Imaging and Identification of Marine Algal Bioactive Compounds by Surface Enhanced Raman Spectroscopy (SERS)

Surface-enhanced Raman spectroscopy (SERS) is a highly selective technique that can be used for imaging of single algae cells. In contrast to normal Raman spectroscopy, SERS utilizes light interaction with colloidal gold or silver particles working as antennas to match the sensitivity of fluorescence measurements. Furthermore, SERS enables a more profound picture of not only the analyte of interest but also the present biological matrix without the need for additional fluorescence labelling. The introduction of an internal standard in the form of a thiol self-assembled monolayer (SAM) on the colloidal gold or silver particles can be used to normalize the SERS response that otherwise would also depend on the locations of the colloid particles in the microscope image.In light of the vast amounts of data that is generated in each spectrum and the large variance in enhancement signal, multivariate analysis is necessary for accurate evaluation. This can be done by the use of transposed orthogonal projections to latent structures (T-OPLS), where the variations of properties in the reference spectra, Y table, and the variation in spectra, X table, are correlated.