Design of Silica-protected Surface-enhanced Raman Scattering Nanoprobe for Immunosorbent Assay

In this study, we present a method of achieving highly sensitive immunoassays based on surface-enhanced Raman scattering (SERS). The biofunctional-nanoprobe-linked immunosorbent assay is a closely related technique with a good linear range and the ability to simultaneously detect antigens with high sensitivity. Herein, we report a novel method based on a sandwich structure composed of a silver monolayer and biocompatible Au-mercaptobenzoic acid (MBA)@SiO2 that was assembled through an immune recognition reaction. To induce a strong plasmonic contribution of the nanoprobes, two or more MBA-adsorbed gold nanoparticles were saturated and loaded into silica. Silica-protected gold nanoaggregates exhibit stable SERS activity and biocompatibility for proteins. The capabilities of the proposed sandwich structure for analytical applications were demonstrated through the use of the SERS technique to detect antigens at very low concentrations. These techniques may prove to be superior to current protocols for biomarker research and clinical diagnosis, which require high sensitivity and quantitation over an extended range.