Surface-Enhanced Raman Spectroscopic-Encoded Beads for Multiplex Immunoassay

Abstract

A new type of encoded bead, which uses surface-enhanced Raman scattering (SERS), is described for multiplex immunoassays. Silver nanoparticles were embedded in sulfonated polystyrene (PS) beads via a polyol method, and they were used as SERS-active substrates. Raman-label organic compounds such as 4-methylbenzenethiol (4-MT), 2-naphthalenethiol (2-NT), and benzenethiol (BT) were then adsorbed onto the silver nanoparticles in the sulfonated PS bead. Although only three kinds of encoding have been demonstrated here, various combinations of these Raman-label organic compounds have the potential to give a large number of tags. The Raman-label-incorporated particles were then coated with a silica shell using tetraethoxyorthosilicate (TEOS) for chemical stability and biocompatibility. The resulting beads showed unique and intense Raman signals for the labeled organic compounds. We demonstrated that SERS-encoded beads could be used for multiplex detection with a model using streptavidin and p53. In our system, the binding event of target molecules and the type of ligand can be simultaneously recognized by Raman spectroscopy using a single laser-line excitation (514.5 nm).

Surface enhanced Raman spectroscopy and its application to molecular and cellular analysis

“…For example, Jun et al (2007) have proposed SERS-encoded polystyrene (PS) beads containing Raman active small compound labeled silver nanoparticles with a silica shell, enabling them to obtain reproducible spectra for multiple samples. As another example, Grubisha et al (2003) have also demonstrated the detection of prostate specific antigen using a sandwich immunoassay based on SERS.…”

Silver Nanoparticles: Sensing and Imaging Applications

“…As encapsulating agent, polymers (Stokes et al, 2006) and silica (Jun et al, 2007) are generally employed. Indeed, silica encapsulated SERS tags are being commercialized.…”

Immunomagnetic nanoparticle-based assays for detection of biomarkers

“…43 (a) Schematic diagram of dot-coded particle synthesis showing polymerization across two adjacent laminar streams to make single-probe, halffluorescent particles (shown in b); (c) diagrammatic representation of particle features for encoding and analyte detection. encoding scheme shown allows the generation of 2 20 (1,048,576) unique codes; (d) differential interference contrast (DIC) image of particles generated by using the scheme shown in (a); (e-g) overlap of fluorescence and DIC images of single-probe (e), multiprobe (f, bottom), and probe-gradient (g, left) encoded particles. A schematic representation of multiprobe particles is also shown (f, top) and a plot of fluorescent intensity along the center line of a gradient particle (g, right).…”

“…However, surface-enhanced Raman signal-based assays are limited by their relatively weak Raman signal, thus requiring amplification of the signal while maintaining an optimal signal-to-noise ratio. 20 …”