Tip-enhanced Raman detection of antibody conjugated nanoparticles on cellular membranes.

Tip enhanced Raman scattering (TERS) microscopy is used to image antibody conjugated nanoparticles on intact cellular membranes. The combination of plasmonic coupling and the resultant electric field obtained from intermediate focusing of a radially polarized source gives rise to Raman images with spatial resolution below 50 nm. Finite element method calculations are used to explain the origins of the observed image resolution and spectroscopic signals. The observed Raman scattering provides information about the biomolecules present near the nanoparticle probes. The results show that aggregates of nanoparticles produce spectroscopic results similar to those reported from other surface enhanced Raman spectroscopies, e.g., shell isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and aggregated nanoparticles; however, TERS enables the detection of isolated nanoparticles on cell membranes where the observed spectra provide information about the interaction of the specific biomolecule conjugated to the nanoparticle probe. These measurements present a new technique for exploring biomolecular interactions on the surface of cells and tissue.