Evaluation and comparison of different quality control methods in radiochemical purity determination of new peptide kits 99mTc-EDDA-Tricine-HYNIC-Tyr3-Octreotide and 99mTc-EDDA-Tricine-HYNIC-Tyr3-Octreotate for imaging somatostatin receptor positive tumors

Using labeled peptides enjoys high importance in nuclear medicine. Somatostatin analogs labeled with different radionuclide are vastly investigated for diagnosis or treatment of somatostatin receptor positive tumors. Labeling somatostatin analogs with 99mTc as alternative of 111In needs doing different quality control method for determination of labeling yield and complex stability for clinic applications. For determining radiochemical purity, three different methods were compared and evaluated including HPLC, TLC and Sep-Pak. All the three methods were suitable for determining of radiochemical purity in peptide kits, although using HPLC was more effective rather than the others. HPLC was the best method for determination of radiochemical purity of the peptide kits. TLC or Sep-Pak method should only be employed if HPLC is not available in nuclear medicine clinics, and after training and gaining sufficient operational experience. In this research, a new monoclonal antibody against colon cancer cells was prepared and antigen concentration in different cells determined by a radioimmunoassay method using iodine (I-125) labeled protein G. 125I-labeled protein G percent binding to white blood cell, HT29, LS180 and MCF7 cell lines were 7.1%, 91.2%, 75.8% and 40.2%, respectively. Regarding importance of monoclonal antibody applications, it is necessary to find an efficient method for their evaluation in cancer therapy. In this method, a radioactive agent with no count restriction was used. Also by this method, amount of the antigen can be easily quantified.