Anticancer Activity of Half-Sandwich Ru, Rh and Ir Complexes with Chrysin Derived Ligands: Strong Effect of the Side Chain in the Ligand and Influence of the Metal

An important challenge in the field of anticancer chemotherapy is the search for new species to overcome the resistance of standard drugs. An interesting approach is to link bioactive ligands to metal fragments. In this work, we have synthesized a set of p-cymene-Ru or cyclopentadienyl-M (M = Rh, Ir) complexes with four chrysin-derived pro-ligands with different -OR substituents at position 7 of ring A. The introduction of a piperidine ring on chrysin led to the highly cytotoxic pro-ligand HL4 and its metal complexes L4-M (SW480 and A549 cell lines, cytotoxic order: L4-Ir > L4-Ru ≈ L4-Rh). HL4 and its complexes induce apoptosis and can overcome cis-platinum resistance. However, HL4 turns out to be more cytotoxic in healthy than in tumor cells in contrast to its metal complexes which displayed higher selectivity than cisplatin towards cancer cells. All L4-M complexes interact with double stranded DNA. Nonetheless, the influence of the metal is clear because only complex L4-Ir causes DNA cleavage, through the generation of highly reactive oxygen species (1O2). This result supports the hypothesis of a potential dual mechanism consisting of two different chemical pathways: DNA binding and ROS generation. This behavior provides this complex with a great effectivity in terms of cytotoxicity.

Visible-Light-Mediated Modification and Manipulation of Biomacromolecules

Chemically modified biomacromolecules-i.e., proteins, nucleic acids, glycans, and lipids-have become crucial tools in chemical biology. They are extensively used not only to elucidate cellular processes but also in industrial applications, particularly in the context of biopharmaceuticals. In order to enable maximum scope for optimization, it is pivotal to have a diverse array of biomacromolecule modification methods at one's disposal. Chemistry has driven many significant advances in this area, and especially recently, numerous novel visible-light-induced photochemical approaches have emerged. In these reactions, light serves as an external source of energy, enabling access to highly reactive intermediates under exceedingly mild conditions and with exquisite spatiotemporal control. While UV-induced transformations on biomacromolecules date back decades, visible light has the unmistakable advantage of being considerably more biocompatible, and a spectrum of visible-light-driven methods is now available, chiefly for proteins and nucleic acids. This review will discuss modifications of native functional groups (FGs), including functionalization, labeling, and cross-linking techniques as well as the utility of oxidative degradation mediated by photochemically generated reactive oxygen species. Furthermore, transformations at non-native, bioorthogonal FGs on biomacromolecules will be addressed, including photoclick chemistry and DNA-encoded library synthesis as well as methods that allow manipulation of the activity of a biomacromolecule.

DNA-interacting properties of two analogous square-planar cis-chlorido complexes: copper versus palladium

Two square-planar coordination compounds, namely [Cu(CPYA)Cl2] (1) and [Pd(CPYA)Cl2] (2), were prepared from the ligand 4-chloro-N-(pyridin-2-ylmethyl)aniline (CPYA) and two chloride salts, and were fully characterized, including by X-ray diffraction. Spectroscopic, electrophoretic and AFM studies revealed that the two isostructural compounds were interacting differently with DNA. In both cases, the initial interaction involves electrostatic contacts of the CPYA ligand in the minor groove (as suggested by molecular docking), but subsequent strong binding occurs with the palladium(II) complex 2, whereas the binding with the copper complex 1 is weaker and concentration dependent. The strong binding of 2 eventually leads to the cleavage of the double strand and the redox activity of 1 allows to oxidatively cleave the biomolecule.

Synthesis and antiproliferative activity of hindered, chiral 1,2-diaminodiamantane platinum(II) complexes

Platinum-based antineoplastic agents play a major role in the treatment of numerous types of cancer. A new bulky, lipophilic, and chiral ligand based on 1,2-diaminodiamantane in both of its enantiomeric forms was employed for the preparation of new platinum(ii) complexes with chloride and oxalate ligands. The dichloride complexes have a higher solubility and were evaluated as anti-proliferation agents for human ovarian cancer cell lines A2780 and cisplatin-resistant A2780cis. Its R,R-enantiomer showed increased efficacy compared to cisplatin for both cancer cell lines. A chromatographic approach was used to estimate the solvent partition coefficient of the dichloride complex. The binding of diamondoid-based platinum complexes to nucleotides was tested for both enantiomers with guanosine monophosphate (GMP) and deoxyguanosine monophosphate (dGMP) and occurs at a similar or faster rate for both isomers compared to cisplatin despite greatly increased steric demand. These findings highlight the potential in 1,2-diaminodiamantane as a viable pharmacophore.

Ru(II)/diclofenac-based complexes: DNA, BSA interaction and their anticancer evaluation against lung and breast tumor cells

Ruthenium(ii) diclofenac-based complexes of the general formula [Ru(dicl)(P-P)(bpy)]PF6 [dicl = diclofenac, bpy = 2,2'-bipyridine, and P-P = 1,4'-bis(diphenylphosphino)butane (dppb) (1), 1,2'-bis(diphenylphosphino)ethane (dppe) (2), 1,3'-bis(diphenylphosphino)propane (dppp) (3) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) (4)] are synthesized. The complexes (1-4) are characterized by elemental analyses, infrared, NMR, and UV-vis spectroscopy and (3) and (4) are characterized by single crystal X-ray diffraction. The DNA binding of complexes (1-4), studied by circular dichroism (CD) and Hoechst 33 258 staining assay, indicates their binding with the minor grooves. The complexes interact with BSA with binding constants (Kb) in the range of 2.5 × 103-5.5 × 104 M-1. The complexes exhibit high cytotoxicity against the tumor cell lines A549, MDA-MB-231, and MCF-7 with IC50 values ranging from 0.56 to 15.28 μM. The complexes are more selective for the hormone-dependent MCF-7 breast tumor cell line and complex (1) is the most potent one. The study demonstrates the anticancer activity of ruthenium(ii)/diclofenac-based complexes.

A Cytotoxic Bis(1,2,3-triazol-5-ylidene)carbazolide Gold(III) Complex Targets DNA by Partial Intercalation

The syntheses of bis(triazolium)carbazole precursors and their corresponding coinage metal (Au, Ag) complexes are reported. For alkylated triazolium salts, di- or tetranuclear complexes with bridging ligands were isolated, while the bis(aryl) analogue afforded a bis(carbene) AuI -CNC pincer complex suitable for oxidation to the redox-stable [AuIII (CNC)Cl]+ cation. Although the ligand salt and the [AuIII (CNC)Cl]+ complex were both notably cytotoxic toward the breast cancer cell line MDA-MB-231, the AuIII complex was somewhat more selective. Electrophoresis, viscometry, UV-vis, CD and LD spectroscopy suggest the cytotoxic [AuIII (CNC)Cl]+ complex behaves as a partial DNA intercalator. In silico screening indicated that the [AuIII (CNC)Cl]+ complex can target DNA three-way junctions with good specificity, several other regular B-DNA forms, and Z-DNA. Multiple hydrophobic π-type interactions involving T and A bases appear to be important for B-form DNA binding, while phosphate O⋅⋅⋅Au interactions evidently underpin Z-DNA binding. The CNC ligand effectively stabilizes the AuIII ion, preventing reduction in the presence of glutathione. Both the redox stability and DNA affinity of the hit compound might be key factors underpinning its cytotoxicity in vitro.

DNA cleavage mechanism by metal complexes of Cu(II), Zn(II) and VO(IV) with a schiff-base ligand

Metal ions and metal complexes are important components of nucleic acid biochemistry, participating both in regulation of gene expression and as therapeutic agents. Three new transition metal complexes of copper(II), zinc(II) and oxidovanadium(IV) with a ligand derived from o-vanillin and thiophene were previously synthesized and their antitumor properties were studied in our laboratory. To elucidate some molecular mechanisms tending to explain the cytotoxic effects observed over tumor cells, we investigated the interaction of these complexes with DNA by gel electrophoresis, UV-Vis spectroscopy, docking studies and molecular dynamics simulations. Our spectroscopy and computational results have shown that all of them were able to bind to DNA, Cu(II) complex is located in the minor groove while Zn(II) and oxidovanadium(IV) complexes act as major groove binding molecules. Interestingly, only the Cu(II) complex caused double-strand DNA nicks, consistent with its higher cytotoxic activities previously observed in tumor cell lines. We propose that the DNA-complex interaction destabilize the molecule either disrupting the phosphodiester bonds or impairing DNA replication, giving those complexes strong antitumor potential.

Square planar Au(III), Pt(II) and Cu(II) complexes with quinoline-substituted 2,2':6',2″-terpyridine ligands: From in vitro to in vivo biological properties

Cancer is the second leading cause of death worldwide. Cisplatin has challenged cancer treatment; however, resistance and side effects hamper its use. New agents displaying improved activity and more reduced side effects relative to cisplatin are needed. In this work we present the synthesis, characterization and biological activities of three complexes with quinoline-substituted 2,2':6',2″-terpyridine ligand: [Pt(4'-(2-quin)-terpy)Cl](SO₃CF₃) (1), [Au(4'-(2-quin)-terpy)Cl](PF₆)₂·CH₃CN (2) and [Cu(4'-(2-quin)-terpy)Cl](PF₆) (3). The three complexes displayed a high antiproliferative activity in ovarian carcinoma cell line (A2780) and even more noticeable in a colorectal carcinoma cell line (HCT116) following the order 3 > 2 > 1. The complexes IC₅₀ are at least 20 × lower than the IC₅₀ displayed by cisplatin (15.4 μM) in HCT116 cell line while displaying at the same time, much reduced cytotoxicity in a normal dermal fibroblast culture. These cytotoxic activities seem to be correlated with the inclination angles of 2-quin unit to the central pyridine. Interestingly, all complexes can interact with calf-thymus DNA (CT-DNA) in vitro via different mechanisms, although intercalation seems to be the preferred mechanism at least for 2 and 3 at higher concentrations of DNA. Moreover, circular dichroism (CD) data seems to indicate that complex 3, more planar, induces a high destabilization of the DNA double helix (shift from B-form to Z-form). Higher the deviation from planar, the lower the cytotoxicity displayed by the complexes. Cellular uptake may be also responsible for the different cytotoxicity exhibited by complexes with 3 > 2 >1. Complex 2 seems to enter cells more passively while complex 1 and 3 might enter cells via energy-dependent and -independent mechanisms. Complexes 1-3 were shown to induce ROS are associated with the increased apoptosis and autophagy. Moreover, all complexes dissipate the mitochondrial membrane potential leading to an increased BAX/BCL-2 ratio that triggered apoptosis. Complexes 2 and 3 were also shown to exhibit an anti-angiogenic effect by significantly reduce the number of newly formed blood vessel in a CAM model with no toxicity in this in vivo model. Our results seem to suggest that the increased cytotoxicity of complex 3 in HCT116 cells and its potential interest for further translation to pre-clinical mice xenografts might be associated with: 1) higher % of internalization of HCT116 cells via energy-dependent and -independent mechanisms; 2) ability to intercalate DNA and due to its planarity induced higher destabilization of DNA; 3) induce intracellular ROS that trigger apoptosis and autophagy; 4) low toxicity in an in vivo model of CAM; 5) potential anti-angiogenic effect.

Unraveling the binding mechanism of an Oxovanadium(IV) - Curcumin complex on albumin, DNA and DNA gyrase by in vitro and in silico studies and evaluation of its hemocompatibility

An oxovanadium(IV) - curcumin based complex, viz. [VO(cur)(2,2´-bipy)(H₂O)] where cur is curcumin and bipy is bipyridine, previously synthesized, has been studied for interaction with albumin and DNA. Fluorescence emission spectroscopy was used to evaluate the interaction of the complex with bovine serum albumin (BSA) and the BSA-binding constant (K_b) was calculated to be 2.56 x 10⁵ M^-1, whereas a single great-affinity binding site was revealed. Moreover, the hemocompatibility test demonstrated that the complex presented low hemolytic fraction (mostly below 1%), in all concentrations tested (0-250 μΜ of complex, 5% DMSO) assuring a safe application in interaction with blood. The binding of the complex to DNA was also investigated using absorption, fluorescence, and viscometry methods indicating a binding through a minor groove mode. From competitive studies with ethidium bromide the apparent binding constant value to DNA was estimated to be 4.82 x 10⁶ M^-1. Stern-Volmer quenching phenomenon gave a Κ_SV constant [1.92 (± 0.05) x 10⁴ M^-1] and k_q constant [8.33 (± 0.2) x 10¹¹ M^-1s^-1]. Molecular docking simulations on the crystal structure of BSA, calf thymus DNA, and DNA gyrase, as well as pharmacophore analysis for BSA target, were also employed to study in silico the ability of [VO(cur)(2,2´-bipy)(H₂O)] to bind to these target bio-macromolecules and explain the observed in vitro activity.

A novel biocompatible formate bridged 1D-Cu(ii) coordination polymer induces apoptosis selectively in human lung adenocarcinoma (A549) cells

Copper compounds are promising candidates for next-generation metal anticancer drugs. Therefore, we synthesized and characterized a formate bridged 1D coordination polymer [Cu(L)(HCOO)₂]_n, (L = 2-methoxy-6-methyl-3-((quinolin-8-ylimino)methyl)chroman-4-ol), PCU1, wherein the Cu(ii) center adopts a square pyramidal coordination environment with adjacent CuCu distances of 5.28 Å. Primarily, in vitro DNA interaction studies revealed a metallopolymer which possesses high DNA binding propensity and cleaves DNA via the oxidative pathway. We further analysed its potential on cancerous cells MCF-7, HeLa, A549, and two non-tumorigenic cells HEK293 and HBE. The selective cytotoxicity potential of PCU1 against A549 cells driven us to examine the mechanistic pathways comprehensively by carrying out various assays viz, cell cycle arrest, Annexin V-FTIC/PI assay, autophagy, intercellular localization, mitochondrial membrane potential 'MMP', antiproliferative assay, and gene expression of TGF-β and MMP-2.

Kinetically labile ruthenium(II) complexes of terpyridines and saccharin: effect of substituents on photoactivity, solvation kinetics, and photocytotoxicity

Herein, we designed six kinetically labile ruthenium(ii) complexes containing saccharin (sac) and 4'-substituted-2,2':6',2''-terpyridines (R-tpy), viz. trans-[Ru(sac)2(H2O)3(dmso-S)] (1) and [RuII(R-tpy)(sac)2(X)] [X = solvent molecule] (2-6). We intentionally kept the labile hydrolysable Ru-X bonds that were potentially activated via solvent-exchange reactions. This strategy generates a coordinative vacancy that allows further binding with potential biological targets. To gain insight into the electronic effects of ancillary ligands on Ru-X ligand-exchange kinetics or photoreactions, we have used a series of substituted terpyridines (R-tpy) and studied their solvation kinetics. The ternary complexes were also studied for their potential utility in Ru-assisted photoactivated chemotherapy (PACT) synergized with release of saccharin as a highly selective carbonic anhydrase IX (CA-IX) inhibitor, over-expressed in hypoxic tumors. The ternary complexes exhibit distorted octahedral geometry around Ru(ii) from two monodentate transoidal saccharin in the axial position, and tridentate terpyridines and labile solvent molecules at the basal plane (2-6). We studied their speciation, solvation kinetics, and photoreactivity in the presence of green LED light (λirr = 530 nm). All the complexes are relatively labile and undergo solvation in coordinating solvents (e.g. DMSO/DMF). The complexes undergo the ligand-substitution reaction, and their speciation and kinetics were studied by UV-Vis, ESI-MS, 1H-NMR, and structural analysis. We also attempted to assess the effect of various substituents on the ancillary terpyridine ligand (R-tpy) in photo-reactivity and ligand-exchange reactions. The photo-induced absorption and emission measurements suggested dissociation of the saccharin from the Ru-center supporting PACT pathways. The complexes display a significant binding affinity with CT-DNA (Kb ∼ 104-105 M-1) and bovine serum albumin (BSA) (KBSA ∼ 105 M-1). Cytotoxicity was studied in the dark and the presence of low energy UV-A light (365 nm) in cervical cancer cells (HeLa) and breast cancer cells (MCF7). Photoirradiation of the complexes induces the generation of reactive oxygen species (ROS) assessed using 1,3-diphenylisobenzofuran (DPBF) and intracellular DCFDA assays. The complexes are sufficiently internalized in cancer cells throughout the cytoplasm and nucleus and induce apoptosis as studied by staining with dual dyes using confocal microscopy.

Single Molecule Magnets of Co2 and Co2La MOFs Synthesized by New Schiff Base Ligand N,N'-bis(o-Vanillinidene) Ethylenediamine (o-VEDH2)

Schiff base ligand N,N'-bis(o-vanillinidene) ethylenediamine (o-VEDH2) has been employed to synthesize new [CoIICoIV(o-VED)(OAc)2(μ2-OAc)(OMe)]•MeOH (1) and [Co 2 IV (o-VED)2(en)2(NCCH3)(OCH3)][La(NO3)6](NO 3 - )•2MeOH•MeCN•H2O (2) metal-organic frameworks (MOFs) that have interesting single molecule magnets (SMMs) property. The synthesized complexes are characterized by single crystal X-ray diffraction, fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and squid magnetic measurement. Single crystal X-ray data show that both complexes crystallize in the monoclinic crystal system with P21/c(14) and P21/n(14) space groups and generate unique MOF-like structures. Overall, both the metal centers of 1 form octahedral geometry with a butterfly core structure. Variable temperature (T) and field (H) solid-state direct-current (dc) and alternative current (ac) magnetic susceptibility measurements were performed on both the complexes over 1.8 to 300 K, which exhibited a ground state spins (S) of 4 and 5 of complexes 1 and 2, respectively. The AC out-phase and in-phase properties of complexes show SMMs. Other properties such as optical, sensing, and DNA-binding interactions were also investigated by the complexes. Complexes 1 and 2 have energy band gaps of 3.7 and 3.03 eV indicating semiconductor properties. Simultaneously, complex 1 was found to sense H2O2 with a rate constant (k) = 1.59 × 10-4 s-1, whereas complex 2 was found to bind with calf-thymus-DNA by intercalation mode with binding constant (K b ) of 1.22 × 105 M-1.

Copper (II)-based halogen-substituted chromone antitumor drug entities: Studying biomolecular interactions with ct-DNA mediated by sigma hole formation and cytotoxicity activity

Copper-based antitumor drug entities 1-3 derived from substituted (F^-, Br^-, -CH₃) 3-formylchromone pharmacophore were synthesized and thoroughly characterized by spectroscopic and single X-ray crystallographic studies. These complexes show structural novelty due to presence of the X-bonds in chromone scaffold which could facilitate higher propensity for nucleic acids via sigma σ-hole interactions. Therefore, structure-activity relationship of 1-3 was studied by performing ct-DNA binding, pBR322 cleavage and cytotoxicity activity to validate their potential to act as chemotherapeutic drug entities. The binding studies of 1-3 with ct- DNA were carried out employing many biophysical techniques and the corroborative results of these experiments showed intercalation mode of binding and the order of binding was found to be 2 > 1 > 3. The structure of drug entities could facilitated strong halogen bonding interaction (in case of 1 &2) and stability of X bond was rationalized by sigma hole region of positive electrostatic potential on the surface of C-X covalent bond, as determined by gas phase B3LYP computational DFT studies. Interestingly, 2 exhibited most avid binding affinity due to presence of Br^- electron withdrawing and polarizable group. Further, cleavage studies of 1-3 with pBR322 plasmid DNA were performed which demonstrated significant cleavage activity, the supercoiled form (Form I) of plasmid DNA was converted to nicked form (Form II) with the appearance of linearized form (Form III) in between two, implicating lethal double strand breaks of DNA. 2 showed predominantly higher cleavage activity following the similar trend as observed for binding studies. The cytotoxicity of the complexes 1-3 was evaluated by MTT assay against the human liver carcinoma (Huh-7) and prostate cancer (DU-145) cell lines; complex 2 exhibited specific and selective cytotoxicity for the DU-145 cancer cell line with LC₅₀ value of 1.6 μM.

Chiroptical property enhancement of chiral Eu(III) complex upon association with DNA-CTMA

DNA-based materials have attracted much attention due to their unique photo-functional properties and potential applications in various fields such as luminescent and biological systems, nanodevices, etc. In this study, the photophysical properties of a chiral Eu(III) complex, namely (Eu(D-facam)₃), within DNA films were extensively investigated. The enhancement of photoluminescence (more than 25-folds increase of luminescence quantum yield) and degree of circularly polarization in luminescence (g_lum = − 0.6) was observed upon interaction with DNA. Various photophysical analyses suggested that the emission enhancement was mainly due to an increase of the sensitization efficiency (high η_sens) from the ligands to Eu(III) and suppression of the vibrational deactivation upon immobilization onto the DNA molecule. From CD and VCD measurements, it was suggested that the coordination structure of Eu(D-facam)₃ was affected by the interaction with DNA, suggesting that the structural change of Eu(D-facam)₃ contributed to the improvement of its luminescent properties.

Activation of the Ir-N(pyridine) Bond in Half-Sandwich Tethered Iridium(III) Complexes

We present four new organometallic half-sandwich iridium(III) complexes of formula [Ir(η⁵:κ¹-C₅Me₄CH₂py)(N,N)](PF₆)₂, bearing a N,N-chelating ligand [ethylenediamine (en), 1; 1,3-diaminopropane (dap), 2; 2,2'-bipyridine (bipy), 3; 1,10-phenanthroline (phen), 4]; and a derivatized cyclopentadienyl ligand, C₅Me₄CH₂C₅H₄N, which forms an additional five-membered chelate. The latter is hemilabile, and the Ir-N(py) bond can be reversibly cleaved by various stimuli. The four complexes are unreactive toward hydrolysis at pH 7. Interestingly, 1 and 2 react with hydrochloric acid and formate, and speciation between closed and open tether complexes can be followed by ¹H NMR spectroscopy. Complex 1 binds to nucleobase guanine (9-ethylguanine, 9-EtG), yet interaction to calf-thymus DNA was not observed. New X-ray structures of closed tether complexes 1-4 and open tether complexes [Ir(η⁵-C₅Me₄CH₂pyH)(en)Cl](PF₆)₂ (1·HCl) and [Ir(η⁵-C₅Me₄CH₂py)(en)H]PF₆ (1·hyd) have been determined. Hydride capture is efficient for 1 and 2. The kinetics of Ir-H bond formation and hydride transfer in a model organic molecule have been investigated, revealing a strong dependence on the temperature. Coincubation of complex 1 with nontoxic concentrations of sodium formate decreases the IC₅₀ value in MCF7 breast cancer cells, indicating the possibility of intracellular activation of the Ir-N(py) tether bond to generate cytotoxic activity via iridium-mediated transfer hydrogenation.

Cisplatin adducts of DNA as precursors for nanostructured catalyst materials

The synthesis and characterisation of novel metal-modified DNA precursors for fuel cell catalyst development are described. Material precursors in the form of metal-DNA complexes were prepared through the reaction of DNA with cisplatin at various loadings and spectroscopically tested to confirm the platinum binding mode and the degree of complexation. The surface morphology of the DNA-metal material was analysed by Scanning Transmission Electron Microscopy (STEM), which revealed the extent of platinum nanocluster formation, with low metal loadings leading to observation of individual platinum atoms. Electrochemical measurements showed a greater electrocatalytic activity for the hydrogen evolution reaction (HER) with increased platinum loadings, shifting the half wave potential, E _1/2, away from the glassy carbon limit towards that of a bulk Pt electrode. This is explained further by Tafel plots, from which a change in the mechanism of the apparent rate limiting step for proton reduction from a Volmer to a Heyrovsky mechanism is postulated as the platinum loading increases.

Synthesis, Characterisation and In Vitro Anticancer Activity of Catalytically Active Indole-Based Half-Sandwich Complexes

The synthesis, characterisation and evaluation of the in vitro cytotoxicity of four indole-based half-sandwich metal complexes towards two ovarian cancer cell lines (A2780 and A2780cisR) and one normal prostate cell line (PNT2) are presented herein. Although capable of inducing catalytic oxidation of NADH and able to reduce NAD+ with high turnover frequencies, in cells and in the presence of sodium formate, these complexes also strongly interact with biomolecules such as glutathione. This work highlights that efficient out-of-cells catalytic activity might lead to higher reactivity towards biomolecules, thus inhibiting the in-cells catalytic processes.

Ruthenium(II) Phosphine/Mercapto Complexes: Their in Vitro Cytotoxicity Evaluation and Actions as Inhibitors of Topoisomerase and Proteasome Acting as Possible Triggers of Cell Death Induction

In this paper, a series of new ruthenium complexes of the general formula [Ru(NS)(dpphpy)(dppb)]PF₆ (Ru1-Ru3), where dpphpy = diphenyl-2-pyridylphosphine, NS ligands = 2-thiazoline-2-thiol (tzdt, Ru1), 2-mercaptopyrimidine (pySm, Ru2), and 4,6-diamino-2-mercaptopyrimidine (damp, Ru3), and dppb = 1,4-bis(diphenylphosphino)butane, were synthesized and characterized by elemental analysis, spectroscopic techniques (IR, UV/visible, and 1D and 2D NMR), and X-ray diffraction. In the characterization, the correlation between the phosphorus atoms and their respective aromatic hydrogen atoms of the compounds in the assignment stands outs, by ¹H-³¹P HMBC experiments. The compounds show anticancer activities against A549 (lung) and MDA-MB-231 (breast) cancer cell lines, higher than the clinical drug cisplatin. All of the complexes are more cytotoxic against the cancer cell lines than against the MRC-5 (lung) and MCF-10A (breast) nontumorigenic human cell lines. For A549 tumor cells, cell cycle analysis upon treatment with Ru2 showed that it inhibits the mitotic phase because arrest was observed in the Sub-G1 phase. Additionally, the compound induces cell death by an apoptotic pathway in a dose-dependent manner, according to annexin V-PE assay. The multitargeted character of the compounds was investigated, and the biomolecules were DNA, topoisomerase IB, and proteasome, as well as the fundamental biomolecule in the pharmacokinetics of drugs, human serum albumin. The experimental results indicate that the complexes do not target DNA in the cells. At low concentrations, the compounds showed the ability to partially inhibit the catalytic activity of topoisomerase IB in the process of relaxation of the DNA plasmid. Among the complexes assayed in cultured cells, complex Ru3 was able to diminish the proteasomal chymotrypsin-like activity to a greater extent.

Monitoring intracellular metal ion complexation with an acetylene-tagged ligand by Raman spectroscopy

We propose to monitor molecular vibrations to identify metal ion-ligand complexation by means of Raman spectroscopy, which has been applied to track vibrational modes of molecules and to obtain a structural fingerprint. We prepared ligand molecules for Zn²⁺ ion complexation with a dipycolylaminoethyl aniline (DPEA) skeleton and phenylacetylene unit as the Raman tag which showed a typical band around 2200 cm^-1. Among the labeled ligands synthesized in this study, A-DPEA showed a strong band attributed to the acetylene unit at 2212 cm^-1, while the addition of Zn²⁺ ion resulted in a band shift to 2220 cm^-1 due to complex formation. The addition of other metal ions and titration experiments showed that A-DPEA bound with Zn²⁺ selectively with a dissociation constant (K _d) that was estimated to be 0.22 μM. We also conducted cellular experiments and found that complexation between A-DPEA and Zn²⁺ also occurred in cells, with a shift in the Raman signal of the ligand from 2212 to 2215 cm^-1. Thus, complex formation of the metal ion was identified by monitoring the Raman band shift.

Stronger Cytotoxicity for Cancer Cells Than for Fast Proliferating Human Stem Cells by Rationally Designed Dinuclear Complexes

Cytostatic metallo-drugs mostly bind to the nucleobases of DNA. A new family of dinuclear transition metal complexes was rationally designed to selectively target the phosphate diesters of the DNA backbone by covalent bonding. The synthesis and characterization of the first dinuclear Ni^II₂ complex of this family are presented, and its DNA binding and interference with DNA synthesis in polymerase chain reaction (PCR) are investigated and compared to those of the analogous Cu^II₂ complex. The Ni^II₂ complex also binds to DNA but forms fewer intermolecular DNA cross-links, while it interferes with DNA synthesis in PCR at lower concentrations than Cu^II₂. To simulate possible competing phosphate-based ligands in vivo, these effects have been studied for both complexes with 100-200-fold excesses of phosphate and ATP, which provided no disturbance. The cytotoxicity of both complexes has been studied for human cancer cells and human stem cells with similar rates of proliferation. Cu^II₂ shows the lowest IC₅₀ values and a remarkable preference for killing the cancer cells. Three different assays show that the Cu^II₂ complex induces apoptosis in cancer cells. These results are discussed to gain insight into the mechanisms of action and demonstrate the potential of this family of dinuclear complexes as anticancer drugs acting by a new binding target.

Ruthenium(II) and Iridium(III) Complexes as Tested Materials for New Anticancer Agents

The oncological use of cisplatin is hindered by its severe side effects and a very important resistance problem. To overcome these problems, scientists have attempted to design new generation transition-metal anticancer complexes. In this study, we present new complexes, ruthenium(II) [(η6-p-cymene)RuCl(py2CO)]PF6 (1), iridium(III) [(η5-Cp)IrCl(py2CO)]PF6 (2), and NH4[IrCl4(py2CO)]·H2O (3), based on di-2-pyridylketone (py2CO). The prepared complexes were characterized by FTIR, 1H, 13C, 15N NMR, UV-Vis, PL and elemental analysis techniques. The single-crystal X-ray structure analysis and comparative data revealed pseudo-octahedral half-sandwich 1 and 2 complexes and octahedral tetrachloroiridate(III) 3 with a rare chelating κ2N,O coordination mode of py2CO. The compounds were tested in vitro against three cancer cell lines-colorectal adenoma (LoVo), myelomonocytic leukaemia (MV-4-11), breast adenocarcinoma (MCF-7), and normal fibroblasts (BALB/3T3). The most promising results were obtained for iridium(III) complex 3 against MV-4-11 (IC50 = 35.8 ± 13.9 µg/mL) without a toxic effect against normal BALB/3T3, which pointed towards its selectivity as a potential anticancer agent. Extensive research into their mode of binding with DNA confirmed for 1 and 2 complexes non-classical binding modes, while the 3D circular dichroism (CD) experiment (ΔTm) suggested that 3 induced the probable formation of covalent bonds with DNA. In addition, the obtained iridium complexes induce ROS, which, in synergy with hydrolysis promoting DNA bonding, may lead to cancer cell death.

Antitumor Activity of Pt(II), Ru(III) and Cu(II) Complexes

Metal complexes are currently potential therapeutic compounds. The acquisition of resistance by cancer cells or the effective elimination of cancer-affected cells necessitates a constant search for chemical compounds with specific biological activities. One alternative option is the transition metal complexes having potential as antitumor agents. Here, we present the current knowledge about the application of transition metal complexes bearing nickel(II), cobalt(II), copper(II), ruthenium(III), and ruthenium(IV). The cytotoxic properties of the above complexes causing apoptosis, autophagy, DNA damage, and cell cycle inhibition are described in this review.

DNA Electrochemical Biosensor Based on Iron Oxide/Nanocellulose Crystalline Composite Modified Screen-Printed Carbon Electrode for Detection of Mycobacterium tuberculosis

Death from tuberculosis has resulted in an increased need for early detection to prevent a tuberculosis (TB) epidemic, especially in closed and crowded populations. Herein, a sensitive electrochemical DNA biosensor based on functionalized iron oxide with mercaptopropionic acid (MPA-Fe3O4) nanoparticle and nanocellulose crystalline functionalized cetyl trimethyl ammonium bromide (NCC/CTAB) has been fabricated for the detection of Mycobacterium tuberculosis (MTB). In this study, a simple drop cast method was applied to deposit solution of MPA-Fe3O4/NCC/CTAB onto the surface of the screen-printed carbon electrode (SPCE). Then, a specific sequence of MTB DNA probe was immobilized onto a modified SPCE surface by using the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling mechanism. For better signal amplification and electrochemical response, ruthenium bipyridyl Ru(bpy)32+ was assigned as labels of hybridization followed by the characteristic test using differential pulse voltammetry (DPV). The results of this biosensor enable the detection of target DNA until a concentration as low as 7.96 × 10-13 M with a wide detection range from 1.0 × 10-6 to 1.0 × 10-12 M. In addition, the developed biosensor has shown a differentiation between positive and negative MTB samples in real sampel analysis.

In vitro biological evaluation and consideration about structure-activity relationship of silver(I) aminoacidate complexes

Two silver(I) aminoacidate complexes {[Ag₄(L-HAla)₄(NO₃)₃]NO₃}_n (AgAla, complex 1, Ala = alanine) and {[Ag(L-Phe)]}_n (AgPhe, complex 2, Phe = phenylalanine) were prepared and characterized by elemental, spectral analysis (FT-IR, NMR techniques) and single crystal X-ray analysis in solid state and their solution stability was measured in biological testing time-scale by ¹H NMR. The bridging coordination modes of the zwitterionic Ala and deprotonated Phe ligands led to the formation of 1D polymeric chains of the complexes. The significant argentophilic interactions are presented in the structure of AgAla. Antimicrobial testing of prepared Ag(I) complexes was evaluated by IC₅₀ and MIC values and were compared with AgGly, silver(I) sulfadiazine and AgNO₃ samples. Moreover, MTS test was used to the testing of broad range antiproliferative activity of studied compounds against different cancer cell lines and also to the investigation of calf thymus DNA interactions by absorption spectroscopy, fluorescence spectroscopy, Ethidium bromide/Hoechst 33258 displacement experiments and circular dichroism spectroscopy. To evaluate the pUC19 DNA fragmentation by silver(I) complexes, the agarose gel electrophoresis was used. In addition to biological evaluation we used lipophilicity measurement results in the discussion about structure-activity relationship (SAR).

Multispectroscopic analysis, atomic force microscopy, molecular docking and molecular dynamic simulation studies of the interaction between [SnMe2Cl2(Me2phen)] complex and ct-DNA in the presence of glucose

In this study, the spectroscopic methods (UV-vis, fluorimetric), Atomic force microscopy, and computational studies (molecular docking and molecular dynamic simulation) were used to investigate the interaction of [SnMe₂Cl₂(Me₂phen)] complex with CT-DNA in the presence of glucose. The results showed the complex in the medium containing glucose has less effect on calf thymus DNA (ct-DNA) than the medium without glucose. Cytotoxicity of [SnMe₂Cl₂(Me₂phen)] complex on MCF-7 cells was examined and showed Sn(IV) complex possesses potential cytotoxicity against this cell line. Molecular docking study showed that Sn(IV) complex interacts with DNA by groove binding mode. Radius of gyration (Rg) was smaller upon binding of the Sn(IV) complex suggesting a more compact structure of DNA in the presence of Sn(IV) complex.Communicated by Ramaswamy H. Sarma.

Two isostructural Co(II) flufenamato and niflumato complexes with bathocuproine: Analogues with a different cytotoxic activity

Two novel Co(II) fenamato complexes containing bathocuproine (bcp), namely [Co(bcp)(flu)₂] (1) and [Co(bcp)(nif)₂] (2) (flu = flufenamato, nif = niflumato) were synthesized and characterized by elemental analysis, single-crystal X-ray structure analysis as well as absorption and fluorescence spectroscopy. Investigation of their molecular structure revealed that both complexes are isostructural and form analogous complex molecules, with a Co(II) atom hexacoordinated by two nitrogen atoms of bcp and four oxygen atoms of two chelate bonded flu (1) and nif (2) ligands in a distorted octahedral arrangement. Surprisingly, the results of cytotoxicity experiments on four cancer cell lines (HeLa, HT-29, PC-3 and MCF-7) have revealed that despite similar structure of the complexes, the nif complex exhibits significantly higher activity, being the most effective against the PC-3 cell line (IC₅₀ (MTT) = 6.11 ± 1.95 μM). Further studies performed on PC-3 cell line have shown that the mechanism of the cytotoxic action of nif complex (2) might involve activation of autophagic processes and apoptosis, while for its flu analogue (1) apoptosis was detected.