Immuno-SERS: from nanotag design to assays and microscopy

Immuno-SERS (iSERS) is a newly emerging technique that combines target recognition through conventional antigen–antibody interaction and signal output through surface-enhanced Raman scattering (SERS) detection. iSERS is analogous to the traditional protein detection assays, whilst the target recognition molecules are labeled with SERS nanotags. A target-specific SERS nanotag is typically composed of a colloidal metal nanoparticle for signal enhancement, Raman reporter molecules adsorbed onto its surface for identification, and biomolecules attached to the SERS target for target-specific recognition. In this chapter, we summarize each component for SERS nanotags in terms of the synthesis of plasmonic nanostructures, the design of Raman reporter molecules as well as the bioconjugation strategies that are used to label the SERS nanotags. We have also highlighted the advances of iSERS assays for protein detection and iSERS microscopy for protein localization in cells and in tissue specimens.