The amplification effect of functionalized gold nanoparticles on the binding of anticancer drug dacarbazine to DNA and DNA bases

The promising application of functionalized gold nanoparticles to amplify the performance of biosensors and relevant biomolecular recognition processes has been explored in this paper. Our observations illustrate the apparent enhancement effect of the gold nanoparticles on the electrochemical response of the anticancer drug dacarbazine (DTIC) binding to DNA and DNA bases, indicating that these functionalized gold nanoparticles could readily facilitate the specific interactions between DTIC and DNA/DNA bases. This raises the potential valuable applications of these biocompatible nanoparticles in the promising biosensors and biomedical engineering.     

SPECTRAL STUDIES ON THE BINDING OF A BISACRIDINIUM DERIVATIVE LUCIGENIN WITH DOUBLE HELIX DNA

ABSTRACT

In this paper, the noncovalent binding of the cationic reagent lucigenin (LC) to DNA was investigated using spectroscopic methods. The results from absorption, circular dichroism and fluorescence studies demonstrated that LC could intercalate into the helix of DNA. Polarization and melting studies further supported the intercalation binding of LC with DNA. The binding constant was obtained by varying the DNA concentration, while keeping the concentration of LC constant. It was of the order of 10⁴ mol^?1 L in DNA base pairs. The experiment also showed that electrostatic interaction played a significant role in the intercalation of LC with DNA. It is supposed to be because of being attracted first by anionic DNA that LC can be intercalated into the interior of the DNA double helix. This research offers a new intercalation functional group to DNA-targeted drug design.     

The application of new nanocomposites: Enhancement effect of polylactide nanofibers/nano-TiO2 blends on biorecognition of anticancer drug daunorubicin

In this contribution, the blending of nano-titanium dioxide (TiO₂) and polylactide (PLA) nanofibers has been adopted as a new nanomaterial to facilitate the biorecognition of an anticancer drug daunorubicin. Our observations demonstrate that upon application of the nano-TiO₂-PLA polymer nanocomposites, the drug molecules could be readily self-assembled on the surface of the new nanocomposites so that considerably enhanced detection sensitivity for the DNA binding behavior could be observed for the relative biorecognition. These results may also imply some potential valuable application of the blending of nano-TiO₂ and PLA nanofibers as a kind of drug carriers in view of the respective good biocompatibility and large surface area of the new nanocomposites.     

T-graphene and its boron nitride analogue as versatile drug delivery systems

In recent years, drug delivery systems based on nanostructures have become some of the most interesting to be studied. In the present work, we have explored a new allotrope of carbon, which is tetragonal, known as T-graphene (TG) and its boron nitride analogue (TBN) as versatile drug delivery systems. The purpose of the present work is to study the interaction of TG and TBN nanosheets with 5-fluorouracil (F), 6-thioguanine (T) and 6-mercaptopurine (M) anticancer drugs using the density functional theory (DFT). We found that the higher value of adsorption energies (more negative) in the solvent phase reveals that the TG and TBN nanosheets can improve their solubility and change their interaction with the drugs in the aqueous phase. Also, our ultraviolet–visible analysis presents that the electronic spectra of the drug–nanosheet complexes show a red shift toward higher wavelengths (lower energies). To go further and gain insight into the binding features of considered systems with studied drugs, the Atoms in Molecules analysis was performed. Our results determine the electrostatic features of the drug–nanosheets bonding. Consequently, the results demonstrated that the TG and TBN could be used as potential carriers for the delivery of anticancer drugs.

     

Metal oxide nanoclusters as drug delivery systems for an anticancer drug: a theoretical study

In this study, the reactivity and electronic sensitivity of the Be₁₂O₁₂, Mg₁₂O₁₂, and Zn₁₂O₁₂ nanoclusters were investigated for 6-thioguanine (TG) anticancer drug using density functional theory calculations at the gas phase and aqueous solution. Our results show that the electronic properties of Mg₁₂O₁₂ and Zn₁₂O₁₂ nanoclusters are significantly sensitive to the presence of TG and the nanoclusters may be a promising candidate for adsorption of this drug. The results show that all complexes are energetically favourable, especially in the aqueous phase. Also, our ultraviolet–visible results show that the electronic spectra of TG/(MO)₁₂ complexes exhibit a blue shift toward lower wavelengths (higher energies). In order to go further and gain insight into the binding features of considered (MO)₁₂ nanoclusters with TG drug, the Atoms in Molecules analysis was performed. Consequently, the results demonstrated that the Mg₁₂O₁₂ and Zn₁₂O₁₂ nanoclusters could be used as potential carriers for the delivery of TG drug.

The results represented that the Mg₁₂O₁₂ and Zn₁₂O₁₂ nanoclusters could be used as potential carriers for delivery of 6-thioguanine drug in the nanomedicine domain.     

Exploration of small hydroxy‐9,10‐anthraquinones as anthracycline analogues: physicochemical characteristics and DNA binding for comparison

Hydroxy‐9,10‐anthraquinones resemble anthracycline‐based anticancer drugs. By varying the pH of the solution, the proton dissociation constants of 1,2,5,8‐tetrahydroxy‐9,10‐anthraquinone (THAQ) were determined. Interaction of THAQ with calf thymus DNA (ct DNA) was studied by UV–Vis spectroscopy to determine the overall binding constant and site size of interaction. The binding constant values (~10⁴) for THAQ interacting with ct DNA at different pH were an order less than that known for anthracyclines. From knowledge of the overall binding constants at different pH values and the first pK of THAQ, the contribution of each form (neutral and monoanionic) towards overall binding with ct DNA could be obtained under physiological conditions. Hence, knowing the contributions of the neutral and monoanionic forms, it now becomes possible to know the overall binding constant for an interaction of THAQ with ct DNA at any pH. The calculated parameters help in understanding the role of the negative charge on the monoanionic form during interaction and suggests suitable chemical modifications that could prevent the development of such negative charges. This could lead to an increase in binding of THAQ to ct DNA. The study also helps to recognize the importance of sugar units in anthracycline anticancer drugs in DNA interaction. Copyright © 2011 John Wiley & Sons, Ltd.     

Unusual case of desmotropy. Combined spectroscopy (1H-14N NQDR) and quantum chemistry (periodic hybrid DFT/QTAIM and Hirshfeld surface-based) study of solid dacarbazine (anti-neoplastic)

Antineoplastic chemo-therapeutic drug 5-(3,3-dimethyl-1-triazenyl)imidazole-4-carboxamide (Dacarbazine, DTIC), has been studied experimentally in solid state by ¹H-¹⁴N NQDR double resonance at 295 K and theoretically by the Density Functional Theory (DFT)/Quantum Theory of Atoms in Molecules (QTAIM) and Hirshfeld surfaces analysis. Only one set of eighteen resonance frequencies was found in the experiment. This indicates the presence of six inequivalent nitrogen sites: –N(CH₃), –NH₂, –NH- and three –N= (of which one is a ring, two are from triazene) in the DTIC molecule. This contradicts the X-ray data which revealed the multiplication of nitrogen sites due to unusual desmotropism. The averaging of NQR frequencies caused by the fast in NQR time-scale exchange of protons in a double-well potential combined with the oscillations of twisted supramolecular synthons was proposed as a potential mechanism responsible for this apparent contradiction. An effective improvement in the quality of the spectrum reproduction was achieved when the calculations were performed assuming the periodic boundary conditions, BLYP functional, the DNP basis set and taking the 3×3×3 k-point separation. The ordering of the nitrogen sites according to the increasing quadrupole coupling constant (QCC): N(3)<N(2)<N(6)<N(1)<N(4)<N(5) reflects the metabolic pathway of DTIC. Two sites N(5) and N(4) with the highest QCC are responsible for the first step – conversion to MTIC (5-[3-methyl-triazen-1-yl]-imidazole-4-carboxamide) required for effective processes of binding dacarbazine to DNA (demethylation of N(5)), and the second step – fast conversion of MTIC to 5-amino-1H-imidazole-4-carboxamide (AIC; remove –N(4)–N(5)HCH₃). N(5) does not participate in any, while N(4) participates in weak C(2)H⋯N(4) interaction which can be readily broken. The four remaining nitrogen atoms N(1), N(2), N(3) and N(6) participate in strong intermolecular N(1)H⋯N(2) and intramolecular N(3)–H⋯N(6) bonds, which stiffen the crystalline structure.     

Influence of Mg+2 and Cu+2 on the Interaction Between Quinolone and Calf Thymus DNA

Mg⁺² and Cu⁺² have different binding capacities to quinolone drugs and have different binding modes with calf thymus DNA. Using the method of absorption and fluorescence spectroscopy, the influence of Mg⁺² and Cu⁺² on the binding between calf thymus DNA and each of four quinolone drugs has been studied. The results show that both Mg⁺² and Cu⁺² can bind with the four drugs. In the absence of divalent metal ions, quinolone drugs interact with DNA double helix by forming hydrogen bonds between the carboxyl and carbonyl groups of the drugs and the phosphate groups of the DNA bases, and the binding capacity shows a close relationship with the drug structures. The two metal ions show different influences on the binding between the drug and DNA, which depends on the type of ion, concentration of the metal ions and the structure of drugs. Mg⁺² in lower concentrations (0.01 mM to 3.0 mM) can act as a bridge between the carboxyl group/carbonyl group of the drug and the phosphate group of the DNA by electrostatic interaction, while Cu⁺² can act as an intermediary ion between carboxyl group/carbonyl group of the drug and the DNA bases by a co-ordinate bond. Both actions can increase the interaction of the ?? electron between the condensed rings of the drugs and the DNA bases. In some conditions, Cu⁺² can weaken the binding between the drug and the DNA by competitive inhibition if there is a site on the drug that can directly bind both DNA bases and Cu⁺².     

Multi-spectroscopic and molecular docking studies on the interaction of new phthalimides with calf-thymus DNA: In vitro free radical scavenging activities

ABSTRACT

In this study, we report the synthesis and biological evaluation of novel phthalimide based Schiff base derivatives as promising antioxidant and DNA-binding agents. The structural investigation of the synthesized compounds was determined by spectral and elemental analysis. In vitro DNA-binding studies of title compounds were carried out by UV–Vis, fluorescence, circular dichroism spectroscopic techniques, cyclic voltammetry, thermal denaturation studies, and hydrodynamic measurements to investigate their potential as DNA-binding agents. The DNA binding constant (K_b) of target compounds was obtained from absorption studies between 1.2 × 10⁵ M^?1 and 1.27 × 10⁵ M^?1, respectively, suggesting that the test compounds have shown good affinity toward calf-thymus DNA. The experimental results of DNA-binding studies reveal a non-intercalative mode of binding between DNA and the synthesized compounds, most probably groove binding. In addition, molecular docking techniques were performed to rationalize the observed binding affinities with the target DNA. Furthermore, antioxidant and free radical scavenging activities of the synthesized compounds were carried out to find out their pharmacological potential. The results indicate that the title compounds displayed good antioxidant activity against DPPH (IC₅₀: 0.727 and 0.656 mg/mL) and H₂O₂ radicals (IC₅₀: 1.072 and 0.911 mg/mL) comparable to standard ascorbic acid.     

Design,synthesis, and in silico studies of novel eugenyloxy propanol azole derivatives having potent antinociceptive activity and evaluation of their β-adrenoceptor blocking property

The design, synthesis, antinociceptive and β-adrenoceptor blocking activities of several eugenyloxy propanol azole derivatives have been described. In this synthesis, the reaction of eugenol with epichlorohydrin provided adducts 3 and 4 which were N-alkylated by diverse azoles to obtain the eugenyloxy propanol azole analogues in good yields. Adducts 3 and 4 were also reacted with azide ion to obtain the corresponding azide 6. The ‘Click’ Huisgen cycloaddition reaction of 6 with diverse alkynes afforded the title compounds in good yields. The synthesized eugenyloxy propanol azole derivatives were in vivo studied for the acute antinociception on male Spargue Dawley rats using tail-flick test. Compounds 5f, 5g, 7b and 11a exhibited potent analgesic properties in comparison with eugenol as a standard drug. In addition, all compounds were ex vivo tested for β-adrenoceptor blocking properties on isolated left atrium of male rats which exhibited partial antagonist or agonist behaviour compared to the standard drugs. The molecular docking study on the binding site of transient receptor potential vanilloid subtype 1 (TRPV1) has indicated that like capsaicin, eugenyloxy propanol azole analogues exhibited the strong affinity to bind at site of TPRV1 in a “tail-up, head-down” conformation and the presence of triazolyl moieties has played undeniable role in durable binding of these ligands to TRPV1. The in silico pharmacokinetic profile, drug likeness and toxicity predictions carried out for all compounds determined that 5g can be considered as potential antinociceptive drug candidate for future research.

     

Spectroscopic Studies of a New Multi-Element Sensitive Fluorescent Probe Derived from 2-(2-pyridyl)benzimidazole: Selective Discrimination of Zn2+ from Its Congeners

ABSTRACT

A new multielement sensitive fluorescent probe, 1-(2-(phenylthio)ethyl)-2-(pyridin-2-yl)-1H-benzo[d]imidazole (L), has been synthesized by the reaction between 2-(pyridyl) benzimidazole and 2-chloroethyl phenyl sulfide. Excitation and emission wavelength of L are at 330 and 371 nm, respectively. Among various transition and nontransition metal ions, it can selectively read Zn²⁺ ion as the emission wavelength of L undergoes a red shift by 31 nm upon binding with Zn²⁺ in methanol. In the presence of Cd²⁺, Hg²⁺, and other common cations, the emission wavelength of L remains unchanged, and thus allows us to discriminate Zn²⁺ from its congeners. Both L and its Zn²⁺ complex are well characterized by different spectroscopic techniques like ¹H-NMR, ESI-TOF (+) mass, FT-IR, and elemental analysis data. The binding constant value of the complexation reaction between L and Zn²⁺ is found as 724.6 M^?1 in methanol. Density functional theoretical (DFT) studies nicely demonstrate the red shift in the emission wavelength of L upon binding with Zn^2+.     

Spectroscopic and Electrochemical Studies on the Interaction of Carmoisine Food Additive with Native Calf Thymus DNA

ABSTRACT

In this work, for the first time interaction between a carmoisine food additive and native calf thymus DNA was monitored using UV-Vis absorption, fluorescence, and circular dichroism (CD) spectroscopy, as well as cyclic voltammetry and viscosity measurements. It can be concluded that carmoisine could interact with DNA via a groove-binding mode as evidenced by a hyperchromic effect of absorption spectra, increases in the fluorescence quenching effect of DNA, certain induced CD spectral changes, and relatively small changes in the viscosity of DNA. The binding constants (K_b) for the carmoisine with DNA was estimated to be 6.2 × 10⁴ M^?1 through spectroscopic titrations. The cyclic voltammetry method showed that both anodic and cathodic peak currents of carmoisine decreased upon addition of the DNA. Circular dichroism spectra indicated that there are certain detectable conformational changes such as conversion from B-like to A-like in the DNA double helix when carmoisine was added.     

Elucidation of the Binding Properties of A Photosensitizer to Salmon Sperm DNA and Its Photobleaching Processes by Spectroscopic Methods

Methylene blue (MB) is a tricyclic heteroaromatic photosensitizer with a promising application in the photodynamic therapy (PDT) for anticancer treatment. The binding properties of MB to salmon sperm DNA have been investigated by the measurements of absorption spectra, quenching experiments and the photobleaching processes. Remarkable hypochromic and bathochromic effects of MB in the presence of increasing amounts of DNA have been observed in the absorption spectra. The quenching of MB by the DNA bases obeys the Stern-Volmer equation and ferrocyanide quenching of MB in the absence and presence of DNA is also measured as extended experiments. Results from the above spectral measurements are all consistent with the intercalative binding mode of MB to DNA with the K _b value of 5.6?×?10³?M^?1. The photobleaching processes of MB and its DNA complex have also been studied, which indicate that the photobleaching of MB and its DNA complex proceed with different mechanisms and the reactive oxygen species are responsible for the self-sensitized photooxidation of MB.     

Interaction of a New Fluorescent Probe with DNA and its Use in Determination of DNA

In this paper we reported a metal complex 1-Zn (2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine-4-hydroxy-phenyl)-ethylene]-pyrazine-Zn) as a fluorescent probe sensing DNA. The result of the competitive experiment of the probe with ethidium bromide (EB) to bind DNA, absorption spectral change and polarization change in the presence and absence of DNA revealed that interaction between the probe and DNA was via intercalation. Ionic strength experiment showed the existence of electrostatic interaction as well. Scatchard plots also confirmed the combined binding modes. The fluorescence enhancement of the probe was ascribed to highly hydrophobic environment when it bound the macromolecules such as DNA, RNA or denatured DNA. The binding constant between the probe and DNA was estimated as 3.13 × 10⁷ mol⁻¹ L. The emission intensity increase was proportional to the concentration of DNA. Based on this, the probe was used to determine the concentration of calf thymus DNA (ct-DNA). The corresponding linear response ranged from 2.50 × 10⁻⁷ to 4.75 × 10⁻⁶ mol L⁻¹, and detection limit was 1.93 × 10⁻⁸ mol L⁻¹ for ct-DNA.     

Locating of Nucleic Acid Intercalators in Yeast Cells by Image Analysis Combined Fluorescence Microscopy

Intracellular distribution in the intact (not fixed) Saccharomyces cerevisiae cells of the nucleic acid intercalators (NAI) was studied using fluorescence microscopy combined with computer image analysis (ImageJ software, NIH, USA). Three NAI—the anthracycline anticancer drug doxorubicin (DR) along with the nucleic acid dyes ethidium (E) and 4′,6-diamidino-2-phenylindole (DAPI)—were used. Staining pattern and ImageJ quantitative analysis data provided evidence that all three NAI were located in the nuclei and in the mitochondria. DR and E, in contrast to DAPI, may be bound to not only DNA, but to the mitochondrial membranes as well. Experiments on the combined application of DR+DAPI and E+DAPI have shown potential competition of DAPI with DR and E for binding sites in the nuclear and mitochondrial DNA. With the approach presented herein, the yeast cells of S. cerevisiae can be used as a model for locating intracellular sites of the fluorescing nucleic acid intercalators. This model may be of help in designing new DNA-targeted drugs and in preliminary studies of their interaction with eukaryotic cells.     

Binding Study of Phenformin with Bovine Serum Album Using a Combined Technique of Equilibrium Dialysis with Flow-Injection Chemiluminescence Detection

ABSTRACT

The interaction between phenformin hydrochloride and bovine serum albumin (BSA) was investigated by the methods of chemiluminescence combined with equilibrium dialysis technique. A novel N-bromosuccinimide (NBS)–eosin Y (EY) chemiluminescence (CL) method was established for the determination of phenformin. The mechanism of this chemiluminescence system was proposed. Optimization studies were performed to determine the phenformin. Under the optimal conditions, the CL intensity was linear for a phenformin concentration over the range of 4.6 × 10^?8 to 5.0 × 10^?5 g/mL. The detection limit was 1.5 × 10^?8 g/mL. The data obtained by the present equilibrium dialysis–CL system were analyzed using the Klotz plot and the Scatchard analysis. The results showed that the Klotz plot and the Scatchard plot are linear with good correlation coefficient, indicating that the phenformin has only one type of binding site on BSA. The binding parameters were the number of the binding sites n (1.02) and the estimated association constant K (2.66 × 10⁴ L/mol). The chemiluminescence system combined with equilibrium dialysis developed in this work demonstrated its use for determination of interaction between drug and protein by using relatively simple instrument.     

Sequence Dependent Ultrafast Electron Transfer of Nile Blue in Oligonucleotides

In this contribution we report studies on the nature of binding of nile blue (NB), a well known DNA intercalating drug, with three synthetic DNA oligonucleotides, (CGCAAATTTGCG)₂, (GCGCGCGCGCGC)₂ and (ATATATATATAT)₂. The nature of fluorescence quenching of the ligand upon complexation with the DNAs has been studied using steady state and picosecond-resolved optical spectroscopic techniques. The geometrical restriction on the probe in the DNA microenvironment is measured using picosecond-resolved rotational anisotropy measurements. Our experiments identify both non-specific electrostatic and intercalative modes of interaction of the probe with the DNAs at lower and higher DNA concentrations, respectively. This dual nature of binding is also confirmed through gel electrophoresis experiments. The nature of electron transfer (ET) reaction of GC base pairs with intercalated NB has also been explored. Competitive binding study reveals that binding affinity of the probe is higher with SDS micelles than with the DNAs within its structural integrity in presence of the micelles, as evidenced from circular dichroism (CD) measurements. The complex rigidity of NB with various DNAs and its fluorescence quenching with DNAs elucidate a strong recognition mechanism between NB and DNA.     

Doxorubicin delivered to MCF-7 cancer cells by superparamagnetic iron oxide nanoparticles: effects on subcellular distribution and cytotoxicity

The clinical use of the anticancer drug doxorubicin (DOX) is limited by strong side effects and phenomena of cell resistance. Drug targeting by binding DOX to nanoparticles could overcome these limitations. We recently described a method to associate DOX to superparamagnetic iron oxide nanoparticles (SPION) in view of magnetic drug targeting (Munnier et al. in Int J Pharm 363:170–176, 2008). DOX is bound to the nanoparticle surface through a pre-formed DOX–Fe²⁺ complex. The DOX-loaded SPION present interesting properties in terms of drug loading and biological activity in vitro. The purpose of this study is to explore the possible mechanisms of the in vitro cytotoxicity of DOX-loaded SPION. The uptake of SPION was followed qualitatively by conventional optical microscopy after Prussian blue staining and quantitatively by iron determination by atomic absorption spectroscopy. The subcellular distribution of intrinsically fluorescent DOX was followed by confocal spectral imaging (CSI) and the subsequent cytotoxicity by the MTT method. We reveal modifications of DOX intracellular interactions for SPION-delivered drug and increased cytotoxicity. These results are discussed in terms of internalization route of the drug and of a potential role of iron oxide nanoparticles in the observed cytotoxicity.     

Drug–DNA interaction: A theoretical study on the binding of thionine with DNAs of varying base composition

The recent studies carried out on the binding of small molecule to deoxyribonucleic acids suggested that the intercalation of a tricyclic heteroaromatic molecule, thionine, with natural DNAs provided thermal stabilization to the DNA complex. In the present study, we reported theoretical analysis of thionine binding with natural DNAs of varying base composition by using an amended Zimm and Bragg theory, to explain the melting behaviour and heat capacity of DNAs with and without thionine binding. We used experimental models of Paul et al. for implementing this study (Paul et al., 2010). The sharpness of transition has been examined in terms of half width and sensitivity parameter (ΔH/σ). The results of theoretical analysis concluded that the various parameters such as heat capacity curve, transition profile, half widths and sharpness of the transition are in good agreement with the experimental measurements for binding of thionine determined through DSC. The theoretical analysis proposed in this study, therefore, may be useful to understand interaction of small molecules with deoxyribonucleic acids. This approach may also be applied to design DNA binding therapeutic molecules and in the process of drug formulation and development.     

Influence of Co(III) Polypyridyl Complexes on Luminescence Behavior,DNA Binding,Photocleavage, Antimicrobial Activity and Molecular Docking Studies

A new ligand FIPB?=?5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)furan-2-yl-2-boronic acid, having three cobalt(III) polypyridyl complexes [Co(phen)₂(FIPB)]³⁺(1) {FIPB?=?5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)furan-2-yl-2-boronic acid}, (phen?=?1,10-Phenanthroline), [Co(bpy)₂(FIPB)]³⁺(2) (bpy?=?2,2’bipyridyl), [Co(dmb)₂(FIPB)]³⁺(3) (dmb?=?4, 4′-dimethyl 2, 2′-bipyridine) have been synthesized and characterized by elemental analysis, ES-MS,¹H-NMR, ¹³C-NMR, UV-Vis and FTIR. Their DNA binding behavior has been explored by various spectroscopic titrations and viscosity measurements, which indicated that all the complexes bind to calf thymus DNA by means of intercalation with different binding strengths. The binding properties of these all three complexes towards calf-thymus DNA (CT-DNA) have been investigated by UV-visible, emission spectroscopy and viscosity measurements.The experimental results suggested that three Co(III) complexes can intercalate into DNA base pairs,but with different binding affinities. Photo induced DNA cleavage studies have been performed and results indicate that three complexes efficiently cleave the pBR322-DNA in different forms. The three synthesized compounds were tested for antimicrobial activity by using Staphylococcus aureus and Bacillus subtilis organisms, these results indicated that complex 1 was more activity compared to other two complexes against both tested microbial strains. The in vitro cytotoxicity of these complexes was evaluatedby MTT assay, and complex 1 shows higher cytotoxicity than complex 2 and 3 on HeLa cells.