DNA-binding and photocleavage, cytotoxicity, apoptosis and antioxidant activity studies of ruthenium(II) complexes

Two ruthenium(II) polypyridyl complexes, namely [Ru(phen)₂(DMDPPZ)](ClO₄)₂ 1 (phen = 1,10-phenanthroline, DMDPPZ = 3,6-dimethyldipyrido[3,2-a:2′,3′-c]phenazine) and [Ru(dmp)₂(DMDPPZ)](ClO₄)₂ 2 (dmp = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and characterized. The DNA-binding properties of the complexes were investigated by spectrophotometric methods, viscosity measurements, and photoactivated cleavage studies. The DNA-binding constants for complexes 1 and 2 have been determined as 8.78 (±0.94) × 10⁵ M⁻¹ (s = 3.02) and 1.26 (±0.35) × 10⁵ M⁻¹ (s = 1.69), respectively. The results suggest that these complexes bind to calf thymus DNA through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than complex 2 under comparable experimental conditions. The cytotoxicities of complexes 1 and 2 have been evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) method. Complex 2 shows higher anticancer potency than complex 1 against four tumor cell lines. The apoptosis-inducing activity was assessed by acridine orange/ethidium bromide staining assay, and the antioxidant activities of these complexes against hydroxyl radical were also explored.     

Ruthenium(II) complexes containing 2,9-dimethyl-1,10-phenanthroline and 4,4′-dimethyl-2,2′-bipyridine as ancillary ligands: synthesis,characterization and DNA-binding

Two new Ruthenium (II) polypyridyl complexes [Ru(dmp)₂(ipbp)](ClO₄)₂ (1) (dmp = 2,9-dimethyl-1,10-phenanthroline, ipbp = 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-4H-1-banzopyran-2-one) and [Ru(dmb)₂(ipbp)](ClO₄)₂ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and ¹H NMR and cyclic voltammetric methods. The DNA-binding behaviors of these complexes were investigated by spectroscopic titration, viscosity measurements, and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf thymus DNA (CT-DNA). Viscosity measurements show that the complexes 1 and 2 interact with CT-DNA by intercalative mode. The DNA-binding affinity of the complex 2 is larger than that of complex 1.     

Experimental and DFT Studies on the DNA-binding Properties of Ruthenium(II) Complexes [Ru(phen)2L]2+(L = o-MOP, o-MP, o-CP and o-NP)

A series of ruthenium(II) complexes with electron-donor or electron-acceptor groups in intercalative ligands, [Ru(phen)₂(o-MOP)]²⁺ (1), [Ru(phen)₂(o-MP)]²⁺ (2), [Ru(phen)₂(o-CP)]²⁺ (3) and [Ru(phen)₂(o-NP)]²⁺ (4), have been synthesized and characterized by elementary analysis, ES-MS, ¹H NMR, electronic absorption and emission spectra. The binding properties of these complexes to CT-DNA have been investigated by spectroscopy and viscosity experiments. The results showed that these complexes bind to DNA in intercalation mode and their intrinsic binding constants (K_b) are 1.1, 0.35, 0.53 and 1.7 × 10⁵ M⁻¹, respectively. The subtle but detectable differences occurred in the DNA-binding properties of these complexes are mainly ascribed to the electron-withdrawing abilities of substituents (–OCH₃ < –CH₃ < –Cl < –NO₂) on the intercalative ligands as well as the intramolecular H-bond (for substituent –OCH₃) which increase the planarity area of the intercalative ligand to some extent. The density functional theory (DFT) calculations were also performed and used to further discuss the trend in the DNA-binding affinities of these complexes.     

DNA-binding,antioxidant activity and in vitro cytotoxicity induced by ruthenium(II) complexes containing polypyridyl ligands

Two new ruthenium(II) polypyridyl complexes, [Ru(dmp)₂(maip)](ClO₄)₂ 1 (maip = 2-(3-aminophenyl)imizado[4,5-f][1,10]phenanthroline and [Ru(dmp)₂(paip)](ClO₄)₂ 2 (paip = 2-(4-aminophenyl)imidazo[4,5-f][1,10]phenanthroline, dmp = 2, 9-dimethyl-1,10-phenanthroline) have been synthesized and characterized. The DNA-binding behaviors of complexes 1 and 2 were studied by viscosity measurements, thermal denaturation, and absorption titration. The results show that the two complexes intercalate between the base pairs of DNA. The DNA-binding constants K _b for complexes 1 and 2 were determined to be 3.23 ± 0.16 × 10⁴ M⁻¹ (s = 0.97) and 4.34 ± 0.65 × 10⁴ M⁻¹ (s = 1.13). The cytotoxicity of these complexes has been evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The IC₅₀ values are 35.70, 41.04, 55.25 and 37.50 for complex 1 and 37.02, 103.08, 130.07 and 37.80 for complex 2 against BEL-7402, C-6, HepG-2 and MCF-7 cell lines, respectively. The antioxidant activity against hydroxyl radical (OH•) was also investigated.     

Investigation of DNA/BSA binding of three Ru(II) complexes by various spectroscopic methods,molecular docking and their antimicrobial activity

An intercalative ligand, ppip (ppip = {2-(4-(piperidin-1-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline}), and its mononuclear Ru(II) polypyridyl complexes, [Ru(phen)₂(ppip)]²⁺ (1) (phen=1,10-phenanthrolene), [Ru(bpy)₂(ppip)]²⁺ (2) (bpy=2,2′-bipyridine) and [Ru(dmb)₂(ppip)]²⁺ (3) (dmb=4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized by elemental analysis and spectroscopic techniques such as UV–vis, IR, ¹H, as well as ¹³C NMR and ESI-MS. The interaction of these complexes with DNA/BSA (bovine serum albumin) was investigated using absorption, emission spectroscopy, viscosity measurements and molecular docking studies. The docking study infers that the binding strength (K_b) of these complexes was in agreement with results from absorption and emission techniques. These studies reveal that these three Ru(II) polypyridyl complexes bind to DNA/BSA. The binding ability of these complexes in the presence of different ions and solvents were also reported. All complexes were effectively cleaving pBR322 DNA in different forms and follows order which is similar to absorption and emission studies. These complexes were effective exhibiting the antimicrobial activity against different microbes Bacillus subtilis, Escherichia coli and Staphylococcus aureus.     

DNA interactions of ruthenium(II) complexes with a polypyridyl ligand: 2-(2, 5-dimethoxyphenyl)-1<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">f</Emphasis>]1,10-phenanthroline

This article describes the synthesis of a polypyridyl ligand, namely 2-(2, 5-dimethoxyphenyl)-1H-imidazo[4,5-f]1,10-phenanthroline (DMPIP) and its Ru(II) complexes, namely [Ru(bipy)₂DMPIP]²⁺ (1), [Ru(dmb)₂DMPIP]²⁺ (2) and [Ru(phen)₂DMPIP]²⁺ (3) ((bipy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine, phen = 1,10-phenanthroline). The complexes were characterized by elemental analysis, plus IR, ¹H-NMR and ¹³C [¹H]-NMR spectra. The interactions of the complexes with calf thymus DNA were investigated. The results indicate that the three complexes can intercalate into DNA. Under irradiation at 365 nm, all three complexes promote the photocleavage of plasmid pBR 322 DNA. Inhibitor studies suggest that singlet oxygen plays a significant role in the cleavage mechanism for the complexes.     

Effects of substituent on the DNA-binding of ruthenium(II) complexes containing asymmetric tridentate intercalative ligands

Three novel unsymmetric tridentate ligands, namely, ptmi (ptmi = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-methoxyisatin), pti (pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin), ptni (ptni = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-nitroisatin), and their complexes [Ru(tpy)(ptmi)](ClO₄)₂ (tpy = 2,2′:6′,2″-terpyridine) (1), [Ru(tpy)(pti)](ClO₄)₂ (2), and [Ru(tpy)(ptni)](ClO₄)₂ (3) were prepared and characterized by elemental analysis, ¹H NMR, ES–MS. The electrochemical behaviors were studied by cyclic voltammetry. The DNA-binding properties of these complexes were investigated by the spectroscopic method, viscosity measurements, and thermal denaturation. Theoretical studies on these complexes were also performed with the density functional theory (DFT) method. The experimental results showed that these complexes bind to calf thymus (CT-DNA) in an intercalative mode. The order of DNA-binding affinities (A) of these complexes is A(1) < A(2) < A(3). The trend in the DNA-binding affinities of this series of complexes can be reasonably explained by the DFT calculations.     

Synthesis, DNA-binding and photocleavage studies of [Ru(phen)2(pbtp)] and [Ru(bpy)2(pbtp)] (phen = 1,10-phenanthroline; bpy = 2,2′-bipyridine; pbtp = 4,5,9,11,14-pentaaza-benzo[b]triphenylene)

Based on the ligand dppz (dppz = dipyrido-[3,2-a:2′,3′-c]phenazine), a new ligand pbtp (pbtp = 4,5,9,11,14-pentaaza-benzo[b]triphenylene) and its polypyridyl ruthenium(II) complexes [Ru(phen)₂(pbtp)]²⁺ (1) (phen = 1,10-phenanthroline and [Ru(bpy)₂(pbtp)]²⁺ (2) (bpy = 2,2′-bipyridine) have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR spectroscopy. The DNA-binding of these complexes were investigated by spectroscopic methods and viscosity measurements. The experimental results indicate that both complexes 1 and 2 bind to CT-DNA in classical intercalation mode, and can enantioselectively interact with CT-DNA. It is interesting to note that the pbtp ruthenium(II) complexes, in contrast to the analogous dppz complexes, do not show fluorescent behavior when intercalated into DNA. When irradiated at 365 nm, both complexes promote the photocleavage of pBR 322 DNA.     

Review: Synthesis,characterization, and DNA-binding properties of Ru(II) molecular “light switch” complexes

This article presents recent progress in our laboratory on the interactions of Ru(II) polypyridyl complexes with calf thymus DNA (CT-DNA). Mixed polypyridyl Ru(II) complexes [Ru(L)₄(AIP)]²⁺ and [Ru(L)₄PyIP]²⁺, where L is 4-amino pyridine and pyridine (AIP?=?2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline; PyIP?=?2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), have been synthesized and characterized by elemental analysis, and physicochemical methods such as ESI-MS, UV-Vis, IR, and NMR spectroscopic techniques. Electronic absorption titrations, fluorescence spectroscopy, viscosity measurements, and salt-dependent studies of CT-DNA in the presence of incremental amounts of all four Ru(II) complexes clearly demonstrate that all four complexes bind to DNA by intercalation. The DNA-binding affinities of these complexes follow the order [Ru(4-APy)₄(PyIP)]^2+?>?[Ru(Py)₄PyIP]^2+?>?[Ru(4-APy)₄(AIP)]^2+?>?[Ru(Py)₄AIP]²⁺. Irradiation of pBR 322 DNA with these complexes results in nicking of the plasmid DNA. All four complexes were screened for antimicrobial activity. All complexes also exhibited DNA “light switch” properties. These results suggest that both ancillary ligand and intercalative ligand influence the binding of these complexes to DNA.     

Synthesis,DNA interaction and photocleavage studies of ruthenium(II) complexes with 2-(pyrrole) imidazo[4,5-f]-1,10-phenanthroline as an intercalative ligand

Three Ru(II) complexes, namely [Ru(bipy)₂PRIP]²⁺ (1), [Ru(dmb)₂PRIP]²⁺ (2), and [Ru(phen)₂PRIP]²⁺ (3) (dmb = 4,4′-dimethyl-2,2′-bipyridine; PRIP = 2-(pyrrole) imidazo [4,5-f]-1,10-phenanthroline) have been synthesized and characterized by elemental analysis, mass spectra, IR, ¹H NMR and ¹³C NMR. The DNA-binding properties of the three complexes with calf-thymus DNA (CT-DNA) were investigated by spectrophotometry, fluorescence methods and viscosity measurements. The results suggest that all three complexes bind to CT-DNA through intercalation. Also, when irradiated at 365 nm, the three complexes promote the photocleavage of plasmid pBR-322 DNA. Under comparable experimental conditions, complex 3 cleaves DNA more effectively than complexes 1 and 2.     

Cellular uptake, cytotoxicity, apoptosis, antioxidant activity and DNA binding of polypyridyl ruthenium(II) complexes

Ruthenium(II) polypyridyl complexes [Ru(phen)₂(APIP)](ClO₄)₂1 and [Ru(phen)₂(HAPIP)](ClO₄)₂2 have been synthesized and characterized. The DNA-binding behaviors were investigated by electronic absorption titration, luminescence spectra, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants K_b for complexes 1 and 2 were determined to be 3.38 (±0.42) × 10⁵ M⁻¹ (s = 1.48) and 3.93 (±0.60) × 10⁵ M⁻¹ (s = 3.14), respectively. The studies on the photocleavage demonstrated that the effects of cleavage are concentration-dependent. The results showed that complexes 1 and 2 interact with CT-DNA by intercalative mode. The cytotoxicity of complexes 1 and 2 has been evaluated by MTT method. The apoptosis assay was carried out with acridine orange/ethidium bromide (AO/EB) staining methods. The cellular uptake showed that complexes can enter into the cytoplasm and accumulate in the nuclei. The antioxidant activity studies suggested that the ligands and complexes may be potential drugs to eliminate the radical.     

Study of the interaction between ruthenium(II) complexes and CT-DNA: synthesis,characterisation, photocleavage and antimicrobial activity studies

Two polypyridyl ligands 6-fluro-3-(1H-imidazo [4,5-f] [1,10]-phenanthroline-2-yl)-4H-chromen-4-one (FIPC), 6-chloro-3-(1H-imidazo [4,5-f] [1,10]-phenanthroline-2-yl)-4H-chromen-4-one (ClIPC) polypyridyl ligands and their Ru(II) complexes [Ru(bipy)₂FIPC]²⁺(1), [Ru(dmb)₂FIPC]²⁺(2), [Ru(phen)₂FIPC]²⁺(3), [Ru(bipy)₂ClIPC]²⁺(4), [Ru(dmb)₂ClIPC]²⁺(5) and [Ru(phen)₂ClIPC]²⁺(6) ((bipy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesised and characterised by elemental analysis, Mass spectra, IR, ¹H and ¹³C-NMR. The DNA-binding of the six complexes to calf-thymus DNA (CT-DNA) has been investigated by different spectrophotometric, fluorescence and viscosity measurements. The results suggest that 1–6 complexes bind to CT-DNA through intercalation. The variation in binding affinities of these complexes is rationalised by a consideration of electrostatic, steric factors and nature of ancillary ligands. Under irradiation at 365 nm, the three complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA. Inhibitor studies suggest that singlet oxygen (¹O₂) plays a significant role in the cleavage mechanism of Ru(II) complexes. Thereby, under comparable experimental conditions [Ru(phen)₂FIPC]²⁺(3), [Ru(phen)₂ClIPC]²⁺(6) cleaves DNA more effectively than 1, 2, 4 and 5 complexes do. The Ru(II) polypyridyl complexes (1–6) have been screened for antimicrobial activities.     

Cytotoxicity, cellular uptake, cell cycle arrest, apoptosis, reactive oxygen species and DNA-binding studies of ruthenium(II) complexes

Three ruthenium(II) polypyridyl complexes [Ru(dmb)₂(dadppz)]²⁺ 1, [Ru(bpy)₂(dadppz)]²⁺ 2 and [Ru(phen)₂(dadppz)]²⁺ 3 were synthesized and characterized by elemental analysis, ES-MS, ¹H NMR and ¹³C NMR. Their DNA-binding behaviors were investigated by absorption titration, fluorescence spectroscopy and viscosity measurements. Cytotoxicity in vitro, apoptosis, cell cycle arrest, cellular uptake and reactive oxygen species assays were performed. The complexes were found to show moderate DNA-binding affinities and high cytotoxicities toward A549, BEL-7402, MG-63 and SKBR-3 cell lines. These complexes can effectively induce apoptosis of BEL-7402. In cell cycle assays, the complexes induced S-phase arrest on BEL-7402 cells and G0/G1-phase arrest on SKBR-3 cells. The DNA-binding experiments showed that the three complexes interact with CT-DNA through an intercalative mode.     

Synthesis,structure, DNA-binding properties,and antioxidant activity of copper(II) and cobalt(II) complexes with bis(<Emphasis Type="Italic">N</Emphasis>-allylbenzimidazol-2-ylmethyl)benzylamine

Bis(N-allylbenzimidazol-2-ylmethyl)benzylamine (babb) and two of its complexes, [Cu(babb)(pic)₂]·H₂O (1) and [Co(babb)₂](pic)₂ (2) (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have similar distorted octahedral structures, but the degree of distortion and the coordinated atoms are different. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that all three compounds bind to DNA via an intercalative binding mode, and their binding affinity for DNA follows the order 2 > 1 > ligand. Additionally, both complexes exhibited potential antioxidant properties in in vitro studies, and complex 1 was the more effective.     

Cytotoxic and DNA-binding properties of two ruthenium(II) porphyrin complexes

Two ruthenium(II) porphyrin complexes [Ru(L)₂Cl(PTP)]⁺ (L = bpy, 1, phen; 2; PTP = 5-(3′-pyridyl)-10,15,20-trimethylphenylporphyrin) have been synthesized and their antitumor activities have been evaluated by MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) methods. Both complexes exhibit high inhibitory activity against the growth of human cervical carcinoma cell line HeLa, both with and without light treatment. However, when treated with light, the inhibitory activity for both complexes increases at low drug concentration. Spectroscopic studies show that both complexes can bind to HeLa DNA tightly with apparent binding constants of 1.54(±0.07) × 10⁵ and 1.01(±0.02) × 10⁵ M⁻¹ for 1 and 2, respectively.     

Synthesis,photophysical, electrochemical,and ion-binding properties of Ru(II) polypyridyl complexes containing benzo-15-crown-5

Two polypyridyl ligands, 5-(4′-ethynylbenzo-15-crown-5)-2,2′-bipyridine (L¹) and 3-bromo-8-(4′-ethynylbenzo-15-crown-5)-1,10-phenanthroline (L²), and their Ru(II) complexes [(bpy)₂RuL](PF₆)₂ have been prepared and characterized. Both complexes exhibit metal-to-ligand charge transfer absorption at around 452 nm and emission at around 640 nm in MeCN solution. Electrochemical studies of the complexes reveal a Ru(II)-centered oxidation at around 1.31 V and three ligand-centered reductions. The binding ability of the complexes with Na⁺ has been investigated by UV/Vis absorption, emission, and electrochemical titrations. Addition of Na⁺ to MeCN solutions of both complexes results in a progressive enhancement of the emission, a red-shift of the UV/Vis absorption, and a progressive cathodic shift of the Ru(II)-centered E _1/2 couple. The stability constants for the 1:1 stoichiometry adducts of the complexes with Na⁺ have been obtained from the UV/Vis absorption titrations.     

Synthesis,characterization and DNA binding studies of ruthenium(II) complexes: [Ru(bpy)<Subscript>2</Subscript>(dtmi)]<Superscript>2+</Superscript> and [Ru(bpy)<Subscript>2</Subscript>(dtni)]<Superscript>2+</Superscript>

Two new ruthenium(II) polypyridyl complexes (1) (dtmi = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin) and (2) (dtni = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and ¹H-n.m.r. The DNA-binding patterns of complexes were investigated by spectroscopic titration, viscosity measurements and thermal denaturation. The results indicate that the complexes (1) and (2) interact with calf thymus DNA (CT-DNA) by intercalative mode. Due to the withdrawing electronic substitutent in the intercalative ligand, ptni, the DNA-binding affinity of the complexes (2) is larger than that complex (1) does.     

Synthesis, characterization and DNA-binding studies of ruthenium(II) mixed-ligand complexes containing dipyrido[1,2,5]oxadiazolo[3,4-b]quinoxaline

A novel ligand dipyrido[1,2,5]oxadiazolo[3,4-b]quinoxaline (dpoq) and its complexes [Ru(bpy)₂(dpoq)]²⁺ and [Ru(phen)₂(dpoq)]²⁺ (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline) have been synthesized and characterized by elemental analysis, electrospray mass spectra and ¹H NMR. The interaction of Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by absorption spectroscopy, fluorescence spectroscopy, thermal denaturation and viscosity measurements. Results suggest that two Ru(II) complexes bind to DNA via an intercalative mode.     

带有位阻基团的钌多吡啶配合物与DNA键合及其光断裂DNA性质的研究

合成了两个钌多吡啶配合物[Ru(bpy)₂DMNP](C1O₄)₂ (Ru1)和[Ru(bpy)₂BOPIP](C1O₄)₂ (Ru2), 应用元素分析、核磁共振对配合物结构进行了表征, 通过电子吸收光谱、荧光光谱、粘度实验以及凝胶电泳技术对配合物与DNA相互作用的性质进行了研究. 结果表明, 配合物与DNA分子之间以插入模式结合. 在紫外光照下, 两种配合物均能使质粒pBR322DNA断裂, 机理研究表明, 其光断裂DNA的活性氧化物种为单线态氧.     

Synthesis,characterization, DNA-binding and DNA-photocleavage studies of [Ru(bpy)2(pmip)] and [Ru(phen)2(pmip)] (pmip = 2-(2′-pyrimidyl)imidazo[4,5-f][1,10]phenanthroline

Two new Ru(II) complexes, [Ru(bpy)₂(pmip)]²⁺ (1) and [Ru(phen)₂(pmip)]²⁺ (2), have been synthesized and characterized by elemental analysis, ESI-MS and ¹H NMR spectra. Their DNA-binding properties were studied by means of UV–VIS, emission and CD spectra, thermal denaturation and viscosity measurements as well as their DNA-photocleavage properties. The experimental results show that both 1 and 2 can bind to DNA in an intercalative mode; the DNA-binding affinity of 2 is greater than that of 1, which suggests that the ancillary ligands have a significant effect on the spectroscopic properties and DNA-binding behavior of the Ru(II) complexes. Under irradiation with UV light, the Ru(II) complexes show excellent efficiency of cleaving DNA. This research may provide valuable insight into the interactions of metal complexes with DNA, knowledge that is an excellent backdrop for the rational design of promising drugs.