SERS Biomolecular Detection Schemes

Generally, SERS detection of biomolecules can be accomplished by two independent ways (i) direct—intrinsic—(often called label-free) and (ii) indirect— extrinsic— using labels. The scheme of different approaches is illustrated in Fig. 5.1. 

The intrinsic SERS detection is possible in case that the biomolecule provides a sufficiently good intrinsic SERS spectrum (Fig. 5.1a). This spectrum can serve for biomolecule identification, quantification and/or determination of its state, such as conformation or complex formation. This method is more reliable than extrinsic SERS labelling as it shows the direct spectral signature of the biomolecule. On the 

1 Schematic illustration of different approaches for SERS biomolecular detection, a Intrinsic detection of biomolecule (protein), b Extrinsic detection of labelled biomolecule (DNA). c Extrinsic detection of biomolecule using SERS tag (metallic NP with RRM). d SERS tag (metallic NP with RRMs, protective shell and antibody) for immunoassay (adapted from Wang et al. 2013. Copyright 2012 American Chemical Society) 

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