One step method labeling monoclonal antibody 3H11 with 99mTc and its preliminary application

In order to improve the accuracy of radioimmunoimaging and its image resolution, a modified Schwartz method was studied to prepare 99mTc labeled anti-gastric cancer monoclonal antibody 3H11. The antibody was incubated with a 1000-fold molar excess of 2-mercaptoethanol (2-ME) for 30 min at room temperature. The pre-antibody was mixed up with 1.1 GBq of 99mTc, glucoheptonate and SnCl2 at pH 7.2 buffer solution for 20∼30 min. The mean labeling efficiency of the labeled antibody was over 95%. The immunoreactivity of 99mTc-3H11 was 80% by ELISA method. The competition test in vitro showed that 99mTc bind with the high affinity sites of antibody. The biodistribution showed that the radioactivity of tumor uptake at 24 h postinjection was the highest. The tumor uptake was 8.98 +- 2.42% ID/g. The ratio of tumor to blood was over 1.5 and that of tumor to liver was more than 2.5 at 24 h postinjection. The tumor was clearly visualized at 22h postinjection. Initial clinical results showed that 99mTc-3H11 was stable in vivo and can well concentrated in the lesion sites. The direct labeling method applied to the preparation of 99mTc labeled antibody 3H11 was successful. 99mTc-3H11 is worthy of further clinical investigation