich assay for HIgG detection. A 25-fold improvement in sensitivity was achieved using silver enhancement technique.