Influence of proline and hydroxyproline as antimicrobial and anticancer peptide components on the silver(I) ion activity: structural and biological evaluation with a new theoretical and experimental SAR approach.

Silver(I) complexes with proline and hydroxyproline were synthesized and structurally characterized and crystal structure analysis shows that the formulas of the compounds are {[Ag2(Pro)2(NO3)]NO3}n (AgPro) (Pro = L-proline) and {[Ag2(Hyp)2(NO3)]NO3}n (AgHyp) (Hyp = trans-4-hydroxy-L-proline). Both complexes crystallize in the monoclinic lattice with space group P21 with a carboxylate bidentate-bridging coordination mode of the organic ligands Pro and Hyp (with NH2+ and COO- groups in zwitterionic form). Both complexes have a distorted seesaw (C2v) geometry around one silver(I) ion with τ4 values of 58% (AgPro) and 51% (AgHyp). Moreover, the results of spectral and thermal analyses correlate with the structural ones. 1H and 13C NMR spectra confirm the complexes species' presence in the DMSO biological testing medium and their stability in the time range of the bioassays. In addition, molar conductivity measurements indicate complexes' behaviour like 1 : 1 electrolytes. Both complexes showed higher or the same antibacterial activity against Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus as AgNO3 (MIC = 0.063 mM) and higher than silver(I) sulfadiazine (AgSD) (MIC > 0.5 mM) against Pseudomonas aeruginosa. In addition, complex AgPro exerted a strong cytotoxic effect against the tested MDA-MB-231 and Jurkat cancer cell lines (IC50 values equal to 3.7 and 3.0 µM, respectively) compared with AgNO3 (IC50 = 6.1 (5.7) µM) and even significantly higher selectivity than cisplatin (cisPt) against MDA-MB-231 cancer cell lines (SI = 3.05 (AgPro); 1.16 (cisPt), SI - selectivity index). The binding constants and the number of binding sites (n) of AgPro and AgHyp complexes with bovine serum albumin (BSA) were determined at four different temperatures, and the zeta potential of BSA in the presence of silver(I) complexes was also measured. The in ovo method shows the safety of the topical and intravenous application of AgPro and AgHyp. Moreover, the complexes' bioavailability was verified by lipophilicity evaluation from the experimental and theoretical points of view.

Ga(III) pyridinecarboxylate complexes: potential analogues of the second generation of therapeutic Ga(III) complexes?

A series of novel Ga(III)-pyridine carboxylates ([Ga(Pic)3]·H2O (GaPic; HPic = picolinic acid), H3O[Ga(Dpic)2]·H2O (GaDpic; H2Dpic = dipicolinic acid), [Ga(Chel)(H2O)(OH)]2·4H2O (GaChel; H2Chel = chelidamic acid) and [Ga(Cldpic)(H2O)(OH)]2 (GaCldpic; H2Cldpic = 4-chlorodipicolinic acid)) have been synthesized by simple one-step procedure. Vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis and X-ray diffraction confirmed complexes molecular structure, inter and intramolecular interactions and their influence to spectral and thermal properties. Moreover, complex species speciation was described in Ga(III)-HPic and Ga(III)-H2Dpic systems by potentiometry and 1H NMR spectroscopy and mononuclear complex species were determined; [Ga(Pic)2]+ (logß021 = 16.23(6)), [Ga(Pic)3] (logß031 = 20.86(2)), [Ga(Dpic)2]- (logß021 = 15.42(9)) and [Ga(Dpic)2(OH)]2- (logß-121 = 11.08(4)). To confirm the complexes stability in 1% DMSO (primary solvent for biological testing), timescale 1H NMR spectra were measured (immediately after dissolution up to 96 h). Antimicrobial activity evaluated by IC50 (0.05 mM) is significant for GaDpic and GaCldpic against difficult to treat and multi-resistant P. aeruginosa. On the other hand, the GaPic complex is most effective against Jurkat, MDA-MB-231 and A2058 cancer cell lines and significantly also decreases the HepG2 cancer cells viability at 75 and 100 µM concentrations in a relatively short time (up to 48 h). In addition, fluorescence measurements have been used to elucidate bovine serum albumin binding activity between ligands, Ga(III) complexes and bovine serum albumin.

Silver(I) pyrrole- and furan-2-carboxylate complexes - From their design and characterization to antimicrobial, anticancer activity, lipophilicity and SAR.

Two silver(I) complexes with biologically relevant heterocyclic ligands, pyrrole and furan-2- carboxylic acid, were synthesized and their composition was confirmed using elemental, spectral, thermal and structural analyses. The {[Ag(Py2c)]}n (AgPy2c, Py2c = pyrrole-2-carboxylate) and {[Ag(Fu2c)]}n (AgFu2c, Fu2c = furan-2-carboxylate) solubility and stability in biological test stock solution were confirmed by 1H NMR spectroscopy. The X-ray analysis has enabled us to determine typical argentophilic interactions and bridging carboxylate coordination mode of both ligands. Potentiometric data analysis by BSTAC program resulted in the determination of the stability constant of only one species, i.e., the ML (M = Ag+, L = Fu2c-), log ßML = 0.59 ± 0.04. Antimicrobial and anticancer tests were performed against selected microorganisms and cell lines with new silver(I) complexes and compared with AgSD (silver(I) sulfadiazine) and cisplatin. From their microbial toxicity point of view, selectivity was determined against lactobacilli (AgPy2c is 8× more effective against S. aureus and E. coli and AgFu2c is 8× more effective against E. coli and 4× against S. aureus). AgFu2c significant anticancer activity was determined against Jurkat cell lines (IC50 = 8.00 µM) and was similar to cisPt (IC50 = 6.3 µM) similarly to its selectivity (SI (AgFu2c) = 7.3, SI (cisPt) = 6.4, SI = selectivity index). In addition, cell cycle arrest was observed already in the Sub-G0 phase during a flow cytometry experiment. To evaluate the AgPy2c and AgFu2c bioavailability we also discuss their Lipinski's Rule of Five.

Antimicrobial and Anticancer Application of Silver(I) Dipeptide Complexes.

Three silver(I) dipeptide complexes [Ag(GlyGly)]n(NO3)n (AgGlyGly), [Ag2(GlyAla)(NO3)2]n (AgGlyAla) and [Ag2(HGlyAsp)(NO3)]n (AgGlyAsp) were prepared, investigated and characterized by vibrational spectroscopy (mid-IR), elemental and thermogravimetric analysis and mass spectrometry. For AgGlyGly, X-ray crystallography was also performed. Their stability in biological testing media was verified by time-dependent NMR measurements. Their in vitro antimicrobial activity was evaluated against selected pathogenic microorganisms. Moreover, the influence of silver(I) dipeptide complexes on microbial film formation was described. Further, the cytotoxicity of the complexes against selected cancer cells (BLM, MDA-MB-231, HeLa, HCT116, MCF-7 and Jurkat) and fibroblasts (BJ-5ta) using a colorimetric MTS assay was tested, and the selectivity index (SI) was identified. The mechanism of action of Ag(I) dipeptide complexes was elucidated and discussed by the study in terms of their binding affinity toward the CT DNA, the ability to cleave the DNA and the ability to influence numbers of cells within each cell cycle phase. The new silver(I) dipeptide complexes are able to bind into DNA by noncovalent interaction, and the topoisomerase I inhibition study showed that the studied complexes inhibit its activity at a concentration of 15 µM.

An in vitro selective inhibitory effect of silver(i) aminoacidates against bacteria and intestinal cell lines and elucidation of the mechanism of action by means of DNA binding properties, DNA cleavage and cell cycle arrest.

Novel silver(i) aminoacidate complexes {[Ag(HVal)(H2O)(NO3)]}n (AgVal) and {[Ag3(HAsp)2(NO3)]}n·nH2O (AgAsp) were prepared, investigated and fully characterized by vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis, X-ray crystallography and mass spectrometry. Their stability in D2O and PBS buffer was verified by time-dependent 1H and 13C NMR measurements. Their in vitro antibacterial activity (against pathogenic Staphylococcus aureus CCM4223, Escherichia coli CCM4787) and that against probiotic bacteria Lactobacillus plantarum CCM7102 and Lactobacillus reuteri (L26) were determined and potential dosing concentration was evaluated. The cytotoxicity of both the complexes against intestinal porcine epithelial (IPEC-1) and human epithelial colorectal adenocarcinoma (CaCo-2) cell lines was determined using the colorimetric MTT assay and against human metastatic melanoma (A2058), human pancreatic adenocarcinoma (PaTu 8902), human cervical adenocarcinoma (HeLa), human colorectal carcinoma (HCT116), human leukaemic T cell lymphoma (Jurkat), and human dermal fibroblasts (HDF) using colorimetric MTS assay. The selectivity index (SI) was identified for intestinal cancer (CaCo-2) and healthy (IPEC-1) cells. The mechanism of action of AgVal and AgAsp was further elucidated and discussed by the study of their binding affinity toward the CT DNA, the ability to cleave the supercoiled form of pUC19 DNA and the ability to influence numbers of cells within each cell cycle.

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

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

Silver pyridine-2-sulfonate complex - its characterization, DNA binding, topoisomerase I inhibition, antimicrobial and anticancer response.

In the current study the ability of silver pyridine-2-sulfonate complex to exert multiple biological activities is compared with the pharmacological action of silver sulfadiazine (AgSD). Polymeric form of {[Ag(py-2-SO3)]}n (AgPS) was synthesized and characterized by analytical techniques (IR, CHN, TG/DTA, MS) and its molecular formula was established. The crystal structure was determined by X-ray diffraction method and the polymeric complex crystallizes in the triclinic P-1 space group. The stability of Ag(I) complex was verified by 1H and 13C NMR measurements and the interaction with calf thymus DNA through UV-VIS and fluorescence quenching experiments was studied. The Ag(I) complex was able to interact with DNA by dual binding mode: partial intercalation along groove binding. The binding constants were calculated to be in the order of 103 M-1. Topoisomerase I inhibition study have shown that silver complex is inhibiting its activity at concentration of 30 µM. The cytotoxic activity of AgPS and AgSD against mouse leukaemia L1210 S, R and T cell line was also evaluated. AgPS showed higher cytotoxicity than AgSD after 48 h incubation. The results suggest that mechanism of cell death is necrosis with a contribution of late apoptosis. Antimicrobial testing indicates higher growth inhibition effect of AgPS with comparison to commercially available AgSD.

New silver complexes with bioactive glycine and nicotinamide molecules - Characterization, DNA binding, antimicrobial and anticancer evaluation.

This study introduces a pair of newly synthesized silver complexes, [Ag2(HGly)2]n(NO3)2n (1) and [Ag(Nam)2]NO3·H2O (2) (Gly - glycine, Nam - nicotinamide), that were prepared and characterized by relevant methods in solid state (elemental, spectral, thermal and structural analysis) and their stability in solution was verified by 1H NMR measurements. Moreover, suitable reaction conditions were observed by potentiometry depending on pH in case of binary system Ag-Gly. X-ray analysis confirmed argentophilic interactions in complex 1 with an Ag1-Ag2 distance of 2.8018(6) Å. Antimicrobial testing indicates higher growth inhibition effect of complex 1 than complex 2. Moreover the effectivity of both complexes against bacteria (Staphylococcus aureus and Escherichia coli) is superior (or similar) to that of the commercially available Ag(I) sulfadiazine, AgSD (used, for example, in Dermazine cream). The binding of the Ag(I) complexes to calf thymus DNA was investigated using electronic absorption, fluorescence and circular dichroism spectrophotometry. The Stern-Volmer quenching constants obtained from the linear quenching plot were estimated in the range from 2.01×103 to 20.34×103M-1. The results of topoisomerase I and topoisomerase II (Topo I and Topo II) inhibition assay suggested that complex 2 inhibits the enzyme activity of both enzymes at a concentration of 2µM. The cytotoxicity of both complexes on L1210 leukemia cells was revealed to be approximately three times higher than that of cisplatin. Moreover, the new Ag(I) complexes also induced apoptosis of the leukemia cells. The high DNA binding activity of these complexes is considered to be responsible for their cytotoxic effects.