Scanning Electron Microscopy and Surface Enhanced Raman Spectroscopy Correlation Studies of Functionalized Composite Organic-Inorganic SERS Nanoparticles on Cancer Cells

Abstract

ABSTRACTComposite Organic-Inorganic Nanoparticles (COINs) are a novel type of surface-enhanced Raman (SER) scattering nanoparticle formed by aggregating inorganic silver particles in the presence of a chosen organic molecule with a distinct Raman fingerprint. Binding between antibody-functionalized COINs and cells is detected primarily using Raman spectroscopy, which measures spectral shifts of the excitation light due to inelastic scattering. It has been suggested that the amount of antibody-conjugated COINs binding on cells will vary according to the antigen-expression levels in cells and will lead to changes in measured SERS intensities. COINs functionalized with antibodies CD54 and CD8 were conjugated to U937 and SupT1 cancer cells and investigated in this study. SERS intensity measurements were obtained from each of the four sample variants and normalized against control samples comprising non-antibody-functionalized COINs with cells. The amount of COINs binding on cells was determined using scanning electron microscopy (SEM) and correlated with the SER spectroscopy intensity. Although we found a positive correlation between the number of COINs binding to cells and their respective SERS intensity, this relationship is not one-to-one, nor does it appear to be linear. We demonstrated that SEM imaging and SER spectroscopy can complement each other to provide information about COINs binding onto cancer cells.