Biomolecular SERS Applications

Abstract

SERS spectroscopy is currently undergoing rapid development as an ultra-sensitive and highly specific analytical technique for biomolecular detection. This chapter gives an overview of SERS study of biomolecules primarily of nucleic acids, proteins, membranes and their components. Both detection schemes—intrinsic and extrinsic—will be introduced. Direct spectral signature of the biomolecule can be obtained by an intrinsic scheme. An extrinsic approach using labelling of target biomolecule or SERS tag consisting of metallic NPs and Raman reporter molecule brings indirect information but much better sensitivity. For example, SERS detection limits for labelled oligonucleotides can be about 10⁻¹¹–10⁻¹² M, which is about three orders of magnitude better than those provided by standard fluorescence technique. Hybridization of a nucleic acid to its complementary target serves to its unambiguous molecular recognizability. For protein detection, immunoassay platforms are employed to detect the target antigens or antibodies (typically small proteins) through specific antibody-antigen binding. SERS tags formed by metallic nanoparticles with attached Raman reporter molecules (and biorecognition element such as an antibody in the case of immunoassays) are used in SERS extrinsic hybridization and immunoassay experiments, thus increasing their sensitivity.