Intercalative Mode Research Articles

Interaction of an electrochemical redox indicator new methylene blue with DNA using biophysical techniques

Electrochemical biosensors (an integrated system of biological constituent and physiochemical detector) have attracted plenty of attention due to its high precision, and importance in clinical diagnosis. In electrochemical biosensors, redox indicators like methylene (MB) blue are used to detect the electrical changes, which by intercalating between DNA base pairs, can produce an intense redox signal on the surface of ssDNA modified electrode. This study reports the interaction between calf thymus DNA (ctDNA) and new methylene blue (NMB), having almost identical basic skeleton to MB. Various techniques like UV-Visible, thermal melting, fluorescence, circular dichroism (CD) spectroscopy and molecular docking have been utilized. Hypochromism and a red shift in UV-Vis spectra revealed the intercalation binding mode for DNA-NMB complex. Nearly identical binding constants were calculated using UV-Visible and fluorescence spectroscopy. The calculated thermodynamic parameters like change in enthalpy (ΔH°) and entropy (ΔS°) were found to be -6.11×104 and -128.96 JK-1mol-1 at 290 K respectively. CD revealed a change into more compact B-DNA conformation after binding with NMB. These studies suggest that intercalation mode, hydrogen bonding, and van der Waals forces might be responsible for DNA-NMB interaction. This work might further facilitate our understanding about DNA-drug interactions for utilizing them for medicinal purposes and nanochemistry.

Tris-(2-pyridyl)-pyrazolyl Borate Zinc(II) Complexes: Synthesis, DNA/Protein Binding and In Vitro Cytotoxicity Studies.

Zn(II) complexes bearing tris[3-(2-pyridyl)-pyrazolyl] borate (Tppy) ligand (1–3) was synthesized and examined by spectroscopic and analytical tools. Mononuclear [TppyZnCl] (1) has a Zn(II) centre with one arm (pyrazolyl-pyridyl) dangling outside the coordination sphere which is a novel finding in TppyZn(II) chemistry. In complex [TppyZn(H2O)][BF4] (2) hydrogen bonding interaction of aqua moiety stabilizes the dangling arm. In addition, solution state behaviour of complex 1 confirms the tridentate binding mode and reactivity studies show the exogenous axial substituents used to form the [TppyZnN3] (3). The complexes (1–3) were tested for their ability to bind with Calf thymus (CT) DNA and Bovine serum albumin (BSA) wherein they revealed to exhibit good binding constant values with both the biomolecules in the order of 104–105 M−1. The intercalative binding mode with CT DNA was confirmed from the UV-Visible absorption, viscosity, and ethidium bromide (EB) DNA displacement studies. Further, the complexes were tested for in vitro cytotoxic ability on four triple-negative breast cancer (TNBC) cell lines (MDA-MB-231, MDA-MB-468, HCC1937, and Hs 578T). All three complexes (1–3) exhibited good IC50 values (6.81 to 16.87 μM for 24 h as seen from the MTS assay) results which indicated that these complexes were found to be potential anticancer agents against the TNBC cells.

Newly Synthesized Benzothiazole Derived Ligand and its Co(III) and Ru(III) Complexes as Biological Potent Molecules: Chemical Preparation, Structure, Antimicrobial, in vitro and in vivo Cytotoxicity Studies

Herein we describe the synthesis of 2-((E)-(2-(benzo[d]thiazol-2-yl)phenylimino)methyl)-5-methoxyphenol imine base (BMM) and its metal complexes such as [Co(BMM)2] C1, [Co(BMM)(ph)] C2, [Ru(BMM)2] C3 and [Ru(BMM)(ph)] C4. The ligand and its complexes were characterized by spectroscopic, TGA, Powder X-ray diffraction (XRD), and elemental analysis. The coordination number and geometry were confirmed by various experimental data. The Co(III) and Ru(III) complexes are assigned to be having octahedral geometry. Further, the experimental results revealed that complex C2 and C4 emerged as moderate DNA binding intercalators compared to standard intercalators and prominent nuclease activity compared with C1 and C3 complexes. The extent of interaction and intercalation mode was confirmed by monitoring electronic absorption studies, fluorescence quenching probe, and viscosity measurement. Furthermore, the complexes C1-C4 were investigated for their in vitro cytotoxic studies against a panel of human cancer cell lines, viz., A549, NIH3T3, MCF-7, and EAC. Also, the cell adhesion and migration behavior were carried out after administering the complex C2 and C4 to respective cancer cell lines. In mice, the toxicities and tolerabilities of the complex C2 and C4 were also investigated through in vivo studies. The resultant complexes were screened for their microbial inhibition studies through the good diffusion method. All the complexes display moderate microbial inhibition properties compared to their uncoordinated analog.

Antimicrobial activity and mechanism of oregano essential oil against Shewanella putrefaciens

AbstractThe aim of the present study was to investigate the antimicrobial mechanism of oregano essential oil (OEO) against Shewanella putrefaciens. Antimicrobial activity of OEO against Shewanella putrefaciens was investigated by the agar disc diffusion method. The change of growth curve, electric conductivity, the integrity of cell membrane, alkaline phosphatase (AKP), and lactate dehydrogenase (LDH) activity were measured to evaluate its antibacterial mechanism. The morphology of bacterial cells was observed by scanning electron microscopy (SEM). The interaction between OEO and Shewanella putrefaciens genomic DNA was measured by ultraviolet–visible (UV–Vis) spectroscopy, and DNA ethidium bromide adduct was analyzed by fluorescence. The results showed that the minimum inhibitory concentration of OEO against Shewanella putrefaciens was 0.09% (v/v), and OEO could inhibit the growth of Shewanella putrefacien with a dose‐dependent manner. The cell membrane and cell wall of Shewanella putrefaciens were destroyed by OEO, which led to the leakage of nucleic acid, protein, and the release of AKP and LDH. The results of SEM confirmed the damaging effect of OEO on the bacterial morphology. The results of UV–Vis and fluorescence titration indicated that binding of the complexes to DNA was an intercalative mode.

Glutamine conjugated organotin(IV) Schiff base compounds: Synthesis, structure, and anticancer properties

AbstractHerein, glutamine conjugated organotin(IV) Schiff base compounds, [(SBGlu‐Naph)Sn (Me)2] (1), [(SBGlu‐Naph)Sn(n‐Bu)2] (2), [(SBGlu‐Sali)Sn (Me)2] (3), [(SBGlu‐Sali)Sn(n‐Bu)2] (4) and [(SBGlu‐Sali)Sn (Ph)2] (5), were synthesized by one‐pot reaction with an aldehyde (2‐hydroxy‐1‐naphthaldehyde) for 1 and 2, and 5‐methyl‐2‐hydroxybenzaldehyde (for 3–5) and respective diorganotin oxide. The compounds were characterized using elemental micro‐analyses, spectroscopic techniques (FT‐IR, 1H NMR, 13C NMR, and 119Sn NMR), mass spectrometry, and single‐crystal X‐ray diffraction analyses. Based on in‐silico ADME (absorption, distribution, metabolism, and excretion) and drug‐likeness properties, compounds 1, 3, and 4 were selected to investigate their DNA/Protein binding properties with calf thymus DNA (CT‐DNA) and bovine serum albumin (BSA) using spectrophotometry and spectrofluorimetry. The intercalative mode of binding with CT‐DNA was supported by molecular docking simulations. The emission spectral data of compounds with CT‐DNA showed 1 as a groove binder, and 3 and 4 as an intercalator which was confirmed by competitive displacement assays. Similarly, static and dynamic mode of interaction between the compounds and BSA was found. Furthermore, these compounds were screened for their cytotoxic activity against two human cancer cell lines; PC‐3 (Prostate) and Mg‐63 (Osteosarcoma) at different concentrations. Quantitative structure–activity relationship (QSAR)‐based regression models were developed and implemented on compounds 1, 3, and 4 that inferred compound 3 to be the most potential candidate for further in vivo studies.

A novel colorimetric, selective fluorescent “turn-off” chemosensor and biomolecules binding studies based on iodosalicylimine schiff-base derivative

We have designed a new iodosalicylimine-derived Schiff-base chemosensor ISNP, which is synthesized by the condensation reaction of 3, 5-diiodosalicylaldehyde with N-phenyl-o-phenylenediamine and characterized by various spectral techniques including FT-IR, 1H NMR, ESI-MS and elemental analysis. A colorimetric, UV–visible absorption and fluorescence spectral analyses revealed that chemosensor ISNP was able to sense Cu2+, F− and H2PO4− ions selectivity. Especially, ISNP preferentially recognized Cu2+ion through a fluorescent “turn-off” response while the colour of ISNP solution was changed from light yellow to violet even in the presence of other metal ions such as Co2+, Ni2+, Zn2+, Pb2+, Hg2+, Sr2+, Cd2+, Ca2+, Na+, K+, Al3+ and Cr3+ ions in CH3CN/H2O (9/1, v/v) solvent mixture. The chemosensor ISNP showed unique Chelation Enhanced Quenching process (CHEQ) effect only with Cu2+ ion, which can be attributed to ISNP–Cu2+ complex formation. In addition, chemosensor ISNP was selectively sensing both F− and H2PO4−anions compared with other anions such as Cl−, Br−, I−, NO3−, SCN− and ClO4−in a fluorescent “turn-off” mode while the colour of the solution was changed from light yellow to dark yellow in THF medium. According to the Job's plots, chemosensor ISNP exhibited a binding stoichiometric ratio of 1:1 with Cu2+, F−, and H2PO4− ions with the detection limit value of 2.0 μM for Cu2+ ion, 1.1 μM for F− ion and 2.4 μM for H2PO4−ion, which are much lower than the values set by WHO guidelines. Furthermore, spectral and docking methods revealed that chemosensor ISNP interacted with calf thymus DNA (CT-DNA) via an intercalation mode with a binding energy of − 6.1 kcal/mol while bovine serum albumin (BSA) or human serum albumin (HSA) was interacted with the chemosensor ISNP through a static fluorescence quenching process. Such a simple and convenient sensing strategy with a great potential for practical applications could provide a promising tool for rapid, sensitive and selective analysis of ions and biomolecules..

A green and sensitive guanine-based DNA biosensor for idarubicin anticancer monitoring in biological samples: A simple and fast strategy for control of health quality in chemotherapy procedure confirmed by docking investigation

Drug efficiency can be considerably boosted while adverse effects can be reduced by precisely monitoring the concentration of anti-cancer drugs. Thus, one of the most important parameters for human health is the monitoring and detection of anticancer drugs during chemotherapy treatment. Herein, a glassy carbon electrode (GCE) was modified by Pt- and Pd-incorporated ZnO nanoparticles-decorated single-wall carbon nanotubes (Pt–Pd–ZnO/SWCNTs) nanocomposites, and ds-DNA (Calf Thymus) that was a biological recognition element, and it was aimed to be utilized as an ultrasensitive and effective electroanalytical biosensor for idarubicin (IDR) monitoring. Various physicochemical characterization techniques including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS) were used to investigate the morphology and structure of the Pt–Pd–ZnO/SWCNTs nanocomposite, which was produced via straightforward chemical precipitation combined with the one-pot method. The layer-by-layer modification technique was implemented to fabricate the ds-DNA/Pt–Pd–ZnO/SWCNTs/GCE to be further utilized as a voltammetric sensor for sensitive monitoring of idarubicin in biological fluids and pharmaceutical substances. The electroanalytical method implemented to detect idarubicin was based to detect the ds-DNA's guanine base signal on the surface of the modified electrode in the absence and presence of the anticancer drug. The results explicated that the developed biosensor performed well in determining idarubicin in concentrations ranging from 1.0 nM to 65 μM, with a detection limit of 0.8 nM. The idarubicin detection ability of the modified electrode in real samples was evaluated, and the recovery data was acquired in the range of 98.0% and 104.75%. In the final step, the preferential intercalative binding mode of idarubicin drug with ds-DNA was approved by molecular docking study. This study paves the way for engineering highly sensitive DNA biosensors to be employed in the monitoring of anticancer drugs by combining the benefits of nanocomposites and valuable information of a molecular docking study.

Synthesize and multi-spectroscopic studies of zinc-naproxen nanodrug as DNA intercalator agent

The zinc-naproxen complex as a nano-drug (NanoD) was synthesized successfully via effective ultrasound-assisted processes. The chemicophysical properties of the NanoD were determined using FT-IR, XRD, SEM, DLS, and EDX mapping analyses. The results confirmed the formation of the 55 nm NanoD laminates. The interaction of the obtained NanoD with calf thymus deoxyribonucleic acid (CT-DNA) was studied as well. Structural and topography changes of DNA in interaction with the NanoD were investigated by atomic force microscopy (AFM). The results of electronic absorption spectroscopy, the DNA-viscosity studies, and competition fluorescence spectroscopy showed that CT-DNA binds to the NanoD through the intercalative binding mode. The data of AFM analysis indicated swollen CT-DNA upon interaction with the NanoD. The in vitro investigation of cytotoxicity of the NanoD on HT-29, Hep G2, and B16–F10 cancer cells as well as normal HFF-1 cells. The obtained results demonstrated high cytotoxicity activity of the NanoD than that of cisplatin in the HT-29 cell line, especially at lower concentrations. On the B16–F10 cell line at lower concentrations (up to 8 μg mL−1), it is comparable to cisplatin and on the Hep G2 cell line and normal HFF-1 cell line at all concentrations, cytotoxicity of cisplatin is more than NanoD.

Benzimidazole-quinoline-based copper complexes: Exploration for their possible antitumor mechanism

In this study, we synthesised and characterised two benzimidazole-quinoline-based copper complexes, namely, [Cu(btmbq)Br]2 (1) and [Cu(btmbq)Cl]2 (2), (btmbq = 3-(1-(1H-benzotriazol-1-y-l)methyl)-6-bromo-1H-benzoimidazol-2-yl)isoquinoline). Both complexes showed strong antitumor abilities against the colon cancer cell line (HCT116) and low cytotoxicity against the normal liver cell line (L-02). The DNA binding affinity was evaluated using CD and fluorescence spectroscopy, and the Ksv and Kapp values were further quantified, revealing that the complexes bound to DNA in the intercalation mode, and caused oxidative damage to pBR322 DNA. Furthermore, complex 1 interfered with the steady-state balance of redox and Ca2+ in HCT116 cells, as well as induced cell mitochondrial membrane potential (Δψm) collapse, ATP dissipation, ultimately arrested the cell cycle in G2 phase and induced cell apoptosis. Further exploration demonstrated that the production of reactive oxygen species (ROS) might be the major contributors to the apoptotic death of HCT116 cells.

Structure elucidation, in vitro binding studies and ROS-dependent anti-cancer activity of Cu(II) and Zn(II) phthaloylglycinate(phen) complexes against MDA-MB-231 cells.

New mononuclear Cu(II) and Zn(II)-based complexes 1 [Cu(L)2(diimine)HOCH3] and 2 [Zn(L)2(diimine)] have been synthesized as anti-cancer chemotherapeutics targeted to tRNA. The structure elucidation of complexes 1 and 2 was carried out by spectroscopic and single X-ray diffraction studies. In vitro interaction studies of complexes 1 and 2 with ct-DNA/tRNA were performed by employing various biophysical techniques to evaluate and predict their interaction behavior and preferential selectivity at biomolecular therapeutic targets. The corroborative results of the interaction studies demonstrated that complexes 1 and 2 exhibited avid binding propensity via intercalative mode of binding toward ct-DNA/tRNA. Electrophoretic assay revealed that the complexes 1 and 2 were able to promote single- and double-strand cleavage of the plasmid DNA at low micromolar concentrations under physiological conditions in the absence of an additional oxidizing or reducing agent. RNA hydrolysis studies revealed that the complexes 1 and 2 could promote tRNA cleavage in a concentration and time-dependent manner. The cytotoxic potential of complexes 1 and 2 was evaluated against the MDA-MB-231 cell line, which showed that the complexes were able to inhibit the cell growth in a dose-dependent manner. The intracellular ROS production and mitochondrial superoxide anion assay revealed that the complexes 1 and 2 induce a dose-dependent activity, suggesting the involvement of ROS-mediated mitochondrial apoptotic pathway leading to cell death.

The Interaction between DNA and Three Intercalating Anthracyclines Using Electrochemical DNA Nanobiosensor Based on Metal Nanoparticles Modified Screen-Printed Electrode.

The screen-printed electrodes have gained increasing importance due to their advantages, such as robustness, portability, and easy handling. The manuscript presents the investigation of the interaction between double-strand deoxyribonucleic acid (dsDNA) and three anthracyclines: epirubicin (EPI), idarubicin (IDA), and doxorubicin (DOX) by differential pulse voltammetry on metal nanoparticles modified by screen-printed electrodes. In order to investigate the interaction, the voltammetric signals of dsDNA electroactive bases were used as an indicator. The effect of various metal nanomaterials on the signals of guanine and adenine was evaluated. Moreover, dsDNA/PtNPs/AgNPs/SPE (platinum nanoparticles/silver nanoparticles/screen-printed electrodes) was designed for anthracyclines–dsDNA interaction studies since the layer-by-layer modification strategy of metal nanoparticles increases the surface area. Using the signal of multi-layer calf thymus (ct)-dsDNA, the within-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 0.58% and 0.73%, respectively, and the between-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 1.04% and 1.26%, respectively. The effect of binding time and concentration of three anthracyclines on voltammetric signals of dsDNA bases were also evaluated. The response was examined in the range of 0.3–1.3 ppm EPI, 0.1–1.0 ppm IDA and DOX concentration on dsDNA/PtNPs/AgNPs/SPE. Electrochemical studies proposed that the interaction mechanism between three anthracyclines and dsDNA was an intercalation mode.

Cu(II) complexes of a bio-compatible aminoguanidine Schiff base: Histidine sensing and DNA-binding studies

Two Cu(II) complexes of pyridoxal-aminoguanidine Schiff base ligand with formula [Cu(HL)Cl]2(OAc)2·4H2O (1) and [Cu(HL)Cl(NCS)].H2O (2) are reported. The ligand and the complexes were characterized by their elemental analyses, ESI-MS, Uv–Vis, IR spectroscopy and cyclic voltammetric measurements. Single crystal structures of complex 1 and 2 were solved by X-ray diffraction. In both the Cu(II) complexes Cu(II) ions are in a square pyramidal geometry having geometry index (τ) value of 0.11 for complex 1 and 0.15 for complex 2. Both the complexes bind to calf-thymus DNA with binding constant comparable to ethidium bromide. Circular dichroism studies revealed an intercalative mode of binding for both the complexes. In addition, the complexes also show promising cleavage of pUC19 supercoiled plasmid DNA with 1 showing the highest cleavage activity of ∼ 99%. In addition, both the complexes selectively recognize l-histidine amino acid. The low detection limit values (0.085 μM and 0.19 μM for complexes 1 and 2, respectively) ascertain the making of an efficient l-histidine biosensor. The absorption, emission and mass spectral results establish the formation of Cu(His)2 complex, with liberation of the fluorescent free ligand as the mechanism of sensing.

Study of versatile coordination modes, antibacterial and radical scavenging activities of arene ruthenium, rhodium and iridium complexes containing fluorenone based thiosemicarbazones

Halide-bridged metal precursors [(arene)MCl2]2 (arene = p-cymene, Cp*; M = Ru, Rh and Ir) on reaction with thiosemicarbazone derivative ligands (L1, L2 and L3) yielded a series of mononuclear ruthenium, rhodium and iridium complexes and their corresponding dinuclear analogues. All these complexes (1-9) were characterized by analytical and spectroscopic techniques. Single-crystal X-ray diffraction studies determined the molecular structures of complexes 1, 5, 7-9. The compounds were screened for their in vitro antibacterial activity against gram-positive Staphylococcus aureus (MTCC 3160, MMSA, ESKAPE) and Bacillus thuringiensis (MTCC 8995) and gram-negative Escherichia coli (MTCC 1687) and Pseudomonas aeruginosa (MTCC 1688, ESKAPE) strains, where they exhibit the significant antibacterial effect. In addition, the compounds were also investigated for antioxidant activities using DPPH radical scavenging assays, in which most of them displayed substantial antioxidant activities. Furthermore, the binding of ligand L3 with biomolecules such as Salmon milt DNA (SM-DNA) investigated by UV-Vis absorption spectroscopy revealed an intercalative mode of interaction.

Synthesis, Spectroscopic, Antibacterial, Antioxidant, DNA Binding and Cleavage, Molecular Docking Studies of Ni(II) and Cu(II) Complexes of S and N Donor Schiff Base Ligands

Binary metal complexes of the ligands (L), H3FPT and H3FP4MT with Ni(II) and Cu(II) metal ions (M) were synthesized and characterized by different spectral and analytical techniques. Among these complexes, Ni(II)- H3FPT complex was found to be polymeric. The ligands and their complexes inhibited the growth of gram positive and gram negative bacterial strains to a moderate extent. The antioxidant nature of ligands and complexes was also established. Intercalative mode of binding of the complexes with calf thymus (CT) DNA was proposed from electronic absorption titrations, fluorescence quenching studies and viscosity measurements. The complexes showed hydrolytic cleavage of plasmid pBR322. Docking studies of metal complexes with DNA revealed that the complexes of H3FP4MT are more active than H3FPT.

Synthesis, characterization, POM analyses and biological evaluation of n-[(2-methoxy-5- nitrophenyl)]-4-oxo-4-[oxy] butenamide based zinc(II) carboxylate complexes

ABSTRACT. The aim of medicinal chemistry is to links many scientific disciplines and allows the scientists in researching and developing new drugs with enhance and targeted properties. In this article we are exploring the preparation of four new zinc(II) carboxylate complexes based on N-[(2-methoxy-5-nitrophenyl)]-4-oxo-4-[oxy]butenamide which were characterized through FT-IR and EDX studies. The DNA binding ability and binding type of complexes were assessed by spectroscopic (UV-Visible) and viscosity measurements, exhibiting an intercalative pattern of interaction. The synthesized compounds were also assessed to know theoretically about their nature by molecular docking studies resulting also in intercalation mode. Analysis of the complexes for biological applications such as anti-microbial, anti-leishmanial, cytotoxicity and DNA damage activities showed that these complexes carries good anti-microbial, anti-leishmanial activity with no toxicity to human blood thyrocytes and DNA. The bioavailability prediction and drug likeness score has also been evaluated through Insilco studies.
 
 KEY WORDS: Zn(II) carboxylate complex, DNA binding, Anti-leishmanial activity, Cytotoxicity, Docking study
 
 Bull. Chem. Soc. Ethiop. 2021, 35(2), 365-380.
 DOI: https://dx.doi.org/10.4314/bcse.v35i2.11

DNA/BSA binding affinity studies of new Pd(II) complex with S-S and N-N donor mixed ligands via experimental insight and molecular simulation: Preliminary antitumor activity, lipophilicity and DFT perspective

Due to the importance of metallo drugs that can bind to DNA and prohibit division of cancer cells, a novel water-like palladium(II) complex, [Pd(phen)(proli-dtc)]NO3 (phen = 1,10-phenanthroline and proli-dtc = pyrrolinedithiocarbamate), has been prepared in this work. The structure of this metal complex was verified utilizing experimental and computational analysis. The central Pd(II) ion was found to be at the center of a square-planar arrangement. The preliminary antitumor activity and lipophilicity of the compound was more impressive than that of cisplatin. Moreover, in-silico prediction demonstrated that this complex has low toxicity effects and possesses high drug-likeness. DFT calculations were conducted to study the reactivity and stability descriptors as well as NBO analysis of the mentioned complex. The binding affinity of Pd(II) complex to CT-DNA was explored utilizing fluorescence, electronic absorption spectroscopy, gel electrophoresis and viscosity test which illustrated that this complex could strongly interact with CT-DNA through hydrophobic interaction (intercalation mode). In addition, the interaction between complex and BSA was investigated by fluorescence, electronic absorption, CD spectroscopy and FRET analysis and the obtained findings illustrated a moderate interaction in BSA-Pd(II) complex system via hydrogen bond and van der Waals forces. The results of electronic absorption and CD spectra exhibited that the complex refolded the BSA by increasing the percentage of α-helix. Docking simulation was also performed to predict the binding pose of the metal complex to both biomolecules.

Crystal structures of three transition metal complexes with salicylaldehyde-4-hydroxy phenylacetyl acylhydrazone and their interactions with CT-DNA and BSA

A salicylaldehyde-4-hydroxy phenyl acetyl acyl hydrazone (C15H14N2O3, HL) and its three complexes ([CuLPy]NO3 (1), [CuLCl(EtOH)] (2) and [CoL2]NO3·EtOH, (3)) were synthesized. The single crystal X-ray diffraction results of 1, 2 and 3 showed that the coordination atoms (N and O atoms) in the complexes exhibited four-coordinated pyramidal, five-coordinated and six-coordinated octahedral geometries centered on the metal ions, respectively. TG-DTG techniques illustrated that the maximum thermal decomposition peak temperatures of these compounds were all higher than 200 ℃, exhibiting strong thermal stabilities. All four compounds, HL, 1, 2 and 3, quenched the intrinsic fluorescence of BSA by means of static processes, as investigated by fluorescence spectra, which suggested that these compounds could effectively combine with BSA to form non-fluorescent ground state complexes. The UV–vis spectra showed that HL, 1, 2 and 3 effectively combined with CT-DNA through intercalative modes. Microcalorimetry tests indicated that the interaction processes of HL, 1 and 2 with BSA and CT-DNA were all spontaneously exothermic and entropy reducing, and each of the interaction durations was within 50 min. The interactions of the four compounds with BSA and CTDNA were also simulated by the molecular docking method, showing that the four compounds had hydrogen bonds and hydrophobic interactions with BSA and CT-DNA. The antibacterial activities of HL, 1, 2 and 3 against S. aureus, P. aeruginosa, B. subtilis and E. coli were determined, revealing that 1 and 2 exhibit stronger inhibition activities against P. aeruginosa than gentamicin sulfate. Complexes 1 and 2 are potential alternative drugs to gentamicin sulfate in the future.

Graphene oxide/graphene quantum dots: A platform for probing ds-DNA-dimethoate interaction and dimethoate sensing

A nanocomposite of graphene oxide and graphene quantum dots ([email protected]) were used for the first time to probe the ds-DNA-dimethoate (DMT) interaction and detect the DMT at a trace level. Graphene quantum dots were electrodeposited onto a glassy carbon electrode (GCE), followed by casting a graphene oxide layer. This platform was employed to adsorb the ds-DNA to fabricate DNA biosensors (ds-DNA/[email protected]/GCE). Microscopic and electrochemical characterizations of the modified electrodes were performed. The GO/GDQs/GCE platform exhibited remarkable electrocatalytic oxidation of DMT from acetate and phosphate buffers. The oxidation process of DMT was pH-dependent and irreversible, proceeding under the mixed adsorption and diffusion-controlled mechanism. The interaction of salmon sperm double-strand DNA (ss-dsDNA) with DMT was investigated using differential pulse voltammetry and UV/vis spectroscopy. Mixed binding modes of intercalation and the electrostatic were ascertained for the interaction of DMT to dsDNA. Such a result was confirmed from the voltammetric data of single-stranded DNA (ssDNA) and the ionic strength study. The UV–Vis study has also supported that finding. The indirect DMT detection is verified by the drop in DNA oxidation signals or increasing DPV peak currents conducted from [Fe(CN)6]3−/4− probe. The decrease in the DNA peak currents linearly correlated to DMT linear range of 10−15 M to 10−10 M with a limit of detection about 10−15 M. The same detection limit was achieved through the increasing the peak current of [Fe(CN)6]3−/4− at DMT linear range of 10−15 to 10−12 M. The mechanism of DMT oxidation on GO/GQDs/GCE was proposed and confirmed by forming a self-assembled layer (SAM) of DMT onto the gold electrode (AuE). The surface DMT undergoes anodic oxidation with Ep close to the one recorded at GO/GQDs modified surface, referring that the amide group is only possible to oxidize, and the sulfur-containing groups are involved in SAM. The DMT-SAM/AuE would present additional evidence for the surface analysis of DMT-DNA interaction where a change in the DMT peak current upon adding DNA was recorded. [email protected]/GCE sensor exhibits a rapid response, reproducibility, a low detection limit, and high selectivity. The present work may expand the use of GO/GQDs modifiers in the field of electrochemical sensors.

Spectroscopic, quantum chemical calculations, antioxidant, anticancer, antimicrobial, DNA binding and photo physical properties of bioactive Cu(II) complexes obtained from trifluoromethoxy aniline Schiff bases

In this study, new three Schiff base ligands and their Cu(II) complexes: 1 [Cu(L1)2], 2 [Cu(L2)2] and 3 [Cu(L3)2], where HL1-HL3 represent Schiff base ligands (HL1 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-6‑chloro-4-fluorophenol, HL2 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-3,5-dimethoxy-phenol and HL3 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-5-(diethylamino)phenol) were synthesized. The structural features were confirmed from their micro analytical, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), UV–visible, mass, magnetic susceptibility measurements, ESR and thermal analysis. The spectroscopic approaches proposed a square planar geometry for all Cu(II) complexes. The stability of the binary metal(II) complexes has been calculated from quantum chemical parameters using highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies. All the tested complexes preferably bind to CT-DNA via intercalation mode as resulted from UV spectroscopy and EB competition assay studies. In addition, the metal complexes exhibited good cleavage ability against the pBR322 DNA in the presence and absence of H2O2 as well as UV light. The antioxidant activity of 1–3 was evaluated by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical with reference of ascorbic acid. Of these, complex 1 show good antioxidant activity. The in vitro cytotoxicity studies of the ligands and their complexes against human lung (A549) and breast (MCF7) cancer cell lines showed significant activity. The Schiff base ligands and their metal complexes were screened for their biological activities and are found to be the complexes have higher activities than the free Schiff bases.

Synthesis, DNA binding, apoptosis and molecular docking of a Mn(II) complex constructed by 2-(1,2,4-Triazol-1-yl)-4-picolinic acid

A new metal–organic complex (MOC), Mn(L)2·4H2O is successfully designed and synthesized by 2-(1,2,4-Triazol-1-yl)-4-picolinic acid ligand and Mn(NO3)2·4H2O in the mixed solvent of methanol and water. The complex was characterized by single-crystal X-ray diffraction, element analysis, Powder X-ray diffraction(PXRD). The binding constant between complex and DNA is 9.3 × 104, indicating that the complex and fish sperm DNA can bind well. Viscosity experiments prove that the complex interacts with DNA in an intercalation mode. Apoptosis and inverted microscope experiments show that the complex has obvious apoptotic effects on cancer cells. In general, the synthesized Mn(II) complex is of great significance to the treatment of cancer.