Fabricating well-defined and highly reproducible platforms for surface-enhanced Raman scattering (SERS) is very important in developing practical SERS sensors. We report a novel SERS platform composed of a single metallic nanowire (NW) on a metallic film. Optical excitation of this novel sandwich nanostructure provides a line of SERS hot spots (a SERS hot line) at the gap between the NW and the film. This single nanowire on a film (SNOF) architecture can be easily fabricated, and the position of hot spots can be conveniently located in situ by using an optical microscope during the SERS measurement. We show that high-quality SERS spectra from benzenethiol, brilliant cresyl blue, and single-stranded DNA can be obtained on a SNOF with reliable reproducibility, good time stability, and excellent sensitivity, and thus, SNOFs can potentially be employed as effective SERS sensors for label-free biomolecule detection. We also report detailed studies of polarization- and material-dependent SERS enhancement of the SNOF structure.

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We investigated in vitro and in vivo glutathione (GSH)-induced intracellular thiopurine anticancer drug release on gold nanoparticle (Au NP) surfaces by means of label-free confocal Raman spectroscopy. Direct monitoring of GSH-triggered release of 6-mercaptopurine (6MP) and 6-thioguanine (6TG) was achieved in real time. Live cell imaging technique provides a nanomolar range release of 6MP and 6TG from Au NP surfaces after the injection of external GSH. In vivo SERS spectra of 6TG were obtained from the subcutaneous sites in living mice after GSH treatment. GSH-triggered releases of Cy5-dye assembled on 6TG-capped Au NPs were also compared using independent fluorescence measurements. Our work demonstrates that the time-lapse Raman spectroscopic tools are useful for monitoring of the controlled release of thiopurine drug molecules in vitro and in vivo.