Figure 4.

Cytotoxicity of conjugates 1, their cytidine analogs 2, and their parent dyes. (a) Compounds 2d and D were shown to be significantly toxic below 10 μM (IC₅₀: 2d, 3.4 ± 0.4; D, 7.1 ± 1.7 μM). Conversely, in the sets 1a, 2a, and A, and 1b, 2b, and B, gemcitabine and compounds 1 are significantly more cytotoxic than the controls 2 and the free dyes (parts b and c, respectively). IC₅₀ values are the following: gem, 8.2 ± 1.7; 1a, 20.9 ± 5.0; 1b, 20.7 ± 3.2 nM).