Evanescent wave absorbance based U-bent fiber probe for immunobiosensor with gold nanoparticle labels

Abstract

This study demonstrates a simple evanescent wave absorbance based sensing scheme for plasmonic sandwich immunoassay with the help of U-bent fiber probes as transducers. High absorbance sensitivity of the U-bent probes (200μm core and 1.5mm bend diameter) is exploited for sensitive detection of a small number of gold nanoparticles (AuNP) labels bound to the probe for the first time. Using 13nm AuNP labels conjugated with recognition antibodies, picomolar detection limit (2pM or 0.3ng/ml) for human immunoglobulin (HIgG) is achieved. The absorbance sensitivity and dynamic range were 0.019 A530nm/log (ng/ml) and 1–105ng/ml respectively. Nonspecific adsorption (NSA) of labels is minimized to less than 2% by PEGylation. The ease in U-bent probe fabrication and simple optoelectronic instrumentation consisting of an LED and a fiber optic spectrometer could facilitate extensive use of U-bent probes for several biosensing applications.