P21. Synthesis, structure and biological study of Gallium(III) complexes as model radiopharmaceuticals

Abstract

Introduction 67Ga radiopharmaceuticals have been associated with the diagnosis of lymphomas and inflammation. This isotope has a half-life of approximately three days and can be utilized for quick and effective basic biological testing. Our interest is therefore the design and synthesis of various gallium complexes which would be evaluated in solid and solution state via nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and X-ray diffraction (XRD). The chemical behaviour in solution state is compared to the absolute configuration of the gallium complexes to improve the understanding of any factors which may influence the biological properties of the metallo-organic complexes. An important aspect in pharmaceutical design is the synthesis of complexes to accommodate aspects such as the ease of synthesis; purity; environmental influences; as well as the synthesis conducted by medical personnel and not synthetic chemists. Material and methods Typical synthetic procedures of chemical entities (pharmaceuticals, ligands, complexes, assemblies, etc.) are classically performed by means of various solution based methods (solvothermal). An (almost) solvent-free method of synthesis (neat, liquid-, seeding-, ion-assisted grinding) has been recognized as potentially faster, environmentally friendly and economically acceptable ways to prepare new and known compounds. We have therefore also re-evaluated the synthetic methods of the carboxamide and Schiff base ligands which could potentially be coordinated to gallium(III). Due to their high charge density, Ga(III) prefer hard donors, such as amine-N and carboxylate-O atoms. Furthermore the nuclear biological potential of the ligands and 67Ga coordinated ligand complexes would be evaluated to determine whether they could potentially be used for PET and SPECT imaging as diagnostic agents. Results Three novel Schiff base ligands (S1, S2 and S3) were prepared by economical and environmentally friendly methods described above and used for the radiolabelling with 67Ga. These ligands were characterized by NMR, IR and XRD. All three radiolabelled ligands utilized by CHO-K1 cells and showed an increase in cellular uptake when compared to the 67Ga chloride control (67 GaCl 3 ). Compared to 67 GaCl 3 , no significant growth delay was observed in the cells regardless of the ligand used for the radiolabeling experiment. An increased amount of radioactivity per cell is required to fully report the conditions needed for effective growth inhibition of cells and the possibility of it being suitable as a potential diagnostic and/or therapeutic pharmaceutical. Conclusion We hereby report the synthesised complexes, their solid and solution state character including the crystal structures of several ligand systems used. In addition to the nuclear biological behaviour compared to gallium(III) chloride control.