Fig. 2.

Single photon emission computed tomography (SPECT) imagings of a single mouse per experiment group at representative time points. After establishing the animal model of tumor xenograft, two injection projects were performed, as described in “Materials and methods”. In the project of intraperitoneal injection, the tumor-bearing mice were injected with 250 μl ¹³¹I-D2C (group A) and free Na¹³¹I (group B), respectively, whereas the other two groups of mice were injected with ¹³¹I-D2C (group C) free Na¹³¹I (group D) for intratumoral injection project. Sequential images of a single mouse taken by SPECT for per experiment group at 24, 72 h and 7 days after injection were showed in (a). Initial radioactivity in the blood and main organs (heart, liver, and so on) tends to decrease over 72 h or 7 days in group B and D but retain in group A and C. Moreover, group C was observed that the radioactivities at tumor tissues were much higher than that of other tissues 24 h after injection. To further investigate the tissue distribution of D2C, all mice were sacrificed on the seventh day after injection; their main organs and tumor tissues were obtained and weighed. A gamma counter was used to measure the radioactivity (cpm/g), and then the radioactivity ratio of the tumors to non-tumors (T/NT) was calculated and was shown in (b), various coloration columns represent radioactivity ratio of tumor to various organs. T/NT value was over 2 in group A and group C (b); it demonstrated that D2C could specifically bind to tumor tissues, consistent with the mentioned SPECT images (a). With respect to the ¹³¹I-D2C distributions in various tissue and organs (cpm/g) of each tissue in four experiment groups at day 7 after injection was measured and shown in Table 1