Abstract:

In this work, a novel asymmetric pentamethine cyanine(Cy5) dye containing one nonionic hydrophilic group with two polyethylene glycol(PEG) ether chains on the indoline “N” was synthesized and characterized by ¹H nuclear magnetic resonance(¹H NMR) and high resolution mass spectrometer(HRMS). The spectra character and light stability of this Cy5 were investigated. The results show that the λ_ab and λ_em of the dye in water are 648 nm and 668 nm, respectively, and Stokes shifts reach 20 nm. The fluorescence quantum yield(Ф) in water is 0.13. After irradiated for 8 h, the photo-degradation of the aqueous soluble dyestuff of 5.8% happens. Albumin Bovine Serum(BSA) is labeled with this Cy5, and the dye/protein molar ratio(D/P) of fluorescent labeling reachs 1.16. By comparing fixed cells staining and viable cells staining, it is found that fixed cells can be overall stained by the new Cy5, the nucleoli of which are the most obvious and can be seen clearly, and that a small amount of the new Cy5 across the cell membrane of viable cells into the cell can stain cytoplasm and cell nucleus weakly, but a lot of the dye clumps together in the viable cell membrane.

Key words: polyethylene glycol ether chain, nonionic hydrophilic group, pentamethine cyanine, fluorescence, cell imaging