Metal complexes as structure-selective binding agents for nucleic acids

Strategies for the Nuclear Delivery of Metal Complexes to Cancer Cells

The nucleus is an essential organelle for the function of cells. It holds most of the genetic material and plays a crucial role in the regulation of cell growth and proliferation. Since many antitumoral therapies target nucleic acids to induce cell death, tumor-specific nuclear drug delivery could potentiate therapeutic effects and prevent potential off-target side effects on healthy tissue. Due to their great structural variety, good biocompatibility, and unique physico-chemical properties, organometallic complexes and other metal-based compounds have sparked great interest as promising anticancer agents. In this review, strategies for specific nuclear delivery of metal complexes are summarized and discussed to highlight crucial parameters to consider for the design of new metal complexes as anticancer drug candidates. Moreover, the existing opportunities and challenges of tumor-specific, nucleus-targeting metal complexes are emphasized to outline some new perspectives and help in the design of new cancer treatments.

Interactions of Mn complexes with DNA: the relevance of therapeutic applications towards cancer treatment

Manganese (Mn) is one of the most significant bio-metals that helps the body to form connective tissue, bones, blood clotting factors, and sex hormones. It is necessary for fat and carbohydrate metabolism, calcium absorption, blood sugar regulation, and normal brain and nerve functions. It accelerates the synthesis of proteins, vitamin C, and vitamin B. It is also involved in the catalysis of hematopoiesis, regulation of the endocrine level, and improvement of immune function. Again, Mn metalloenzymes like arginase, glutamine synthetase, phosphoenolpyruvate decarboxylase, and Mn superoxide dismutase (MnSOD) contribute to the metabolism processes and reduce oxidative stress against free radicals. Recent investigations have revealed that synthetic Mn-complexes act as antibacterial and antifungal agents. As a result, chemists and biologists have been actively involved in developing Mn-based drugs for the treatment of various diseases including cancer. Therefore, any therapeutic drugs based on manganese complexes would be invaluable for the treatment of cancer/infectious diseases and could be a better substitute for cisplatin and other related platinum based chemotherapeutic drugs. From this perspective, attempts have been made to discuss the interactions and nuclease activities of Mn(II/III/IV) complexes with DNA through which one can evaluate their therapeutic applications.

Aqueous coordination polymer complexes: From colloidal assemblies to bulk materials

1-dimensional (1D) coordination polymers refer to the macromolecules that have metal ions incorporated in their pendent groups or main chain through metal-binding ligand groups. They have intrinsic advantages over traditional polymers to regulate the polymer structures and functions owing to the nature of the metal-ligand bond. Consequently, they have great potential for the development of smart and functional structures and materials and therapeutic agents. Water-soluble 1D coordination polymers and assemblies are an important subtype of coordination polymers with distinctive interests for demanding applications in aqueous systems, such as biological and medical applications. This review highlights the recent progress and research achievements in the design and use of water-soluble 1D coordination polymers and assemblies. The overview covers the design and structure control of 1D coordination polymers, their colloidal assemblies, including nanoparticles, nanofibers, micelles and vesicles, and fabricated bulk materials such as membraneless liquid condensates, security ink, hydrogel actuators, and smart fabrics. Finally, we discuss the potential applications of several of these coordination polymeric structures and materials and give an outlook on the field of aqueous coordination polymers.

From Chemotherapy to Phototherapy - Changing the Therapeutic Action of a Metallo-Intercalating RuII -ReI Luminescent System by Switching its Sub-Cellular Location

The synthesis of a new heterodinuclear ReI RuII metallointercalator containing RuII (dppz) and ReI (dppn) moieties is reported. Cell-free studies reveal that the complex has similar photophysical properties to its homoleptic M(dppz) analogue and it also binds to DNA with a similar affinity. However, the newly reported complex has very different in-cell properties to its parent. In complete contrast to the homoleptic system, the RuII (dppz)/ReI (dppn) complex is not intrinsically cytotoxic but displays appreciable phototoxic, despite both complexes displaying very similar quantum yields for singlet oxygen sensitization. Optical microscopy suggests that the reason for these contrasting biological effects is that whereas the homoleptic complex localises in the nuclei of cells, the RuII (dppz)/ReI (dppn) complex preferentially accumulates in mitochondria. These observations illustrate how even small structural changes in metal based therapeutic leads can modulate their mechanism of action.

Evaluation of Ruthenium(II) N-Heterocyclic Carbene Complexes as Enzymatic Inhibitory Agents with Antioxidant, Antimicrobial, Antiparasitical and Antiproliferative Activity

A series of [RuCl₂(p-cymene)(NHC)] complexes were obtained by reacting [RuCl₂(p-cymene)]2 with in situ generated Ag-N-heterocyclic carbene (NHC) complexes. The structure of the obtained complexes was determined by the appropriate spectroscopy and elemental analysis. In addition, we evaluated the biological activities of these compounds as antienzymatic, antioxidant, antibacterial, anticancer, and antiparasitic agents. The results revealed that complexes 3b and 3d were the most potent inhibitors against AchE with IC₅₀ values of 2.52 and 5.06 μM mL^-1. Additionally, 3d proved very good antimicrobial activity against all examined microorganisms with IZ (inhibition zone) over 25 mm and MIC (minimum inhibitory concentration) < 4 µM. Additionally, the ligand 2a and its corresponding ruthenium (II) complex 3a had good cytotoxic activity against both cancer cells HCT-116 and HepG-2, with IC₅₀ values of (7.76 and 11.76) and (4.12 and 9.21) μM mL^-1, respectively. Evaluation of the antiparasitic activity of these complexes against Leishmania major promastigotes and Toxoplasma gondii showed that ruthenium complexes were more potent than the free ligand, with an IC₅₀ values less than 1.5 μM mL^-1. However, 3d was found the best one with SI (selectivity index) values greater than 5 so it seems to be the best candidate for antileishmanial drug discovery program, and much future research are recommended for mode of action and in vivo evaluation. In general, Ru-NHC complexes are the most effective against L. major promastigotes.

Template synthesis, DNA binding, antimicrobial activity, Hirshfeld surface analysis, and 1D helical supramolecular structure of a novel binuclear copper(ii) Schiff base complex

A new binuclear copper(ii) Schiff base complex [Cu2 L2 - (NO3)2]·2CH3OH (1) [L = 2,6-bis((E)-(p-tolylimino)methyl)-4-methoxyphenol] was synthesized using a template method in which the tridentate N2O Schiff base ligand was derived from [1 + 2] condensation of 2,6-diformyl-4-methoxyphenol and p-methyl aniline in the presence of copper(ii) ions as the template agent. The X-ray diffraction analyses revealed that this complex crystallizes in the monoclinic system with space group P21/n. The most remarkable structural feature of 1 is that it contains two types of 1D right-handed helical chains. The molecules are linked by intermolecular hydrogen bonds and π⋯π interactions, then a 3D supramolecular network was constructed. Moreover, the intermolecular interactions on the crystal packing of 1 have been further studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Binding interaction of this complex with calf thymus DNA (CT-DNA) has been investigated using absorption and emission studies, viscosity experiments and circular dichroism studies. Complex 1 shows significant binding to the DNA. The results of fluorescence spectroscopy and UV absorption spectroscopy, CD spectroscopy and viscosity indicated that this complex interacted with CT-DNA in a groove binding mode where the binding constant was 1.3 ± 0.2 × 104 L mol-1. Our fluorimeteric study showed that the reaction between 1 and CT-DNA was exothermic (ΔH = 59.6 kJ mol-1; ΔS = 268.79 J mol-1 K-1). Antibacterial activities of the complex were screened by the disc diffusion method against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 23212 and S. epidermidis ATCC 34384), and three Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumonia ATCC 70063). The results indicated that this complex demonstrated acceptable antibacterial activities.

Arene-Ruthenium(II) Complexes with Carbothiamidopyrazoles as a Potential Alternative for Antibiotic Resistance in Human

To meet the demand for alternatives to commonly used antibiotics, this paper evaluates the antimicrobial potential of arene-ruthenium(II) complexes and their salts, which may be of value in antibacterial treatment. Their antimicrobial activity (MIC, MBC/MFC) was examined in vitro against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris and Candida albicans and compared with classic antibiotics used as therapeutics. Selected arene-ruthenium(II) complexes were found to have synergistic effects with oxacillin and vancomycin against staphylococci. Their bactericidal effect was found to be associated with cell lysis and the ability to cut microbial DNA. To confirm the safety of the tested arene-ruthenium(II) complexes in vivo, their cytotoxicity was also investigated against normal human foreskin fibroblasts (HFF-1). In addition, the antioxidant and thus pro-health potential of the compounds, i.e., their nonenzymatic antioxidant capacity (NEAC), was determined by two different methods: ferric-TPTZ complex and DPPH assay.

Evaluation of antitumor potential of Cu(II) complex with hydrazone of 2-acetylthiazole and Girard’s t reagent

In this paper, the previously synthesized Cu(II) complex ([CuL1(N3) (CH3OH)]BF4) with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)- hydrazinyl)ethan-1-aminium chloride, has been characterized and its biological activity has been studied in detail. The Cu(II) complex consists of ligand coordinated in a deprotonated, formally neutral zwitter-ionic form, via NNO atoms, one azido ligand and one methanol molecule. The Cu(II) complex was selected due to results of the cytotoxic activity, the brine shrimp test and DPPH radical scavenging activity, which were previously performed. The effects of Cu(II) complex on cell cycle phase distribution of cervical adenocarcinoma HeLa cells were investigated in order to examine the mechanisms of its anticancer activity. The measurement of intracellular ROS levels in HeLa and HaCaT cell lines were evaluated in order to explore their possible generation and the role in cytotoxic activity. The possible anti-invasive and anti-angiogenic properties of Cu(II) complex were evaluated. DNA binding experiments, including fluorescence displacement study and DNA cleavage experiments, were performed in order to obtain information on the type of DNA-metal complex interactions.

A heterotrinuclear bioinspired coordination complex capable of binding to DNA and emulation of nuclease activity

The investigation of compounds capable of strongly and selectively interacting with DNA comprises a field of research in constant development. In this work, we demonstrate that a trinuclear coordination complex based on a dinuclear Fe(III)Zn(II) core designed for biomimicry of the hydrolytic enzyme kidney bean purple acid phosphatase, containing an additional pendant arm coordinating a Pd(II) ion, has the ability to interact with DNA and to promote its hydrolytic cleavage. These results were found through analysis of plasmid DNA interaction and cleavage by the trinuclear complex 1 and its derivatives 2 and 3, in addition to the analysis of alteration in the DNA structure in the presence of the complexes through circular dichroism and DNA footprinting techniques. The suggested covalent interaction of the palladium-containing complex with DNA was analysed using an electrophoretic mobility assay, circular dichroism, high resolution gel separation techniques and kinetic analysis. This is a new and promising metal complex targeted to nucleic acids and acting in two separate ways: strong DNA interaction and hydrolytic cleavage.

Covalent and noncovalent interactions of coordination compounds with DNA: An overview

Deoxyribonucleic acid plays a central role in crucial cellular processes, and many drugs exert their effects through binding to DNA. Since the discovery of cisplatin and its derivatives considerable attention of researchers has been focused on the development of novel anticancer metal-based drugs. Transition metal complexes, due to their great diversity in size and structure, have a big potential to modify DNA through diverse types of interactions, making them the prominent class of compounds for DNA targeted therapy. In this review we describe various binding modes of metal complexes to duplex DNA based on covalent and noncovalent interactions or combination of both. Specific examples of each binding mode as well as possible cytotoxic effects of metal complexes in tumor cells are presented.

Dual-Emissive Tris-Heteroleptic Ruthenium Complexes: Tuning the DNA-Triggered Ratiometric Emission Response by Ancillary Ligands

Three tris-heteroleptic mononuclear Ru(II) complexes with dual fluorescence and phosphorescence-[Ru(dpma)(bpy)(phen)]²⁺ (1²⁺), [Ru(dpma)(bpy)(dppz)]²⁺ (2²⁺), and [Ru(dpma)(phen)(dppz)]²⁺ (3²⁺)-have been designed and used as ratiometric light-response probes for DNA, where dpma is di(pyrid-2-yl)(methyl)-amine, bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Single crystals of complex 2(PF₆)₂ have been obtained and studied by X-ray analysis. The interactions of these complexes with different DNAs are investigated by means of spectroscopic methods, viscosity measurements, and molecular modeling. In the presence of calf thymus DNA, complexes 2(PF₆)₂ and 3(PF₆)₂ show the emergence of a new lower-energy phosphorescence emission band; meanwhile, the higher-energy fluorescence emission band is essentially unchanged, functioning as an intrinsic internal reference. These two complexes exhibit stronger preference for calf thymus DNA over single-strand DNA (d(A)₁₆ and d(C)₁₆). In contrast, no binding interaction between 1(PF₆)₂ and calf thymus DNA is observed. The intrinsic binding constants (K_b) of 2(PF₆)₂ and 3(PF₆)₂ with calf thymus DNA are determined to be (1.4 ± 0.4) × 10⁵ and (9.5 ± 0.15) × 10⁴ M^-1, respectively. In addition, these spectroscopic results are compared with those of the prototype complex [Ru(bpy)₂(dppz)]²⁺ (4²⁺), and density functional theory and time-dependent density functional theory calculations are employed to elucidate these experimental findings.

A Minimal Load-and-Lock RuII Luminescent DNA Probe

Threading intercalators bind DNA with high affinities. Here, we describe single-molecule studies on a cell-permeant luminescent dinuclear ruthenium(II) complex that has been previously shown to thread only into short, unstable duplex structures. Using optical tweezers and confocal microscopy, we show that this complex threads and locks into force-extended duplex DNA in a two-step mechanism. Detailed kinetic studies reveal that an individual stereoisomer of the complex exhibits the highest binding affinity reported for such a mono-intercalator. This stereoisomer better preserves the biophysical properties of DNA than the widely used SYTOX Orange. Interestingly, threading into torsionally constrained DNA decreases dramatically, but is rescued on negatively supercoiled DNA. Given the "light-switch" properties of this complex on binding DNA, it can be readily used as a long-lived luminescent label for duplex or negatively supercoiled DNA through a unique "load-and-lock" protocol.

Synthesis, characterization and multiple targeting with selectivity: Anticancer property of ternary metal phenanthroline-maltol complexes

The cobalt(II), copper(II) and zinc(II) complexes of 1,10-phenanthroline (phen) and maltol (mal) (complexes 1, 2, 3 respectively) were prepared from their respective metal(II) chlorides and were characterized by FT-IR, elemental analysis, UV spectroscopy, molar conductivity, p-nitrosodimethylaniline assay and mass spectrometry. The X-ray structure of a single crystal of the zinc(II) analogue reveals a square pyramidal structure with distinctly shorter apical chloride bond. All complexes were evaluated for their anticancer property on breast cancer cell lines MCF-7 and MDA-MB-231, and normal cell line MCF-10A, using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and morphological studies. Complex 2 was most potent for 24, 48 and 72 h treatment of cancer cells but it was not selective towards cancer over normal cells. The mechanistic studies of the cobalt(II) complex 1 involved apoptosis assay, cell cycle analysis, dichloro-dihydro-fluorescein diacetate assay, intracellular reactive oxygen species assay and proteasome inhibition assay. Complex 1 induced low apoptosis, generated low level of ROS and did not inhibit proteasome in normal cells. The study of the DNA binding and nucleolytic properties of complexes 1-3 in the absence or presence of H₂O₂ or sodium ascorbate revealed that only complex 1 was not nucleolytic.

Photoinduced DNA Cleavage and Photocytotoxic of Phenanthroline-Based Ligand Ruthenium Compounds

The photophysical and biological properties of two new phenanthroline-based ligand ruthenium complexes were investigated in detail. Their DNA interaction modes were determined to be the intercalation mode using spectra titration and viscosity measurements. Under irradiation, obvious photo-reduced DNA cleavages were observed in the two complexes via singlet oxygen generation. Furthermore, complex 2 showed higher DNA affinity, photocleavage activity, and singlet oxygen quantum yields than complex 1. The two complexes showed no toxicity towards tumor cells (HeLa, A549, and A375) in the dark. However, obvious photocytotoxicities were observed in the two complexes. Complex 2 exhibited large PIs (phototherapeutic indices) (ca. 400) towards HeLa cells. The study suggests that these complexes may act as DNA intercalators, DNA photocleavers, and photocytotoxic agents.

Nanocatalytic Innate Immunity Activation by Mitochondrial DNA Oxidative Damage for Tumor-Specific Therapy

The innate immune system plays a key role in protecting the human body from tumors, which, unfortunately, is largely counteracted by their immune-suppression function. Such an immune suppression has been reported to be induced by the immunosuppressive microenvironment, including the exhausted cytotoxic T lymphocytes (CTLs) and tumor-promoting M2-polarized macrophages. Here, a novel tumor-immunotherapeutic modality based on the nanocatalytic innate immunity activation by tumor-specific mitochondrial DNA (mtDNA) oxidative damage is proposed. In detail, a nanocatalytic medicine, Fe2+ -Ru2+ -loaded mesoporous silica nanoparticle named as MSN-Ru2+ /Fe2+ (MRF), is constructed to induce oxidative damage in the mtDNA of tumor cells. Such an oxidative mtDNA is able to escape from the tumor cells and acts as an immunogenic damage-associated molecular pattern to M1-polarize tumor-associated macrophages (TAMs), resulting in the reactivated immunoresponse of macrophages against cancer cells, and the subsequent inflammatory response of innate immunity. Most importantly, the treatment strategy based on regulating the innate immune response of TAMs not only stops the primary tumor progression, but also almost completely inhibits the growth of distant tumors in the periods of treatments.

Design, Synthesis and Pharmacological Evaluation of Three Novel Dehydroabietyl Piperazine Dithiocarbamate Ruthenium (II) Polypyridyl Complexes as Potential Antitumor Agents: DNA Damage, Cell Cycle Arrest and Apoptosis Induction

The use of cisplatin is severely limited by its toxic side-effects, which has spurred chemists to employ different strategies in the development of new metal-based anticancer agents. Here, three novel dehydroabietyl piperazine dithiocarbamate ruthenium (II) polypyridyl complexes (6a–6c) were synthesized as antitumor agents. Compounds 6a and 6c exhibited better in vitro antiproliferative activity against seven tumor cell lines than cisplatin, they displayed no evident resistance in the cisplatin-resistant cell line A549/DPP. Importantly, 6a effectively inhibited tumor growth in the T-24 xenograft mouse model in comparison with cisplatin. Gel electrophoresis assay indicated that DNA was the potential targets of 6a and 6c, and the upregulation of p-H2AX confirmed this result. Cell cycle arrest studies demonstrated that 6a and 6c arrested the cell cycle at G1 phase, accompanied by the upregulation of the expression levels of the antioncogene p27 and the down-regulation of the expression levels of cyclin E. In addition, 6a and 6c caused the apoptosis of tumor cells along with the upregulation of the expression of Bax, caspase-9, cytochrome c, intracellular Ca²⁺ release, reactive oxygen species (ROS) generation and the downregulation of Bcl-2. These mechanistic study results suggested that 6a and 6c exerted their antitumor activity by inducing DNA damage, and consequently causing G1 stage arrest and the induction of apoptosis.

Combining PARP Inhibition with Platinum, Ruthenium or Gold Complexes for Cancer Therapy

Platinum drugs are heavily used first-line chemotherapeutic agents for many solid tumours and have stimulated substantial interest in the biological activity of DNA-binding metal complexes. These complexes generate DNA lesions which trigger the activation of DNA damage response (DDR) pathways that are essential to maintain genomic integrity. Cancer cells exploit this intrinsic DNA repair network to counteract many types of chemotherapies. Now, advances in the molecular biology of cancer has paved the way for the combination of DDR inhibitors such as poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) and agents that induce high levels of DNA replication stress or single-strand break damage for synergistic cancer cell killing. In this review, we summarise early-stage, preclinical and clinical findings exploring platinum and emerging ruthenium anti-cancer complexes alongside PARPi in combination therapy for cancer and also describe emerging work on the ability of ruthenium and gold complexes to directly inhibit PARP activity.

Mononuclear ruthenium(ii) theranostic complexes that function as broad-spectrum antimicrobials in therapeutically resistant pathogens through interaction with DNA

Six luminescent, mononuclear ruthenium(ii) complexes based on the tetrapyridophenazine (tpphz) and dipyridophenazine (dppz) ligands are reported. The therapeutic activities of the complexes against Gram-negative bacteria (E. coli, A. baumannii, P. aeruginosa) and Gram-positive bacteria (E. faecalis and S. aureus) including pathogenic multi- and pan-drug resistant strains were assessed. Estimated minimum inhibitory and bactericidal concentrations show the activity of the lead compound is comparable to ampicillin and oxacillin in therapeutically sensitive strains and this activity was retained in resistant strains. Unlike related dinuclear analogues the lead compound does not damage bacterial membranes but is still rapidly taken up by both Gram-positive and Gram-negative bacteria in a glucose independent manner. Direct imaging of the complexes through super-resolution nanoscopy and transmission electron microscopy reveals that once internalized the complexes' intracellular target for both Gram-negative and Gram-positive strains is bacterial DNA. Model toxicity screens showed the compound is non-toxic to Galleria mellonella even at exposure concentrations that are orders of magnitude higher than the bacterial MIC.

Antibacterial activity of ruthenium polypyridyl complexes against Staphylococcus aureus and biofilms

There is clearly a need for the development of new classes of antimicrobials to fight against multidrug-resistant bacteria. Here, we designed and synthesized of three ruthenium polypyridyl complexes: [Ru(bpy)₂(BTPIP)](ClO₄)₂ (Ru(II)-1), [Ru(bpy)₂(ETPIP)](ClO₄)₂ (Ru(II)-2) and [Ru(bpy)₂(CAPIP)](ClO₄)₂ (Ru(II)-3) (N-N = bpy = 2,2'-bipyridine), their antimicrobial activities against S. aureus were assessed. The lead complexes of this set, Ru(II)-1(MIC = 0.016 mg/mL), was tested against biofilm. We also investigated whether bacteria can easily develop resistance to Ru(II)-1. The result demonstrated that S. aureus could not easily develop resistance to the ruthenium complexes. In addition, aimed to test whether ruthenium complexes treatment could increase the susceptibility of S. aureus to antibiotics, the synergism between Ru(II)-1 and common antibiotics against S. aureus were investigated using the checkerboard method. Interesting, Ru(II)-1 could increased the susceptibility of S. aureus to some aminoglycoside antibiotics(kanamycin and gentamicin). Finally, in vivo bacterial infection treatment studies were also conducted through murine skin infection model. These results confirmed ruthenium complexes have good antimicrobial activity in vitro and in vivo.

Recent Studies on the Antimicrobial Activity of Transition Metal Complexes of Groups 6–12

Antimicrobial resistance is an increasingly serious threat to global public health that requires innovative solutions to counteract new resistance mechanisms emerging and spreading globally in infectious pathogens. Classic organic antibiotics are rapidly exhausting the structural variations available for an effective antimicrobial drug and new compounds emerging from the industrial pharmaceutical pipeline will likely have a short-term and limited impact before the pathogens can adapt. Inorganic and organometallic complexes offer the opportunity to discover and develop new active antimicrobial agents by exploiting their wide range of three-dimensional geometries and virtually infinite design possibilities that can affect their substitution kinetics, charge, lipophilicity, biological targets and modes of action. This review describes recent studies on the antimicrobial activity of transition metal complexes of groups 6–12. It focuses on the effectiveness of the metal complexes in relation to the rich structural chemical variations of the same. The aim is to provide a short vade mecum for the readers interested in the subject that can complement other reviews.

Platinum(II) Terpyridine Anticancer Complexes Possessing Multiple Mode of DNA Interaction and EGFR Inhibiting Activity

Platinum(II) terpyridine complexes has attracted increasing attention as they have displayed great potential as antitumor agents due to their high intercalation affinity with nucleic acids. Epidermal growth factor receptor (EGFR) is often overexpressed in various tumor cells, leading to uncontrolled growth of tumor, and is regarded as an important target for developing novel antitumor drugs. Herein, we report four platinum(II) terpyridine complexes bearing EGFR inhibiting 4-anilinoquinazoline derivatives as potent multi-targeting antiproliferation agents against a series of cancer cells. EGFR inhibition assay revealed that these complexes are highly potent EGFR inhibitors. But competitive DNA binding assay and docking simulations also suggested that these complexes exhibited multiple modes of DNA interaction, especially great affinity toward DNA minor groove. Finally, cellular uptake and distribution measurements by inductively coupled plasma mass spectrometry (ICP-MS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) demonstrated that both nucleus DNA and membrane proteins are important targets for their anticancer mechanisms. The complexes herein can therefore be regarded as promising multi-targeting anticancer agents.

Binuclear and tetranuclear Zn(ii) complexes with thiosemicarbazones: synthesis, X-ray crystal structures, ATP-sensing, DNA-binding, phosphatase activity and theoretical calculations

Two Zinc(ii) complexes [Zn₄(L¹)₄]·2H₂O (1) and [Zn₂(L²)₂]·2H₂O (2) of pyruvaldehydethiosemicarbazone ligands are reported. The complexes were characterized by elemental analysis, IR, NMR, UV-vis spectroscopy and by single-crystal X-ray crystallography. X-ray crystal structure determinations of the complexes show that though Zn : ligand stoichiometry is 1 : 1 in both the complexes, the molecular unit is tetranuclear for 1 and binuclear for 2. Both the complexes show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium in the presence of other anions like AcO⁻, NO₃⁻, F⁻, Cl⁻, H₂PO₄⁻, HPO₄²⁻ and P₂O₇²⁻. The UV-titration experiments of complexes 1 and 2 with ATP results in binding constants of 2.0(±0.07) × 10⁴ M⁻¹ and 7.1(±0.05) × 10³ M⁻¹ respectively. The calculated detection limits of 6.7 μM and 1.7 μM for 1 and 2 respectively suggest that the complexes are sensitive detectors of ATP. High selectivity of the complexes is confirmed by the addition of ATP in presence of an excess of other anions. DFT studies confirm that the ATP complexes are more favorable than those with the other inorganic phosphate anions, in agreement with the experimental results. Phosphatase like activity of both complexes is investigated spectrophotometrically using 4-nitrophenylphosphate (NPP) as a substrate, indicating the complexes possess significant phosphate ester hydrolytic efficiency. The kinetics for the hydrolysis of the substrate NPP was studied by the initial rate method at 25 °C. Michaelis–Menten derived kinetic parameters indicate that rate of hydrolysis of the P–O bond by complex 1 is much greater than that of complex 2, the k_cat values being 212(±5) and 38(±2) h⁻¹ respectively. The DNA binding studies of the complexes were investigated using electronic absorption spectroscopy and fluorescence quenching. The absorption spectral titrations of the complexes with DNA indicate that the CT-DNA binding affinity (K_b) of complex 1 (2.10(±0.07) × 10⁶ M⁻¹) is slightly greater than that of 2 (1.11(±0.04) × 10⁶ M⁻¹). From fluorescence spectra the apparent binding constant (K_app) values were calculated and they are found to be 5.41(±0.01) × 10⁵ M⁻¹ for 1 and 3.93(±0.02) × 10⁵ M⁻¹ for 2. The molecular dynamics simulation demonstrates that the Zn(ii) complex 1 is a good intercalator of DNA.

A binuclear and a tetranuclear zinc(ii) of pyruvaldehyde thiosemicarbazone show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium. The DNA binding and phosphatase activities of the complexes are also reported.

First dinuclear rhodium(II) complexes with triazolopyrimidines and the prospect of their potential biological use

Five novel rhodium(II) complexes of general formula [Rh₂(μ-OOCCH₃)₄L₂], where L is a triazolopyrimidine derivative, in particular dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) for (1), 5,7-diethyl-1,2,4-triazolo[1,5-a]pyrimidine (detp) for (2), 7-isobutyl-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine (ibmtp) for (3), 7-hydroxy-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine (HmtpO) for (4) and 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) for (5) are reported. These first representatives of paddle-wheel dirhodium complexes with triazolopyrimidines have been characterized by IR and NMR spectroscopy as well as by single-crystal X-ray diffraction studies. Three of the new complexes (1), (2) and (5) were thoroughly screened in vitro for their cytotoxicity against human breast cancer cell line MCF-7 and L929 murine fibroblast cells. Favorably, they show significantly less effective inhibition on the cell growth of L929 than cisplatin under identical conditions. Complexes (1) and (5) display moderate cytotoxic activity (IC₅₀ = 16.3-21.5 μM) against MCF-7 cells which is induced via reactive oxygen species-independent pathways. Extensive studies of rhodium complexes (1), (2) and (5) against microorganisms have shown that the tested compounds exhibit antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) while (5) significantly inhibited the growth of Malassezia furfur. The highest antibacterial, and antifungal activity, was observed for (5).

Making the Right Link to Theranostics: The Photophysical and Biological Properties of Dinuclear RuII-ReI dppz Complexes Depend on Their Tether

The synthesis of new dinuclear complexes containing linked Ru^II(dppz) and Re^I(dppz) moieties is reported. The photophysical and biological properties of the new complex, which incorporates a N,N'-bis(4-pyridylmethyl)-1,6-hexanediamine tether ligand, are compared to a previously reported Ru^II/Re^I complex linked by a simple dipyridyl alkane ligand. Although both complexes bind to DNA with similar affinities, steady-state and time-resolved photophysical studies reveal that the nature of the linker affects the excited state dynamics of the complexes and their DNA photocleavage properties. Quantum-based DFT calculations on these systems offer insights into these effects. While both complexes are live cells permeant, their intracellular localizations are significantly affected by the nature of the linker. Notably, one of the complexes displayed concentration-dependent localization and possesses photophysical properties that are compatible with SIM and STED nanoscopy. This allowed the dynamics of its intracellular localization to be tracked at super resolutions.

Sousa EH, de França Lopes LG, Teixeira EH, Vasconcelos MA, Martins PHR, Medeiros EJT, Batista AA, Holanda AKM. Biphosphinic ruthenium complexes as the promising antimicrobial agents

There is an urgent need for new antimicrobial compounds to combat the growing threat of widespread antibiotic resistance. Ruthenium compounds have shown promising activities including two biphosphinic compounds as described here.

Two ruthenium polypyridyl complexes functionalized with thiophen: synthesis and antibacterial activity against Staphylococcus aureus

Ruthenium polypyridyl complex Ru(ii)-2 could increase the susceptibility of S. aureus to the aminoglycoside antibiotic (kanamycin).

Assessment of cytotoxic and genotoxic potentials of a mononuclear Fe(II) Schiff base complex with photocatalytic activity in Trigonella

BACKGROUND

In recent times, coordination complexes of iron in various oxidation states along with variety of ligand systems have been designed and developed for effective treatment of cancer cells without adversely affecting the normal cell and tissues of various organs.

METHODS

In this study, we have evaluated the mechanism of action of a Fe(II) Schiff base complex in the crop plant Trigonella foenum-graecum L. (Fenugreek) as the screening system by using morphological, cytological, biochemical and molecular approaches. Further functional characterization was performed using MCF-7 cell line and solid tumour model for the assessment of anti-tumour activity of the complex.

RESULTS

Our results indicate efficiency of the Fe(II) Schiff base complex in the induction of double strand breaks in DNA. Complex treatment clearly induced cytotoxic and genotoxic damage in Trigonella seedlings. The Fe-complex treatment caused cell cycle arrest via the activation of ATM-ATR kinase mediated DNA damage response pathway with the compromised expression of CDK1, CDK2 and CyclinB1 protein in Trigonella seedlings. In cultured MCF-7 cells, the complex induces cytotoxicity and DNA fragmentation through intracellular ROS generation. Fe-complex treatment inhibited tumour growth in solid tumour model with no additional side effects.

CONCLUSION

The growth inhibitory and cytotoxic effects of the complex result from activation of DNA damage response along with oxidative stress and cell cycle arrest.

GENERAL SIGNIFICANCE

Overall, our results have provided comprehensive information on the mechanism of action and efficacy of a Fe(II) Schiff base complex in higher eukaryotic genomes and indicated its future implications as potential therapeutic agent.

Systematic investigation of the antiproliferative activity of a series of ruthenium terpyridine complexes

Due to acquired resistance or limitations of the currently approved drugs against cancer, there is an urgent need for the development of new classes of compounds. Among others, there is an increasing attention towards the use of Ru(II) polypyridyl complexes. Most studies in the literature were made on complexes based on the coordination of N-donating bidentate ligands to the ruthenium core whereas studies on 2,2':6', 2″-terpyridine (terpy) coordinating ligands are relatively scare. However, several studies have shown that [Ru(terpy)2]²⁺ derivatives are able bind to DNA through various binding modes making these compounds potentially suitable as chemotherapeutic agents. Additionally, light irradiation of these compounds was shown to enable DNA cleavage, highlighting their potential use as photosensitizers (PSs) for photodynamic therapy (PDT). In this work, we present the systematic investigation of the potential of 7 complexes of the type [Ru(terpy)(terpy-X)]2+ (X = H (1), Cl (2), Br (3), OMe (4), COOH (5), COOMe (6), NMe2 (7)) as potential chemotherapeutic agents and PDT PSs. Importantly, six of the seven complexes were found to be stable in human plasma as well as photostable in acetonitrile upon continuous light irradiation (480 nm). The determination of the distribution coefficient logP values for the 7 complexes revealed their good water solubility. Complex 7 was found to be cytotoxic in the micromolar range in the dark as well as to have some phototoxicity upon light exposure at 480 nm in non-cancerous retinal pigment epithelium (RPE-1) and cancerous human cervical carcinoma (HeLa) cells. SYNOPSIS: The systematic investigation of the potential of 7 complexes of the type [Ru(terpy)(terpy-X)]²⁺ (terpy: 2,2':6', 2″-terpyridine; X = H (1), Cl (2), Br (3), OMe (4), COOH (5), COOMe (6), NMe2 (7)) as potential chemotherapeutic agents and photosensitizers for photodynamic therapy is presented.

Using Nanoscopy To Probe the Biological Activity of Antimicrobial Leads That Display Potent Activity against Pathogenic, Multidrug Resistant, Gram-Negative Bacteria

Medicinal leads that are also compatible with imaging technologies are attractive, as they facilitate the development of therapeutics through direct mechanistic observations at the molecular level. In this context, the uptake and antimicrobial activities of several luminescent dinuclear Ru^II complexes against E. coli were assessed and compared to results obtained for another ESKAPE pathogen, the Gram-positive major opportunistic pathogen Enterococcus faecalis, V583. The most promising lead displays potent activity, particularly against the Gram-negative bacteria, and potency is retained in the uropathogenic multidrug resistant EC958 ST131 strain. Exploiting the inherent luminescent properties of this complex, super-resolution STED nanoscopy was used to image its initial localization at/in cellular membranes and its subsequent transfer to the cell poles. Membrane damage assays confirm that the complex disrupts the bacterial membrane structure before internalization. Mammalian cell culture and animal model studies indicate that the complex is not toxic to eukaryotes, even at concentrations that are several orders of magnitude higher than its minimum inhibitory concentration (MIC). Taken together, these results have identified a lead molecular architecture for hard-to-treat, multiresistant, Gram-negative bacteria, which displays activities that are already comparable to optimized natural product-based leads.

Recent Developments in the Interactions of Classic Intercalated Ruthenium Compounds: [Ru(bpy)₂dppz]2+ and [Ru(phen)₂dppz]2+ with a DNA Molecule

[Ru(bpy)₂dppz]²⁺ and [Ru(phen)₂dppz]²⁺ as the light switches of the deoxyribose nucleic acid (DNA) molecule have attracted much attention and have become a powerful tool for exploring the structure of the DNA helix. Their interactions have been intensively studied because of the excellent photophysical and photochemical properties of ruthenium compounds. In this perspective, this review describes the recent developments in the interactions of these two classic intercalated compounds with a DNA helix. The mechanism of the molecular light switch effect and the selectivity of these two compounds to different forms of a DNA helix has been discussed. In addition, the specific binding modes between them have been discussed in detail, for a better understanding the mechanism of the light switch and the luminescence difference. Finally, recent studies of single molecule force spectroscopy have also been included so as to precisely interpret the kinetics, equilibrium constants, and the energy landscape during the process of the dynamic assembly of ligands into a single DNA helix.