Indium-111 maltolate complex as a cell labeling agent for SPECT imaging

Introduction: Due to the cell labeling potentials of various metal-maltol complexes, the idea of developing a possible cell labeling imaging agent using single photon emission computed chromatography (SPECT) with [In]-maltolate complex has been investigated. Methods: [In] labeled 3-hydroxy-2-methyl-4H-pyran-4-onate ([In]-maltolate) was prepared using freshly prepared [In]InCl3 and 3-hydroxy-2-methyl-4H-pyran-4-onate in a sodium salt form in 25 min at 45C. Stability of the complex was checked in final formulation and human serum for 48 h. The partition coefficient was calculated for the compound followed by biodistribution and imaging studies. [In]-maltolate was successively used in the radiolabeling of red blood cells for diagnostic studies. Results: The complex was prepared successfully (radiochemical purity: >98% ITLC, >98% HPLC, specific activity: 15-17 GBq/mmol, log P=0.278). The complex is mostly washed out from the circulation through kidneys in 24h. the cell labeling efficacy was significant at the time of experiment. Conclusion: [In]-maltolate can be an interesting cell imaging agent due to stability and cell avidity of metal maltol complexes, however, further biodistribution studies in various cells as well as diagnostic protocols is necessary.