Refolding and unfolding of CT-DNA by newly designed Pd(II) complexes. Their synthesis, characterization and antitumor effects

Effect of geometric isomerism on the anticancer property of new platinum complexes with glycine derivatives as asymmetric N, O donate ligands against human cancer

In this project, to fallow the anticancer ability of new Pt drugs, several new Pt complexes were synthesized with the asymmetric bidentate glycine derivatives, as named propyl- and hexyl glycine (L), in the general formula: [Pt(NH3)2(L)]NO3, and cis- and trans-[Pt(L)2]. The structure of two cis- and trans-[Pt(propylgly)2] complexes was proved by single crystallography analysis. However, all complex structures were characterized by various methods of 1H NMR, 13C NMR, 195Pt NMR, FTIR, LC-Mass, and Raman spectroscopy. To study the passage of water-soluble complexes of [Pt(NH3)2(L)]NO3 via cell membrane, their solubility, and lipophilicity were analyzed. In addition, the cytotoxic properties of these complexes were evaluated against normal and malignant cell lines (skin, breast, and lung cancer cells). The results indicated that they were either comparable to cisplatin or less damaging than carboplatin and oxaliplatin. It was expected that due to less steric effect, and the presence of length aliphatic hydrocarbon chain in the complex structure, trans-[Pt(hexylgly)2] is more toxic on cancerous cell lines than trans-[Pt(propylgly)2]. Cellular accumulation of all complexes was evaluated on A549 and MCF7 cell lines, and the amount of platinum metal (ng) was measured by the ICP method. Results showed that trans-[Pt(hexylgly)2] complex has the highest accumulation inside both mentioned cell lines and [Pt(NH3)2(L)]NO3 complexes behave like clinical Pt-drugs. Ultimately, the interaction patterns of DNA were examined using spectroscopic methods and molecular docking simulations for all substances.

Effect of Cu(II) compound containing dipicolinic acid on DNA damage: a study of antiproliferative activity and DNA interaction properties by spectroscopic, molecular docking and molecular dynamics approaches

A polymeric compound formulized as [Cu(µ-dipic)2{Na2(µ-H2O)4]n.2nH2O (I), where dipic is 2,6-pyridine dicarboxylic acid (dipicolinic acid, H2dipic), was synthesized by sonochemical irradiation. The initial in-vitro cytotoxic activity of this complex compared with renowned anticancer drugs like cisplatin, versus HCT116 colon cell lines, shows promising results. This study investigated the interaction mode between compound (I) and calf-thymus DNA utilizing a range of analytical techniques including spectrophotometry, fluorimetry, partition coefficient analysis, viscometry, gel electrophoresis and molecular docking technique. The results obtained from experimental methods reveal complex (I) could bind to CT-DNA via hydrogen bonding and van der Waals forces and the theoretical methods support it. Also, complex (I) indicates nuclease activity in the attendance of H2O2 and can act as an artificial nuclease to cleave DNA with high efficiency.Communicated by Ramaswamy H. Sarma.

A novel Cu(II)-based DNA-intercalating agent: Structural and biological insights using biophysical and in silico techniques

A new mixed-ligand Cu(II) complex formulated as [Cu(dipic)(amp)(H₂O)].H₂O (dipic: pyridine-2,6-dicarboxylic acid, amp: 2-amino-4-methylpyridine), was synthesized and structurally characterized by FTIR spectroscopy, CHN analysis, and the single-crystal X-ray crystallographic method. The complex crystallizes in an orthorhombic space group Pna2_1, and the coordination environment around the metal center was found to be a pentacoordinate CuN₂O₂O_W distorted square-pyramidal geometry. In order to systematically explore a detailed in vitro and in silico study of the DNA binding of the title complex, various biophysical (UV-Vis absorption spectroscopy, fluorescence, competitive binding with ethidium bromide) and theoretical (DFT, molecular docking simulation, and QM/MM) methods were applied which revealed that the complex could intercalate with the insertion of the amp ligand between the DNA base pairs. The experimental thermodynamic parameters of the interaction revealed the spontaneity of the process and the domination of the hydrophobic interactions in the association and stabilization of the DNA-Cu(II) complex adduct, which was in line with the docking and QM/MM data. In vitro cytotoxic potential of the complex against the human breast adenocarcinoma (MCF-7) cells was examined using MTT assay, which indicated that cancerous cells showed inhibition in presence of the complex.

Synthesis, characterization, cytotoxicity and DNA/BSA binding of two amino acid palladium(II) complexes derived from alanine and valine

Two novel palladium(II)-amino acid complexes, [Pd(Ala)2]·H2O (PA) and [Pd(Val)2].H2O (PV) (Ala = alanine; Val = valine) were synthesized and characterized through FTIR, UV/Vis, 1H-NMR spectroscopies, CHN analysis, X-ray crystallography and molar conductivity measurement. Furthermore, cytotoxicity of Pd(II) complexes against human leukemia cancer cell line, MOLT4 showed promising cancer cell death (CC50 = 0.71 ± 0.046 µM for PA; CC50 = 0.85 ± 0.063 µM for PV) that were less than cisplatin (1.59 ± 0.25 µM). Moreover, the interaction of both the complexes with DNA and BSA was studied using UV-Vis absorption and emission spectroscopic techniques that demonstrated the bindings occurred via van der Waals forces and hydrogen bond. Furthermore, the fluorescence titration showed that static quenching mechanism plays predominate role in binding process. All results showed that both complexes have more binding tendency to DNA in compared to BSA that can be a significant achievement for further medical purposes as a potential antitumor candidate. Finally, molecular docking simulation was performed for PA and PV complexes with DNA and BSA and demonstrated both complexes bind to the groove of DNA mainly by hydrogen bond and interact with site I of BSA via hydrogen bond as well.

Comparison on binding interactions of quercetin and its metal complexes with calf thymus DNA by spectroscopic techniques and viscosity measurement

Quercetin (Qu) and its metal complexes have received great attention during the last years, due to their good antioxidant, antibacterial, and anticancer activities. In this contribution, binding interactions of Qu and Qu-metal complexes with calf thymus DNA (ctDNA) were investigated and compared systematically by using spectroscopic techniques and viscosity measurement. UV-vis absorption spectra of ctDNA-compound systems showed obvious hypochromic effect. Relative viscosity and melting temperature of ctDNA increased after the addition of Qu and Qu-metal complexes, and the change tendency is Qu-Cr(III) > Qu-Mn(II) > Qu-Zn(II) > Qu-Cu(II) > Qu. Fluorescence competition experiments show that hydrogen bonds and van der Waals interaction play an important role in the intercalative binding of Qu and Qu-metal complexes with ctDNA. Qu and Qu-metal complexes could unwind the right-handed B-form helicity of ctDNA and further affect its base pair stacking. Space steric hindrance might be responsible for the differences in the intercalative binding between ctDNA and different Qu-metal complexes. These results provide new information for the molecular understanding of binding interactions of Qu-metal complexes with DNA and the strategy for research of structural influences.

Binding interaction of a heteroleptic silver(I) complex with DNA: A joint experimental and computational study

A new heteroleptic Ag(I) complex formulated as [Ag(daf)(phen)]NO₃, where daf and phen stand for 4,5-diazafluoren-9-one and 1,10-phenanthroline, respectively, has been prepared and structurally characterized by elemental analysis, spectroscopic methods (IR, ¹HNMR, and UV-Vis) and cyclic voltammetry. The geometry optimization around Ag(I) at the level of DFT has demonstrated that the Ag(I) center has been nested in a tetrahedral N4 coordination geometry which found to be in close agreement with the experimentally proposed structure. The bond lengths, angles, and the HOMO/LUMO energies have been calculated to substantiate the geometry of the complex. The DNA binding property of the Ag(I) complex has been explored in detail both theoretically (DFT and molecular docking) and experimentally (UV-Vis absorption spectroscopy, circular dichroism spectroscopy, luminescence quenching, competitive binding with ethidium bromide, cyclic voltammetry, and gel electrophoresis), indicating the good affinity of the Ag(I) complex for the intercalation (K_b (binding constant) = 3.45 × 10⁵ M^-1). Providing a fuller picture of Ag(I) complex-DNA interaction, the energy-minimized structure of the complex has been docked to the DNA with a d(AGACGTCT)₂ sequence and the results are in close agreement with experimental achievements and make a deeper insight into the relationship between the structure and biological activity of the complex.

Nonionic but water soluble, [Glycine-Pd-Alanine] and [Glycine-Pd-Valine] complexes. Their synthesis, characterization, antitumor activities and rich DNA/HSA interaction studies

Two novel, neutral and water soluble Pd(II) complexes of formula [Pd(Gly)(Ala)] (1) and [Pd(Gly)(Val)] (2) (Gly, Ala, and Val are anionic forms of glycine, alanine, and valine amino acids, respectively) have been synthesized and characterized by FT-IR, UV-Vis, ¹H-NMR, elemental analysis, and molar conductivity measurement. The data revealed that each amino acid binds to Pd(II) through the nitrogen of -NH₂ and the oxygen of -COO^- groups and acts as a bidentate chelate. These complexes have been assayed against leukemia cells (K₅₆₂) using MTT method. The results indicated that both of the complexes display more cytotoxicity than the well-known anticancer drug, cisplatin. The interaction of the compounds with calf thymus DNA (CT-DNA) and human serum albumin (HSA) were assayed by a series of experimental techniques including electronic absorption, fluorescence, viscometry, gel electrophoresis, and FT-IR. The results indicated that the two complexes have interesting binding propensities toward CT-DNA as well as HSA and the binding affinity of (1) is more than (2). The fluorescence data indicated that both complexes strongly quench the fluorescence of ethidium bromide-DNA system as well as the intrinsic fluorescence of HSA via static quenching procedures. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the fluorescence studies showed that hydrogen bonds and van der Waals interactions play a major role in the binding of the complexes to DNA and HSA. We suggest that both of the Pd(II) complexes exhibit the groove binding mode with CT-DNA and interact with the main binding pocket of HSA. Communicated by Ramaswamy H. Sarma.