Preparation and Evaluation of Novel Folate Isonitrile (99m)Tc Complexes as Potential Tumor Imaging Agents to Target Folate Receptors

In order to seek novel technetium-99m folate receptor-targeting agents, two folate derivatives (CN5FA and CNPFA) were synthesized and radiolabeled to obtain [(99m)Tc]Tc-CN5FA and [(99m)Tc]Tc-CNPFA complexes, which exhibited high radiochemical purity (>95%) without purification, hydrophilicity, and good stability in vitro. The KB cell competitive binding experiments indicated that [(99m)Tc]Tc-CN5FA and [(99m)Tc]Tc-CNPFA had specificity to folate receptor. Biodistribution studies in KB tumor-bearing mice illustrated that [(99m)Tc]Tc-CN5FA and [(99m)Tc]Tc-CNPFA had specific tumor uptake. Compared with [(99m)Tc]Tc-CN5FA, the tumor/muscle ratios of [(99m)Tc]Tc-CNPFA were higher, resulting in a better SPECT/CT imaging background. According to the results, the two (99m)Tc complexes have potential as tumor imaging agents to target folate receptors.