A novel silver iodide metalo-drug: Experimental and computational modelling assessment of its interaction with intracellular DNA, lipoxygenase and glutathione

Amine-substituted heterocyclic thioamide Cu(I) and Ag(I) complexes as effective anticancer and antibacterial agents targeting the periplasm of E. coli bacteria

Metal complexes showing dual activity against cancer and bacterial infections are currently the focus of significant interest for their potential in treating life-threatening diseases. Aiming to investigate the impact of ligand substituents on these bioactivity properties of Group 11 d10 metal complexes, we herein present a series of mononuclear Cu(I) and Ag(I) complexes featuring the bis-NH2-substituted heterocyclic thioamide dap2SH (=4,6-diaminopyrimidine-2-thione), namely [AgCl(dap2SH)(PPh3)2] (1), [CuBr(dap2SH)(PPh3)2] (2), [CuBr(dap2SH)(xantphos)] (3), [Ag(dap2S)(xantphos)] (4), and [Cu(dap2S)(xantphos)] (5) (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene). Complexes were characterized by means of different physicochemical methods (i.e., single crystal X-ray diffraction as well as FTIR, NMR, UV-Vis and fluorescence spectroscopy), and studied in-vitro for their antibacterial and anticancer activity against a variety of bacterial strains and cancer cell lines. Complexes 1-3 effectively inhibited both Gram (+) and Gram (-) bacterial growth, while cellular uptake studies for the most potent complex 1 against E. coli bacteria revealed the accumulation of Ag(I) ions in the periplasm of the bacteria. A high anti-proliferative effect was observed for 1 and 5 against A549, MCF7 and PC3 cancer cell lines, with 1 being capable of inducing apoptosis in A549 cells, as suggested by flow cytometry analysis. DNA interaction studies revealed the capacity of 1 to intercalate between base-pairs of CT DNA. All complexes had a moderate-to-high capacity to scavenge free radicals preventing oxidative stress. Molecular docking calculations, in combination with the experimentally obtained data, provided insights for potential mechanisms of the bioactivity of the complexes.

Inhibition of Cancer Cell Proliferation and Bacterial Growth by Silver(I) Complexes Bearing a CH3-Substituted Thiadiazole-Based Thioamide

Ag(I) coordination compounds have recently attracted much attention as antiproliferative and antibacterial agents against a wide range of cancer cell lines and pathogens. The bioactivity potential of these complexes depends on their structural characteristics and the nature of their ligands. Herein, we present a series of four Ag(I) coordination compounds bearing as ligands the CH₃-substituted thiadiazole-based thioamide 5-methyl-1,3,4-thiadiazole-2-thiol (mtdztH) and phosphines, i.e., [AgCl(mtdztH)(PPh₃)₂] (1), [Ag(mtdzt)(PPh₃)₃] (2), [AgCl(mtdztH)(xantphos)] (3), and [AgmtdztH)(dppe)(NO₃)]_n (4), where xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene and dppe = 1,2-bis(diphenylphosphino)ethane, and the assessment of their in vitro antibacterial and anti-cancer efficiency. Among them, diphosphine-containing compounds 3 and 4 were found to exhibit broad-spectrum antibacterial activity characteristics against both Gram-(+) and Gram-(-) bacterial strains, showing high in vitro bioactivity with IC₅₀ values as low as 4.6 μΜ. In vitro cytotoxicity studies against human ovarian, pancreatic, lung, and prostate cancer cell lines revealed the strong cytotoxic potential of 2 and 4, with IC₅₀ values in the range of 3.1-24.0 μΜ, while 3 and 4 maintained the normal fibroblast cells' viability at relatively higher levels. Assessment of these results, in combination with those obtained for analogous Ag(I) complexes bearing similar heterocyclic thioamides, suggest the pivotal role of the substituent groups of the thioamide heterocyclic ring in the antibacterial and anti-cancer efficacy of the respective Ag(I) complexes. Compounds 1-4 exhibited moderate in vitro antioxidant capacity for free radicals scavenging, as well as reasonably strong ability to interact with calf-thymus DNA, suggesting the likely implication of these properties in their bioactivity mechanisms. Complementary insights into the possible mechanism of their anti-cancer activity were provided by molecular docking calculations, exploring their ability to bind to the overexpressed fibroblast growth factor receptor 1 (FGFR1), affecting cancer cells' functionalities.

Halogen, chalcogen, and hydrogen bonding in organoiodine cocrystals of heterocyclic thiones: imidazolidine-2-thione, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercaptobenzoxazole, and 2-mercaptobenzothiazole

Through the combination of heterocyclic thiones with variation in the identity of the heterocyclic elements, namely, imidazolidine-2-thione, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercaptobenzoxazole, and 2-mercaptobenzothiazole with the common halogen-bond donors 1,2-, 1,3-, and 1,4-diiodotetrafluorobenzene, 1,3,5-trifluorotriiodobenzene, and tetraiodoethylene, a series of 18 new crystalline structures were characterized. In most cases, N-H...S hydrogen bonding was observed, with these interactions in imidazole-containing structures typically resulting in two-dimensional motifs (i.e. ribbons). Lacking the second N-H group, the thiazole and oxazole hydrogen bonding resulted in only dimeric pairs. C-I...S and C-I...I halogen bonding, as well as C=S...I chalcogen bonding, served to consolidate the packing by linking the hydrogen-bonding ribbons or dimeric pairs.

Nrf2 signaling pathway in trace metal carcinogenesis: A cross-talk between oxidative stress and angiogenesis

A large number of people worldwide are affected by chronic metal exposure, which is known to be associated with different type of malignancies. The mechanisms of metal carcinogenicity are complex in nature, and excessive reactive oxygen species (ROS) generation induced by chronic metal exposure, among the other factors, has been proposed as one of the major mechanisms involved in that process. In tumor cells, ROS buildup may lead to cell death through intrinsic and extrinsic signaling pathways. Furthermore, ROS-mediated redox signaling has a crucial role in angiogenesis, which is recognized as an essential step in tumor progression. There are several redox-modulating pathways and among them, the nuclear factor erythroid2-related factor2 (Nrf2), as a sensor of oxidative or electrophilic stress, has introduced as a master regulator of cellular response against environmental stresses. Activation of Nrf2 signaling induces expression of wide variety of antioxidant and detoxification enzymes genes. Thus, this transcription factor has recently received much attention as a target for cancer chemoprevention. But meanwhile, constitutive Nrf2 activation in cancerous cells may promote cancer progression and resistance to chemotherapy. The current review describes the major underlying mechanisms involved in carcinogenesis of trace metals: copper, silver, and cadmium, with a special focus on the Nrf2 signaling pathway as a crossroad between oxidative stress and angiogenesis.

Conjugation of triphenylantimony(V) with carvacrol against human breast cancer cells

The organoantimony derivative of formula trans-O,O-[Ph₃Sb^V(Carv)₂] (TPAC) (CarvH = carvacrol) is obtained by the oxidation of triphenylstibine (Ph₃Sb^III) with hydrogen peroxide in the presence of carvacrol (CarvH). Physical methods such as X-ray Fluorescence (XRF) spectroscopy, single crystal and powder X-ray diffraction analysis (XRD and PXRD), Attenuated Total Reflection Fourier Transform Infra-red (ATR-FTIR) spectroscopy, Thermogravimetric Differential Thermal Analysis (TG-DTA) and Differential Scanning Calorimetry (DTG/DSC), confirm the retention of the formula of TPAC throughout the sample mass in solid state, while UV-Vis spectroscopy in the solution. TPAC is the first example of carvacrol (the main ingredient of oregano) covalently bonded to any metal ion. Only the trans-O,O-[Ph₃Sb(Carv)₂] isomer was isolated suggesting stereo-selectivity of the preparation route. TPAC inhibits in vitro both human breast adenocarcinoma cell lines: MCF-7 (positive to hormones receptor (HR +)), MDA-MB-231 (negative to hormones receptor (HR-)) stronger than normal human fetal lung fibroblast cells (MRC-5). The MCF-7 cells morphology, DNA fragmentation, Acridine Orange/Ethidium Bromide (AO/EB) Staining, cell cycle arrest and mitochondrial membrane permeabilization tests suggest an apoptotic pathway for cell death, especially, through the mitochondrion damage. The binding type of TPAC toward the calf thymus CT-DNA was initially deduced ex vivo from the differentiation of the DNA solution viscosity. Fluorescence spectroscopy confirms the interaction mode suggested. Spectroscopic evidence (FTIR, UV-Vis) suggest that glutathione (GSH) (a tripeptide over-expressed in tumor cells) induces conversion of non-active pentavalent antimony, which is contained in TPAC, to active trivalent one, providing a new strategy for the development of targeted chemotherapeutics.

Multifunctional Silver(I) Complexes with Metronidazole Drug Reveal Antimicrobial Properties and Antitumor Activity against Human Hepatoma and Colorectal Adenocarcinoma Cells

Simple Summary

Our previous studies demonstrated that a silver(I) nitrate complex with metronidazole presented greater photo-stability, antimicrobial, cytotoxic and genotoxic properties than silver(I) nitrate. These advantages make the complex a better candidate for clinical therapy than pure salt. Therefore, in this study, we decided to synthetize and determine the chemical, cytotoxic and antimicrobial properties of [Ag(MTZ)₂]₂SO₄, a novel metronidazole silver(I) complex, in comparison with pure salt Ag₂SO₄ and [Ag(MTZ)₂NO₃]. The photo-stability, cytotoxicity toward cancer cells and antimicrobial activity of [Ag(MTZ)₂]₂SO₄ is higher than Ag₂SO₄. What is more, we found that the novel synthetized complex shows better cytotoxicity against cancer cells than [Ag(MTZ)₂NO₃]. Both complexes have similar biological activity against the majority of tested bacterial strains.

Abstract

Silver salts and azole derivatives are well known for their antimicrobial properties. Recent evidence has demonstrated also their cytotoxic and genotoxic potential toward both normal and cancer cells. Still, little is known about the action of complexes of azoles with silver(I) salts. Thus, the goal of the study was to compare the chemical, cytotoxic and antimicrobial properties of metronidazole complexes with silver(I) nitrate and silver(I) sulfate to metronidazole and pure silver(I) salts. We synthetized a novel complex, [Ag(MTZ)₂]₂SO₄, and confirmed its chemical structure and properties using ¹H and ¹³C NMR spectroscopy and X-Ray, IR and elemental analysis. To establish the stability of complexes [Ag(MTZ)₂NO₃] and [Ag(MTZ)₂]₂SO₄, they were exposed to daylight and UV-A rays and were visually assessed. Their cytotoxicity toward human cancer cells (HepG2, Caco-2) and mice normal fibroblasts (Balb/c 3T3 clone A31) was determined by MTT, NRU, TPC and LDH assays. The micro-dilution broth method was used to evaluate their antimicrobial properties against Gram-positive and Gram-negative bacteria. A biofilm eradication study was also performed using the crystal violet method and confocal laser scanning microscopy. The photo-stability of the complexes was higher than silver(I) salts. In human cancer cells, [Ag(MTZ)₂]₂SO₄ was more cytotoxic than Ag₂SO₄ and, in turn, AgNO₃ was more cytotoxic than [Ag(MTZ)₂NO₃]. For Balb/c 3T3 cells, Ag₂SO₄ was more cytotoxic than [Ag(MTZ)₂]₂SO₄, while the cytotoxicity of AgNO₃ and [Ag(MTZ)₂NO₃] was similar. Metronidazole in the tested concentration range was non-cytotoxic for both normal and cancer cells. The complexes showed increased bioactivity against aerobic and facultative anaerobic bacteria when compared to metronidazole. For the majority of the tested bacterial strains, the silver(I) salts and complexes showed a higher antibacterial activity than MTZ; however, some bacterial strains presented the reverse effect. Our results showed that silver(I) complexes present higher photo-stability, cytotoxicity and antimicrobial activity in comparison to MTZ and, to a certain extent, to silver(I) salts.

Biocompatible silver(I) complexes with heterocyclic thioamide ligands for selective killing of cancer cells and high antimicrobial activity - A combined in vitro and in silico study

A series of heteroleptic Ag(I) complexes bearing 4,6-dimethyl-2-pyrimidinethiol (dmp2SH), i.e., [AgCl(dmp2SH)(PPh₃)₂] (1), [Ag(dmp2SH)(PPh₃)₂]NO₃ (2), [Ag(dmp2SΗ)(xantphos)]NO₃ (3), [Ag(μ-dmp2S)(PPh₃)]₂ (4), [Ag(dmp2S)(xantphos)] (5), [Ag(μ-dmp2S)(DPEphos)]₂ (6) (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene and DPEPhos = bis[(2-diphenylphosphino)phenyl]ether) were synthesized. The complexes display systematic variation of particular structural characteristics which were proved to have a significant impact on their in vitro cytotoxicity and antimicrobial properties. A moderate-to-high potential for bacteria growth inhibition was observed for all complexes, with 2, 3 and 5 being particularly effective against Gram-(+) bacteria (IC₅₀ = 1.6-4.5 μM). The three complexes exhibit high in vitro cytotoxicity against HeLa and MCF-7 cancer cells (IC₅₀ = 0.32-3.00 μΜ), suggesting the importance of coordination unsaturation and cationic charge for effective bioactivity. A very low cytotoxicity against HDFa normal cells was observed, revealing a high degree of selectivity (selectivity index ~10) and, hence, biocompatibility. Fluorescence microscopy using 2 showed effective targeting on the membrane of the HeLa cancer cells, subsequently inducing cell death. Binding of the complexes to serum albumin proteins is reasonably strong for potential uptake and subsequent release to target sites. A moderate in vitro antioxidant capacity for free radicals scavenging was observed and a low potential to destroy the double-strand structure of calf-thymus DNA by intercalation, suggesting likely implication of these properties in the bioactivity mechanisms of these complexes. Further insight into possible mechanisms of bioactivity was obtained by molecular modeling calculations, by exploring their ability to act as potential inhibitors of DNA-gyrase, human estrogen receptor alpha, human cyclin-dependent kinase 6, and human papillomavirus E6 oncoprotein.

Novel Gold and Silver Carbene Complexes Exert Antitumor Effects Triggering the Reactive Oxygen Species Dependent Intrinsic Apoptotic Pathway

Cisplatin and other platinum-based drugs are well-known valid anticancer drugs. However, during chemotherapy, the presence of numerous side effects and the onset of frequent phenomena of resistance has pushed many research groups to devise new metal-based compounds holding improved anticancer properties and fewer undesired effects. Amongst the variety of synthesized compounds, significant antiproliferative effects have been obtained by employing organometallic compounds, particularly those based on silver and gold. With this in mind, we synthesized four compounds, two silver complexes and two gold complexes, with good inhibitory effects on the in vitro proliferation of breast and ovarian cancer-cell models. The antitumor activity of the most active compound, that is, AuL4, was found to be ninefold higher than that of cisplatin, and this compound induced dramatic morphological changes in HeLa cells. AuL4 induced PARP-1 cleavage, caspases 3/7 and 9 activation, mitochondria disruption, cytochrome c release in cancer-cell cytoplasm, and the intracellular production of reactive oxygen species. Thus, AuL4 treatment caused cancer-cell death by the intrinsic apoptotic pathway, whereas no cytotoxic effects were recorded upon treating non-tumor cell lines. The reported outcomes may be an important contribution to the expanding knowledge of medicinal bio-organometallic chemistry and enlarge the available anticancer toolbox, offering improved features, such as higher activity and/or selectivity, and opening the way to new discoveries and applications.

Synthesis, structures and biomolecular interactions of new silver(i) 5,5-diethylbarbiturate complexes of monophosphines targeting Gram-positive bacteria and breast cancer cells

New silver(i) 5,5-diethylbarbiturate complexes exhibit very high antimicrobial activity against Gram-positive bacteria and kill MCF-7 cells, damaging mitochondria and DNA.

Structural, photolysis and biological studies of novel mixed metal Cu(I)-Sb(III) mixed ligand complexes

Direct reaction of copper(I) halides with triphenylstibine (tpSb) and 2-mercapto-thiazolidine (tzdtH) in 1:1:1 molar ratio, results in the formation of the [CuX(μ2-S)-tzdtH)(tpSb)]2 (X=Cl (1), Br (2) and I (3)) complexes. The complexes have been characterized by melting point, FT-IR, UV-vis, (1)H NMR spectroscopic data and X-ray crystallography. Complexes 1-3 are di-nuclear and they are the first examples of mixed metals (CuSb), mixed ligand (thioamide, stibine and halogen) containing complexes. Two μ2-S (1-3) atoms bridge the two copper(I) ions with tetrahedral geometry. The coordination sphere around copper atoms is completed by one Sb from tpSb and one halogen (chlorine, bromine or iodine) atom. Intermolecular via N-H⋯X (Cl (1) and Br (2)) interactions stabilized the assembly. The short coppercopper bond distances of 3.103 (1), 3.061 (2) and 3.110, 3.108 (3) Ǻ found in 1-3 indicates d(10)-d(10) interaction between metal centers. The complexes exhibit high photo-sensitivity to UVB light. The complexes 1-3 and the already known [Cu(μ2-I)(tpSb)2]2 (4) were tested for their in vitro cytotoxic activity against human cancer cell lines: MCF-7 (breast, estrogen receptor (ER) positive), MDA-MB-231 (breast, estrogen receptor (ER) negative) and MRC-5 (normal human fetal lung fibroblast cells) with sulforhodamine B (SRB) colorimetric assay. Since estrogen receptors (ERs) are located in MCF-7, in contrast to MDA-MB-231 cells, the estrogenic effect of 1-4 on MCF-7 cells was studied by the mean of methylene blue assay. Compound 4 exhibits the highest estrogenic effect. None of 1-4 exceeds the activity of cisplatin against MCF-7 cells, but they are more active than cisplatin towards MDA-MB-231 cells. UVB light increases the effectiveness of complexes on MCF-7 cells which in the case of 4 is up to 28% higher than the corresponding initial complex (without irradiation).

Antibacterial activity of silver camphorimine coordination polymers

[Ag(NO₃)(OC₁₀H₁₄NC₆H₄NC₁₀H₁₄O)] is the first bi-camphor silver coordination polymer structurally characterized. It displays bactericidal activity against Gram-negative and Gram-positive strains comparable to drugs in use.

New antibacterial, non-genotoxic materials, derived from the functionalization of the anti-thyroid drug methimazole with silver ions

The new silver(I) compound {[AgBr(μ2-S-MMI)(TPP))]2} (1) and the known one [AgCl(TPP)2(MMI)] (2) were obtained by refluxing toluene solutions of silver(I) halide with triphenylphosphine (TPP) and the anti-thyroid drug 2-mercapto-1-methyl-imidazole or methimazole (MMI). The complexes were characterized by m.p., vibrational spectroscopy (mid-FT-IR), (1)H, (31)P-NMR, UV-Vis spectroscopic techniques and X-ray crystallography. The antibacterial effect of 1 and 2 against the bacterial species Pseudomonas aeruginosa (PAO) and Escherichia coli was evaluated. Compound 1 exhibits comparable activity to the corresponding one of the silver nitrate which is an antibacterial drug in use. The in vivo genotoxicity of 1-2 by the mean of Allium cepa test shows no alterations in the mitotic index values due to the absence of chromosomal aberrations. The mechanism of action of the title compounds is evaluated. The DNA binding tests indicate the ability of the complexes 1-2 to modify the activity of the bacteria. The binding constants of 1-2 towards CT-DNA indicate interaction through opening of the hydrogen bonds of DNA. Docking studies on DNA-complexes interactions confirm the binding of both complexes 1-2 in the major groove of the CT-DNA. In conclusion the silver complex 1 is an anti-bacterial and non-genotoxic material, which can be applied to antibacterial drug in the future.