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.

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.

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.

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.

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.

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%).

Anti-candidal activity of Astragalus verus in the in vitro and in vivo guinea pig models of cutaneous and systemic candidiasis

This study was design to evaluate the anti-candidal activity of Astragalus verus Olivier, Fabaceae (Av). The GC/MS analysis of essential oils of Av showed that aqueous extract contains thymol while hexadecanoic acid, 1,2-benzenedicarboxylic acid, diisooctyl ester and phytol were found as major components of methanol and acetone extracts. The aqueous extract showed anti-candidal activity in the concentration 320 mg/mL using disc diffusion method and its minimum inhibitory concentration (MIC) was 160 mg/mL. To induce cutaneous candidiasis, the dorsum of immunocompromised guinea pigs was infected with Candida albicans and animals were divided into five groups (n=5 for each): NC, received a vehicle; PC, received topical ketoconazole 2% and three other groups which received topical 10, 20 and 40% aqueous extract of Av. On ninth day postinfection, skins were cultured and colony forming unite per gram (CFU/g) skin was recorded. Systemic candidiasis was obtained by intravenous inoculation of C. albicans, 4000 CFU/g body weight. Here, animals have been divided into five groups like cutaneous candidiasis but their medications have been delivered in drinking water for ten days before induction of infection. On second day postinfection, all internal tissues were taken for determining CFU/g tissue. The aqueous extract (40%) prevented heavy burden of C. albicans in tissues and skin in oral and topical application, respectively. The results indicate that Av represents a potential source of anti-candidal drug.

Chemical composition and effect of an essential oil of Salix aegyptiaca L., Salicaceae, (musk willow) in hypercholesterolemic rabbit model

The essential oils (EO) of Salix aegyptiaca L., Salicaceae (SA), leaves were extracted using the hydrodistillation method and their chemical composition was further determined by GC-MS. 1,4-Dimethoxybenzene was the main isolated compound. Other major isolated constitutes were phenylethyl alcohol, carvone, citronellol, methyleugenol, eugenol, n-tetradecane and 4'-methoxyacetophenone. Twenty rabbits were equally divided into four groups: Normal control (NC) which fed a standard diet and three cholesterol-fed groups: HC, HC+1.0 percent SA and HC+3.0 percent SA groups which received 0.0 percent, 1.0 percent and 3.0 percent EO, respectively for four weeks. The serum lipid and lipoprotein profiles and atherogenic index (AI) were measured weekly. The high cholesterol diet significantly raised the TC, LDL-C, VLDL-C, HDL-C, TG and AI level compared with NC group. HC+1.0 percent SA and HC+3.0 percent SA groups showed similar results compared with HC group. It can be concluded that the EO of SA leaves could not prevent dyslipidemia that occurred in rabbits following inclusion of cholesterol in diet in both dose-and time-dependent manners.