Time-resolved observation of surface-enhanced Raman scattering from gold nanoparticles during transport through a living cell.

We perform time-resolved observation of living cells with gold nanoparticles using surface-enhanced Raman scattering (SERS). The position and SERS spectra of 50-nm gold nanoparticles are simultaneously observed by slit-scanning Raman microscopy with high spatial and temporal resolution. From the SERS observation, we confirm the attachment of the particles on the cell surface and the entry into the cell with the subsequent generation of SERS signals from nearby molecules. We also confirm that the strong dependence of SERS spectra on the position of the particle during the transportation of the particle through the cell. The obtained SERS spectra and its temporal fluctuation indicate that the molecular signals observable by this technique are given only from within a limited volume in close proximity to the nanoparticles. This confirms the high spatial selectivity and resolution of SERS imaging for observation of biomolecules involved in cellular events in situ.