Preparation and Analysis on Biological Activity of ~(99)Tc~m-RC-160

RC-160 (Vapreotide) is labeled with 99Tcm by a direct method and the biological activity of 99Tcm-RC-160 is identified by combined with somatostatin receptor. The labeling yield is about 45% using sodium ascorbate as reductant; the labeling yield is 68% using stannous tartrate as reductant. The radiochemical purity of 99Tcm-RC-160 is more than 95% after purification through HLB cartridge; it is still more than 95% after 4 hours. The concentration of cysteine used to replace 50% 99Tcm from 99Tcm-RC-160 is 5 mmol/L, so that the internal and external stability of 99Tcm-RC-160 is good. 99Tcm-RC-160 have high affinity with somatostatin receptor (Kd = 0. 83 + 0. 09 nmol/L,Bmax = 45 + 3 nmol/g).