A first insight into the cytotoxic action mode of copper(i) iodide or copper(i) thiocyanate complexes with a phosphine derivative of sparfloxacin (a 3^rdgeneration fluoroquinolone antibiotic agent) and 2,9-dimethyl-1,10-phenanthroline or 2,2′-biquinoline as auxiliary ligands.

In this paper we present new copper(I) iodide or copper(I) thiocyanate complexes with hydroxymethyldiphenylphosphine (PPh₂(CH₂OH)) or phosphine derivatives of sparfloxacin, a 3^rd generation fluoroquinolone antibiotic agent (PPh₂(CH₂–Sf)) and 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,2′-biquinoline (bq) auxiliary ligands. The synthesised complexes were fully characterised by NMR and UV-Vis spectroscopy as well as by mass spectrometry. Selected structures were additionally analysed using X-ray and DFT methods. All complexes proved to be stable in solution in the presence of water and atmospheric oxygen for several days. The cytotoxic activity of the complexes was tested against two cancer cell lines (CT26 – mouse colon carcinoma and A549 – human lung adenocarcinoma). Applying two different incubation times, the studies enabled a preliminary estimation of the dependence of the selectivity and the mechanism of action on the type of diimine and phosphine ligands. The results obtained showed that complexes with PPh₂(CH₂–Sf) are significantly more active than those with PPh₂(CH₂OH). On the other hand, the relative impact of diimine on cytotoxicity is less pronounced. However, the dmp complexes are characterised by strong inhibitory properties, while the bq ones are rather not. This confirms the interesting and promising biological properties of the investigated group of copper(I) complexes, which undoubtedly are worthy of further biological studies.

The cytotoxic effect of iodide or thiocyanate copper(I) complexes (1-PSf, 2-PSf, 3-PSf, 4-PSf) with phosphine derived from sparfloxacin (HSf) and 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,2′-biquinoline (bq) as diimine auxiliary ligands was proved in vitro on somatic (MRC-5) and neoplastic (MCF7) human cell lines. Differences in mode of action were investigated in-depth for the selected dmp and bq complexes (1-PSf, 3-PSf, respectively) by elucidation of the following: (i) the efficiency to produce reactive oxygen species (ROS) in biological systems (cyclic voltammetry); (ii) their impact on mitochondrial membrane potential; (iii) potency for the activation of caspases 3 and 9; (iv) influence on the degree of DNA degradation (comet assay). It was concluded that the apoptosis of cancer cells is directly connected to the caspase-dependent mitochondrial pathway and supported by ROS production along with irreversible DNA fragmentation. Finally, it was demonstrated that the selected copper(I) complex encapsulated inside liposomes (1-PSf-L) exhibited enhanced accumulation inside cancer cells. This resulted in its higher cytotoxicity against cancer cells with therapeutic index of ca. 60. Increased selective accumulation in active neoplasm with simultaneous enhanced bioavailability and reduced systemic toxicity of liposomal formulation of copper(I) complexes can result in the development of new copper-based therapeutics and their successful implementation in anticancer chemotherapy.

Copper(II) complexes with 2-ethylpyridine (1 and 2), 2-(hydroxyethyl)pyridine (3) and 2-(hydroxymethyl)pyridine (4) have been synthesized and characterized. All inorganic compounds have been studied by X-ray diffraction, thermogravimetry, vibrational and EPR spectroscopy as well as theoretical methods. The geometry of the complexes 1, 3 and 4 adopts nearly perfect geometry close to square planar (1, 4) or square pyramid (3) stereochemistry, respectively. The distortion of five coordinated copper(II) ions in complex 2 indicates intermediate geometry between square pyramidal and trigonal pyramidal geometry. Further, the magnetic measurements have shown antiferromagnetic behaviour of the prepared complexes in a wide range of temperatures. The antiferromagnetic behaviour of 2 should originate from the superexchange interactions between each copper(II) ion by the mixed chloride and μ₄-O ion pathways. Besides, the weak antiferromagnetic character of 2 can be also attributed to the presence of intrachain exchange between dimeric units through double oxide ion. In complex 3, strong antiferromagnetic coupling between Cu(II) centres in the Cu₂O₂Cl₂ moiety is found. The cytotoxicity of all compounds was tested in vitro against various cancer cell lines: human lung adenocarcinoma (A549), human breast adenocarcinoma (MCF7), human prostate carcinoma; derived from metastatic site: brain (DU-145) and two normal cell lines: human embryonic kidney (HEK293T) and human keratinocyte (HaCat). Furthermore, Pluronic P-123 micelles loaded with selected complexes (1 and 3) were proposed to overcome low solubility and to minimize systemic side effects. More detailed study revealed that complex 3 loaded inside micelles causes DU-145 cells' death with simultaneous decrease of mitochondrial membrane potential and a high level of reactive oxygen species generation. The stability of the compounds 1–4 in DMSO was confirmed by UV-Vis and FT-IR spectra studies.