Biodistribution and SPECT Imaging of ⁹⁹Tc^m Labeling NGR Peptide in Nude Mice Bearing Human HePG2 Hepatoma

A peptide containing the Asn-Gly-Arg （NGR）sequence was radiolabeled by ⁹⁹Tc^m and its radiochemical characteristics, biodistribution and SPECT imaging in nude mice bearing human HePG2 hepatoma were evaluated. ⁹⁹Tc^m-NGR was prepared directly with a labeling yield higher than 90%, and the radiochemical purity (RCP) higher than 95%. Nude mice bearing human HePG2 hepatoma were randomly divided into 6 groups with 3 mice in each group. The control group mice were blocked by injecting 100 μg unlabeled NGR 0.5 h before ⁹⁹Tc^m-NGR injection. The mice were sacrificed at 1、2、4、8、12 h after caudal intravenous injection of 7.4 MBq ⁹⁹Tc^m-NGR. The uptakes of kidney and liver were very high. Tumor uptake was （2.52±0.62）%ID/g at 1 h， with the highest uptake of (7.26±2.71 ）%ID/g. At 12 h, the uptake was still （3.93±1.93）%ID/g. In comparison, the uptake of the blocked control group was （1.29±0.85）%ID/g. The SPECT static images of 3 mice and the tumor/muscle (T/NT) value were obtained. The highest T/NT value was 3.25 at 4 h. The xenografted tumor became visible at 1h and the clearest image of the tumor was observed at 12 h. Results from this work shows that ⁹⁹Tc^m-NGR can be efficiently prepared, can favorably target tumor angiogenesis, and should be a potential probe in tumor therapy.