Copper(I)–Phosphine Polypyridyl Complexes: Synthesis, Characterization, DNA/HSA Binding Study, and Antiproliferative Activity

Signaling Mechanism of Cuproptosis Activating cGAS-STING Immune Pathway

Copper-mediated programmed cell death, which influences the regulation of tumor progression, is an effective approach for antitumor molecular therapy. Unlike apoptosis, copper complex-induced cuproptosis by lipid-acylated protein aggregation triggers the mitochondrial proteotoxic stress response, which could be associated with immunomodulation. However, it remains a great challenge to understand the distinctive molecular mechanisms that presumably activate immunity by cuproptosis. Here, the new nonlabeling fluorescent molecular tools of Cu-DPPZ-Py+ and Cu-DPPZ-Ph are synthesized and used to investigate the differential immune signaling mechanisms induced by copper-mediated cuproptosis or apoptosis. With Cu-DPPZ-Py+ and Cu-Elesclomol, there is strong evidence that the triggering cuproptosis significantly drives mitochondrial DNA (mtDNA) release to activate innate immunity via cyclic GMP-AMP synthase-stimulation of interferon genes (cGAS-STING), which can improve T cell antitumor immunity in vivo. By contrast, it is observed that Cu-DPPZ-Ph treated tumor cells could release intracellular caspase-3, resulting in apoptosis-associated immunosuppression. This study supports insights into how cuproptosis bridges cGAS-STING immune pathways, contributing to the development of cuproptosis-based antitumor immunotherapy.

Design, Synthesis, Biological Evaluation and in Silico Studies of Curcumin Pyrrole Conjugates

Curcumin conjugated heterocyclic compounds are potent candidates with drug likeness against various bacterial pathogens. A set of curcumin-based pyrrole conjugates (CPs) were synthesized and characterized by FT-IR, 1H and 13C NMR and HR-MS techniques. The results of free radical scavenging activity of the synthesized CPs, evaluated by FRAP and CUPRAC assays, showed the potency of these compounds as effective antioxidants. CP3 exhibits the highest antioxidant activity amongst the CPs. The bactericidal efficacy of CPs was screened against ESKAP bacterial pathogens, and CPs were found to possess better antibacterial property than curcumin, specifically against staphylococcus aureus bacteria. In addition, serum albumin (BSA and HSA) binding interaction of these CPs were determined by UV-visible and fluorescence spectrophotometric techniques. In-silico molecular docking study was performed to determine the binding patterns of molecular targets against Staphylococcus aureus tyrosyl tRNA synthetase, and serum albumin proteins. The structure-activity relationship showed that the presence of multiple phenolic hydroxyl groups, and electron withdrawing groups on the structure of CP molecule, enhances its antioxidant and antibacterial activity, respectively.

Aminoguanidine-based bioactive proligand as AIEE probe for anticancer and anticovid studies

The emission features of a novel bioactive compound, 1,3-bis(2-hydroxy-3,5-diiodophenyl-methylideneamino)guanidine is found impressive with aggregation induced emission enhancement. The nitrogen and iodine rich multidentate proligand was characterized physicochemically. SCXRD and Hirshfeld surface investigation have revealed the presence of significant triangular iodine bonding apart from hydrogen bonding, weak C-H⋯π and π⋯π intermolecular interactions. These interactions collectively contribute to the solid-state packing arrangement of the molecules within the crystal lattice. The band gap of the compound was estimated experimentally and is supported with theoretical calculations. The solid-state fluorescence quantum yield of Φ = 0.36 emphasizes the utility of the proligand and the AIEE characteristics is attributed to restricted intramolecular motions as indicated by fluorescence lifetime decay studies. Strong interaction of the compound with calf thymus DNA was explored experimentally and found to align with in silico docking results. Notably, in vitro anticancer assessment on MCF-7 breast cancer cells show an IC50 value of 181.05 μg mL-1 and signifying its potent cytotoxic properties. Also, the compound is found to have lesser cytotoxicity against L929 normal cell line with an IC50 value of 356.54 μg mL-1. Computational studies further underscore the exceptional binding affinity with active sites in the SARS-CoV-2 main protease 3CLpro, surpassing established repurposed drugs. Furthermore, the proligand demonstrates excellent putative affinity towards the SARS-CoV-2 spike glycoprotein, accompanied by its distinctive AIEE attributes, drug likeness and DNA binding capability rendering it a valuable tool for prospective research investigations.

Silver(I) complexes containing N-heterocyclic carbene azole drugs: Synthesis, characterization, cytotoxic activity, and their BSA interactions

Cancer is one of the main public health problems globally, there is a public demand for better drugs. Rational strategies or approaches are used to improve the success of drug discovery. Our strategy was to the repurposing of well-known antifungal agents as potential anticancer drugs, such as Clotrimazole (CTZ) and Ketoconazole (KTZ). We prepared the respective iodide imidazolium salt L1: (CTZ-Me)I and L2: (KTZ-Me)I to be the intermediates toward the synthesis of its respective NHC ligand and achieve the respective silver(I)-monoNHC and silver(I)-bisNHC derivatives: [Ag(L1)I] (1), [AgI(L2)] (2) [Ag(L1)2]I. (3), [Ag(L2)2]I. (4), as well as their corresponding coordination compounds [Ag(CTZ)2]NO3 (5) and [Ag(KTZ)2]NO3 (6) where these ligands (CTZ and KTZ) coordinate to silver through the N-imidazole atom. These compounds (L1, L2 and complexes 1-6) exhibited significant activity against the tested cancer cell lines (B16-F1, murine melanoma strains and CT26WT, murine colon carcinoma). The silver(I) complexes were more active than the free ligands, complexes 2 and 4 being the most selective in B16-F1 cancer cell line. Two possibles biological targets such as DNA and albumin were examined for the observed anticancer activity. Results show that DNA is not the main target, however, the interactions with albumin suggest it can transport/delivery the metal complexes.

A binuclear Cu(I)-phosphine complex as a specific HSA site I binder: synthesis, X-ray structure determination, and a comprehensive HSA interaction analysis

In this research, we present a method for synthesis and a detailed description of geometry characterization of a novel binuclear Cu(I) phosphine complex, along with analysis of its interaction with HSA using spectroscopic and simulation methods. The Cu atoms are coordinated in a tetrahedral geometry, which results in coordination by two nitrogen atoms from the N,N'-(ethane-1,2-diyl)bis(1-(pyridin-2-yl)methanimine ligand (L), a chloride, and a PPh3. The complex binding constant to HSA in a biochemical environment was determined to be ∼106, which is indicative of a strong interaction. The fluorescence of HSA is significantly quenched by binding to the complex via a static mechanism, whereas the microenvironment of the tryptophan residue remains unchanged. A spontaneous binding process was indicated by a negative value for ΔG. Thermodynamic signatures reflect the dominance of hydrophobic forces during the interaction. The site marker competitive experiment combined with docking simulation analysis revealed the closeness position of the complex binding site to warfarin location in specific ligand site I of HSA. The information generated in the present study would be valuable to understand the interaction mechanistic and pharmacological behavior of Cu(I) complexes.Communicated by Ramaswamy H. Sarma.

Biological activity of mixed chelate copper(II) complexes, with substituted diimine and tridentate Schiff bases (NNO) and their hydrogenated derivatives as secondary ligands: Casiopeína's fourth generation

We synthesize and characterize nine copper(II) compounds. Four with general formula [Cu(NNO)(NO₃)] and five mixed chelates [Cu(NNO)(N-N)]⁺, where NNO corresponds to asymmetric salen ligands (E)-2-((2-(methylamino)ethylimino)methyl)phenolate (L1) and (E)-3-((2-(methylamino)ethylimino)methyl)naphthalenolate (LN1); and their hydrogenated derivatives 2-((2-(methylamino)ethylamino)methyl)phenolate (LH1) and 3-((2-(methylamino)ethylamino)methyl)naphthalenolate (LNH1); and N-N correspond to 4,4'-dimethyl-2,2'-bipiridyne(dmbpy) or 1,10-phenanthroline (phen). Using EPR, the geometries of the compounds in solution in DMSO were assigned, [Cu(LN1)(NO₃)] and [Cu(LNH1)(NO₃)] a square-planar, [Cu(L1)(NO₃)], [Cu(LH1)(NO₃)], [Cu(L1)(dmby)]⁺ and [Cu(LH1)(dmby)]⁺ a square-based pyramid; and [Cu(LN1)(dmby)]⁺, [Cu(LNH1)(dmby)]⁺ and [Cu(L1)(phen)]⁺ and elongated octahedral. By X-ray it was observed that [Cu(L1)(dmby)]⁺ and. [Cu(LN1)(dmby)]⁺ presented a square-based pyramidal, and [Cu(LN1)(NO₃)]⁺ a square-planar geometry. The electrochemical study showed that copper reduction process is a quasi-reversible system, where the complexes with hydrogenated ligands were less oxidizing. The cytotoxicity of the complexes was tested by MTT assay, all the compounds showed biological activity in HeLa cell line, the mixed compounds were the more active ones. Naphthalene moiety, imine hydrogenation and aromatic diimine coordination, increased biological activity. A structure-activity relationships were found: Log(IC₅₀) =  - 1.01(E_pc) - 0.35(Conjugated Rings) + 0.87, for Schiff base complexes and Log(IC₅₀) = 0.078(E_pc) - 0.32(Conjugated Rings) + 1.94, for hydrogenated complexes; the less oxidizing species with a great number of conjugated rings presented the best biological activity. Complexes-DNA binding constants were obtained by uv-vis studies using CT-DNA, the results suggested that the complexes can interact through the grooves, except the phenanthroline mixed complex that intercalate with DNA. Gel electrophoresis study with pBR 322 showed that compounds can produce changes in the form of DNA and some complexes can cleave DNA in the presence of H₂O₂.

Heteroleptic Copper Complexes as Catalysts for the CuAAC Reaction: Counter-Ion Influence in Catalyst Efficiency

A series of nine cationic heteroleptic aryl-BIAN-copper(I) (BIAN = bis-iminoacenaphthene) complexes with the general formula [Cu((E-C6H4)2BIAN)(PPh3)2][X] (E = p-Me, p-iPr, o-iPr; X = BF4, OTf, NO3) 1X–3X were synthesized and fully characterized using several analytical techniques, including NMR spectroscopy and single-crystal X-ray diffraction. Except for complexes 2BF4 and 3BF4, which were already reported in our previous works, all remaining complexes are herein described for the first time. Two different strategies were used for the preparation of the complexes: complexes bearing BF4− or OTf− counter-ions (1BF4, 1OTf, 2OTf, and 3OTf) were obtained using the appropriate copper(I) precursors [Cu(NCMe)4][BF4] or [Cu(NCMe)4][OTf], whereas for derivatives 1NO3–3NO3, [Cu(PPh3)2NO3] was used. Their activity as catalysts for the copper azide-alkyne cycloaddition (CuAAC) was assessed alongside other high activity, previously reported Cu(I) complexes. Comparative studies to determine the influence of the counter-ion and of the aryl substituents were performed. All complexes behaved as active catalysts under neat reaction conditions, at 25 °C and in short reaction times without requiring the use of any additive, with complex 2NO3 being the most efficient derivative, along with other NO3−-bearing complexes.

Tuning anticancer properties and DNA-binding of Pt(ii) complexes via alteration of nitrogen softness/basicity of tridentate ligands†

Nine tridentate Schiff base ligands of the type (N^N^O) were synthesized from reactions of primary amines {2-picolylamine (Py), N-phenyl-1,2-diaminobenzene (PhN), and N-phenyl-1,2-diaminoethane(EtN)} and salicylaldehyde derivatives {3-ethoxy (OEt), 4-diethylamine (NEt₂) and 4-hydroxy (OH)}. Complexes with the general formula Pt(N^N^O)Cl were synthesized by reacting K₂PtCl₄ with the ligands in DMSO/ethanol mixtures. The ligands and their complexes were characterized by NMR spectroscopy, mass spectrometry and elemental analysis. The DNA-binding behaviours of the platinum(ii) complexes were investigated by two techniques, indicating good binding affinities and a two-stage binding process for seven complexes: intercalation followed by switching to a covalent binding mode over time. The other two complexes covalently bond to ct-DNA without intercalation. Theoretical calculations were used to shed light on the electronic and steric factors that lead to the difference in DNA-binding behavior. The reactions of some platinum complexes with guanine were investigated experimentally and theoretically. The binding of the complexes with bovine serum albumin (BSA) indicated a static interaction with higher binding affinities for the ethoxy-containing complexes. The half maximal inhibitory concentration (IC₅₀) values against MCF-7 and HepG2 cell lines suggest that platinum complexes with tridentate ligands of N-phenyl-o-phenylenediamine or pyridyl with 3-ethoxysalicylimine are good chemotherapeutic candidates. Pt-Py-OEt and Pt-PhN-OEt have IC₅₀ values against MCF-7 of 13.27 and 10.97 μM, respectively, compared to 18.36 μM for cisplatin, while they have IC₅₀ values against HepG2 of 6.99 and 10.15 μM, respectively, compared to 19.73 μM for cisplatin. The cell cycle interference behaviour with HepG2 of selected complexes is similar to that of cisplatin, suggesting apoptotic cell death. The current work highlights the impact of the tridentate ligand on the biological properties of platinum complexes.

The article illustrates the design flexibility of tridentate ligands and the resultant platinum complexes, highlighting the impact of this design flexibility on the anticancer potential.

Preparation, cytotoxic activity and DNA interaction studies of new platinum(II) complexes with 1,10-phenanthroline and 5-alkyl-1,3,4-oxadiazol-2(3H)-thione derivatives

This work describes the synthesis, characterization and in vitro anticancer activity of two platinum(II) complexes of the type [Pt(L1)₂(1,10-phen)] 1 and [Pt(L2)₂(1,10-phen)] 2, where L1 = 5-heptyl-1,3,4-oxadiazole-2-(3H)-thione, L2 = 5-nonyl-1,3,4-oxadiazole-2-(3H)-thione and 1,10-phen = 1,10-phenanthroline. As to the structure of these complexes, the X-ray structural analysis of 1 indicates that the geometry around the platinum(II) ion is distorted square-planar, where two 5-alkyl-1,3,4-oxadiazol-2-thione derivatives coordinate a platinum(II) ion through the sulfur atom. A chelating bidentate phenanthroline molecule completes the coordination sphere. We tested these complexes in two breast cancer cell lines, namely, MCF-7 (a hormone responsive cancer cell) and MDA-MB-231 (triple negative breast cancer cell). In both cells, the most lipophilic platinum compound, complex 2, was more active than cisplatin, one of the most widely used anticancer drugs nowadays. DNA binding studies indicated that such complexes are able to bind to ct-DNA with K_b values of 10⁴ M^-1. According to data from dichroism circular and fluorescence spectroscopy, these complexes appear to bind to the DNA in a non-intercalative, probably via minor groove. Molecular docking followed by semiempirical simulations indicated that these complexes showed favorable interactions with the minor groove of the double helix of ct-DNA in an A-T rich region. Thereafter, flow cytometry analysis showed that complex 2 induced apoptosis and necrosis in MCF-7 cells.

Elucidating the Molecular Structure of Hydrophobically Modified Polyethylenimine Nanoparticles and Its Potential Implications for DNA Binding

The structural properties of the polyethylenimine (PEI) polymer are generally tuned and selectively modified to reinforce its potential in a broad spectrum of applied domains of medicine, healthcare, material design, sensing, and electronic optimization. The selective modification of the polymer brings about changes in its interfacial characteristics and behavior. The current work involves the synthesis of naphthalimide conjugated polyethylenimine organic nanoparticles (NPEI-ONPs). The interfacial molecular structure of NPEI-ONPs is explored in an aqueous medium at pH 7.4 using surface tensiometry and sum-frequency generation vibrational spectroscopy (SFG-VS). The hydrophobic functionalization rendered a concentration-dependent surface coverage of NPEI-ONPs, where the SFG-VS analysis exhibited the molecular rearrangement of its hydrophobic groups at the interface. The interaction of NPEI-ONPs with double-stranded DNA (dsDNA) is carried out to observe the relevance of the synthesized nanocomposites in the biomedical domain. The bulk-specific studies (i.e., thermal denaturation, viscometry, zeta (ζ) potential, and ATR-FTIR) reveal the condensation of dsDNA in the presence of NPEI-ONPs, making its structure more compact. The interface-sensitive SFG-VS showcased the impact of the dsDNA and NPEI-ONP interaction on the interfacial molecular behavior of NPEI-ONPs at the air-aqueous interface. Our results exhibit the potential of such hydrophobically functionalized ONPs as promising candidates for developing biomedical sealants, substrate coatings, and other biomedical domains.

Tuning the anticancer properties of Pt(ii) complexes via structurally flexible N-(2-picolyl)salicylimine ligands

Three tridentate Schiff base ligands were synthesized from the reactions between 2-picolylamine and salicylaldehyde derivatives (3-ethoxy (OEt), 4-diethylamino (NEt2) and 4-hydroxy (OH)). Complexes with the general formula Pt(N^N^O)Cl were obtained from reactions between the ligands and K2PtCl4. The ligands and their complexes were characterized by NMR spectroscopy, mass spectrometry and elemental analysis. Further confirmation of the structure of Pt-OEt was achieved by single-crystal X-ray diffraction. The DMSO/chlorido exchange process at Pt-OEt was investigated by monitoring the change in conductivity, revealing very slow dissociation in DMSO. Moreover, solvent/chlorido exchange for Pt-OEt and Pt-NEt2 were investigated by NMR spectroscopy in DMSO and DMSO/D2O; Pt-NEt2 forms an adduct with DMSO while Pt-OEt forms adducts with DMSO and water. The DNA-binding behaviour of the platinum(ii) complexes was investigated by two techniques. Pt-NEt2 has the best apparent binding constant. The intercalation mode of interaction with ct-DNA was suggested by molecular docking studies and the increase in the relative viscosity of ct-DNA with increasing concentrations of the platinum(ii) complexes. However, the gradual decrease in the relative viscosity over time at constant concentration of platinum(ii) complexes indicated a shift from intercalation to a covalent binding mode. Anticancer activities of the ligands and their platinum(ii) complexes were examined against two cell lines. The platinum(ii) complexes exhibit superior cytotoxicity to that of their ligands. Among the platinum(ii) complexes, Pt-OEt possesses the best IC50 against both cell lines, its cytotoxicity being comparable to that observed for cisplatin. Cell cycle arrest in the HepG2 cell line upon treatment with Pt-OEt and Pt-NEt2 was investigated and compared to that of cisplatin; the change in the cell accumulation patterns supports the presumption of an apoptotic cell death pathway. The optimized structures of the B-DNA trimer adducts with the platinum complexes showed hydrogen-bonding interactions between the ligands and nucleobases, affecting the inter-strand hydrogen bonding within the DNA, and highlighting the strong ability of the complexes to induce conformational changes in the DNA, leading to the activation of apoptotic cell death. In summary, the current study demonstrates promising new anticancer platinum(ii) complexes with highly flexible tridentate ligands; the functional groups on the ligands are important in tuning their DNA binding/anticancer properties.

Nuclease-like metalloscissors: Biomimetic candidates for cancer and bacterial and viral infections therapy

Despite the extensive and rapid discovery of modern drugs for treatment of cancer, microbial infections, and viral illnesses; these diseases are still among major global health concerns. To take inspiration from natural nucleases and also the therapeutic potential of metallopeptide antibiotics such as the bleomycin family, artificial metallonucleases with the ability of promoting DNA/RNA cleavage and eventually affecting cellular biological processes can be introduced as a new class of therapeutic candidates. Metal complexes can be considered as one of the main categories of artificial metalloscissors, which can prompt nucleic acid strand scission. Accordingly, biologists, inorganic chemists, and medicinal inorganic chemists worldwide have been designing, synthesizing and evaluating the biological properties of metal complexes as artificial metalloscissors. In this review, we try to highlight the recent studies conducted on the nuclease-like metalloscissors and their potential therapeutic applications. Under the light of the concurrent Covid-19 pandemic, the human need for new therapeutics was highlighted much more than ever before. The nuclease-like metalloscissors with the potential of RNA cleavage of invading viral pathogens hence deserve prime attention.

Half-Sandwich Cyclometalated RhIII Complexes Bearing Thiolate Ligands: Biomolecular Interactions and In Vitro and In Vivo Evaluations

A class of cyclometalated RhIII complexes [Cp*Rh(ppy)(SR)] bearing thiolate ligands, Cp* = pentamethylcyclopentadienyl, ppy = 2-phenylpyridinate, and R = pyridyl (Spy, 2), pyrimidyl (SpyN, 3), benzimidazolyl (Sbi, 4), and benzothiazolyl (Sbt, 5), were produced and identified by means of spectroscopic methods. The in vitro cytotoxicity of the RhIII compounds in three different human mortal cancerous cell lines (ovarian, SKOV3; breast, MCF-7; lung, A549) and a normal lung (MRC-5) cell line were evaluated, indicating the selectivity of these cyclometalated RhIII complexes to cancer cells. Complex 5, selected for in vivo experiment, has shown an effective inhibition of tumor growth in SKOV3 xenograft mouse model relative to control (p-values < 0.05 and < 0.01). Importantly, the outcomes of H&E (hematoxylin and eosin) staining and hematological analysis revealed negligible toxicity of 5 compared to cisplatin on a functioning of the main organs of mouse. Molecular docking, UV-vis, and emission spectroscopies (fluorescence, 3D fluorescence, synchronous) techniques were carried out on 1-5 to peruse the mechanism of the anticancer activities of these complexes. The obtained data help to manifest the binding affinity between the rhodium compounds and calf thymus DNA (CT-DNA) through the interaction by DNA minor groove and moderate binding affinity with bovine serum albumin (BSA), particularly with the cavity in the subdomain IIA. It can be concluded that the Rh-thiolate complexes are highly promising leads for the development of novel effective DNA-targeted anticancer drugs.

Experimental and Theoretical DFT Study of Cu(I)/N,N-Disubstituted-N'-acylthioureato Anticancer Complexes: Actin Cytoskeleton and Induction of Death by Apoptosis in Triple-Negative Breast Tumor Cells

Six complexes with the general formula [Cu(acylthioureato)(PPh3)2] were synthesized and characterized using spectroscopic techniques (IR, UV/visible, and 1D and 2D NMR), mass spectrometry, elemental analysis, and X-ray diffraction. Interpretation of the in vitro cytotoxicity data of Cu(I) complexes took into account their stability in cell culture medium. DFT calculations showed that NMR properties, such as the shielding of carbon atoms, are affected by relativistic effects, supported by the ZORA Hamiltonian in the theoretical calculations. Additionally, the calculation of the energies of the frontier molecular orbitals predicted that the structural changes of the acylthiourea ligands did not cause marked changes in the reactivity descriptors. All complexes were cytotoxic to the evaluated tumor cell lines [MDA-MB-231 (triple-negative breast cancer, TNBC), MCF-7 (breast cancer), and A549 (lung cancer)]. In the MDA-MB-231 cell line, complex 1 significantly altered the cytoskeleton of the cells, reducing the density and promoting the condensation of F-actin filaments. In addition, the compound caused an increase in the percentage of cells in the fragmented DNA region (sub-G0) and induced cell death via the apoptotic pathway starting at the IC50 concentration. Taken together, the results show that complex 1 has cytotoxic and apoptotic effects on TNBC cells, which is a cell line originating from an aggressive, difficult-to-treat breast cancer.

A simple method for obtaining human albumin and its use for in vitro interaction assays with indole-thiazole and indole-thiazolidinone derivatives

This work aimed to develop a simple and low-cost method to obtain human serum albumin (HSA) and its consequent application for in vitro drug interaction assays. The HSA was purified by classic principles of plasma precipitation and thermocoagulation, using a multiple-stage fractionation. The quality of the final product was assessed by electrophoresis, protein dosage by the Lowry method and the pharmacopeial thermal stability. At the end, an isotonic solution of HSA with a total protein concentration of 2.7 mg·mL^-1 was obtained, which was visualized as a single band corresponding to the molecular weight of 66 kDa. After the thermal stability test, there was no indication of turbidity or color change of the solution. Finally, the HSA was useful for interaction assays with indole-thiazole and indole-thiazolidinone derivatives through UV-vis absorption and fluorescence spectroscopic studies, as well as by docking molecular analysis. Derivatives quenched the intrinsic fluorescence of HSA, disrupted the tryptophan residues microenvironment, and probably bind at Sudlow's site I. Therefore, the simplified methodology developed in this work proved to be effective in obtaining HSA that can be applied to research goals including drug interaction assays.

Synergy of DNA intercalation and catalytic activity of a copper complex towards improved polymerase inhibition and cancer cell cytotoxicity

Improving the binding of metal complexes to DNA to boost cancer cell cytotoxicity requires fine tuning of their structural and chemical properties. Copper has been used as a metal center in compounds containing intercalating ligands due to its ability to catalytically generate reactive oxygen species (ROS), such as hydroxyl radicals (OH˙). We envision the synergy of DNA binding and ROS generation in proximity to target DNA as a powerful chemotherapy treatment. Here, we explore the use of [Cu(2CP-Bz-SMe)]2+ (2CP-Bz-SMe = 1,3-bis(1,10-phenanthrolin-2-yloxy)-N-(4-(methylthio)benzylidene)propan-2-amine) for this purpose by characterizing its cytotoxicity, DNA binding, and ability to affect DNA replication through the polymerase chain reaction - PCR and nuclease assays. We determined the binding (Kb) and Stern-Volmer constants (KSV) for complex-DNA association of 5.8 ± 0.14 × 104 and 1.64 (±0.08), respectively, through absorption titration and competitive fluorescence experiments. These values were superior to those of other Cu-complex intercalators. We hypothesize that the distorted trigonal bipyramidal geometry of [Cu(2CP-Bz-SMe)]2+ allows the phenanthroline fragments to be better accommodated into the DNA double helix. Moreover, the aromaticity of these fragments increases the local hydrophobicity thus increasing the affinity for the hydrophobic domains of DNA. Nuclease assays in the presence of common reducing agents ascorbic acid, nicotinamide adenine dinucleotide, and glutathione showed the effective degradation of DNA due to the in situ generation of OH˙. The [Cu(2CP-Bz-SMe)]2+ complex showed cytotoxicity against the following human cancer cells lines A549, MCF-7, MDA-MB-231 and MG-63 with half maximal inhibitory concentration (IC50) values of 4.62 ± 0.48, 5.20 ± 0.76, 5.70 ± 0.42 and 2.88 ± 0.66 μM, respectively. These low values of IC50, which are promising if compared to that of cisplatin, are ascribed to the synergistic effect of ROS generation with the intercalation ability into the DNA minor grooves and blocking DNA replication. This study introduces new principles for synergizing the chemical and structural properties of intercalation compounds for improved drug-DNA interactions targeting cancer.

Identification of potent anticancer copper(ii) complexes containing tripodal bis[2-ethyl-di(3,5-dialkyl-1H-pyrazol-1-yl)]amine moiety

A series of heteroleptic copper(ii) complexes of the composition [Cu(L^1-5)Cl]X, where X = ClO₄ and/or PF₆ and [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl))-(6-methyl-(2-pyridylmethyl))]amine (L¹), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl))-(3,4-dimethoxy-(2-pyridylmethyl))]amine (L²), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl)-(2-quinolymethyl)]amine (L³), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazolyl)-(di(3,5-dimethyl-1H-pyrazol-1-yl-methyl))]amine (L⁴) and [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl)-(5-methyl-3-phenyl-1H-pyrazol-1-yl-methyl)]amine (L⁵), were prepared and thoroughly characterized including single-crystal X-ray diffraction technique. The in vitro cytotoxicity of complexes against A2780, A2780R, HOS and MCF-7 human cancer cell lines was evaluated using the MTT test. The results revealed that complexes [Cu(L¹)Cl]PF₆ (1-PF₆), [Cu(L²)Cl]ClO₄ (2-ClO₄) and [Cu(L³)Cl]PF₆ (3-PF₆) are the most effective, with IC₅₀ values ranging from 1.4 to 6.3 μM, thus exceeding the cytotoxic potential of metallodrug cisplatin (IC₅₀ values ranging from 29.9 to 82.0 μM). The complexes [Cu(L⁴)Cl]PF₆ (4-PF₆) and [Cu(L⁵)Cl]PF₆ (5-PF₆) showed only moderate cytotoxicity against A2780, with IC₅₀ = 53.6 μM, and 33.8 μM, respectively. The cell cycle profile, time-resolved cellular uptake, interactions with small sulfur-containing biomolecules (cysteine and glutathione), intracellular ROS production, induction of apoptosis and activation of caspases 3/7 were also evaluated in the case of the selected complexes. It has been found that the best performing complexes 1 and 2 cause cell arrest in the G2/M phase and induce apoptosis via the increase in production of ROS, dominantly due to the overproduction of superoxide.

Effect of Net Charge on DNA-Binding, Protein-Binding and Anticancer Properties of Copper(I) Phosphine-Diimine Complexes

The syntheses of [Cu(PPh3)2(L)]NO3 and [Cu(PPh3)2(L-SO3Na)]NO3 were achieved through the reaction of Cu(PPh3)2NO3 and equimolar amount of the ligands (L = 5,6-diphenyl-3-[2-pyridyl]-1,2,4-triazine; LSO3Na = 5,6-diphenyl-3-[2-pyridyl]-1,2,4-triazine-4,4′-disulfonic acid disodium salt). The complexes were characterized by NMR and IR spectroscopy and mass spectrometry. The compounds exhibit similar absorption and emission spectra, suggesting a similar electronic structure. Ct-DNA binding studies show the strong influence of the net charge as Cu-L (positively charged) is able to bind to ct-DNA while Cu-LSO3Na (negatively charged) is not. The net charge of the complexes affects the thermodynamic and kinetic binding parameters toward human serum albumin. HSA-binding of the complexes was further investigated by molecular docking, revealing different binding sites on the HSA protein as a function of the net charge. The different anticancer activities of the complexes towards ovcar-3 and hope-62 cancer cell lines are suggestive of a role for the overall charge of the complexes. Interaction with the DNA is not the major mechanism for this class of complexes. The overall net charge of the pharmacophore (anticancer agent) should be a key consideration in the design of anticancer metal complexes.

DNA-Binding and Cytotoxicity of Copper(I) Complexes Containing Functionalized Dipyridylphenazine Ligands

A set of copper(I) coordination compounds with general formula [CuBr(PPh₃)(dppz-R)] (dppz-R = dipyrido[3,2-a:2’,3’-c]phenazine (Cu-1), 11-nitrodipyrido[3,2-a:2’,3’-c]phenazine (Cu-2), 11-cyanodipyrido[3,2-a:2’,3’-c]phenazine (Cu-3), dipyrido[3,2-a:2’,3’-c]phenazine-11-phenone (Cu-4), 11,12-dimethyldipyrido[3,2-a:2’,3’-c]phenazine (Cu-5)) have been prepared and characterized by elemental analysis, ¹H-NMR and ³¹P-NMR spectroscopies as well as mass spectrometry. The structure of Cu-1 was confirmed by X-ray crystallography. The effect of incorporating different functional groups on the dppz ligand on the binding into CT-DNA was evaluated by absorption spectroscopy, fluorescence quenching of EtBr-DNA adducts, and viscosity measurements. The functional groups affected the binding modes and hence the strength of binding affinities, as suggested by the changes in the relative viscosity. The differences in the quenching constants (K_sv) obtained from the fluorescence quenching assay highlight the importance of the functional groups in altering the binding sites on the DNA. The molecular docking data support the DNA-binding studies, with the sites and mode of interactions against B-DNA changing with the different functional groups. Evaluation of the anticancer activities of the five copper compounds against two different cancer cell lines (M-14 and MCF-7) indicated the importance of the functional groups on the dppz ligand on the anticancer activities. Among the five copper complexes, the cyano-containing complex (Cu-3) has the best anticancer activities.

Alteration of Anticancer and Protein-Binding Properties of Gold(I) Alkynyl by Phenolic Schiff Bases Moieties

A set of five gold complexes with the general formula Au(PR₃)(C≡C-C₆H₄-4-R′) (R = PPh₃, R′ = –CHO (1), R = PCy₃, R′ = –CHO (2), R = PPh₃, R′ = –N=CH-C₆H₄-2-OH (3), R = PPh₃, R′ = –N=CH-C₆H₄-4-OH (4), R = PCy₃, R′ = –N=CH-C₆H₄-2-OH (5)) were synthesized and characterized by elemental analysis, ¹H-NMR spectroscopy, ³¹P-NMR spectroscopy, and mass spectrometry. The structures of complexes 2 and 5 were determined by X-ray crystallography. The effects of the structural modifications on the protein binding affinities and anticancer activities of the five gold complexes were assessed. Fluorescence quenching experiments to assess binding to human serum albumin (HSA) revealed that the Schiff base complexes (3, 4, and 5) had binding constants that were superior to their parent aldehyde complexes and highlighted the position of the hydroxy group because complex 4 (4-hydroxy) had a binding constant 6400 times higher than complex 3 (2-hydroxy). The anticancer activities of the complexes against the OVCAR-3 (ovarian carcinoma) and HOP-62 (non-small-cell lung) cancer cell lines showed that the Schiff bases (3–5) were more cytotoxic than the aldehyde-containing complexes (1 and 2). Notably, compound 4 had cytotoxic activity comparable to that of cisplatin against OVCAR-3, demonstrating the significance of the para position for the hydroxy group. Molecular docking studies against the enzyme thioredoxin reductase (TrxR) and human serum albumin were conducted, with docking scores in good agreement with the experimental data. The current study highlights how small structural modifications can alter physiochemical and anticancer properties. Moreover, this simple design strategy using the aldehyde group can generate extensive opportunities to explore new gold(I)-based anticancer drugs via condensation, cyclization, or nucleophilic addition reactions of the aldehyde.

Cu(I) complexes as new antiproliferative agents against sensitive and doxorubicin resistant colorectal cancer cells: synthesis, characterization, and mechanisms of action

Cancer is one of the worst health issues worldwide, representing the second leading cause of death. Current chemotherapeutic drugs face some challenges like the acquired resistance of the tumoral cells and low specificity leading to unwanted side effects. There is an urgent need to develop new compounds that may target resistant cells. The synthesis and characterization of two Cu(i) complexes of general formula [Cu(PP)(LL)][BF4], where PP is a phosphane ligand (triphenylphosphine or 1,2-bis(diphenylphosphano) ethane) and LL = is a heteroaromatic bidentate ligand (4,4'-dimethyl-2,2'-bipyridine and 6,3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). The new compounds were fully characterized by spectroscopic techniques (NMR, FTIR and UV-vis.), elemental analysis (C, H, N and S) and two structures were determined by single X-ray diffraction studies. The antiproliferative potential of the new Cu(i) complexes were studied in tumor (breast adenocarcinoma, ovarian carcinoma and in colorectal carcinoma sensitive and resistant to doxorubicin) and normal (fibroblasts) cell lines. Complexes 1-4 did not show any antiproliferative potential. Amongst the complexes 5-8, complex 8 shows high cytotoxic potential against colorectal cancer sensitive and resistant to doxorubicin and low cytotoxicity towards healthy cells. We show that complexes 5-8 can cleave pDNA and, in particular, the in vitro pDNA cleavage is due to an oxidative mechanism. This oxidative mechanism corroborates the induction of reactive oxygen species (ROS), that triggers HCT116 cell death via apoptosis, as proved by the increased expression of BAX protein relative to BCL-2 protein and the depolarization of mitochondrial membrane potential, and via autophagy. Additionally, complex 8 can block the cell cycle in the G1 phase, also exhibiting a cytostatic potential. Proteomic analysis confirmed the apoptotic, autophagic and cytostatic potential of complex 8, as well as its ability to produce ROS and cause DNA damage. The interference of the complex in folding and protein synthesis and its ability to cause post-translational modifications was also verified. Finally, it was observed that the complex causes a reduction in cellular metabolism. The results herein demonstrated the potential of Cu(i) complexes in targeting doxorubicin sensitive and resistant cells which is positive and must be further explored using in vivo animal models.

Self-assembly of cuprous iodide cluster-based calix[4]resorcinarenes and photocatalytic properties

Cluster-based complexes 1 and 2 with [Cu6I5] and [Cu8I8] polynuclear motifs were constructed via a conformation-adaptive self-assembly strategy, respectively. Two Cu(i) complexes exhibited photocatalytic activity to the CuAAC reaction in water solution.

DNA-Binding Capabilities and Anticancer Activities of Ruthenium(II) Cymene Complexes with (Poly)cyclic Aromatic Diamine Ligands

Ruthenium(II) arene complexes of the general formula [RuCl(η⁶-p-cymene)(diamine)]PF₆ (diamine = 1,2-diaminobenzene (1), 2,3-diaminonaphthalene (2), 9,10-diaminophenanthrene (3), 2,3-diaminophenazine (4), and 1,2-diaminoanthraquinone (5) were synthesized. Chloro/aqua exchange was evaluated experimentally for complexes 1 and 2. The exchange process was investigated theoretically for all complexes, revealing relatively fast exchange with no significant influence from the polycyclic aromatic diamines. The calf thymus DNA (CT-DNA) binding of the complexes increased dramatically upon extending the aromatic component of the diamines, as evaluated by changes in absorption spectra upon titration with different concentrations of CT-DNA. An intercalation binding mode was established for the complexes using the increase in the relative viscosity of the CT-DNA following addition of complexes 1 and 2. Theoretical studies showed strong preference for replacement of water by guanine for all the complexes, and relatively strong Ru-N_guanine bonds. The plane of the aromatic systems can assume angles that support non-classical interactions with the DNA and covalent binding, leading to higher binding affinities. The ruthenium arenes illustrated in this study have promising anticancer activities, with the half maximal inhibitory concentration (IC₅₀) values comparable to or better than cisplatin against three cell lines.

New copper(I) complexes selective for prostate cancer cells

A new family of eighteen Cu(i) complexes of the general formula [Cu(PP)(LL)][BF4], where PP is a phosphane ligand and LL represents an N,O-heteroaromatic bidentate ligand, has been synthesized and fully characterized by classical analytical and spectroscopic methods. Five complexes of this series were also characterized by single crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated in breast (MCF7) and prostate (LNCap) human cancer cells and in a normal prostate cell line (RWPE). In general, all compounds showed higher cytotoxicity for the prostate cancer cells than for the breast cells, with IC50 values in the range 0.2-2 μM after 24 h of treatment. The most cytotoxic compound, [Cu(dppe)(2-ap)][BF4] (16), where dppe = 1,2-bis(diphenylphosphano) ethane and 2-ap = 2-acetylpyridine, showed a high level of cellular internalization, generation of intracellular ROS and activation of the cell death mechanism via apoptosis/necrosis. Owing to its high cytotoxic activity for LNCap cells, being 70-fold higher than that for normal prostate cells (RWPE), complex (16) was found to be the most promising for further research in prostate cancer models.

Equilibrium and site selective analysis for DNA threading intercalation of a new phosphine copper(I) complex: Insights from X-ray analysis, spectroscopic and molecular modeling studies

To clarify the interaction of phosphine copper(I) complex with DNA, our study reports the synthesis of a new phosphine copper(I) complex, along with a detailed analysis of the geometry characterization and its interaction with double-stranded DNA. The triclinic phase Cu(PPh₃)₂(L)(I) with a tetrahedral geometry was identified as the product of the reaction of copper(I) iodide with (E,E)-N,N'-1,2-Ethanediylbis[1-(3-pyridinyl)methanimine] ligand and triphenylphosphine by single-crystal X-ray analysis. Molecular interaction of the synthesized complex with the calf thymus deoxyribonucleic acid (ct-DNA) was investigated in the physiological buffer (pH 7.4) by multi-spectroscopic approaches associated with a competitive displacement towards Hoechst 33258 and methylene blue (MB) as groove and intercalator probes. The fluorescence and UV/Vis results detected the formation of a complex-DNA adduct in the ground-state with a binding affinity in order of 10⁴ M^-1, which is in keeping with both groove binders and intercalators. The thermodynamic parameters, ΔS⁰ = -200.31 ± 0.08 cal/mol·K and ΔH⁰ = -63.11 ± 0.24 kcal/mol, confirmed that the van der Waals interaction is the main driving force for the binding process. Moreover, the ionic strength and pH effect experiments demonstrated the electrostatic interactions between the complex and DNA is negligible. Analysis of the molecular docking simulation declared the flat (E,E)-N,N'-1,2-Ethanediylbis[1-(3-pyridinyl)methanimine] part of the complex was inserted between the sequential A…T/A…T base pairs, while the phosphine substituents were located in the groove, i.e. threading intercalation. Besides, the cytotoxicity of the complex against the MCF-7 human breast cancer cells was detected at IC50 = 10 μg/mL.

Influence of the introduction of a triphenylphosphine group on the anticancer activity of a copper complex

Aiming at obtaining new copper complexes with good cytotoxicity against cancer cells, triphenylphosphine (TPP) was introduced to obtain insight into the influence of the co-ligands. In this paper, two copper complexes, Cu(2-pbmq)(CH₃OH)Br₂ (1) and [Cu(2-pbmq)(TPP)Br]₂ (2) were designed, synthesized, and characterized by X-ray crystallography, 2-((2-(pyrazin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl))quinolone (2-pbmq), to investigate the influence of the TPP group on the anticancer activity of the metal complex. Although the presence of the TPP group diminished the intensity of the interaction properties of the complex with DNA, the in vitro anticancer activity and cellular uptake of the TPP-containing complex were markedly superior to those of its TPP-lacking counterpart. Detailed studies on the more potently cytotoxic complex 2 revealed that it accumulated in nucleus, arrested the cell cycle at the G0-G1 phase, causing mitochondrial dysfunction, involving the potential simultaneous mitochondrial membrane collapse, cellular ATP level depletion, and Ca²⁺ leakage, eventually inducing cell apoptosis. In summary, the introduction of a TPP group enhances the biological activity and cytotoxicity of the complex.

A Supramolecular Interaction of a Ruthenium Complex With Calf-Thymus DNA: A Ligand Binding Approach by NMR Spectroscopy

Lawsone itself exhibits interesting biological activities, and its complexation with a metal center can improve the potency. In this context a cytotoxic Ru-complex, [Ru(law)(dppb)(bipy)] (law = lawsone, dppb = 1,4-bis(diphenylphosphino)butane and bipy = 2,2'-bipyridine), named as CBLAU, was prepared as reported. In this work, NMR binding-target studies were performed to bring to light the most accessible interaction sites of this Ru-complex toward Calf-Thymus DNA (CT-DNA, used as a model), in a similar approach used for other metallic complexes with anti-cancer activity, such as cisplatin and carboplatin. Advanced and robust NMR binding-target studies, among them Saturation Transfer Difference (STD)-NMR and longitudinal relaxometry (T1), were explored. The 1H and 31P -NMR data indicate that the structure of Ru-complex remains preserved in the presence of CT-DNA, and some linewidth broadening is also observed for all the signals, pointing out some interaction. Looking at the binding efficiency, the T1 values are highly influenced by the formation of the CBLAU-DNA adduct, decreasing from 11.4 s (without DNA) to 1.4 s (with DNA), where the difference is bigger for the lawsone protons. Besides, the STD-NMR titration experiments revealed a stronger interaction (KD = 5.9 mM) for CBLAU-DNA in comparison to non-complexed lawsone-DNA (KD = 34.0 mM). The epitope map, obtained by STD-NMR, shows that aromatic protons from the complexed lawsone exhibits higher saturation transfer, in comparison to other Ru-ligands (DPPB and bipy), suggesting the supramolecular contact with CT-DNA takes place by the lawsone face of the Ru-complex, possibly by a spatial π-π stacking involving π-bonds on nucleic acids segments of the DNA chain and the naphthoquinone group.

Copper(ii) complexes with alloferon analogues containing phenylalanine H6F and H12F stability and biological activity lower stabilization of complexes compared to analogues containing tryptophan

Copper(ii) complex formation processes between alloferon 1 (Allo1) (H1 GVSGH6 GQH9 GVH12G) analogues where the phenylalanine residue is introduced in the place of His residue H6F and H12F have been studied by potentiometric, UV-visible, CD and EPR spectroscopic, and MS methods. For the phenylalanine analogues of alloferon 1, complex speciation has been obtained for a 1 : 1, 2 : 1 and 3 : 1 metal-to-ligand molar ratio. At physiological pH and in 1 : 1 metal-to-ligand molar ratio the phenylalanine analogues of alloferon 1 form a CuL complex similar to that of alanine analogues with the 4N{NH2,N1Im,2NIm} coordination mode. The stability of the complexes of the phenylalanine analogues is higher in comparison to those of alanine analogues, but lower in comparison to those containing tryptophan. Injection of Allo12F into insects induced prominent apoptotic changes in all hemocytes. The presence of apoptotic bodies only in the insect hemolymph testifies to the fact that Allo12F is an extremely pro-apoptotic peptide.