Selective response of dopamine in the presence of ascorbic acid on carbon paste electrode modified with titanium phosphated silica gel

Titanium phosphate grafted on the surface of silica gel (devoted briefly as Si-TiPH) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The Si-TiPH bulk modified carbon paste electrode was used for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The modified electrode offers an excellent and stable response for the determination of DA in the presence of AA. The differential pulse voltammetry peak current was found to be linear with the DA concentration in the range 2 × 10⁻⁷ to 1 × 10⁻⁶ and 2 × 10⁻⁶ to 6 × 10⁻⁵ mol L⁻¹. The detection limit of the proposed method in the presence of 2.0 × 10⁻⁵ M of AA was found to be 4.3 × 10⁻⁸ mol L⁻¹ for DA determination. The proposed method was successfully applied for the determination of DA in injections.     

Synthesis and Spectral Characteristics of Novel Fluorescent Dyes Based on Pyrimido[4,5‐d] [1,2,4]triazolo[4,3‐a]pyrimidine

Different derivatives of a novel heterocyclic system, i.e., pyrimido[4,5‐d] [1,2,4]triazolo[4,3‐a]pyrimidine, are synthesized in moderate‐to‐good yields. These compounds exhibit excellent photochromism upon photoirradiation. The photophysical characterizations of these new compounds were evaluated by UV/VIS absorption and fluorescence emission studies. The emission spectra in various solvents are also presented and discussed. The changes are due to the intramolecular H‐bonding of pyrimido‐triazolo‐pyrimidine with H₂O, and photoinduced electron and general solvent effect. These compounds display high fluorescence quantum yields and are reported as new fluorophores.     

Reductive dechlorination of 2,4-dichlorophenol by Pd/Fe nanoparticles prepared in the presence of ultrasonic irradiation

Palladium/Iron (Pd/Fe) nanoparticles were prepared by using ultrasound strengthened liquid phase reductive method to enhance dispersion and avoid agglomeration. The dechlorination of 2,4-dichlorophenol (2,4-DCP) by Pd/Fe nanoparticles was investigated to understand its feasibility for an in situ remediation of contaminated groundwater. Results showed that 2,4-DCP was first adsorbed by Pd/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The induction of ultrasound during the preparation of Pd/Fe nanoparticles further enhanced the removal efficiency of 2,4-DCP, as a result, the phenol production rates increased from 65% (in the absence of ultrasonic irradiation) to 91% (in the presence of ultrasonic irradiation) within 2 h. Our data suggested that the dechlorination rate was dependent on various factors including Pd loading percentage over Fe⁰, Pd/Fe nanoparticles availability, temperature, mechanical stirring speed, and initial pH values. Up to 99.2% of 2,4-DCP was removed after 300 min reaction with these conditions: Pd loading percentage over Fe⁰ 0.3 wt.%, initial 2,4-DCP concentration 20 mg L^?1, Pd/Fe dosage 3 g L^?1, initial pH value 3.0, and reaction temperature 25 °C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0468 min^?1.     

A vertically aligned carbon nanotube-based impedance sensing biosensor for rapid and high sensitive detection of cancer cells

A novel vertically aligned carbon nanotube based electrical cell impedance sensing biosensor (CNT-ECIS) was demonstrated for the first time as a more rapid, sensitive and specific device for the detection of cancer cells. This biosensor is based on the fast entrapment of cancer cells on vertically aligned carbon nanotube arrays and leads to mechanical and electrical interactions between CNT tips and entrapped cell membranes, changing the impedance of the biosensor. CNT-ECIS was fabricated through a photolithography process on Ni/SiO(2)/Si layers. Carbon nanotube arrays have been grown on 9 nm thick patterned Ni microelectrodes by DC-PECVD. SW48 colon cancer cells were passed over the surface of CNT covered electrodes to be specifically entrapped on elastic nanotube beams. CNT arrays act as both adhesive and conductive agents and impedance changes occurred as fast as 30 s (for whole entrapment and signaling processes). CNT-ECIS detected the cancer cells with the concentration as low as 4000 cells cm(-2) on its surface and a sensitivity of 1.7 × 10(-3)Ω cm(2). Time and cell efficiency factor (TEF and CEF) parameters were defined which describe the sensor's rapidness and resolution, respectively. TEF and CEF of CNT-ECIS were much higher than other cell based electrical biosensors which are compared in this paper.     

TiO2‐nanoparticles as efficient catalysts for the synthesis of pyridine dicarbonitriles

The catalytic effects of two forms of nano‐TiO₂, which are prepared via an ordinary or a magnetized process, are investigated in the synthesis of pyridine dicarbonitriles by one‐pot multicomponent reaction of 4‐methyl thiophenol, malononitrile, and aryl aldehydes. The results have shown that both prepared nano‐TiO₂ exhibited high catalytic activities toward the synthesis of pyridine dicarbonitrile derivatives but the nano‐TiO₂, which is prepared via a magnetized process, has shown better catalytic activity. Furthermore, this new catalytic method for the synthesis of pyridine dicarbonitriles provides rapid access to the desired compounds in high yields and so a simple work‐up procedure in the presence of water at room temperature. Therefore, this method represents a significant improvement incompatible of the other methods that are available for the synthesis of pyridine dicarbonitriles.     

Hydrocarbon oxidation catalyzed by vanadium polyoxometalate supported on mesoporous MCM-41 under ultrasonic irradiation

Vanadium polyoxometalate (PVMo) supported on mesoporous MCM-41, MCM-41-NH(2), as efficient and heterogeneous catalysts, with large surface area, for hydrocarbon oxidation with hydrogen peroxide is reported. Oxidation of the alkenes and alkanes gave product selectivities, which are similar to those observed for corresponding homogeneous catalyst. PVMo-MCM was prepared by introduction of PVMo into the mesoporous molecule sieves of MCM-41 by impregnation and adsorption techniques. The samples were characterized by X-ray diffraction (XRD), thermal gravimetric-differential thermal analysis (TG-DTA), FT-IR, scanning electron microscopy (SEM), UV-Vis and cyclic voltametry (CV). Ultrasonic irradiation has a particular effect on MCM-41 structural uniformity and reduced the reaction times and improved the product yields. In addition, the solid catalysts could be recovered and reused several times without loss of its activity.     

Biological Evaluation,Phytochemical Screening,and Fabrication of Indigofera linifolia Leaves Extract-Loaded Nanoparticles

Indigofera linifolia is a medicinally important plant, and by virtue of its rich phytochemical composition, this plant is widely used as essential component in traditional medication systems. Due to its wide range of medicinal applications, the extract-loaded chitosan (Ext+Ch), extract-loaded PEG (Ext+PEG), and extract-loaded locust bean gum (Ext+LGB) nanoparticles (NPs) were prepared in the present study. The prepared NPs were then evaluated for their antibacterial, antioxidant, and antidiabetic potentials. Antibacterial activities of the crude extract and the synthesized NPs were performed following standard procedures reported in the literature. The antioxidant capabilities of extract and NPs were evaluated using DPPH free radical scavenging assay. The antidiabetic potential of the samples was evaluated against α-amylase and α-glucosidase. Ext+PEG NPs showed more potent antibacterial activity against the selected strains of bacteria with the highest activity against Escherichia coli. The lowest antibacterial potential was observed for Ext+LGB NPs. The Ext+LGB NPs IC₅₀ value of 39 μg/mL was found to be the most potent inhibitor of DPPH free radicals. Ext+LGB NPs showed a greater extent of inhibition against α-glucosidase and α-amylase with an IC₅₀ of 83 and 78 μg/mL, whereas for the standard acarbose the IC₅₀ values recorded against the mentioned enzymes were 69 and 74 μg/mL, respectively. A high concentration of phenolics and flavonoids in the crude extract was confirmed through TPC and TFC tests, HPLC profiling, and GC–MS analysis. It was considered that the observed antibacterial, antidiabetic, and antioxidant potential might be due the presence of these phenolics and flavonoids detected. The plant could thus be considered as a potential candidate to be used as a remedy of the mentioned health complications. However, further research in this regard is needed to isolate the exact responsible compounds of the observed biological potentials exhibited by the crude extract. Further, toxicity and pharmacological evaluations in animal models are also needed to establish the safety or toxicity profile of the plant.     

Phytochemical study,potential cytotoxic and antioxidant activities of selected food byproducts (Pomegranate peel,Rice bran,Rice straw & Mulberry bark)

Abstract

The aim of the study is to evaluate common food by-products (Pomegranate peel, Rice bran, Rice straw & Mulberry bark) to screen out their medicinal importance such as cytotoxic & antioxidant activities. HPLC revealed that all tested samples were rich in phenolics. Tested samples exerted significant antioxidant activity with high potency to Pomegranate peel. All tested extracts were able to reduce cell viability of tested cell lines in a dose-response manner after treatment. In most cases, the IC50 values were under 30 μg/ml except IC50 of pomegranate peel against breast cell line (42.4?ug/ml). The antioxidant and cytotoxic properties of pomegranate peel, rice bran, rice straw and mulberry bark have been attributed to synergetic effects of phenolic phytochemicals.     

Highly sensitive and selective measurements of cobalt by catalytic adsorptive cathodic stripping voltammetry

A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of the cobalt-MTB (methyl thymol blue) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by nitrite. The optimum conditions for the analysis of cobalt include pH 9.0 (ammonia buffer), 2.0 μM methyl thymol blue, 0.8 M sodium nitrite and an accumulation potential of −0.5 V (versus Ag/AgCl). The peak current is proportional to the concentration of cobalt over the entire concentration range tested (0.02–500 ng ml⁻¹) with a detection limit of 0.005 ng ml⁻¹ for an accumulation time of 60 s. The method was applied to determination of cobalt in a mineral water sample and some analytical grade salts with satisfactory results.