Technetium(I) tricarbonyl complexed with the N-heterocyclic aldehyde thiosemicarbazones: potential precursors of the radiopharmaceuticals

[99mTc]Technetium and Rhenium Dithiocarbazate Complexes: Chemical Synthesis and Biological Assessment

BACKGROUND/OBJECTIVES

Dithiocarbazates (DTCs) and their metal complexes have been studied regarding their property as anticancer activities. In this work, using S-benzyl-5-hydroxy-3-methyl-5-phenyl-4,5-dihydro-1H-pirazol-1-carbodithionate (H2bdtc), we prepared [ReO(bdtc)(Hbdtc)] and [[99mTc]TcO(bdtc)(Hbdtc)] complexes for tumor uptake and animal biodistribution studies.

METHODS

Re complex was prepared by a reaction of H2bdtc and (NBu4)[ReOCl4], the final product was characterized by IR, 1H NMR, CHN, and MS-ESI. 99mTc complex was prepared by the reaction of H2bdtc and [[99mTc]TcO4- and analyzed by planar and HPLC radiochromatography, and the stability was evaluated against amino acids and plasma. Biodistribution was performed in C57B/6 mice with B16F10 and TM1M implanted tumor.

RESULTS

Re is asymmetric coordinated by two dithiocarbazate ligands, one with O,N,S chelation, and the other with N,S chelation; [[99mTc]TcO(bdtc)(Hbdtc)] was prepared with a radiochemical yield of around 93%. The radioactive complex is hydrophobic (LogP = 1.03), stable for 6 h in PBS and L-histidine solution; stable for 1 h in plasma, but unstable in the presence of L-cysteine. Ex vivo biodistribution demonstrated that the compound has a fast and persistent (until 2 h) uptake by the spleen (55.46%), and tumor B16F10 and TM1M uptake is lower than 1%. In vivo SPECT/CT imaging confirmed ex vivo biodistribution, except by heterogenous TM1M accumulation but not in the B16-F10 lineage.

CONCLUSIONS

H2bdtc proved to be an interesting chelator for rhenium or [99mTc]technetium. The right spleen uptake opened the opportunity to deepen the study of the molecule in this tissue and justifies future studies to identify the reason of heterogenous uptake in TM1M tumor uptake.

Synthesis, Crystal Structures, and Antimicrobial and Antitumor Studies of Two Zinc(II) Complexes with Pyridine Thiazole Derivatives

Two pyridine thiazole derivatives, namely, 4-(pyridin-2-yl)-2-(2-(pyridin-2-ylmethylene)hydrazinyl)thiazole (L1) and 4-(pyridin-3-yl)-2-(2-(pyridin-4-ylmethylene)hydrazinyl)thiazole (L2), were afforded by a cyclization reaction between α-haloketone and thioamide, and their Zn(II) complexes were prepared by the reaction of ligands and corresponding metal salts, respectively, and characterized by X-ray diffraction and elemental analysis. Both crystals were obtained by ether diffusion and crystallized in a monoclinic system. The in vitro antimicrobial activity of the Zn(II) complexes and ligands was screened using the microplate reader method, and in vitro antitumor activities of the complexes were evaluated by MTT, with a view to developing new improved bioactive materials with novel properties. The biological activity studies of the compounds showed that the metal complexes were more active than the free ligands, and some compounds had absolute specificity for certain bacteria or cancer cell lines.

Thiosemicarbazonate complexes with affinity for amyloid-β fibers: synthesis, characterization and biological studies

Aim: Obtain radioimages of amyloid-β fibers using 99mTc-complexes. Methodology: Tridentate thiosemicarbazone and thiocarbonohydrazone ligands containing fragments (stilbene, azobenzene, benzothiazole or benzoxazole) with affinity for amyloid-ß fibers and its Re(I) complexes have been prepared. The molecular structures of several ligands and complexes were determined by x-ray diffraction. Binding affinity studies toward Aß1-42 fibers were performed for the ligands and Re(I) complexes. The ability of formation of some 99mTc(I) complexes, their biodistribution and in vivo stability have been established. Results & conclusion: Complexes of stilbene and benzothiazole thiosemicarbazonates show similar affinity for amyloid-β fibers to the free ligand. These 99mTc complexes present a reasonable in vivo stability and a low capability to cross the blood–brain barrier although not sufficient to brain amyloid imaging.