Towards quantitative multi-color nanodiagnostics: spectral multiplexing with six silica-encapsulated SERS labels

Quantitative multiplexing experiments using mixtures of up to six spectrally distinct surface-enhanced Raman scattering (SERS) nanoparticle labels are demonstrated. The SERS labels comprise gold nanoparticles, Raman reporter molecules chemisorbed onto the metal surface, and a silica shell providing chemical and mechanical stability as well as spectral reproducibility. Spectral unmixing is performed with a simple least-square algorithm because the overall SERS signal of the mixtures can be represented as a linear combination of the known spectral signatures from the individual silica-protected labels. In contrast, simple spectral unmixing using unprotected SERS particles, i.e. without a silica shell, was not successful because of band shifts and alternating peak heights in the mixtures, which is indicative of perturbing interactions between the SERS labels. Copyright (c) 2016 John Wiley & Sons, Ltd.