Direct Radiolabeled ⁹⁹Tc^m-EGF and Biological Distribution in C6 Rats

The method of technetium-99m direct radiolabeling of epidermal growth factor (EGF) and the biological distribution characteristics of ⁹⁹Tc^mEGF in C6bearing rats were explored. Following reduction of EGF（2.5 μg） with 2ME（20 mL/L， 10 μL）， EGF was labeled with ⁹⁹Tc^m in the presence of SnCl₂（0.5 μg）. The results show that radiochemical purity of ⁹⁹Tc^m-EGF is more than 95% and ⁹⁹Tc^m-EGF is of the characteristic of stability. The biological activity analyzed by the culture of endothelial cells shows that there is no significant difference between ⁹⁹Tc^m-EGF and EGF（P＞0.05）. Biological distribution is observed at different time point after injection of ⁹⁹Tc^mEGF into tumorbearing Wistar rats, and shows ⁹⁹Tc^mEGF is mainly accumulated in liver, kidney and spleen and least accumulated in the brain. Tumor take relatively high concentration of ⁹⁹Tc^mEGF and the uptake ratio of tumor to normal tissue is 2.25 at 4 h. So ⁹⁹Tc^mEGF prepared by this direct method appears to be a feasible way to detect the tumors expressing high EGFR（such as glioma）.