Cyanine5 NHS ester is a ideal reactive dye for the labeling of peptides, proteins, and oligonucleotides which contain the amino-groups. Recently, among the life science research and diagnostics, Dye color quantity can be detected in gel electrophoresis by naked eye as the dye color is very intense and as small as 1 nanomol. For biomolecule labeling, the labeling reagent has low aqueous solubility, using of organic co-solvent to dissolve this molecular is necessary for efficient reaction. First, Cyanine dye should be dissolved in organic solvent and then added to a solution of biomolecule in appropriate aqueous buffer. For more sophisticated targets such as easily degradable proteins, when use of DMF or DMSO is undesirable, consider using water-soluble Cy5 NHS ester which does not require co-solvent, and has very similar fluorescent properties.
In mice, Cy5-labeled polyplexes was intravenous injected to evaluate the targeting ability of polyplexes in tumor-bearing nude mice. Heart, liver, spleen, lung, kidney and tumor, were removed after the mice were sacrificed and the fluorescence intensities of Cy5-labeled polyplexes were immediately examined [1].
Reference:
[1] Chen, K. ; Chen, Q.; Wang, K.; Zhu, J.; Li, W.; Li, W.; Qiu, L.; Guan, G.; Qiao, M.; Zhao, X.; Hu, H.; Chen, D. Synthesis and characterization of a PAMAM-OH derivative containing an acid-labile β-thiopropionate bond for gene delivery. International Journal of Pharmaceutics, 2016, 509(1–2), 314–327.