The development of compact and highly active plasmonic nanotags tuned on the first transparency window of biological tissues is under demand for cell imaging applications. The optical activity of bare plasmonic nanoparticles is determined by morphology but the more complex core-shell systems require experimental verification as a shell may change the expected trends. A comparative study of fluorescence core-shell nanotags with different morphology of gold core is presented in this work. Four types of gold nanoparticles (nanostars, nanobones, short and long nanorods), differing in the surface roughness were used for preparation of complex nanotags with a polymer shell containing cyanine 5.5 dye inside and surface functionalized with folic acid as a model delivery vector. The obtained core-shell nanotags were characterized with transmission electron microscopy, UV-Vis absorption spectroscopy and zeta potential measurements. Imaging performance of the obtained nanotags was studied with a fluorescence microscope on human pancreatic cancer cells, indicating a successful internalization of all nanotags by cancer cells and fluorescence intensity depending on the spectral overlap between the dye, plasmonic band of gold core and laser wavelength. The tags based on gold nanorods showed the brightest fluorescence among the studied systems. Scanning electron microscopy of the cells incubated with nanotags proved their internalization in membrane and cytoplasm. The cell viability assay showed reduced cytotoxicity and good biocompatibility up to the concentration enough for cell imaging. The obtained results suggested that compact core-shell nanotags can be used for targeting the folate receptor positive tumor cells.
Keywords: Cell imaging; Core-shell structure; Fluorescent tags; Folic acid; Gold nanoparticles; Sulfo-cyanine 5.5.
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