Polymer Microbead-Based Surface Enhanced Raman Scattering Immunoassays

The high sensitive surface enhanced Raman scattering (SERS) makes its broad utilization in biomolecule recognition. In this study, a highly specific polymer microbead-based Raman/SERS immunoassay system is developed and evaluated. Different analytical techniques such as UV–visible spectrophotometry, transmission electron microscopy, Raman spectrometry, and fluorescence microscopy have been employed to investigate the feasibility and effectiveness of gold nanoparticles (AuNPs) and polymer microbeads for immunoglobulin (IgG) recognition. The developed polymer microbead-based Raman/SERS immunoassay includes functional polystyrene (PS) microbeads, AuNPs, and SERS reporters, where the carboxylated PS microbeads serve as the immune-solid support, and the self-assembled monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA) formed on the surface of 50 nm AuNPs is used as the SERS tags. Antibodies (donkey antigoat IgG) are bioconjugated to the PS microbeads, which are able to selectively recognize the 4-MBA/AuNP-conjugated antigens (goat antihuman IgG). The specific recognition of matched antibody and antigen can be confirmed by both fluorescence imaging and Raman/SERS analysis. By combining the Raman signals of polymer microbeads and SERS tags, the system could have promising application for simultaneous multiplex detection in homogeneous immunoassay systems.