Abstract
Octreotide, a cyclopeptide with eight amino acids, is a somatostatin analog with the affinity to somatostatin receptors. The aim of the study is to develop 99mTc(I)-HYNIC-octreotide as radiopharmaceutical for somatostatin receptor scintigraphy. HYNIC-octreotide is synthesizd by the method of solid-phase peptide synthesis with disulfide bonding developed by Institute of Nuclear Energy Research. HYNIC and [99mTc(CO)3(OH2)3]+ were prepared respectively according to the previous reports. Octreotide was labeled with [99mTc(CO)3(OH2)3]+ via HYNIC as a bifunctional chelator. 99mTc(I)-HYNIC-octreotide was prepared by mixing the [99mTc(CO)3(OH2)3]+ solution with HYNIC-octreotide in saline at 75℃. According to the results, the radiochemical purity for 99mTc(I)-HYNIC-octreotide was greater than 90%. The labeling technique for 99mTc(I)-HYNIC-octreotide has been successfully established in this study. The HYNIC-octreotide efficiently inhibited the binding ability of 125I-Tyr11-somatostatin with somatostatin receptor regarding to the retention of its receptor-binding affinity. In the animal model, 99mTc(I)-HYNIC-octreotide was uptaken by the pancreas tumor cells (AR42J) implanted into the SCID mice, and the result showed by showing a clear image for the tumor. These results demonstrated that 99mTc(I)-HYNIC-octreotide is potential for imaging pancreas tumors via somatostatin receptors .