Preparation of ¹²⁴I, Antibody Labeling and Micro-PET/CT Imaging of Labeled Compounds

To provide a method for the production of ¹²⁴I by using a medical cyclotron and the method of ¹²⁴I labeling, ¹²⁴I was prepared using a nuclear reaction of ¹²⁴Te (p, n) ¹²⁴I. Firstly, a ¹²⁴TeO₂/Al₂O₃ target was obtained by pressing, and then bombarded with a cyclotron for 3-8 hours. After 12 hours, impurity nuclides produced by the side reaction were removed. Finally, a Na¹²⁴I solution was obtained by iodine sublimation radiochemical separation method. Analyze the purity of Na¹²⁴I and label it with anti-mesothelin (MSLN) antibody, then inject it into the tail vein of KM mice to observe the distribution of ¹²⁴I-anti-MSLN. The obtained ¹²⁴TeO₂/Al₂O₃ target was bombarded with 12.5 MeV energy and 20 μA proton beam to obtain 340.4-1121.1 MBq nuclide products, and after purification, 274.2-758.5 MBq of high-purity Na¹²⁴I solution was obtained. The final radioactive concentration of the obtained Na¹²⁴I solution was greater than 54840 Bq/μL. Using the Na¹²⁴I solution to label an anti-MSLN antibody, ¹²⁴I-anti-MSLN probe with a radiochemical purity greater than 99% was obtained. The probe was injected into KM mice via the tail vein, and significant uptake of the probe was observed in the thyroid region of the mice through Micro-PET/CT imaging. This uptake can be blocked by feeding 0.5% KI solution 3 days in advance, and the metabolic behavior conforms to the metabolic pattern of the ¹²⁴I labeled antibody probe in KM mice. This study summarized the purification of ¹²⁴I samples of 25 batches in our unit, and tthe equipment and methods involved in the purification process and the use of Na¹²⁴I after purification were summarized. In order to provide reference for the production and efficient purification of ¹²⁴I. The results showed that the purified ¹²⁴I had high nuclear purity and chemical purity, which met the requirements of radiolabeling. The average recovery rate was higher than 70%, and the automatic purification process was safe and reliable.