Electrochemical enzyme-based blood uric acid biosensor: new insight into the enzyme immobilization on the surface of electrode via poly-histidine tag.

In a new approach, we considered the special affinity between Ni and poly-histidine tags of recombinant urate oxidase to utilize Ni-MOF for immobilizing the enzyme. In this study, a carbon paste electrode (CPE) was modified by histidine-tailed urate oxidase (H-UOX) and nickel-metal-organic framework (Ni-MOF) to construct H-UOX/Ni-MOF/CPE, which is a rapid, sensitive, and simple electrochemical biosensor for UA detection. The use of carboxy-terminal histidine-tailed urate oxidase in the construction of the electrode allows the urate oxidase enzyme to be positioned correctly in the electrode. This, in turn, enhances the efficiency of the biosensor. Characterization was carried out by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and field emission scanning electron microscopy (FE-SEM). At optimum conditions, the biosensor provided a short response time, linear response within 0.3-10 µM and 10-140 µM for UA with a detection limit of 0.084 µM, repeatability of 3.06%, and reproducibility of 4.9%. Furthermore, the biosensor revealed acceptable stability and selectivity of UA detection in the presence of the commonly coexisted ascorbic acid, dopamine, L-cysteine, urea, and glucose. The detection potential was at 0.4 V vs. Ag/AgCl.

Silver-coated magnetic nanoparticles as an efficient delivery system for the antibiotics trimethoprim and sulfamethoxazole against E. Coli and S. aureus: release kinetics and antimicrobial activity.

Trimethoprim and sulfamethoxazole are prescribed for a broad spectrum of bacteria. However, the use of these medicines is restricted due to the risk of microbial resistance in the body. Nanotechnology is a strategy for overcoming this problem by helping develop novel drug delivery systems. This study aims to assess the ability of Fe3O4/Ag and Fe3O4@SiO2/Ag nanoparticles to improve efficiency of the traditional formulation of trimethoprim and sulfamethoxazole. Fe3O4/Ag and Fe3O4@SiO2/Ag were found to have sphere-like morphologies with average sizes of 33.2 and 35.1 nm, respectively. The values of the zeta potential for the pure sulfamethoxazole and trimethoprim were -30.6 and -10.0 mV, respectively, which increased to zero or even larger positive values after being conjugated with the NPs. The study of the release kinetics showed that 64.7% of the medicines were released from the carriers within 40 days. The values of MIC for sulfamethoxazole, trimethoprim, Fe3O4/Ag/sulfamethoxazole, Fe3O4/Ag/trimethoprim, Fe3O4@SiO2/Ag/sulfamethoxazole, and Fe3O4@SiO2/Ag/trimethoprim against Escherichia coli were calculated to be 12, 9, 4, 4, 4, and 4 µg/mL, respectively. Besides, the relevant values against Staphylococcus aureus were measured to be 12, 9, 4, 4, 3, and 2 µg/mL, respectively. The use of synthesized nanomaterials for the delivery of these antibiotics leads to smaller doses compared to their traditional forms.

WO3 nanoplates decorated with polyaniline and CdS nanoparticles as a new photocatalyst for degradation of imidacloprid pesticide from water.

This study focused on the photocatalytic degradation of imidacloprid (IM) in water as the model pesticides. The effective division of photogenerated charge carriers is important in the photocatalytic reactions. So, a new PANI/WO3-CdS photocatalyst was synthesized by a simple method. The prepared PANI/WO3-CdS nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy compatible with energy dispersive spectroscopy (FESEM-EDS), and X-ray diffraction (XRD). Degradation of IM pesticide under visible light irradiation was carried out to investigate the photocatalytic efficiency of the prepared nanocomposite. The effect of operational parameters on the degradation performance of pesticides was studied by response surface methodology (RSM). The optimum conditions for photocatalytic degradation of IM (94.7%) were found to be 10 ppm of IM, 150 mg of PANI/WO3-CdS, and pH = 3.0. The apparent rate constant of IM photodegradation over PANI/WO3-CdS was 0.016 min-1. According to results, PANI/WO3-CdS can serve as an efficient, and recyclable photocatalyst for imidacloprid degradation in an aqueous media.

A novel ultrasonic reverse micelle-assisted electrospun efficient route for Eu-MOF and Eu-MOF/CA composite nanofibers: a high performance photocatalytic treatment for removal of BG pollutant.

Considering the novel applications of metal organic frameworks (MOFs) in photocatalytic fields, in this study, new nanostructures of Eu-MOF have been synthesized using effective, facile, cost-effective, and fast reverse micelle (RM) as well as ultrasound assisted reverse micelle (UARM) methods under the optimal conditions. In order to improve the properties, these nanostructures were extended in the form of fibrous networks. To find nanostructure with distinctive features, thermogravimetric analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, and N2 adsorption/desorption analysis were applied. The results revealed that the samples synthesized by UARM method had a crystallite size of 27.5 nm and thermal stability of 252 °C. Therefore, the UARM Eu-MOF sample was selected as the desirable sample. Also, its application was studied as a novel nanophotocatalyst with the ideal properties in the field of brilliant green dye removal. The photocatalytic results indicated the influence of initial dye concentration, pH, photocatalyst dosage, and contact time parameters on the photocatalytic properties with an efficiency of 99.80%. This study provides a new strategy for developing desirable methods, extended structures, and the photocatalytic applications of these products.

Synthesis and photocatalytic activity of porous ZnO stabilized by TiO2 and Fe3O4 nanoparticles: investigation of pesticide degradation reaction in water treatment.

The present research studies the photocatalytic degradation of a pesticide using TiO2 and Fe3O4 nanoparticles supported on ZnO mesoporous (mZnO) substrate. Chlorpyrifos is an organophosphate pesticide with a C9H11Cl3NO3PS chemical formula. It is broadly utilized in agricultural fields to control product pests. The chlorpyrifos toxicity is acute and still dangerous to any aquatic organisms. The mZnO/TiO2-Fe3O4 material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and N2 adsorption and desorption (Brunauer-Emmett-Teller; BET). In order to optimize three important operating parameters, i.e., chlorpyrifos concentration, mZnO/TiO2-Fe3O4 nanocomposite amount, and pH, for photocatalytic degradation of chlorpyrifos, response surface methodology (RSM) was applied. The central composite design (CCD) including 20 experiments was used to conduct experiments. The highest photodegradation performance of about 94.8% was obtained for a chlorpyrifos concentration of 8 ppm, a pH of 10, and an amount of mZnO/TiO2-Fe3O4 nanocomposite of 60 mg. The degradation of chlorpyrifos using mZnO/TiO2-Fe3O4 presented good performance (more than 94%). The photocatalytic reaction followed pseudo-first-order kinetics with a rate constant of 0.058 min-1 for chlorpyrifos degradation. The results propose that mZnO/TiO2-Fe3O4 nanocomposite is a suitable alternative for the degradation of chlorpyrifos in aqueous solution. The improved photocatalytic efficiency could be attributed to the effective separation of electron-hole pairs via a Z-scheme mechanism.

Synthesis of Fe3O4/CdS-ZnS nanostructure and its application for photocatalytic degradation of chlorpyrifos pesticide and brilliant green dye from aqueous solutions.

Chlorpyrifos (CP) is an organophosphorus pesticide used to control pests in agriculture. Brilliant green (BG) is a cationic dye widely used in textile and dyeing industry. However, the presence of pollutants in the aquatic environment has harmful effects on the environment and humans. Photocatalytic degradation can be appropriate method for water purification. Therefore, the Fe3O4/CdS-ZnS magnetic nanocomposite was synthesized and characterized by Brunauer-Emmett-Teller (BET) surface area analysis, Energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), UV-Vis-diffuse reflectance spectroscopy (DRS), and field emission scanning electron microscopy (FESEM) analyses and was used to degrade pollutants such as chlorpyrifos pesticide and brilliant green dye under visible light with source 300 W. Parameters that may be effective on photocatalytic degradation include pH, photocatalyst amount, contaminant concentration, photocatalyst and contaminant contact temperature and duration, light intensity as well as distance of light source from the reaction vessel. In the present study, the parameters that have the most influence on the degradation process were experimentally optimized, including pH, photocatalyst amount, photocatalyst reuse, and initial concentration. The study of the photocatalytic degradation rate of chlorpyrifos and brilliant green in optimal conditions (pH = 7, the concentration of pollutants = 10 ppm, volume of pollutants = 5 mL, and photocatalyst amounts for CP and BG were 0.0100 and 0.0015 g respectively) was obtained by Langmuir-Hinshelwood model. According to this model, the kapp value for CP and BG were respectively 0.0315 and 0.0119 min-1 respectively. It has been concluded that the composition of CdS and ZnS caused inhibition of the recombination of photogenerated charge carriers, leading to high catalytic efficiency. Based on the results, the synthesized nanocatalyst showed that it has the ability to photocatalytic degradation of chlorpyrifos and brilliant green in aqueous solutions.

Developing a novel sensor based on ionic liquid molecularly imprinted polymer/gold nanoparticles/graphene oxide for the selective determination of an anti-cancer drug imiquimod.

Despite its useful properties, imiquimod (IMQ), known as an anti-cancer drug, can be harmful to the skin at high concentrations. Therefore, we have developed a novel electrochemical sensor to determine IMQ, for the first time. A glassy carbon electrode (GCE) was modified by a new composite comprising of ionic liquid-based molecularly imprinted polymer (MIP) and gold nanoparticles/graphene oxide (Au/GO). The MIP/Au/GO nanocomposite was synthesized through non-covalent imprinting process in the presence of IMQ, as template molecule and characterized by SEM and FT-IR. The square wave voltammetry technique (SWV) was applied for IMQ determination in 0.1 M phosphate buffer solution (PBS) at pH 7.0. Several parameters affecting the IMQ quantification were evaluated and optimized. Under the optimized conditions, the sensor presented a linear range of 0.02-20.0 µM, a limit of quantification and detection of 0.02 µM and 0.006 µM, respectively. Low RSD values indicate the good repeatability and reproducibility of the modified electrodes in preparation and determination procedures. The satisfactory results indicated that the proposed sensor could be successfully applied for IMQ determination in real samples.

Decoration of graphene oxide with NiO@polypyrrole core-shell nanoparticles for the sensitive and selective electrochemical determination of piceatannol in grape skin and urine samples.

For the first time, we developed an electrochemical sensor for piceatannol based on a new type of nanocomposite: graphene oxide nano sheets decorated with core-shell NiO@polypyrrole nanoparticles (NiO@Ppy/GO) mixed with nafion and casted on the surface of glassy carbon electrode. The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) techniques. The square wave voltammetry as a sensitive technique and cyclic voltammetry were selected for the quantification of piceatannol in 0.1 M phosphate buffer solution (pH 7.0). Several parameters were evaluated such as pH value, scan rate and supporting electrolyte type for the determination of piceatannol. In addition, selectivity and repeatability measurements were also evaluated. Under the optimized conditions, linear range and limit of detection were obtained 0.01-10.0 µM and 0.003 µM, respectively. Relative standard deviation for 3.0 µM and 6.5 µM were calculated 3.25% and 1.83%, respectively. The proposed sensor was applied successfully for the quantification analysis of piceatannol in grape skin essential oil and urine sample with satisfactory results.

Application of silica coated magnetite nanoparticles modified with Cu(I)-neocuproine as nanosorbent to simultaneous separation-preconcentration of trace amounts of nitrate and nitrite.

A novel, inexpensive and sensitive type of magnetic nanosorbent based on the functionalized silica-coated Fe3O4 nanoparticles was prepared and used for the adsorption of trace amounts of nitrite and nitrate ions. The work is based on selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine which are covalently bounded on nanoparticles. Nitrite was determined according to its reaction with barbituric acid to give violuric acid and determination of nitrate was based on its reduction to nitrite in the presence of Zn/NaCl. After formation of violuric acid, the absorbance was measured spectrophotometrically at 310 nm. The quantitative recoveries were obtained at pH 5.5 for the analytes. Under optimum conditions, the limits of detection in the original solutions were 0.49 µg L-1 and 0.40 µg L-1 for nitrate and nitrite, respectively. The linearity ranges were found to be 1.5 to 2.8 × 103 µg L-1(NO3-) and 1.2 to 1.9 × 103 µg L-1 (NO2-). The preconcentration factor was 120 for nitrate and 150 for nitrite. This method has been successfully applied to the determination of trace amounts of nitrite and nitrate in various water and food samples and also accuracy was confirmed by the analysis of the spiked recovery test.

Magnetic ionic liquid assisted single-drop microextraction of ascorbic acid before its voltammetric determination.

For the first time, we coupled a microextraction technique using a magnetic ionic liquid with voltammetric determination. A hydrophobic magnetic ionic liquid that contains the tetrachloromanganate(II) anion, namely, aliquat tetrachloromanganate(II), was synthesized and used for the extraction of ascorbic acid from aqueous solutions followed by voltammetric determination. The extraction procedure was carried out using a single drop microextraction technique in which the ascorbic acid containing magnetic ionic liquid was separated with a magnet and then cast onto the surface of a carbon paste electrode modified with TiO2 nanoparticles for the voltammetric quantification of the extracted ascorbic acid. Electrochemical quantification was carried out in a blank phosphate buffer solution. After optimizing different experimental conditions, a linear concentration range of 1.50-40.0 nM with a detection limit of 0.43 nM was obtained for the determination of ascorbic acid. The presented approach was successfully applied to the determination of ascorbic acid in samples of vitamin C effervescent tablets and orange juice.

Ag-4-ATP-MWCNT electrode modified with dsDNA as label-free electrochemical sensor for the detection of daunorubicin anticancer drug.

This paper describes the synthesis of Ag-4-ATP-MWCNT nanocomposite and its use as a modifier of working electrode. The surface of the electrochemical Ag-4-ATP-MWCNT electrode was modified with a double-stranded DNA (dsDNA) to detect daunorubicin-DNA interactions. Differential pulse voltammetry was applied to develop an electroanalytical procedure for the determination of daunorubicin and evaluate its interaction with dsDNA immobilized on the electrode surface. After the optimization of operational parameters, the linear dependence of the peak current on the daunorubicin concentration was observed in the range of 0.10×10-8 to 1.00×10-5molL-1, with the detection and quantification limits of 3.00×10-10 and 1.00×10-9molL-1, respectively. The proposed biosensor was successfully applied to validate its capability for the determination of daunorubicin in human serum and urine samples.

Electrospun composite nanofibers of poly vinyl pyrrolidone and zinc oxide nanoparticles modified carbon paste electrode for electrochemical detection of curcumin.

A simple and novel ferrocene-nanofiber carbon paste electrode was developed to determine curcumin in a phosphate buffer solution at pH=8. ZnO nanoparticles were produced via a sonochemical process and composite nanofibers of PVP/ZnO were prepared by electrospinning. The characterization was performed by SEM, XRD and IR. The results suggest that the electrospun composite nanofibers having a large surface area promote electron transfer for the oxidation of curcumin and hence the FCNFCPE exhibits high electrocatalytic activity and performs well in regard to the oxidation of curcumin. The proposed method was successfully applied for measurement of curcumin in urine and turmeric as real samples.

A Quercetin Biosensor Based on Chitosan-Entrapped Carbon Nanotube Paste Electrode Coated with DNA.

This paper presents an easy, fast, low cost, and sensitive approach for the electrochemical determination of quercetin based on its intercalation into DNA double helix. Electrochemical studies of the interaction between quercetin and DNA showed a decrease in peak currents with a reduction in redox reversibility of quercetin in the presence of the DNA. The electrochemical behavior of quercetin at a chitosan-entrapped carbon nanotube paste electrode coated with DNA was studied. A considerable increase was observed in the oxidation signal of quercetin at the DNA-coated electrode compared with a DNA-free electrode, indicating the preconcentration of quercetin due to its interaction with the surface-confined DNA layer. After optimizing the main experimental parameters influencing the biosensor response, its performance was evaluated from an analytical point of view. Two linear dependences of the anodic peak current of quercetin on its concentration were observed in the ranges of 0.40-7.50 and 7.50-30.0 µmol/L, with LOD and LOQ of 0.039 and 0.13 µmol/L, respectively. The proposed biosensor was successfully applied to the analysis of black and green tea extracts for their quercetin content.

Extraction and preconcentration of hemin from human blood serum and breast cancer supernatant.

A green, facile, fast, and sensitive liquid-phase microextraction method is presented for the extraction and preconcentration of hemin in the presence of free iron ions prior to flame atomic absorption spectroscopic determination. In this technique, an anion-functionalized task-specific ionic liquid is used as the extracting solvent. The interface between the extracting solvent and the bulk aqueous phase containing hemin is enormously enlarged by dispersing the ionic liquid to the aqueous phase with the help of ultrasound radiation. Hemin is selectively extracted into the ionic liquid after interaction with the functional group of the ionic liquid. Then, the concentration of the extracted hemin is determined through the absorbance of the iron ions contained in the hemin structure using flame atomic absorption spectroscopy. Different experimental parameters affecting the extraction efficiency have been optimized. Under the optimized conditions, the proposed method has a hemin concentration linear range of 0.020-0.80 mg/L with a detection limit of 0.0080 mg/L. This method has been successfully applied to the extraction and determination of hemin in human serum and supernatant samples.

Simultaneous Separation and Preconcentration of Trace Amounts of Cu(II), Ni(II), Zn(II), and Cd(II) with Modified Nanoporous Pumpellyite Zeolite.

A procedure for determination of trace levels of Cu(II), Zn(II), Ni(II), and Cd(II) by flame atomic absorption spectrometry using a preconcentration system has been proposed. In this system, we used modified nanoporous pumpellyite zeolite loaded with 2-phenyl-4-[1-(2-thienyl) methylidene]-5-oxazolone as a sorbent for extracting Cu(II), Zn(II), Ni(II), and Cd(II) ions from real samples. Several parameters such as pH of the sample solution, amount of nanoporous pumpellyite zeolite, amount of ligand, volumes of sample and eluent, type of eluent, flow rates of sample and eluent, and the effects of diverse ions on the preconcentration were investigated. The LODs for Cu(II), Zn(II), Ni(II), and Cd(II) in the original solution were 2.6, 1.3, 3.2, and 1.1 ng/mL, respectively. The preconcentration factor was 250 for Zn and Ni, 100 for Cd, and 125 for Cu. The developed method was applied to the determination of trace metal ions in certified reference material tea leaves and water samples with satisfactory results.

A microextraction procedure based on a task-specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves.

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination.

Spectrofluorimetric determination of melatonin in kernels of four different Pistacia varieties after ultrasound-assisted solid-liquid extraction.

Melatonin is normally consumed to regulate the body's biological cycle. However it also has therapeutic properties, such as anti-tumor, anti-aging and protects the immune system. There are some reports on the presence of melatonin in edible kernels such as walnuts, but the extraction of melatonin from pistachio kernels is reported here for the first time. For this, the methanolic extract of pistachio kernels was exposed to gas chromatography/mass spectrometry analysis which confirmed the presence of melatonin. A fluorescence-based method was applied for the determination of melatonin in different extracts. When excited at λ=275 nm, the fluorescence emission intensity of melatonin was measured at λ=366 nm. Ultrasound-assisted solid-liquid extraction was used for the extraction of melatonin from pistachio kernels prior to fluorimetric determination. To achieve the highest extraction recovery, the main parameters affecting the extraction efficiency such as extracting solvent type and volume, temperature, sonication time and pH were evaluated. Under the optimized conditions, a linear dependence of fluorescence intensity on melatonin concentration was observed in the range of 0.0040-0.160 µg mL(-1), with a detection limit of 0.0036 µg mL(-1). This method was applied successfully for measuring and comparing the melatonin content in the kernels of four different varieties of Pistacia including Ahmad Aghaei, Akbari, Kalle Qouchi and Fandoghi. In addition, the results obtained were compared with those obtained using GC/MS. A good agreement was observed indicating the reliability of the proposed method.

Application of a thiourea-containing task-specific ionic liquid for the solid-phase extraction cleanup of lead ions from red lipstick, pine leaves, and water samples.

Here, task-specific ionic liquid solid-phase extraction is proposed for the first time. In this approach, a thiourea-functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid-phase extraction column are used for the selective extraction and preconcentration of ultra-trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5-40.0 ng/mL with the detection limit of 0.13 ng/mL (3(Sb)/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.

Comparison of the essential oil content and composition of the spathe, buds and pollen of Phoenix dactylifera.

Several medicinal applications have been reported for different components of date palm. The inflorescence of the male date tree is composed of spathe that surrounds many buds containing pollen. In this study, a comparison between the content and composition of the essential oils obtained from these three components of an inflorescence was made. After obtaining each oil using hydro-distillation method, the oil yield was measured as the weight ratio of the oil to the distilled sample (w/w %) and the chemical composition of the oil was determined by gas chromatography-mass spectrometry analysis. It was observed that the pollen possessed the most oil content (1.47%) composed of 68.04% oleic acid, whereas the content of this fatty acid in the spathe and bud oils was found to be less than 0.05% and 5.65%, respectively. Spathe oil was dominated by 3,4-dimethoxytoluene (52.90%) while the main constituent of the bud oil was trans-caryophyllene (44.20%).