Reactivity of a cytostatic active N,N-donor-containing dinuclear Pt(II) complex with biological relevant nucleophiles

Heterodinuclear Ru-Pt Complexes Bridged with 2,3-Bis(pyridyl)pyrazinyl Ligands: Studies on Kinetics, Deoxyribonucleic Acid/Bovine Serum Albumin Binding and Cleavage, In Vitro Cytotoxicity, and In Vivo Toxicity on Zebrafish Embryo Activities

Di- and poly-homo/heteronuclear complexes have great potential as anticancer drugs. Here, we report their reactivity, deoxyribonucleic acid (DNA)/bovine serum albumin (BSA) binding and cleavage interactions, in vitro cytotoxicity, and in vivo zebrafish embryo toxicity of [(phen)₂Ru(μ-L)PtCl₂]²⁺ (phen = 1,10-phenanthroline and L = 2,3-bis(2-pyridyl)pyrazine, bpp, C₁ ; 2,3-bis(2-pyridyl)quinoxaline, bpq, C_2ial ; 2,3-bis(2-pyridyl)benzo[g]quinoxaline, bbq, C₃ ) anticancer prodrugs. The substitution reactivity increases from C₁ to C₃ owing to an increase in the π-conjugation on the bridging chelate which facilitates π-back bonding. As a result, the electrophilicity index on the C₃ complex increases than that on the complex C₂ followed by C₁ which leads to higher rates of substitution and thus the reactivity order follows C₁ < C₂ < C₃ . The coordination of Ru at one end of each of the complexes enhances water solubility. Moreover, the charge addition of the two metal ions increases their reactivity toward substitution in addition to ensuring electrostatic interactions at target sites such as the DNA/BSA. Spectroscopic (UV-vis absorption and fluorescence quenching) titration and viscosity measurement results of the interactions of C_1/2/3 with CT-DNA established the formation of stable, nonconvent C_1/2/3 -DNA adducts with DNA most likely via the intercalative binding mode. Furthermore, studies with BSA showed a good binding affinity of these complexes owing to hydrophobic interactions with the coordinated ligands. The interactions of these complexes with DNA/BSA are in line with the reactivity trend, and all these experimental findings were further supported by molecular docking analysis. In vitro MTT cytotoxic activities on human breast cancer cell line MCF-7 revealed that all the complexes have high cytotoxicity activity (IC₅₀ > 9 μM); furthermore, the selectivity index and SI values were higher (>3). Complex C₃ showed the highest cytotoxicity with IC₅₀ = 3.1 μM and SI value (5.55) against MCF7 cell lines and these values were comparable to those of the cisplatin (IC₅₀ and SI values are 5.0 μM and 4.02, respectively). In vivo toxicological assessments on zebrafish embryos revealed that all the Ru-Pt complexes (C_I/2/3 ) have poor embryo acute toxic effects over 96 h postfertilization, hpf with LC₅₀ > 65.2 μM. The complex C₃ has shown the lowest embryo toxicity (LC₅₀ = 148.8 μM), which is comparable to that of commercial cisplatin (LC₅₀ = 181.1 μM). Based on the cytotoxicity results, complexes C₂ and C₃ could be considered for further development as chemotherapeutic agents against MCF breast cancer cells.

Ligands with Two Monoanionic N,N-Binding Sites: Synthesis and Coordination Chemistry

Polytopic ligands have become ubiquitous in coordination chemistry because they grant access to a variety of mono- and polynuclear complexes of transition metals as well as rare-earth and main-group elements. Nitrogen-based ditopic ligands, in which two monoanionic N,N-binding sites are framed within one molecule, are of particular importance and are therefore the primary focus of this review. In detail, bis(amidine)s, bis(guanidine)s, bis(β-diimine)s, bis(aminotroponimine)s, bis(pyrrolimine)s, and miscellaneous bis(N,N-chelating) ligands are reviewed. In addition to the general synthetic protocols, the application of these ligands is discussed along with their coordination chemistry, the multifarious binding modes, and the ability of these ligands to bridge two (or more) metal(loids).

Reversible Interconversion of a Static Metallosupramolecular Cage Assembly into a High-Speed Rotor: Stepless Adjustment of Rotational Exchange by Nucleophile Addition

The self-assembled cage ROT-1 was prepared from the pyridine-terminated rotator 1, the phenanthroline-appended stator 2, DABCO, and copper(I) ions in a ratio of 1:1:1:4. This four-component assembly is held together by two pyridine→[Cu(phenAr₂)]⁺ as well as two DABCO→zinc porphyrin interactions (phenAr₂ = 2,9-diarylphenanthroline) and does not show any motion on the NMR time scale ( k < 0.1 s^-1, 298 K). However, it is converted to the fast nanorotor ROT-1 _x^CD₃CN by addition of CD₃CN [ x = (v/v)% of acetonitrile in dichloromethane] due to acceleration of both pyridine→copper(I) dissociation steps. Now the rotator is able to visit all four copper(I)-loaded phenanthroline stations of the stator. Depending on the amount of CD₃CN, the exchange frequency of the nanorotor varies from 0.7 s^-1 (CD₃CN:CD₂Cl₂ = 1:29) to 8000 s^-1 (CD₃CN:CD₂Cl₂ = 1:5) at 25 °C. When iodide (I^-) is added to the static assembly ROT-1, the rotational speed increases even more drastically ( k = 20 000 s^-1), again due to accelerating the rate-determining pyridine→copper(I) dissociation step. In both cases, a sigmoidal relationship is established between exchange frequency and the concentration of added nucleophile (CD₃CN or iodide) that suggests the presence of a cooperative effect. Reversible switching between the static assembly and fast rotor was performed several times without any decomposition of the system. In contrast, addition of the common nucleophile PPh₃ to ROT-1 does not increase the rotational speed, a finding that is explained on thermodynamic grounds.

Enhanced anti-cancer efficacy to cancer cells by a novel monofunctional mononuclear platinum(ii) complex containing a mixed S,N,S-donor ligand

A novel platinum–intercalator hybrid complex (1) exhibits a cytotoxicity comparable to that of cisplatin against MCF-7 cell lines, and more potent activities against HeLa and A-549 cell lines, especially against the former.

Design, Synthesis, and Biological Features of Platinum(II) Complexes with Rigid Steric Hindrance

A series of platinum(II) complexes, with N-monosubstituted 1R,2R-diaminocyclohexane bearing methoxy-substituted benzyl groups as carrier ligands, were designed and synthesized. The newly prepared compounds, with chloride anions as leaving groups, were found to be very active against the tested cancer cell lines, including a cisplatin-resistant cell line. Despite their efficacy against tumor cells, they also showed low toxicity to a human normal liver cell line. Among them, complex 1 had superior cytotoxic activity against A549, HCT-116, MCF-7, SGC7901, and SGC7901/CDDP cancer cell lines. The DNA binding assay is of further special interest, as an unusual monofunctional binding mode was found, due to the introduction of a rigid substituted aromatic ring in the 1R,2R-diaminocyclohexane framework as steric hindrance. The linkage of complex 1 with DNA was stable and insensitive to nucleophilic attack. Moreover, studies including cellular uptake, gel electrophoresis, apoptosis and cell cycle, and Western blot analysis have provided insight into the high potency of this compound.