Probing Intrinsic and Extrinsic Components in Single Osteosarcoma Cells by Near-infrared Surface-enhanced Raman Scattering

We report on the capabilities of near-infrared surface-enhanced Raman scattering (SERS) using gold nanoparticles to obtain detailed chemical information with high spatial resolution from within single cancer cells, living or fixed. Colloidal gold particles, 60 nm in size, were introduced into live human osteosarcoma cells by endocytosis by adding them to the growth medium. Rapid SERS mapping of cells indicated that not only could rich vibrational spectra be obtained from intrinsic cellular constituents both in the cytoplasm and nucleus and but also the distribution of extrinsic molecules introduced into the cells, in this case, rhodamine 6G could be characterized, suggesting that the intracellular distribution of chemotherapeutic agents could potentially be measured by this technique. We show that the SERS signal intensity from the cellular components increases and more spectral detail is acquired from dried cells when compared with hydrated cells in buffer. The data also show spectral fluctuations, mainly in intensity but also in peak position, which are dependent upon the intensity of the excitation light and are probably due to diffusion of molecules on the surface of the gold nanoparticles. A detailed understanding of the origins of these effects is still not complete, but the ability to acquire very sensitive SERS inside living cancer cells indicates the potential of this technique as a useful tool in biomedicine.