Gold nanolabels for SERS imaging excitable by red lasers

Optical labels excitable by red lasers are promising for the diagnostics and treatment of certain types of cancer as the lasers with a wavelength from the range of 630–660 nm are considered relatively safe and effectively penetrate into tissues on a depth up to 5 mm. Such optical labels can be used quite effectively in surface-enhanced Raman scattering (SERS) imaging. The goal of present work consists in the design of plasmonic labels, which give intense signal under red light excitation, their characterization and probing on live cells. Gold nanostars (NS) were synthesized by a single-stage method to be used as a metal core and were studied by scanning electron microscopy and UV-Vis spectroscopy which confirmed their morphology and showed the maximum of absorption band in the middle of red region. NS further were coated with a multilayer polymer shell with incorporated cyanine 5.5 dye. Folic acid was introduced as a model delivery vector. The pronounce SERS spectra of obtained labels were registered in solution phase. The further study of labels incubated with PANC-1 cell line showed the SERS response at focus on the cell cytoplasm. The MTT assay revealed that the labels don't have a toxic effect in the concentration range of 0.05 to 1 mg/l for atomic gold on the same cell line. The obtained results demonstrate a high potential of nanostar-based labels for diagnostic and therapeutic purposes which can be conducted using medical red lasers.