Automatic synthesis of N-succinimidyl 4-18F-fluorobenzoate and its utility for 18F labeled C2A domain of synaptotagmin I

Objective: To develop and optimize a module for the automatic production of N-succinimidyl-4-[18F] fluorobenzoate (18F-SFB) that is used for further 18F labelling C2A domain of Synaptotagmin I . The conjugated compound was applied for detecting the tumor apoptosis in rabbit model after chemotherapy. Methods: GE TRACERlab and TRACERlab FXF-N modules were modified and programmed to automatically produce 18F-SFB which was further analyzed by high performance liquid chromatography (HPLC).C2A-glutathione S transferase (GST) was conjugated with 18F-SFB (18F-FB-C2A-GST) and subsequently purified by HPLC. Two rabbits grafted with VX2 lung cancer were first treated with chemotherapy and then, 37 MBq of 18F-FB-C2A-GST was administered via the auricular vein. Serial PET/CT imagings were performed at 0.5, 1 and 2 h post-injection respectively. Tumor apoptosis was examined by pathological study. Results: The TRACERlab FXFDG and TRACERlab FXF-N modules were successfully adapted to synthesize 18F-SFB, with the radiochemical yield (76.41±4.00)% (n=10), the corrected yield (45.43±5.90) % and the radiochemical purity about 95%. The whole procedure for labeling 18F-SFB was about 87 min. From PET/CT imagings, significant uptake was found in the tumor after chemotherapy, but no obvious up-take was found in heart, lungs and liver. HE staining demonstrated large number of apoptotic bodies within the tumor tissues. Conclusions: 18F-SFB can be automatically synthesized. 18F-FB-C2A-GST might be useful for the detection of apoptosis in tumor after chemotherapy. (authors)