Combining immunolabeling and surface-enhanced Raman spectroscopy on cell membranes.

We applied surface-enhanced Raman spectroscopy (SERS) to immunolabeled endothelial cells to derive enhanced spectra of the biomolecular makeup of the cellular surface. A two-step immunolabeling protocol with gold-conjugated antibodies coupled with silver enhancement to attach silver nanoparticles to the cell surface was employed. This approach generated ∼50-fold SERS enhancement of spectral signals. The SERS spectra exhibited several SERS-enhanced peaks associated with cell membrane components. The SERS detection of silver nanoparticles proved more far more sensitive than conventional light microscopy techniques. The SERS enhancement allowed us to carry out spectral mapping using wavenumbers associated with membrane components that correlated directly with the distribution of silver nanoparticles. SERS has the potential to detect immunolabeling at lower levels than is possible using conventional immunolabeling methods while simultaneously providing unique, spatially defined, biochemical information.