Non-enzymatic glucose sensor based on a g-C3N4/NiO/CuO nanocomposite.

In this paper, a non-enzymatic glucose sensor was developed based on a g-C3N4/NiO/CuO nanocomposite immobilized on a glassy carbon electrode (GCE). Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) were utilized for the characterization of the synthesized g-C3N4/NiO/CuO nanocomposite. The electrocatalytic activity of the nanocomposite was investigated by cyclic voltammetry, and the amperometric technique was applied for monitoring glucose. The g-C3N4/NiO/CuO/GCE exhibited better electrocatalytic performance than g-C3N4/GCE, g-C3N4/CuO/GCE and g-C3N4/NiO/GCE. Under optimized conditions, the proposed sensor offered a linearity ranging from 0.4 µM to 8.5 mM with a detection limit of 0.1 µM and a sensitivity of 362.12 µA mM-1 cm-2. The constructed sensor displayed favorable reproducibility, outstanding selectivity, and long-term performance. These results reveal that the sensor is a promising candidate for blood glucose sensing.

Theoretical and Instrumental Studies of the Competitive Interaction Between Aromatic α-Aminobisphosphonates with DNA Using Binding Probes.

Fluorescence spectroscopy, UV-visible absorption spectroscopy, circular dichroism (CD) spectroscopy, viscometry, cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were applied to investigate the competitive interaction of DNA with two aromatic α-aminobisphosphonates and neutral red dye (NR, intercalator) and Hoechst (Ho, groove binder) as spectroscopic probes, in a Tris-hydrogen chloride buffer solution (pH 7.4). The principal component analysis (PCA) was applied to determine the number of chemical components presented in complexation equilibrium of DNA with the aromatic α-aminobisphosphonates (B1 and B2). The spectroscopic and voltammetric studies showed that the groove binding mode of interaction is predominant in the solution containing DNA and α-aminobisphosphonates. Furthermore, the results indicated that α-aminobisphosphonate with the lengthy N-alkyl chains had a stronger interaction. The PCA and theoretical quantum mechanical and molecular mechanic methods were also utilized to determine the structure of DNA with the two α-aminobisphosphonates (B1 and B2).

The fabrication of a new electrochemical sensor based on electropolymerization of nanocomposite gold nanoparticle-molecularly imprinted polymer for determination of valganciclovir.

A new sensitive and selective electrochemical sensor was successfully developed for the determination of valganciclovir. It is based on one-step electropolymerization of the molecularly imprinted polymer composed from 2,2'-dithiodianiline, gold nanoparticles, and valganciclovir on a glassy carbon electrode modified with carboxyl-functionalized multiwalled carbon nanotubes via cyclic voltammetry. The gold nanoparticles were introduced into the polymer composite for the development of electrical response by facilitating charge transfer. The fabrication process of the sensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized condition calibration curve of the imprinted sensor has two linear concentration ranges from 1.0 to 500.0nM and 500.0 to 2000.0nM, with the limit of detection of 0.3nM. The relative standard deviation (RSD) for seven parallel determination of 1.0µM valganciclovir at optimum conditions was found to be 2.9%. The imprinted sensor has the advantages of high porous surface structure, ease of preparation, good reproducibility, good repeatability and high selectivity and sensitivity. Furthermore, the proposed method was successfully intended for the determination of valganciclovir in real samples.

Fabrication of an electrochemical sensor based on computationally designed molecularly imprinted polymer for the determination of mesalamine in real samples.

A novel electrochemical sensor based on mesalamine molecularly imprinted polymer (MIP) film on a glassy carbon electrode was fabricated. Density functional theory (DFT) in gas and solution phases was developed to study the intermolecular interactions in the pre-polymerization mixture and to find the suitable functional monomers in MIP preparation. On the basis of computational results, o-phenylenediamine (OP), gallic acid (GA) and p-aminobenzoic acid (ABA) were selected as functional monomers. The MIP film was cast on glassy carbon electrode by electropolymerization of solution containing ternary monomers and then followed by Ag dendrites (AgDs) with nanobranch deposition. The surface feature of the modified electrode (AgDs/MIP/GCE) was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Under the optimal experimental conditions, the peak current was proportional to the concentration of mesalamine ranging from 0.05 to 100 µM, with the detection limit of 0.015 µM. The proposed sensor was applied successfully for mesalamine determination in real samples.

Chemical composition and anxiolytic evaluation of Achillea Wilhelmsii C. Koch essential oil in rat.

Herbal based remedies are used worldwide to treat psychiatric disorders. The aim of this study was to analyse the essential oil composition of Achillea Wilhemsii C. Koch (Asteraceae) and to evaluate its anxiolytic effects in the elevated plus maze (EPM) model of anxiety in rat. Gas chromatography/mass spectrometry (GC/MS) analysis of the essential oil showed that the main compounds of the oil were p-ocimen (23%), 1, 8-cineole (20.8%) and carvone (19.13%). The EPM results showed that 1 mg/kg (i.p.) of the oil significantly (P<0.05) increased the percentage of the time spent and the number of entries in the open arms of the maze while it did not change the total number of entries in the maze arms. These effects were not reversed with 2 mg/kg flumazenil and 5 mg/kg naloxone. We concluded that a minimum dose of 1 mg/kg of the oil has anxiolytic effects which are not probably mediated through GABA and opioid receptors.

Chemical composition and antioxidant activity of the essential oil and various extracts of Haplophyllum robustum Bge.

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil and various extracts of Haplophyllum robustum. GC-MS analysis of the oil resulted in the identification of 30 compounds, representing 99.2% of the oil; 1,8-cineole (38.1%), myrcene (10.7%), α-pinene (8.5%), 4-terpineol (7.0%) and sabinene (6.1%) were the main components. The antioxidant potential of the oil and extracts was evaluated using three separate methods: inhibition of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), ß-carotene-linoleic acid assay and reducing power systems. The essential oil of the plant was able to reduce the stable free radical DPPH with an IC(50) of 72.0 ± 1.2 µg mL(-1) (the IC(50) for ascorbic acid was determined as 5.8 ± 0.4 µg mL(-1)). The essential oil also showed strong reducing power. The level of total phenolics was highest in the essential oil (179.5 ± 2.1 µg mg(-1)).

DNA-binding, DNA cleavage and cytotoxicity studies of two anthraquinone derivatives.

The interaction of native calf thymus DNA (CT-DNA) with two anthraquinones including quinizarin (1,4-dihydroxy anthraquinone) and danthron (1,8-dihydroxy anthraquinone) in a mixture of 0.04M Brittone-Robinson buffer and 50% of ethanol were studied at physiological pH by spectrofluorometric and cyclic voltammetry techniques. The former technique was used to calculate the binding constants of anthraquinones-DNA complexes at different temperatures. Thermodynamic study indicated that the reactions of both anthraquinone-DNA systems are predominantly entropically driven. Furthermore, the binding mechanisms on the reaction of the two anthraquinones with DNA and the effect of ionic strength on the fluorescence property of the system have also been investigated. The results of the experiments indicated that the binding modes of quinizarin and danthron with DNA were evaluated to be groove binding. Moreover, the cytotoxic activity of both compounds against human chronic myelogenous leukemia K562 cell line and DNA cleavage were investigated. The results indicated that these compounds slightly cleavage pUC18 plasmid DNA and showed minor antitumor activity against K562 (human chronic myeloid leukemia) cell line.

Determination of the chemical composition and in vitro antioxidant activities of essential oil and methanol extracts of Echinophora platyloba DC.

This study was designed to examine the chemical composition and in vitro antioxidant activity of essential oil and methanol extracts of Echinophora platyloba from Iran. Gas chromatography (GC) and GC/MS (mass spectrometry; MS) analysis of the essential oil resulted in the identification of 29 compounds, which comprised 97.4% of the oil. The main constituents were found to be: (Z)-ß-ocimene (26.7%), Δ-3-carene (16.2%) and limonene (6.6%). Antioxidant activities of the essential oil and the methanolic extracts from E. platyloba were evaluated using three different test systems, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ß-carotene-linoleic acid bleaching and reducing power assays. In the DPPH system, the highest radical-scavenging activity was shown by the polar sub-fraction of methanol extract (71.2 ± 1.11 µg mL(-1)). Also in the second case, the relative inhibition capacity (%) of the essential oil (68.0 ± 1.14%) was found to be the stronger one. In addition, the amounts of total phenol components in the polar sub-fractions of methanolic extract (67.5 ± 0.48 µg mg(-1)), nonpolar sub-fractions of methanol extract (35.3 ± 0.12) and the oil (83.3 ± 0.24 µg mg(-1)) were determined.

DNA-binding study of anthraquinone derivatives using chemometrics methods.

This work presents the interaction of two anthraquinones including quinizarin (1, 4-dihydroxyanthraquinone) and danthron (1, 8-dihydroxyanthraquinone) with CT-DNA in a mixture of Brittone-Robinson buffer (pH=7) with 50% of ethanol by UV-vis absorption, circular dichroism spectroscopic methods and viscosity measurements. The PCA and INDICES methods were used for predicting the number of light-absorbing components. Partially intercalative and hydrogen binding were found to be the dominant binding modes between anthraquinones and CT-DNA. The effect of ionic strength and pH on the behavior of the above system and also the interaction of anthraquinones with ds and ss-DNA were used to confirm the mentioned binding modes. The EQUISPEC software and nonlinear least-squares analysis were applied for binding constant determination.

Spectrophotometric study of complex formations between 1-(2-pyridylazo)-2-naphthol (PAN) and some metal ions in organic solvents and the determination of thermodynamic parameters.

The complexation reactions between Ni(2+), Co(2+) and Zn(2+) metal ions with PAN in methanol (MeOH), acetonitrile (AN) and dimethyl sulfoxide (DMSO) were studied using a spectrophotometric method. The stability constants of the resulting complexes were determined from computer fitting absorbance mole-ratio data. The results revealed that the stability constants of complexes are varying in order of Ni(2+)

Fabrication of a novel iron(III)-PVC membrane sensor based on a new 1,1'-(iminobis(methan-1-yl-1-ylidene))dinaphthalen-2-ol synthetic ionophore for direct and indirect determination of free iron species in some biological and non-biological samples.

In this novel, the iron(III)-PVC membrane sensor was investigated based on a new 1,1'-(iminobis(methan-1-yl-1-ylidene))dinaphthalen-2-ol (IBMYD) synthetic ionophore as a suitable carrier. The best performance was observed for the membrane composition including 33.0% PVC, 65.0% TEHP, 1.0% NaTPB and 1.0% ionophore. The electrode displayed a linear potential response over a wide concentration range from 1.0 x 10(-7) to 1.0 x 10(-1)mol L(-1), with a detection limit of 5.0 x 10(-8)mol L(-1) and a good Nernstian slope of 19.9+/-0.3 mV decade(-1). The sensor possessed some advantages such as short conditioning time, very fast response time (<12s) and especially good discriminating ability towards Fe(III) ions over a wide variety of alkali, alkaline earth, transition, and heavy metal ions. The potential response of the proposed sensor was independent of the pH of the test solution, in the pH working range from 3.0 to 6.3. The fabricated electrode was applied for at least 2 months, without any measurable divergence in the potential characteristics. The optimized sensor was used successfully for direct and indirect determination of free iron species in some different synthetic and real samples with satisfactory results.

Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry.

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.

Zirconium ion selective electrode based on bis(diphenylphosphino) ferrocene incorporated in a poly(vinyl chloride) matrix.

A novel potentiometric zirconium--PVC matrix membrane sensor incorporating bis(diphenylphosphino) ferrocene as an electroactive material and tris(2-ethylhexyl)phosphate as solvent mediator is described. In mixed acetate buffer solution of pH 4.8, the sensor displays a rapid and linear response for zirconium ion over the concentration range 1.0 x 10(-1) to 1.0 x 10(-7) mol L(-1) with a good slope of 59.7+/-0.3 mV per decade and detection limit 1.8 x 10(-8) mol L(-1). The best performance was obtained with membrane composition 33% PVC, 65% TEHP, 1% NaTPB and 1% ionophore. The proposed electrode revealed excellent selectivity for zirconium ion over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.15-7.8. The electrode was applied for at least 1 month without any considerable divergence in the potential responses. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of zirconium ions with sodium fluoride and in determination of zirconium ion in some alloy, tape and waste water samples.

Highly selective and sensitive copper membrane electrode based on a new synthesized Schiff base.

Bis(2-hydroxyacetophenone)butane-2,3-dihydrazone (BHAB) was used as new N-N Schiffs base which plays the role of an excellent ion carrier in the construction of a Cu(II) membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 55% o-nitrophenyloctyl ether (NPOE), 7% BHAB and 8% oleic acid (OA). This sensor shows very good selectivity and sensitivity towards copper ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition and pH and influence of additive anionic on the response properties of electrode were investigated. The electrode exhibits a Nernstian behavior (with slope of 29.6mV per decade) over a very wide concentration range (5.0x10(-8) to 1.0x10(-2)molL(-1)) with a detection limit of 3.0x10(-8)molL(-1) (2.56ngmL(-1)). It shows relatively fast response time, in whole concentration range (<15s), and can be used for at least 12 weeks in the pH range of 2.8-5.8. The proposed sensor was successfully used to determination of copper in different water samples and as indicator electrode in potentiometric titration of copper ion with EDTA.

DNA interaction with Al-N,N'-bis(salicylidene)2,2'-phenylendiamine complex.

The Al(III) complex, [Al(salophen)2H2O]NO3, was synthesized and characterized by spectroscopic (NMR and FT-IR) techniques. Then the binding of Schiff base complex of [Al(salophen)]+ type, where salophen denotes N,N'-bis(salicylidene) 2,2-phenylendiamine to calf thymus DNA, has been investigated by spectrophotometric, circular dichroism, spectrofluorometric, melting temperature and viscosimetric techniques. This Al(III) complex showed absorption hyperchromism in the range of 310-390 nm, increase in melting temperature, some structural changes in specific viscosity, when bound to calf thymus DNA. The binding constant has been determined using absorption measurement and found to be 1.82 x 10(3)M(-1) and 1.31 x 10(3)M(-1) in HEPES and Tris-HCl buffers, respectively. Also the fluorescence spectral characteristics and interaction of Al-salophen complex with DNA have been studied. Al-salophen bound to DNA showed a marked increase in the fluorescence intensity along with a bathochromic shift (5 nm). The intersection point of the binding isotherm indicated a binding site size of 12 bp per bound complex molecule in both HEPES and Tris-HCl buffers. The experimental results showed that the Al-salophen complex bound to DNA by non-intercalative mode and major groove binding was the preferred mode of interaction.

Application of adsorptive stripping voltammetry to the simultaneous determination of bismuth and copper in the presence of nuclear fast red.

A sensitive and selective method for the simultaneous determination of copper and bismuth by adsorptive stripping was developed using nuclear fast red (2-anthracenesulfonic acid, 4-amino-9,10-dihydro-1,3-dihydroxy-9,10-dioxo-, monosodium salt) as selective complexing agent onto hanging mercury drop electrode. In a single scan both metals gave peaks that were distinctly separated by 85 mV allowing their determination in the presence of each other. Optimal analytical conditions were found to be: nuclear fast red concentration of 80 microM, pH of 2.8 and adsorptive potential of -300 mV versus Ag/AgCl. With accumulation time of 180s the peaks currents are proportional to concentration of copper and bismuth over the 1-100 and 5-60 ng mL(-1) range with detection limits of 0.2 and 1.2 ng mL(-1), respectively. The procedure was applied to simultaneous determination of copper and bismuth in some real samples.

Cathodic adsorptive stripping voltammetric determination of uranium (VI) complexed with 2, 6-pyridinedicarboxylic acid.

Uranium (VI) (U(VI)) forms a complex with dipicolinic acid (2, 6-pyridinedicarboxylic acid).This complex can be used for a highly sensitive and selective determination of uranium by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode (HMDE) as working electrode. Influence of effective parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the sensitivity and selectivity were studied. The detection limit (3sigma of the blank value) obtained under the optimal experimental conditions is 0.27 x 10(-9)M after 150s of the accumulation time. The peak current is proportional to the concentration of U(VI) in the range of 1 x 10(-9) to 1.2 x 10(-7)M. The relative standard deviation of 2.5% at the 3.5 x 10(-8)M level was obtained. The interference of some metal ions and anions were studied. The application of this method was tested in the determination of uranium in synthetic and natural water samples.

PVC-based bis(2-nitrophenyl)disulfide sensor for zinc ions.

A PVC membrane electrode based on bis(2-nitrophenyl)disulfide carrier exhibits a very good response for Zn(2+) in a wide concentration range (from 2.9x10(-7) to 3.2x10(-2) mol l(-1)) with a slope of 29.9+/-0.4 mV per decade of Zn(2+) concentration. The response time of the sensor is about 10 s and the membrane can be used for more than 3 months without any observed divergence in potentials. The proposed sensor exhibits very good selectivity for Zn(2+) over many cations and can be used in a wide pH range (2-9). This assembly served also as an indicator electrode in potentiometric titrations involving zinc ions and direct potentiometric determination of zinc ions in real and synthetic samples.

Chromium(III) ion selective electrode based on glyoxal bis(2-hydroxyanil).

A poly(vinyl chloride) membrane based on glyoxal bis(2-hydroxyanil) as membrane carrier was prepared and investigated as a Cr(III)-selective electrode. The electrode has a linear dynamic range of 3.0x10(-6)-1.0x10(-2) mol l(-1), with a Nernstian slope of 19.8+/-0.5 mV per decade and a detection limit of 6.3x10(-7) mol l(-1). It has a fast response time of <20 s and can be used for at least 3 months without any considerable divergence in potential. The proposed electrode revealed good sensitivities for Cr(III) over a wide variety of metal ions and could be used in a pH range of 2.7-6.5. Above all, the membrane sensor has been used very successfully for the analysis of some food materials and alloys for the determination of Cr(III) ion.

Copper(II)-selective electrode using 2,2'-dithiodianiline as neutral carrier.

Poly(vinyl chloride) membrane electrode, that is highly selective and sensitive to Cu(II) ions, was developed by using 2,2'-dithiodianiline and dibutyl phthalate as carrier and plasticizer, respectively. The electrode exhibits good potentiometric response for Cu(II) over a wide concentration range (5.0x10(-2)-7.0x10(-7) mol l(-1)) with Nernstian slope of 30+/-1 mV per decade. The response time of the electrode is 10 s and it has been used for a period of one month and exhibits good selectivity towards Cu(2+) in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb(2+), Cd(2+) and Fe(+2) which are known to interfere with many other copper electrodes.