Abstract: The improvement of the amphipathicity of cyanine dyes is conducive to the improvement of its own antitumor activity. In this paper, the feasibility of converting trimethine indocyanine dye (Cy3) into multifunctional small-molecule chemotherapy drug was explored for the first time. Two amphipathic trimethine indocyanine dyes of Cy3-DIPEG and Cy3-SO₃-DIPEG containing polyethylene glycol(PEG) chains on the indol “N” were designed and synthesized in yields of about 40%. The structure of the product was identified by ¹H NMR and ¹³C NMR spectroscopy and mass spectroscopy. The maximal fluorescence emission wavelengths of Cy3-DIPEG and Cy3-SO₃-DIPEG in water are about 570 nm, and their fluorescence quantum yields (Ф) are 0.06 and 0.13, respectively. The antitumor activities of two dyes on human colorectal cancer cell lines (SW480 and HCT-116) were tested in vitro by the thiazole blue (MTT) assay and the antitumor mechanism was initially explored by subcellular localization experiments. The results show that Cy3-DIPEG can accumulate in mitochondria through the tumor cell membrane, and significantly inhibit the proliferation of human colorectal cancer cells, but Cy3-SO₃-DIPEG cannot penetrate into the tumor cell and has no antitumor activity.

Key words: multifunctional chemotherapeutics, trimethine indocyanine, amphipathic, spectral property, antitumor