Synthesis, structure, DNA/BSA binding and antibacterial studies of NNO tridentate Schiff base metal complexes

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.

Anticounterfeiting Feature of a Writable and Self-Erasable Ni(II)-Metallogel Pad via Fluorescent "Turn-On" Detection of Cyanide

A Schiff base 5-(2-hydroxy-3-methoxybenzylidieneamino)-1-H-imidazole-4-carboxamide (HL) comprising multibinding sites has been synthesized with the aim of fabricating a supramolecular gel. The gelator HL was characterized by FT-IR, 1H & 13C NMR, and ESI-MS techniques and also formed a [Ni(L)2] complex. The gelation property of HL was investigated with various metal ions, wherein Ni(II) selectively forms a mechanically and thermally stable supramolecular metallogel (MG) in the presence of a triethylamine base in DMF-MeOH media. Characterization of MG was accomplished with different spectro-analytical techniques such as FT-IR, ESI-MS, powder-XRD, SEM, rheological investigations, UV/vis, and fluorescence. The gelator HL displays moderate emission upon addition of Ni2+ and gives "turn-off" fluorescence output by forming the complex [Ni(L)2] (MG) due to the chelation-enhanced quenching of fluorescence (CHEQ). Job plot and ESI-MS data suggested a 2:1 stoichiometry between HL and Ni(II) in MG. Further, MG exhibited highly selective and ultrasensitive "turn-on" fluorescence signaling with CN- in the background presence of several cations and anions. The limit of detection (LoD) of MG was determined to be 6.9 × 10-9 M for CN- using the fluorescence technique. Notably, MG behaves as a fluorescent writable pad material explicitly with CN- under 365 nm UV light but not under ordinary light and the fluorescent text is self-erased after 15 min. Hence, MG can be used as a metallogel pad in the presence of CN- to communicate secret messages. Overall, the present work explores the fabrication of a thermo- and mechanostable Ni(II)-metallogel (MG), which selectively and ultrasensitively detects CN- both in the solution phase and in the gel form, wherein MG behaves as a writable and self-erasable pad with anticounterfeiting features for practical applications.

Design, spectral characterization, quantum chemical investigation, biological activity of nano-sized transition metal complexes of tridentate 3-mercapto-4H-1,2,4-triazol-4-yl-aminomethylphenol Schiff base ligand

A tridentate Schiff base ligand, H2MTIP, was produced by condensing salicylaldehyde with 4-amino-4H-1,2,4-triazole-3-thiol. The ligand was then used to create nanosized complexes of Pt(II), Ni(II), Cu(II), and Pd(II). The complexes have the composition [Pt/Ni/Cu/or Pd(MTIP)(H2O)], this conclusion is supported by molar conductance, magnetic moments, elemental analyses, spectral analyses. In DFT analysis, the 6-31+ g(d,p) basis set was used to fully optimize the energy with respect to the shapes of Schiff base ligand and metal complexes. Pt(II), Ni(II), Cu(II), and Pd(II) complexes have been assigned square-planar geometries. At the same time, the intense diffraction peaks in X-ray diffractograms show their crystalline features with particle sizes in the nanoscale range. The binding interaction of calf thymus DNA with these metal complexes and their insulin-like activity was examined in vitro by inhibiting α-amylase. The study investigated the in-vitro activity of several complexes and identified Pt(II) complex as the one with the highest activity. The researchers then tested this complex for in-vivo antidiabetic activity in induced diabetic rats using the STZ model, and it significantly lowered blood glucose levels. The antioxidant activity and toxicity level of Pt(II) complex were also excellent, suggesting that it could be a good candidate for further research as a possible diabetes drug.Communicated by Ramaswamy H. Sarma.

Synthesis, structural characterization, antioxidant, cytotoxic activities and docking studies of schiff base Cu(II) complexes

By combining hydrazide with 2-Acetylpyridine, a hydrazone ligand (HL) was successfully created. Several copper (II) salts have been used to create three copper (II) hydrazone complexes (acetate, sulphate, and chloride). The hydrazide ligand and its copper (II) complexes (1-3) were studied via variety of analytical techniques, including elemental analysis, electronic, infrared, UV-vis Spectrum, XRD study, thermal analysis, also molar conductivity amounts. The spectrum results indicate that in all complexes, the ligand exhibits monobasic tridentate behavior. Octahedral geometries were present in all metal complexes. The Coats-Redfern equations were used to compute and describe the dynamics properties of several steps of TGA (Ea, A, ΔH*, ΔS*, and ΔG*). Calculations using the density functional theory (DFT) were done at the molecular studio software toward examine ligands agent's and its complexes' best structures. The MCF-7 in addition to HepG-2 cell lines was resistant to tumor-inducing effects of the copper (II) chelates. The in vitro antioxidant capacities of all complexes have been estimated via DPPH free radical scavenger assays. Furthermore, zones of inhibition length accustomed to test antimicrobial effect of particular complexes in vitro towards Staphylococcus aureus (Gram positive bacteria) E. coli (Gram negative bacteria). Both absorption spectra and viscosity measurements in calf thymus DNA binding have been used to study the complexes. In order to explore docking research of copper (II) chelates, the crystallographic construction of the SARS-active CoV-2's site protein (PDB ID:6XBH) was used (COVID-19) and breast cancer distorted (PDB ID: 3hb5).

Visible light-driven photocatalysts, quantum chemical calculations, ADMET-SAR parameters, and DNA binding studies of nickel complex of sulfadiazine

A 3D-supramolecular nickel integrated Ni-SDZ complex was synthesized using sodium salt of sulfadiazine as the ligand and nickel(II) acetate as the metal salt using a condensation process and slow evaporation approach to growing the single crystal. The metal complex was characterized for its composition, functional groups, surface morphology as well as complex 3D structure, by resorting to various analytical techniques. The interacting surface and stability as well as reactivity of the complex were carried out using the DFT platform. From ADMET parameters, human Intestinal Absorbance data revealed that the compound has the potential to be well absorbed, and also Ni-SDZ complex cannot cross the blood-brain barrier (BBB). Additionally, the complex's DNA binding affinity and in-vivo and in-vitro cytotoxic studies were explored utilizing UV-Vis absorbance titration, viscosity measurements, and S. pombe cells and brine shrimp lethality tests. In visible light radiation, the Ni-SDZ complex displayed exceptional photo-degradation characteristics of approximately 70.19% within 70 min against methylene blue (MB).

Synthesis, DNA binding and biological evaluation of benzimidazole Schiff base ligands and their metal(ii) complexes

Two novel benzimidazole ligands (E)-2-((4-(1H-benzo[d]imidazole-2-yl)phenylimino)methyl)-6-bromo-4-chlorophenol (L1) and (E)-1-((4-(1H-benzo[d]imidazole-2-yl)phenylimino)methyl)naphthalene-2-ol (L2) with their corresponding Cu(ii), Ni(ii), Pd(ii) and Zn(ii) complexes were designed and synthesized. The compounds were characterized by elemental, IR, and NMR (1H & 13C) spectral analyses. Molecular masses were determined by ESI-mass spectrometry, and the structure of ligand L1 was confirmed by single crystal X-ray diffraction analysis. Molecular docking was carried out for the theoretical investigation of DNA binding interactions. The results obtained were verified experimentally by UV/Visible absorption spectroscopy in conjunction with DNA thermal denaturation studies. It was observed that ligands (L1 and L2) and complexes (1-8) were moderate to strong DNA binders, as evident from the binding constants (K b). The value was found to be highest for complex 2 (3.27 × 105 M-1) and lowest for 5 (6.40 × 103 M-1). A cell line study revealed that breast cancer cells were less viable to the synthesized compounds compared to that of standard drugs, cisplatin and doxorubicin, at the same concentration. The compounds were also screened for in vitro antibacterial activity for which complex 2 showed a promising broad-spectrum effect against all tested strains of bacteria, almost in the proximity of the reference drug kanamycin, while the rest of the compounds displayed activity against selected strains.

Correlating the charge transfer efficiency of metallic sulfa-isatins to design efficient NLO materials with better drug designs

The present study presents synthesis, characterization and first principle studies on metal chelates, (1-12), of sulfonamide-isatin reacted ligands (S¹-S³). All the products were evaluated by various physical and spectral (UV, IR, NMR, MS) means. The octahedral geometry for Co⁺², Ni⁺² and Zn⁺², while square planner geometry for Cu⁺² chelates were confirmed by their spectroscopic and magnetic data. Their physical chemistry investigation show the ability of aromatic rings to stabilize sulfonamide rings across NH-π interactions at their optimized geometries. The nonlinear optical response for all the compounds disclosed that the z-axis has the most contributions. An efficient electron injection and hole studies for Au and Al electrodes having the energies of - 0.1-3.1 and 0.0-11.8 eV respectively were noted. Their bioactive character was shown by global reactivity calculated from FMO energy gaps. The enzyme inhibitory results were found to be 45-61% and IC₅₀ = 102-122 µL, for compound (4), (10), (8), (5) and (12) against the amylase, protease, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) respectively The antibacterial findings showed significant action having 11-17 mm for (2), (7) and (10) for bacterial species, Escherichia coli and Micrococcus luteus. The DPPH and ferric reducing power assay was used to evaluate the antioxidant capacity with 49.0 ± 0.09-66.2 ± 0.08% and IC₅₀ = 102.3-122.4 µL range. In comparison to ligands, the results showed that all metal chelates had higher bioactivity. The chelation was the primary cause of their increased bioactivity. These findings suggested that such metal-based compounds might be used as antimicrobial, and antioxidant options in future to cope drug resistance.

Quinoline Functionalized Schiff Base Silver (I) Complexes: Interactions with Biomolecules and In Vitro Cytotoxicity, Antioxidant and Antimicrobial Activities

A series of fifteen silver (I) quinoline complexes Q1-Q15 have been synthesized and studied for their biological activities. Q1-Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1-L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO₃, AgClO₄ and AgCF₃SO₃. Q1-Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)₂]NO₃Q1, [Ag(L1)₂]ClO₄Q6, [Ag(L2)₂]ClO₄Q7, [Ag(L2)₂]CF₃SO₃Q12 and [Ag(L4)₂]CF₃SO₃Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes' moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC₅₀ between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)₂]ClO₄Q7 with a benzothiazole moiety and [Ag(L4)₂]ClO₄Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.

Chromium Coordination Compounds with Antimicrobial Activity: Synthetic Routes, Structural Characteristics, and Antibacterial Activity

A major threat to public health worldwide is that the antimicrobial activity of the established drugs is constantly reduced due to the resistance that bacteria develop throughout the years. Some transition metal complexes show higher antibacterial activity against several bacteria compared to those of clinically used antibiotics. Novel classes of molecules provide new challenges and seem promising to solve the crisis that the overuse of antibiotics has led over the last years. This review discusses the challenges of chromium-based metallodrugs as antimicrobial agents. In particular, the synthetic routes, the structural characteristics, as well as the antimicrobial activity of 32 chromium (III) complexes have been presented.

Molecular-Scale Investigations Reveal Noncovalent Bonding Underlying the Adsorption of Environmental DNA on Mica

Mineral-soil organic matter (SOM including DNA, proteins, and polysaccharides) associations formed through various interactions, play a key role in regulating long-term SOM preservation. The mechanisms underlying DNA-mineral and DNA-protein/polysaccharide interactions at nanometer and molecular scales in environmentally relevant solutions remain uncertain. Here, we present a model mineral-SOM system consisting of mineral (mica)-nucleic acid (environmental DNA, eDNA)/protein (bovine serum albumin)/polysaccharide (alginate), and combine atomic force microscopy (AFM)-based dynamic force spectroscopy and PeakForce quantitative nanomechanical mapping using DNA-decorated tips. Single-molecule binding and adhesion force of eDNA to mineral and to mineral adsorbed by protein/polysaccharide reveal the noncovalent bonds and that systematically changing ion compositions, ionic strength, and pH result in significant differences in organic-organic and organic-mineral binding energies. Consistent with the bond-strength measurements, protein, rather than polysaccharide, promotes mineral-bound DNA molecules by ex situ AFM deposition observations in relatively high concentrations of divalent cation-containing acidic solutions. These molecular-scale determinations and nanoscale observations should substantially improve our understanding of how environmental factors influence the organic-mineral interfacial interactions through the synergy of collective noncovalent and/or covalent bonds in mineral-organic associations.

Synthesis, thermal and surface activity of cationic single chain metal hybrid surfactants and their interaction with microbes and proteins

A series of water-soluble metal functionalized surfactants have been prepared using commercially available surfactant cetyl pyridinium chloride and transition metal salts. These complexes were characterized in the solid state by elemental analysis, FTIR, 1H NMR and thermogravimetric analysis. The interfacial surface activity and aggregation behaviour of the metallosurfactants were analysed through conductivity, surface tension and small angle neutron scattering measurements. Our results show that the presence of metal ions as co-ions along with counter ions favours micellization at a low critical micellization concentration (CMC). Small angle neutron scattering revealed that the metallomicelles are of a prolate ellipsoidal shape and exhibit strong counterion binding. This article further describes the interaction of the metallosurfactants with transport protein Bovine Serum Albumin (BSA) using different spectroscopic techniques. A spectroscopic study was used to study the binding, interaction and quenching mechanism of BSA with the metallosurfactants. Gel electrophoresis (SDS-PAGE) and circular dichroism (CD) investigated the structural and conformational changes produced in BSA due to the metallosurfactants. The results indicate that there is an alteration in the secondary structure of BSA due to the electrostatic interaction between positive head groups and metal co-ions of the metallosurfactants and negatively charged amino acids of BSA. As the concentration increases, the α-helicity of BSA decreases and all the three studied metallosurfactants gave comparable results. Finally, the in vitro cytotoxicity and antimicrobial activity of the metallosurfactants were evaluated against erythrocytes and microorganisms, which showed prominent effects related to the presence of a metal ion in metallomicelles of the hybrid surfactants.

Facile template synthesis of water-soluble triazine-based Schiff base ligand bridged-coordination polymers of Co(ii), Ni(ii), and Cu(ii): structure, biomolecular interactions, and cytotoxic activity

For the first time, a new hydrazone Schiff base ligand and its Co(ii), Ni(ii), and Cu(ii) complexes were synthesised and characterised. Their antioxidant and binding activities towards CT-DNA and BSA were evaluated.

Zinc(ii) centered biologically active novel N,N,O donor tridentate water-soluble hydrazide-based O-carboxymethyl chitosan Schiff base metal complexes: synthesis and characterisation

In this study, novel eco-friendly and water-soluble chitosan Schiff base derivatives have been designed for potential use in antimicrobial applications.

Luminescent bis(benzo[d]thiazolyl)quinoxaline: facile synthesis, nucleic acid and protein BSA interaction, live-cell imaging, biopharmaceutical research and cancer theranostic application

A series of quinoxaline-2-hydroxyphenylbenzothiazole scaffolds were synthesized and characterized using NMR, UV, fluorescence spectroscopy and LCMS. These newly synthesized compounds were found to be cytotoxic in human epithelioid cervix carcinoma (HeLa) and human colon cancer cell lines (Caco-2). Selectivity of the compounds 7e and 7g are more than 9 fold higher in Caco-2 cells with respect to the normal cell line HEK-293. The most fluorescent compound 7e has displayed high cytoselectivity, significant cellular uptake in HeLa cells and strong binding efficacy with DNA and BSA. The most potent compound 7g has primarily classified as BCS class 4 and BDDCS class 4.

A series of luminescent bis(benzo[d]thiazolyl)quinoxalines have been synthesized and their fluorescence properties, anticancer potency, DNA and BSA interactions, cellular uptake, and metabolic stabilities are investigated.