Biodistribution and SPECT imaging study of (99m)Tc labeling NGR peptide in nude mice bearing human HepG2 hepatoma.

A peptide containing Asn-Gly-Arg(NGR) sequence was synthesized and directly labeled with (99m)Tc. Its radiochemical characteristics, biodistribution, and SPECT imaging were evaluated in nude mice bearing human HepG2 hepatoma. Nude mice bearing HepG2 were randomly divided into 5 groups with 5 mice in each group and injected with ~7.4 MBq (99m)Tc-NGR. The SPECT images were acquired in 1, 4, 8, and 12 h postinjection via caudal vein. The metabolism of tracers was determined in major organs at different time points, which demonstrated rapid, significant tumor uptake and slow tumor washout. The control group mice were blocked by coinjecting unlabelled NGR (20 mg/kg). Tumor uptake was (2.52 ± 0.83%) ID/g at 1 h, with the highest uptake of (3.26 ± 0.63%) ID/g at 8 h. In comparison, the uptake of the blocked control group was (1.65 ± 0.61%) ID/g at 1 h after injection. The SPECT static images and the tumor/muscle (T/NT) value were obtained. The highest T/NT value was 7.58 ± 1.92 at 8 h. The xenografted tumor became visible at 1 h and the clearest image of the tumor was observed at 8 h. In conclusion, (99m)Tc-NGR can be efficiently prepared and it exhibited good properties for the potential SPECT imaging agent of tumor.