Anti-cancer property and DNA binding interaction of first row transition metal complexes: A decade update

Metal ions carry out a wide variety of functions, including acid-base/redox catalysis, structural functions, signaling, and electron transport. Understanding the interactions of transition metal complexes with biomacromolecules is essential for biology, medicinal chemistry, and the production of synthetic metalloenzymes. After the coincidental discovery of cisplatin, importance of the metal complexes in biochemistry became a top priority for inquiry. In this review, a decade update on various synthetic strategies to first row transition metal complex and their interaction with DNA through non-covalent binding are explored. Moreover, this effort provides an excellent analysis on the efficacy of theoretical and practical approaches to the systematic generation of new non-platinum based metallodrugs for anti-cancer therapeutics.

Studies on synthesis and influence of sterically driven Ni(II)-terpyridine (NNN) complexes on BSA/DNA binding and anticancer activity

The present work demonstrates the synthesis, structural diversity and coordination behavior of some selected new Ni(II)-Tpy complexes. The structural analysis revealed the coordination of the selected terpyridine ligands with the core metal atom in two different modes via dimeric species (1:1 fashion) through the Cl-bridging and a bis(Tpy)-Ni complex (2:1 fashion). Perhaps the most striking manifestations of these Ni(II)-Tpy complexes are BSA/DNA binding ability and anticancer activity. In addition, the cytotoxicity studies of Tpy ligand (4-([2,2':6',2″-terpyridin]-4'-yl)phenyl 5-methylthiophene-2-carboxylate) and the Ni(II) complexes were carried out using lung cancer cell line (A549), breast cancer cell line (MCF-7) and normal cell line (Vero cell). The cytotoxicity results were compared with the cisplatin control group. Notably, bis-terpyridyl complex 3C (R = 4-([2,2':6',2″-terpyridin]-4'-yl)phenyl 4-isopropoxybenzoate) demonstrates better activity with the IC50 value of 23.13 ± 3 μm for A549 and 22.7 ± 3 for MCF-7. The DFT calculations reveal the significant energy differences of HOMO and LUMO for the ligands and their corresponding Ni(II) complexes. The Tpy ligands and Ni(II)-Tpy complexes were investigated for BSA binding and further all the Ni(II) complexes were analyzed for DNA binding studies.

Computational and experimental examinations of new antitumor palladium(II) complex: CT-DNA-/BSA-binding, in-silico prediction, DFT perspective, docking, molecular dynamics simulation and ONIOM

Since the design of metal complexes with better biological activities is important, herein a new palladium(II) complex bearing en and acac (en and acac stand for ethylenediamine and acetylacetonato, respectively) as its ligands, [Pd(en)(acac)]NO3 complex, was synthesized and fully characterized. Quantum chemical computations of the palladium(II) complex were done via DFT/B3LYP method. Cytotoxicity activity of the new compound on leukemia cell line (K562) was assessed via MTT method. The findings indicated that the metal complex has remarkable cytotoxic effect than cisplatin. OSIRIS DataWarrior software was employed to calculate in-silico physicochemical and toxicity parameters of the synthesized complex which rendered significant results. To comprehend the interaction type of new metal compound with macromolecules, the in depth investigation of interaction of mentioned complex with CT-DNA and BSA was accomplished by fluorescence, UV-Visible absorption spectroscopy, viscosity measurement, gel electrophoresis, FRET analysis and circular dichroism (CD) spectroscopy. On the other hand, computational molecular docking was carried out and the obtained data demonstrated that H-bond and van der Waals forces are the dominant forces for the binding of the compound to the mentioned biomolecules. Molecular dynamics simulation was also done and confirmed the stability of best docked pose of palladium(II) complex inside DNA or BSA over the time and in presence of water solvent. Also, Our own N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) methodology based on the hybridization of quantum mechanics and molecular mechanics (QM/MM) methodology was accomplished to inquire about binding of Pd(II) complex with DNA or BSA.HIGHLIGHTSNew biologically active Pd(II) complex was synthesized and characterized.The in silico studies of the designed complex and its ligands were accomplished by OSIRIS DataWarrior softwareInteraction with CT-DNA and BSA was assessed by various spectroscopic methods.Molecular docking simulation supported the interaction with both macromolecules.Based on ONIOM analysis, the structures of the complex and biomolecules are altered after binding. Communicated by Ramaswamy H. Sarma.

The Therapeutic Potential in Cancer of Terpyridine-Based Metal Complexes Featuring Group 11 Elements

Terpyridine-based complexes with group 11 metals emerge as potent metallodrugs in cancer therapy. This comprehensive review focuses on the current landscape of anticancer examples, particularly highlighting the mechanisms of action. While Cu(II) complexes, featuring diverse ancillary ligands, dominate the field, exploration of silver and gold species remains limited. These complexes exhibit significant cytotoxicity against various cancer cell lines with a commendable selectivity for non-tumorigenic cells. DNA interactions, employing intercalation and groove binding, are pivotal and finely tuned through terpyridine ligand functionalization. In addition, copper complexes showcase nuclease activity, triggering apoptosis through ROS generation. Despite silver's high affinity for nitrogen donor atoms, its exploration is relatively sparse, with indications of acting as intercalating agents causing DNA hydrolytic cleavage. Gold(III) compounds, overshadowing gold(I) due to stability concerns, not only intercalate but also induce apoptosis and disrupt the mitochondrial membrane. Further investigations are needed to fully understand the mechanism of action of these compounds, highlighting the necessity of exploring additional biological targets for these promising metallodrugs.

Copper(II) Complexes with 2,2':6',2″-Terpyridine Derivatives Displaying Dimeric Dichloro-μ-Bridged Crystal Structure: Biological Activities from 2D and 3D Tumor Spheroids to In Vivo Models

Eight 2,2':6',2″-terpyridines, substituted at the 4'-position with aromatic groups featuring variations in π-conjugation, ring size, heteroatoms, and methoxy groups, were employed to enhance the antiproliferative potential of [Cu2Cl2(R-terpy)2](PF6)2. Assessing the cytotoxicity in A2780 (ovarian carcinoma), HCT116 (colorectal carcinoma), and HCT116DoxR (colorectal carcinoma resistant to doxorubicin) and normal primary fibroblasts revealed that Cu(II) complexes with 4-quinolinyl, 4-methoxy-1-naphthyl, 2-furanyl, and 2-pyridynyl substituents showed superior therapeutic potential in HCT116DoxR cells with significantly reduced cytotoxicity in normal fibroblasts (42-129× lower). Besides their cytotoxicity, the Cu(II) complexes are able to increase intracellular ROS and interfere with cell cycle progression, leading to cell death by apoptosis and autophagy. Importantly, they demonstrated antimetastatic and antiangiogenic properties without in vivo toxicity. In accordance with their nuclear accumulation, the Cu(II) complexes are able to cleave pDNA and interact with bovine serum albumin, which is a good indication of their ability for internalization and transport toward tumor cells.

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.

Synthesis and anticancer mechanisms of four novel platinum(II) 4'-substituted-2,2':6',2''-terpyridine complexes

Mitophagy, a selective autophagic process, has emerged as a pathway involved in degrading dysfunctional mitochondria. Herein, new platinum(II)-based chemotherapeutics with mitophagy-targeting properties are proposed. Four novel binuclear anticancer Pt(II) complexes with 4'-substituted-2,2':6',2''-terpyridine derivatives (tpy1-tpy4), i.e., [Pt2(tpy1)(DMSO)2Cl4]·CH3OH (tpy1Pt), [Pt(tpy2)Cl][Pt(DMSO)Cl3]·CH3COCH3 (tpy2Pt), [Pt(tpy3)Cl][Pt(DMSO)Cl3] (tpy3Pt), and [Pt(tpy4)Cl]Cl·CH3OH (tpy4Pt), were designed and prepared. Moreover, their potential antitumor mechanism was studied. Tpy1Pt-tpy4Pt exhibited more selective cytotoxicity against cisplatin-resistant SK-OV-3/DDP (SKO3cisR) cancer cells compared with those against ovarian SK-OV-3 (SKO3) cancer cells and normal HL-7702 liver (H702) cells. This selective cytotoxicity of Tpy1Pt-tpy4Pt was better than that of its ligands (i.e., tpy1-tpy4), the clinical drug cisplatin, and cis-Pt(DMSO)2Cl2. The results of various experiments indicated that tpy1Pt and tpy2Pt kill SKO3cisR cancer cells via a mitophagy pathway, which involves the disruption of the mitophagy-related protein expression, dissipation of the mitochondrial membrane potential, elevation of the [Ca2+] and reactive oxygen species levels, promotion of mitochondrial DNA damage, and reduction in the adenosine triphosphate and mitochondrial respiratory chain levels. Furthermore, in vivo experiments indicated that the dinuclear anticancer Pt(II) coordination compound (tpy1Pt) has remarkable therapeutic efficiency (ca. 52.4%) and almost no toxicity. Therefore, the new 4'-substituted-2,2':6',2''-terpyridine Pt(II) coordination compound (tpy1Pt) is a potential candidate for next-generation mitophagy-targeting dinuclear Pt(II)-based anticancer drugs.

Protein interactions, molecular docking, antimicrobial and antifungal studies of terpyridine ligands

Resistance to antibiotics/antibacterials/antifungals in pathogenic microbes has been developing over the past few decades and has recently become a commonplace public-health peril. Thus, alternative nontoxic potent antibiotic agents are covertly needed to control antibiotic-resistant outbreaks. In an effort to combat the challenges posed by the co-occurrence of multidrug resistance, two terpyridine ligands 4'-(4-N,N'-dimethylaminophenyl)-2,2':6',2″-terpyridine (L1) and 4'-(4-tolyl)-2,2':6',2″-terpyridine (L2) have been designed, prepared and confirmed their structure by spectral studies. Thereafter, antimicrobial assay was performed against gram positive and negative bacterial strains along with fungal strains. Both compounds L1 and L2 exhibited remarkable inhibitory activities against bacteria, Escherichia coli and Staphylococcus aureus at MIC values 6.25 and 3.125 µg/ml, respectively. In addition, in silico molecular docking studies were ascertained with bacterial DNA gyrase and fungal demethylase. Furthermore, both L1 and L2 could bind Bovine Serum Albumin (BSA) protein and binding interaction has been studied with the help of UV-Visible and fluorescence spectroscopy. While fluorescence of BSA unperturbed in the presence of L2, an addition of L1 to the solution of BSA resulted significant quenching. The binding constant calculations at different temperature confirmed that the fluorescence quenching between BSA and L1 is predominantly static in nature. The toxicity of L1 and L2 was checked using Drosophila melanogaster. The toxicity analysis suggest both the dyes are non-cytotoxic in nature.Communicated by Ramaswamy H. Sarma.

In vitro anti-proliferative, and in silico ribonucleotide reductase and pharmacokinetics studies of heteroleptic silver(I), nickel(II) and copper(II) complexes of 4-methyl-3-thiosemicarbazones and ibuprofen

OBJECTIVES

The present research focuses on the in vitro anti-proliferative, and in silico ribonucleotide reductase and pharmacokinetics studies of twelve heteroleptic metal complexes of the general formulae [Ag(L^1-4)(ibu)] (1-4) and [M(L^1-4)(ibu)₂] (5-12), where L^1-4 = 2-(1-(4-substitutedphenyl)ethylidene)-N-methylhydrazinecarbothioamide, ibu = non-steroidal anti-inflammatory drug (ibuprofen), and M = Cu(II) and Ni(II).

METHODS

Various spectroscopic techniques were used to authenticate the structure of the synthesized complexes. UV-Vis and cyclic voltammetry techniques were used to analyse the stability and the reducing ability of the complexes. In vitro anti-proliferative studies by MTT assay, apoptotic behaviour and cellular uptake studies were investigated followed by the in silico interaction with ribonucleotide reductase (RNR) enzyme.

RESULTS

The spectral studies predicted distorted tetrahedral geometry around silver(I) ion and distorted octahedral geometry around nickel(II) and copper(II) ions. The reducing ability of the copper(II) complexes was analysed using ascorbic acid by UV-Vis and cyclic voltammetry techniques, which authenticate the reducing ability of the complexes and the possible interactions within the cells. The in vitro anti-proliferative activity of the synthesized complexes against three cancerous (estrogen positive (MCF-7), estrogen negative (MDA-MB-231) and pancreatic (PANC-1)) and one normal (MCF-10a) cell lines by MTT assay showed enhanced activity for copper(II) complexes 11 and 12 containing the hydrophobic substituents. The apoptotic and cellular uptake studies showed that the complex 12 is readily taken up by PANC-1 cell lines and induces ROS-mediated mitochondrial and caspase-dependent apoptosis. The in silico studies indicated hydrogen bonding, hydrophobic and π-pair (π-π, π-σ and π-cation) interactions between the complexes and the ribonucleotide reductase (RNR) enzyme. The in silico pharmacokinetics studies of the complexes predicted the drug-likeness characteristics of the complexes.

CONCLUSION

The synthesized complexes are found to be less toxic to normal cells and inhibit the growth of cancerous cells by inducing mitochondrial-mediated and caspase dependent apoptotic pathway in PANC-1 cells.

Discovery of Novel Dimeric Pyridinium Bromide Analogues Inhibits Cancer Cell Growth by Activating Caspases and Downregulating Bcl-2 Protein

Flexible dimeric substituted pyridinium bromides with primary and tertiary amines are prepared by conventional and solvent-free methods. The formation of compounds 2 and 4 is much easier than that of compounds 1 and 3 because of the benzyl carbon which is more electropositive than the primary alkyl carbon. The newly synthesized dimeric pyridinium compounds are optimized using DFT and B3LYP 6-31 g(d,p). The in vitro antiproliferative activity is studied in lung (A549) and breast cancer cell lines (MDA-MB 231). Among the four compounds, 1,1'-(1,3-phenylene bis(methylene)bis 2-aminopyridinium bromide 4 showed potent anticancer activity when compared to the standard drug 5-fluorouracil. 1,1'-(1,3-Phenylene bis(methylene)bis 2-aminopyridinium bromide 4 is not toxic to normal cell lines 3T3-L1 and MRC-5 cell lines. Also, 1,1'-(1,3-phenylene bis(methylene)bis 2-aminopyridinium bromide 4-induced apoptosis in cancer cell lines is examined using AO/EB and Hoechst staining, which is further supported by cell cycle analysis. Western blot analysis showed that 1,1'-(1,3-phenylene bis(methylene)bis 2-aminopyridinium bromide 4 induces apoptosis through the extrinsic apoptotic pathway by upregulating caspase 3 and caspase 9. This compound also downregulates intrinsic apoptotic proteins, including Bcl-2, Bcl-x, and Bad. From the present study results, it is confirmed that 1,1'-(1,3-phenylene bis(methylene)bis 2-aminopyridinium bromide 4 has potent anticancer activity when compared to other compounds.

Synthesis, characterization and anticancer properties: A series of highly selective palladium(II) substituted-terpyridine complexes

Ten new palladium(II) complexes [PdCl(L^1-10)]Cl have been synthesized by the reaction of palladium(II) chloride and ten 4'-(substituted-phenyl)-2,2':6',2''-terpyridine ligands bearing hydrogen(L¹), p-hydroxyl(L²), m-hydroxyl (L³), o-hydroxyl (L⁴), methyl (L⁵), phenyl (L⁶), fluoro (L⁷), chloro (L⁸), bromo (L⁹), or iodo (L¹⁰). Their structures were confirmed by FT-IR, ¹H NMR, elemental analysis and/or single crystal X-ray diffraction analysis. Their in vitro anticancer activities were investigated based on five cell lines, including four cancer cell lines (A549, Eca-109, Bel-7402, MCF-7) and one normal cell line (HL-7702). The results show that these complexes possess a strong killing effect on the cancer cells but a weak proliferative inhibition on the normal cells, implying their high inhibitory selectivity for the proliferation of the cancer cell lines. Flow cytometry characterization reveals that these complexes affect cell proliferation mainly in the G0/G1 phase and induce the late apoptotic of the cells. The quantity of palladium(II) ion in extracted DNA was determined by ICP-MS, which proved that these complexes target genomic DNA. And the strong affinity of the complexes with CT-DNA were confirmed by UV-Vis spectrum and circular dichroism (CD). The possible binding modes of the complexes with DNA were further explored by molecular docking. As the concentration of complexes 1-10 gradually increases, the fluorescence intensity of bovine serum albumin (BSA) decreases by a static quenching mechanism.

Multi-target activity of copper complexes: Antibacterial, DNA binding, and molecular docking with SARS-CoV-2 receptor

A series of pendant-armed mixed-ligand copper(II) complexes of the type [CuL^1-3(diimine)] (1-6) have been synthesized by the reaction of pendant-armed ligands N,N-bis(2-(((E)-2-hydroxy-5-methylbenzylidene)amino)ethyl)benzamide (H₂L¹), N,N-bis(2-(((E)-2-hydroxy-5-methylbenzylidene)amino)ethyl)-4-nitrobenzamide (H₂L²) and N,N-bis(2-(((E)-2-hydroxy-5-methylbenzylidene)amino)ethyl)-3,5-dinitrobenzamide (H₂L³) with diimine = 2,2'-bipyridyl (bpy) or 1,10-phenanthroline (phen) in the presence of copper(II) chloride and analyzed using various spectroscopic methods. All the spectroscopic results support that the complexes adopt a pentagonal-bipyramidal shape around the copper ion. Gram-positive and Gram-negative bacteria were used to test all the complexes for antibacterial activity and all the complexes had greater potency against gram-negative pathogens. DNA-binding experiments of complexes with calf thymus DNA revealed a major-groove binding pattern, further supported by molecular docking studies. Complexes have significantly interacted with SARS-CoV-2 receptor via π-π, π-σ, π-alkyl, π-anion, π-cation, alkyl, hydrogen bond, van der Waals, and electrostatic interactions. The estimated binding energy and inhibition constant of these complexes are higher than standard drugs, chloroquine, and molnupiravir.

A New Concept of Enhancing the Anticancer Activity of Manganese Terpyridine Complex by Oxygen-Containing Substituent Modification

Eleven manganese 4'-substituted-2,2':6',2″-terpyridine complexes (1a-1c and 2a-2h) with three non-oxygen-containing substituents (L^1a-L^1c: phenyl, naphthalen-2-yl and naphthalen-1-yl, L^1a-L^1c) and eight oxygen-containing substituents (L^2a-L^2h: 4-hydroxyl-phenyl, 3-hydroxyl-phenyl, 2-hydroxyl-phenyl, 4-methoxyl-phenyl, 4-carboxyl-phenyl, 4-(methylsulfonyl)phenyl, 4-nitrophenyl and furan-2-yl) were prepared and characterized by IR, elemental analysis or single crystal X-ray diffraction. In vitro data demonstrate that all of these show higher antiproliferative activities than cisplatin against five human carcinoma cell lines: A549, Bel-7402, Eca-109, HeLa and MCF-7. Compound 2d presents the strongest antiproliferative effect against A549 and HeLa cells, with IC₅₀ values being 0.281 μM and 0.356 μM, respectively. The lowest IC₅₀ values against Bel-7402 (0.523 μM) Eca-109 (0.514 μM) and MCF-7 (0.356 μM) were obtained for compounds 2h, 2g and 2c, respectively. Compound 2g with a nitro group showed the best results on the whole, with relevantly low IC₅₀ values against all the tested tumor cells. The DNA interactions with these compounds were studied by circular dichroism spectroscopic and molecular modeling methods. Spectrophotometric results revealed that the compounds have strong affinities in binding with DNA as intercalators, and the binding induces DNA conformational transition. Molecular docking studies indicate that the binding is contributed by the π-π stacking and hydrogen bonds. The anticancer activities of the compounds are correlated with their DNA binding ability, and the modification of oxygen-containing substituents significantly enhanced the anticancer activity, which could provide a new rationale for the future design of terpyridine-based metal complexes with antitumor potential.

Mononuclear copper(ii) Schiff base complex: synthesis, structure, electrical analysis and protein binding study

A mononuclear copper(ii)-Schiff base complex has been explored for dual applications – complete electrical analysis and BSA protein binding study.

Synthesis of Palladium(II) Complexes via Michael Addition: Antiproliferative Effects through ROS-Mediated Mitochondrial Apoptosis and Docking with SARS-CoV-2

Metal complexes have numerous applications in the current era, particularly in the field of pharmaceutical chemistry and catalysis. A novel synthetic approach for the same is always a beneficial addition to the literature. Henceforth, for the first time, we report the formation of three new Pd(II) complexes through the Michael addition pathway. Three chromone-based thiosemicarbazone ligands (SVSL1-SVSL3) and Pd(II) complexes (1-3) were synthesized and characterized by analytical and spectroscopic tools. The Michael addition pathway for the formation of complexes was confirmed by spectroscopic studies. Distorted square planar structure of complex 2 was confirmed by single-crystal X-ray diffraction. Complexes 1-3 were subjected to DNA- and BSA-binding studies. The complex with cyclohexyl substituent on the terminal N of thiosemicarbazone (3) showed the highest binding efficacy toward these biomolecules, which was further understood through molecular docking studies. The anticancer potential of these complexes was studied preliminarily by using MTT assay in cancer and normal cell lines along with the benchmark drugs (cisplatin, carboplatin, and gemcitabine). It was found that complex 3 was highly toxic toward MDA-MB-231 and AsPC-1 cancer cells with IC50 values of 0.5 and 0.9 μM, respectively, and was more efficient than the standard drugs. The programmed cell death mechanism of the complexes in MDA-MB-231 cancer cells was confirmed. Furthermore, the complexes induced apoptosis via ROS-mediated mitochondrial signaling pathway. Conveniently, all the complexes showed less toxicity (≥50 μM) against MCF-10a normal cell line. Molecular docking studies were performed with VEGFR2, EGFR, and SARS-CoV-2 main protease to illustrate the binding efficiency of the complexes with these receptors. To our surprise, binding potential of the complexes with SARS-CoV-2 main protease was higher than that with chloroquine and hydroxychloroquine.

New derivatives of 4'-phenyl-2,2':6',2″-terpyridine as promising anticancer agents

Terpyridine derivatives are known from their broad application including anticancer properties. In this work we present the newly synthesized 4'-phenyl-2,2':6',2″-terpyridine group with high antiproliferative activity. We suggest that these compounds influence cellular redox homeostasis. Cancer cells are particularly susceptible to any changes in the redox balance because of their handicapped and inefficient antioxidant cellular systems. The antiproliferative activity of the studied compounds was tested on five different cell lines that represent several types of tumours; glioblastoma, leukemia, breast, pancreatic and colon. Additionally, we also tested their selectivity towards normal cells. We performed molecular biology studies in order to detect the response of a cell to its treatment with the compounds that were tested. We looked at the in-depth changes in the proteins and cellular pathways that lead to cell cycle inhibition (G0/G1 and S), and consequently, death on the apoptosis and autophagy pathways. We proved that the studied compounds targeted DNA as well. Special attention was paid to the targets connected with ROS generation.

Evaluation of catacholase mimicking activity and apoptosis in human colorectal carcinoma cell line by activating mitochondrial pathway of copper(II) complex coupled with 2-(quinolin-8-yloxy)(methyl)benzonitrile and 8-hydroxyquinoline

To evaluate the cytotoxic potential of metal-based chemotherapeutic candidate towards the colorectal cancer, we have synthesized a new copper(II) complex [Cu(qmbn)(q)(Cl)] (1) (where, qmbn = 2-(quinolin-8-yloxy)(methyl)benzonitrile and q = 8-hydroxyquinoline) and structurally characterized by single crystal X-ray, Powder-XRD, FTIR and thermogravimetric analysis (TGA). The structural analysis reveals that copper(II) ions exist in a distorted square pyramidal (τ = ~0.1), with ligation of a chloride ion, oxygen atom and two nitrogen atoms at equatorial position and one oxygen atom at apical position. The cytotoxicity potential of complex 1 was executed against human colorectal cell lines (HCT116), which showed that 1 induces mitochondrion-mediated apoptotic cell death via activation of the Bax (pro-apoptotic protein) caspases-3 and 9 proteins. Interestingly, complex 1 was found to be a good candidate as electron-transfer catalyst which mimics catacholase with high turnover frequency (k_cat = 1.03 × 10² h^-1) for the conversion of the model substrate 3,5-di-tertbutylcatechol (3,5-DTBC) to 3,5-di-tertbutylquinone (3,5-DTBQ). Furthermore, molecular docking studies revealed that complex 1 was successfully localized inside the binding pocket of protein kinase (Akt), which validate the mechanism and mode of interaction of 1 that displayed cytotoxic activity experimentally. The obtained outcomes reveal that the complex 1 could be utilized as an encouraging perspective in the development of new therapeutic candidate for colon cancer.

Spectrofluorimetric analysis of the binding of a target molecule to serum albumin: tricky aspects and tips

Protein binding heavily modulates drug activity. Therefore, the binding features need to be elucidated when chemistry researchers study new molecules (metal complexes) to be used as drugs. This paper concerns the experimental and data treatment aspects of the mechanistic analysis of the binding to a fluorescent protein (the golden standard serum albumin) by using direct fluorescence titrations. Fluorescence data are not rarely only qualitatively used, neglecting further treatments which could offer a precious detailed picture of the behavior of the drug. We aim to spread a mechanistic approach, discussing the critical aspects for correctly designing the experiments and treating the data. The researcher may confirm adduct formation and evaluate binding constants (Stern-Volmer K_SV or other types of K). Also, we discuss here, with the help of literature examples, the correct use of temperature dependence of K to extract thermodynamic parameters, comment on enthalpy-entropy compensation, together with the use of synchronous spectra and exchange experiments to gain information on the binding type and site. We think that this tutorial/critical synopsis can be of help for the increasing community dealing with these experiments, which are valuable but often much more tricky than it might appear at first sight.

Study on the substitution effects of zinc benzoate terpyridine complexes on photoluminescence, antiproliferative potential and DNA binding properties

Six zinc(II) complexes, [Zn(OCOPh)₂L^R] (R = 1, 2, 3, 4, 5, 6) were synthesized by the reaction of zinc benzoate and six para-substituted 4-phenyl-terpyridine complexes and their structures were confirmed by elemental analysis, FT-IR, ¹H NMR and X-ray single crystal diffraction analysis. Their photoluminescent properties in solid and in solutions of DMSO were studied. Three human cancer cell lines were used for antiproliferative potential: human lung cancer cell line (A549), human esophageal cancer cell line (Eca-109) and human breast cancer cell line (MCF-7). The results have shown that these zinc complexes have good inhibitory effects on cancer cells, which are better than that of the commonly used clinical drug cisplatin. The ability of the complexes to binding to CT-DNA was studied by UV spectroscopy and fluorescence titration, while the interaction between the complexes and CT-DNA, AT6, GC6 short-chain DNA sequences and G-quadruplex were analyzed by circular dichroism (CD). It is found that these complexes can bind to DNA, and the binding mode is mainly intercalator. The docking of the complexes with the DNA fragment was simulated using molecular docking software. All the results clearly display that the substituents at these ligands of the complexes have the substitution effects on the properties of photoluminescence, antiproliferative potential and DNA binding study.

RK, Pillegowda M, Periyasamy G, Suchetan PA, Butcher RJ, Foro S, Nagaraju G. Synthesis, crystal structures, photophysical, electrochemical studies, DFT and TD-DFT calculations and Hirshfeld analysis of new 2,2′:6′,2′′-terpyridine ligands with pendant 4′-(trimethoxyphenyl) groups and their homoleptic ruthenium complexes

[Ru(L1)₂](PF₆)₂ (1) and [Ru(L2)₂](PF₆)₂ (2): X-ray structures, CH⋯F/O, OH⋯F/N, CH⋯O/π, π⋯π interactions, absorption and emission spectra, DFT/TD-DFT, Hirshfeld analysis.

Studies on the influence of the nuclearity of zinc(ii) hemi-salen complexes on some pivotal biological applications

Experimental and theoretical corroboration of the various biological applications of two nuclearity-dependent dimeric and trimeric Zn(ii) hemi-salen complexes.

Platinum(II) coordination compounds with 4'-pyridyl functionalized 2,2':6',2″-terpyridines as an alternative to enhanced chemotherapy efficacy and reduced side-effects

Two platinum(II) coordination compounds, [PtCl(4'-R¹-terpy)](SO₃CF₃) (1) and [PtCl(4'-R²-terpy)](SO₃CF₃) (2), with 4'-(2-pyridyl)-2,2':6',2″-terpyridine (4'-R¹-terpy) or 4'-(3-pyridyl)-2,2':6',2″-terpyridine (4'-R²-terpy) were synthesized and the impact of the pendant pyridyl ring on the structure and cytotoxic activity of Pt(II)-terpyridine complexes was explored. The single-crystal X-ray diffraction analysis confirmed square planar coordination of the cations [PtCl(4'-Rⁿ-terpy)]⁺. The mode of binding of 1 and 2 to calf thymus DNA was examined by UV-Vis absorption titration, ethidium displacement assay and reaction with 9-ethylguanine, and the mixed covalent-intercalative mode was demonstrated. The cytotoxicity of the Pt(II) complexes against six cancer cell lines and three normal ones was determined using MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and compared to cisplatin. The IC₅₀ values for the compound 2 towards the cancer cell lines are in the low micromolar range. Most remarkably, 2 was over 4 times more effective than 1 and cisplatin against non-small lung adenocarcinoma (A549), and its selectivity index was ~60-80 times higher than that for 1 and cisplatin. The mechanisms underlying the loss of viability under treatment of 2 was further investigated including F-actin staining, mitotic index analysis, cytometric cell cycle analysis, Fluorescein isothiocyanate (FITC) -conjugated Annexin V antibody and propidium iodide (PI) staining, measurements of reactive oxygen species (ROS) in cells, analysis of changes in the mitochondrial mass and potential and quantitative real time polymerase chain reaction (qRT-PCR) genes analysis. The compound 2 was found to have a pro-oxidative effect by strong stimulation of cells for the production of reactive oxygen species and cytostatic effect through cell cycle arrest.

Biocompatibility, in Vitro Antiproliferative, and in Silico EGFR/VEGFR2 Studies of Heteroleptic Metal(II) Complexes of Thiosemicarbazones and Naproxen

Eight heteroleptic nickel(II) and copper(II) complexes of the type [M(L^1-4)(nap)₂] (1-8), where L^1-4 = 2-(1-(4-substitutedphenyl)ethylidene)hydrazinecarbothioamide, nap = naproxen, and M = Ni(II) or Cu(II), have been synthesized and characterized. UV-vis and EPR spectral studies showed distorted octahedral geometry around metal(II) ions. The cyclic voltammogram of complexes 1-8 displayed an irreversible one-electron transfer process in the cathodic region (E_pc = -0.66 to -1.43 V), and nickel(II) complexes 1-4 displayed an irreversible one-electron oxidation process in the anodic region (E_pa = 0.75 to 1.10 V). The obtained magnetic moment values (1.82-1.93 μ_B) for copper(II) complexes 5-8 indicate distortion from octahedral geometry, which is further supported by EPR studies. The geometry of the complexes is retained in both solid and solution phases as evidenced from UV-vis and EPR studies. All the complexes showed stability for almost 72 h in biologically relevant solutions. The reducing ability of the copper(II) complexes in the presence of ascorbic acid was analyzed by UV-vis and cyclic voltammetry techniques, which indicates the reduction of the copper(II) to a copper(I) center, and possible interaction within the cells. An in vitro antiproliferative study revealed the nontoxic nature of complexes to normal human dermal fibroblast (NHDF) up to a concentration of 100 ng/mL. The antiproliferative activity of the complexes was tested against three cancerous (human breast adenocarcinoma (MCF-7), hepatoma (HepG2), and lung (A549)) cell lines using MTT reduction assay, which showed enhanced activity for complexes 4 and 8 containing the hydrophobic substituent. Apoptotic and cellular uptake studies showed that complex 8 is readily taken up by HepG2 cell lines and induces ROS-mediated mitochondrial and caspase-dependent apoptosis. In silico studies indicated hydrogen bonding, hydrophobic, and π-pair (π-π, π-σ, and π-cation) interactions between the complexes and EGFR/VEGFR2 kinase receptors.

DNA profiling and in vitro cytotoxicity studies of tetrazolo[1,5-a]pyrimidine-based copper(II) complexes

A series of N-benzoylated mononuclear copper(II) complexes of the type [Cu(L^1-6)Cl₂] (1-6), where L¹= ethyl 4-benzoyl-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L²= ethyl 4-(4-nitrobenzoyl)-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L³ = ethyl 4-benzoyl-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁴ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁵ = ethyl 4-benzoyl-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate and L⁶ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate have been synthesized and characterized by spectral methods. Electron paramagnetic resonance spectra of complexes show four lines, characteristic of square planar geometry. The binding studies of the complexes with calf thymus DNA (CT-DNA) revealed groove mode of binding, which were further supported by molecular docking studies. Gel electrophoresis experiments demonstrated the ability of the complexes to cleave plasmid DNA in the absence of activators. Further, the cytotoxicity activity of the complexes were examined on three cancerous cell lines (lung (A549), cervical (HeLa) and colon (HCT-15)), and on two normal cells (human embryonic kidney (HEK) and peripheral blood mononuclear cells (PBMC)) by MTT assay.

Evolution of 1, 3, 5-trisubstituted bipyrazole scaffold based platinum(II) complexes as a biological active agent

Square planar mononuclear platinum(II) complexes having general formula [Pt(Lⁿ)Cl₂], (where, Lⁿ = L^1-4) were synthesized with neutral bidentate heterocyclic 1,3,5-trisubstituted bipyrazole based ligands. The synthesized compounds were characterized by physicochemical method such as TGA, molar conductance, micro-elemental analysis and magnetic moment, and spectroscopic method such as, FT-IR, UV-vis, ¹H NMR, ¹³C NMR and mass spectrometry. Biological applications of the compounds were carried out using in vitro brine shrimp lethality bioassay, in vitro antimicrobial study against five different pathogens, and cellular level cytotoxicity against Schizosaccharomyces pombe (S. Pombe) cells. Pt(II) complexes were tested for DNA interaction activities using electronic absorption titration, viscosity measurements study, fluorescence quenching technique and molecular docking assay. Binding constants (K_b) of ligands and complexes were observed in the range of 0.23-1.07 × 10⁵ M^-1 and 0.51-3.13 × 10⁵ M^-1, respectively. Pt(II) complexes (I-IV) display an excellent binding tendency to biomolecule (DNA) and possess comparatively high binding constant (K_b) values than the ligands. The DNA binding study indicate partial intercalative mode of binding in complex-DNA. The gel electrophoresis activity was carried out to examine DNA nuclease property of pUC19 plasmid DNA.

A Perspective - can copper complexes be developed as a novel class of therapeutics?

Although copper-ligand complexes appear to be promising as a new class of therapeutics, other than the family of copper(ii) coordination compounds referred to as casiopeínas these compounds have yet to reach the clinic for human use. The pharmaceutical challenges associated with developing copper-based therapeutics will be presented in this article along with a discussion of the potential for high-throughput chemistry, computer-aided drug design, and nanotechnology to address the development of this important class of drug candidates.

Spectroscopic, Computational, Antimicrobial, DNA Interaction, In Vitro Anticancer and Molecular Docking Properties of Biochemically Active Cu(II) and Zn(II) Complexes of Pyrimidine-Ligand

Biochemically active Cu(II) and Zn(II) complexes [CuL(ClO₄)₂(1) and ZnL(ClO₄)₂(2)] have been synthesized from N,N donor Schiff base ligand L derived from4,6-dichloropyrimdine-5-carboxaldehyde with 4-(2-aminoethyl)morpholine. The L, complexes 1 and 2 have been structurally characterized by elemental analysis, ¹H-NMR, FTIR, MS, UV-Visible and ESR techniques. The results obtained from the spectral studies supports the complexes 1 and 2 are coordinated with L through square planar geometry. DFT calculations results supports, the ligand to metal charge transfer mechanism can occur between L and metal(II) ions. The antimicrobial efficacy results have been recommended that, complexes 1 and 2 are good anti-pathogenic agents than ligand L. The interaction of complexes 1 and 2 with calf thymus (CT) DNA has been studied by electronic absorption, viscometric, fluorometric and cyclic voltammetric measurements. The calculated K_b values for L, complexes 1 and 2 found from absorption titrations was 4.45 × 10⁴, L; 1.92 × 10⁵, 1 and 1.65 × 10⁵, 2. The Ksv values were found to be 3.0 × 10³, 3.68 × 10³and 3.52 × 10³ for L, complexes 1 and 2 by using competitive binding with ethidium bromide (EB). These results suggest that, the compounds are interacted with DNA may be electrostatic binding. The molecular docking studies have been carried out to confirm the interaction of compounds with DNA. Consequently, in vitro anticancer activities of L, complexes 1 and 2 against selected cancer (lung cancer A549, liver cancer HepG2 and cervical carcinoma HeLa) and normal (NHDF) cell lines were assessed by MTT assay.

A new Schiff-base chemosensor for selective detection of Cu2+ and Co2+ and its copper complex for colorimetric sensing of S2- in aqueous solution

A new Schiff-base colorimetric chemosensor 1 was developed for the detection of Cu²⁺, Co²⁺ and S^2-. Sensor 1 could simply monitor Cu²⁺ and Co²⁺ by a color change from colorless to yellow. The binding modes of 1 to Cu²⁺ and Co²⁺ were determined to be a 2 : 1 complexation stoichiometry through Job's plot and ESI-mass spectrometry analysis. The detection limits (0.02 μM and 0.63 μM) for Cu²⁺ and Co²⁺ were lower than the recommended values (31.5 μM and 1.7 μM) by the World Health Organization (WHO) for Cu²⁺ and the Environmental Protection Agency (EPA) for Co²⁺, respectively. Importantly, 1 could detect and quantify Cu²⁺ in real water samples. In addition, the Cu²⁺-2·1 complex could be used as a highly selective colorimetric sensor for S^2- in the presence of other anions without any interference. Moreover, the sensing mechanisms of Cu²⁺ and Co²⁺ by 1 were explained by theoretical calculations.

Copper complexes as prospective anticancer agents: in vitro and in vivo evaluation, selective targeting of cancer cells by DNA damage and S phase arrest

A series of six new bis(thiosemicarbazone)copper(i) complexes of the type [Cu(L^1–6)₂Cl] (1–6) have been synthesized and characterized. The molecular structure of the ligand L⁴ was determined by the single crystal XRD method. All the complexes adopted trigonal planar (Y-shaped) geometry. All the complexes strongly bind with CT-DNA via intercalative mode, which was further supported by molecular docking studies. Further, the complexes were effectively bind with BSA as observed by UV-Vis and fluorescence spectra. All the complexes effectively cleave pBR322 DNA through hydrolytic pathway as evidenced from T4 ligase experiments. All the complexes interact with the anticancer receptor focal adhesion kinase (FAK) via electrostatic, van der Waals, hydrogen bonding, σ–π and π–π interactions. In vitro cytotoxicity of the complexes were assessed by MTT assay against four cancer cell lines such as human breast adenocarcinoma (MCF-7), cervical (HeLa), epithelioma (Hep-2) and Ehrlich ascites carcinoma (EAC), and two normal cell lines namely normal human dermal fibroblasts (NHDF) and L6 myotubes with respect to the commercially used anticancer drug cisplatin. All the complexes induce apoptosis in EAC cells, which was confirmed by AO/EB, Hoechst 33258 and PI staining methods. The complexes block cell cycle progression of EAC cells in S phase (DNA synthesis). The cellular uptake studies confirmed the ability of the complexes to go into the cytoplasm and accumulation in the cell nuclei. In the in vivo anticancer studies, the complexes significantly reduce the tumour volume in female Swiss albino mice. Overall, our results ensure the role of thiosemicarbazone-based copper(i) complexes as prospective anticancer agents, induction of apoptosis and S phase arrest with the mitochondrial controlled pathway.

The thiosemicarbazone-based copper(i) complexes causing S phase arrest and apoptosis involving the mitochondrial controlled pathway has been investigated.