The structures, cytotoxicity, apoptosis and molecular docking controlled by the aliphatic chain of palladium(II) complexes

Abstract

A new series of Pd(II) complexes derived from benzenealkyl dicarboxylate ligands, [Pd(Ln)(phen)] (phen=2,9-dimethyl-1,10-phenanthroline, complex 1: L1=phenylmalonate; complex 2: L2=benzylmalonate; complex 3: L3=(2-phenylethyl)malonate; complex 4: L4=(3-phenylpropyl)malonate) have been synthesized under room temperature condition. These complexes contain a long dicarboxylate aliphatic chain. They were characterized by elemental analysis, infrared spectroscopy, single crystal X-ray diffraction. The binding of complexes with fish sperm DNA (FS-DNA) was investigated by UV absorption and fluorescence spectra. Gel electrophoresis assay demonstrated the ability of the complexes to cleave the pBR322 plasmid DNA. The cytotoxic activity of the complexes was tested against two different cancer cell lines, HeLa and HL-60. Cytotoxic activity studies showed the four complexes exhibited significant cancer cell inhibitory rate. Further flow cytometry experiments showed that the cytotoxic Pd(II) complexes induced apoptosis of HL-60 tumor cell lines. The molecular dynamic simulations and docking methods were used to predict the DNA binding affinity of Pd(II) complexes by the resulting relative binding energy of complexes with DNA −6.01, −6.25, −7.24 and −7.59kcal/mol, while with DNA-topoisomerase I (Topo I) −7.98, −9.25, −10.2 and −11.5kcal/mol, respectively. The good visualization images supported with the experimental results of structure–activity relationship between cytotoxicity and carbon chain length.