New Pt(II) diiodido complexes containing bidentate 1,3,4-thiadiazole-based ligands: Synthesis, characterization, cytotoxicity

Abstract

Two diiodidoplatinum(II) complexes [PtI2(L1)] (1) and [PtI2(L2)] (2) with isomeric bidentate 1,3,4-thiadiazole-based N-donor ligands (L1, L2) were prepared and characterized by multinuclear NMR spectroscopy, elemental analysis, infrared spectroscopy and mass spectrometry. Complexes 1 and 2 were hydrolytically stable in 50% DMF-d7/50% D2O and 50% DMF-d7/50% PBS in D2O (pH 7.4). Cytotoxicity of 1 and 2 was evaluated on five human cancer cell lines, i.e. lung carcinoma (A549), hepatocellular carcinoma (HepG2), melanoma (A375), prostate carcinoma (DU-145) and breast carcinoma (MCF-7). Only the HepG2 (IC50 = 22.0 and 17.8 μM for 1 and 2, respectively) and A549 (IC50 = 18.5 μM for 1) cells were sensitive to the studied complexes, but their in vitro cytotoxicity was slightly lower than determined for the reference drug cisplatin (IC50 = 12.0 and 12.3 μM at the HepG2 and A549 cells, respectively). Both complexes 1 and 2 effectively quenched the fluorescence of the EtBr-DNA system (EtBr = ethidium bromide) but did not interact covalently with guanosine monophosphate used as a model DNA molecule.