Surface-Enhanced Raman Scattering-Based Competitive Immunoassay of Poly-γ-D-Glutamic Acid for Highly Sensitive Detection of Anthrax

Abstract

Anthrax is a highly acute disease caused by the bacterium Bacillus anthracis. In this article, we report a highly sensitive detection techniqu e for pathogenic B. anthracis, based on the use of a surface-enhanced Raman scat- tering (SERS)-active magnetic sensor. Gold nanoparticles (GNPs) and magnetic beads were used as SERS nanotags and supporting substrates, respectively. Here, an SERS-based competitive immunoassay platform is described for the quantitative evaluation of the anthrax marker. Poly-γ- D-glutamic acid (PGA) capsules were used as a target biomarker for the highly sensitive detection of B. anthracis because PGA is known to be closely associated with the pathogenesis of B. anthracis infection. The SERS-based competitive assay reveals an extraordinarily high sensitivity for PGA with a limit of detection of ~1.0 ng/mL. This work provides a con- ceptually new immunoassay prototype for fast and sensitive detection of PGA markers.