Mandana Amiri

Electrocatalytic determination of sumatriptan on the surface of carbon-paste electrode modified with a composite of cobalt/Schiff-base complex and carbon nanotube.

The electrochemical oxidation of sumatriptan on the surface of carbon paste electrode modified with multi-walled carbon nanotube and cobalt methyl-salophen complex is studied by using cyclic voltammetry and polarization studies. The results indicate that the drug is irreversibly oxidized in a one electron oxidation mechanism. It was found that the peak potential shifted negatively with increasing pH, confirms that H(+) participate in the oxidation process. The electrode is shown to be very effective for the detection of sumatriptan in the presence of other biological reductant compounds. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of sumatriptan, ascorbic acid and uric acid, which makes it suitable for the simultaneous detection of sumatriptan in the presence of these compounds in clinical and pharmaceutical preparations. It can be concluded that multi-walled carbon nanotube and Shiff base complex have synergic effect on electroacatalytic oxidation of sumatriptan. A linear range of 1-1000μM and detection limit of 0.3μM was obtained for sumatriptan from DPV measurements using this electrode in 0.1M acetate buffered solution of pH 5.0. The electrode has been applied successfully for the determination of sumatriptan in synthetic serum and commercial tablets.

Synthesis, characterization, and immobilization of nickel(II) tetradentate Schiff-base complexes on clay as heterogeneous catalysts for the oxidation of cyclooctene

Nickel(II) tetradentate Schiff-base complexes of N,N′-(bis(pyridin-2-yl)formylidene)ethane-1,2-diamine (L1), N,N′-(bis(pyridin-2-yl)formylidene)cyclohexane-1,2-diamine (L2), N,N′-(bis(pyridin-2-yl)formylidene)benzene-1,2-diamine (L3), N,N′-(bis(pyridin-2-yl)formylidene)meso-stilben-1,2-diamine (L4), and N,N′-(bis(pyridin-2-yl)formylidene)propane-1,3-diamine (L5) were synthesized, characterized, and immobilized on sodium montmorillonite. The complexes were characterized by IR spectroscopy, diffuse reflectance spectra (DRS), and atomic absorption spectroscopy (AAS). IR and DRS data of the heterogeneous catalysts show that the Ni(II) complexes were physically entrapped within the sodium montmorillonite clay. The supported complexes show good catalytic activity for the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxygen source in acetonitrile. The Ni-catalyzed oxidation proceeds with 62.3% selectivity for epoxidation with 69% conversion for supported [Ni(L5)].

Development of the catalytic reactivity of an oxo–peroxo Mo(VI) Schiff base complex supported on supermagnetic nanoparticles as a reusable green nanocatalyst for selective epoxidation of olefins

A novel ancillary branch coated oxo–peroxo Mo(VI)tetradentate Schiff base complex on superparamagnetic nanoparticles was prepared and characterized by IR spectroscopy, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), diffuse reflectance spectra (DRS) and atomic absorption spectroscopy (AAS). The catalyst was used for the selective epoxidation of cyclooctene, cyclohexene, styrene, indene, α-pinene, 1-hepten, 1-octene, 1-dodecen and trans-stilben using tert-butyl hydroperoxide as an oxidant in 1,2-dichloroethane. This catalyst is efficient for the oxidation of cyclooctene, with a moderate 100% selectivity for epoxidation with 97% conversion in 30 min. We were able to separate the supermagnetic nanocatalyst by using an external magnetic field, and to use the catalyst at least five successive times without significant decrease in conversion. The proposed supermagnetic nanocatalyst has advantages in catalytic activity, selectivity, catalytic reaction time and reusability by easy separation.

Nickel (II) incorporated AlPO-5 modified carbon paste electrode for determination of thioridazine in human serum.

In this approach, synthesis of nickel (II) incorporated aluminophosphate (NiAlPO-5) was performed by using hydrothermal method. The diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques were applied in order to characterize synthesized compounds. The NiAlPO-5 was used as a modifier in carbon paste electrode for the selective determination of thioridazine which is an antidepressant drug. This research is the first example of an aluminophosphate being employed in electroanalysis. The effective catalytic role of the modified electrode toward thioridazine oxidation can be attributed to the electrocatalytic activity of nickel (II) in the aluminaphosphate matrix. In addition, NiAlPO-5 has unique properties such as the high specific surface area which increases the electron transfer of thioridazine. The effects of varying the percentage of modifier, pH and potential sweep rate on the electrode response were investigated. Differential pulse voltammetry was used for quantitative determination as a sensitive method. A dynamic linear range was obtained in the range of 1.0×10(-7)-1.0×10(-5)mol L(-1). The determination of thioridazine in real samples such as commercial tablets and human serum was demonstrated.

Carbon nanoparticles with tosyl functional group for distinguishing voltammetric peaks of ascorbic acid and uric acid.

In this approach, electro-oxidation of a mixture of uric acid and ascorbic acid at the surface of tosyl surface carbon nanoparticles/glassy carbon electrode has been performed. The electro-oxidation of these compounds at bare electrode is sluggish and there is no suitable peak separation between them. However, using functionalized carbon nanoparticles, two well-defined anodic peaks with a considerable enhancement in the peak current and a remarkable peak potential separation near 452 mV is obtained. The porous interfacial layer of the carbon nanoparticles modified electrode with a high specific surface area increases the conductive area; molecules can penetrate through the conductive porous channels onto the electrode more easily so leading to higher sensitivity and selectivity. The dynamic linear ranges of 1.0 × 10(-5) to 3.0 × 10(-3)M and 1.0 × 10(-7) to 1.0 × 10(-4)M with detection limits 1.0 × 10(-5)M and 2.0 × 10(-8)M (for S/N=3) were obtained for ascorbic acid and uric acid, respectively. Analytical utility of the modified electrode has been examined successfully using human urine samples and vitamin C commercial tablets.

Electrochemical methodologies for the detection of pathogens.

Bacterial infections remain one of the principal causes of morbidity and mortality worldwide. The number of deaths due to infections is declining every year by only 1% with a forecast of 13 million deaths in 2050. Among the 1400 recognized human pathogens, the majority of infectious diseases is caused by just a few, about 20 pathogens only. While the development of vaccinations and novel antibacterial drugs and treatments are at the forefront of research, and strongly financially supported by policy makers, another manner to limit and control infectious outbreaks is targeting the development and implementation of early warning systems, which indicate qualitatively and quantitatively the presence of a pathogen. As toxin contaminated food and drink are a potential threat to human health and consequently have a significant socioeconomic impact worldwide, the detection of pathogenic bacteria remains not only a big scientific challenge but also a practical problem of enormous significance. Numerous analytical methods, including conventional culturing and staining techniques as well as molecular methods based on polymerase chain reaction amplification and immunological assays, have emerged over the years and are used to identify and quantify pathogenic agents. While being highly sensitive in most cases, these approaches are highly time, labor, and cost consuming, requiring trained personnel to perform the frequently complex assays. A great challenge in this field is therefore to develop rapid, sensitive, specific, and if possible miniaturized devices to validate the presence of pathogens in cost and time efficient manners. Electrochemical sensors are well accepted powerful tools for the detection of disease-related biomarkers and environmental and organic hazards. They have also found widespread interest in the last years for the detection of waterborne and foodborne pathogens due to their label free character and high sensitivity. This Review is focused on the current electrochemical-based microorganism recognition approaches and putting them into context of other sensing devices for pathogens such as culturing the microorganism on agar plates and the polymer chain reaction (PCR) method, able to identify the DNA of the microorganism. Recent breakthroughs will be highlighted, including the utilization of microfluidic devices and immunomagnetic separation for multiple pathogen analysis in a single device. We will conclude with some perspectives and outlooks to better understand shortcomings. Indeed, there is currently no adequate solution that allows the selective and sensitive binding to a specific microorganism, that is fast in detection and screening, cheap to implement, and able to be conceptualized for a wide range of biologically relevant targets.

Positively charged carbon nanoparticulate/sodium dodecyl sulphate bilayer electrode for extraction and voltammetric determination of ciprofloxacin in real samples

In this study, ciprofloxacin, a second-generation fluoroquinolone antibiotic, has been analyzed in human serum and a pharmaceutical preparation by a modified carbon paste electrode. The modified electrode was prepared using a layer-by-layer method with functionalized carbon nanoparticles and sodium dodecyl sulphate. Carbon nanoparticles (Emperor 2000™) were functionalized with ethylene diamine using a chemical method. The functionalized carbon nanoparticles were studied with scanning electron microscopy and FTIR spectroscopy. The modified electrode was characterized with electrochemical impedance spectroscopy and cyclic voltammetry. The ability of modified electrode to adsorb ciprofloxacin was investigated. The extraction parameters such as time, pH and agitation rate were optimized. In optimum conditions, ciprofloxacin was adsorbed at the surface of electrode and its electro-oxidation was studied. Differential pulse voltammetry was applied for quantitative determinations. Two linear ranges 5.0 × 10−7 to 1.0 × 10−5 mol L−1 and 3.0 × 10−8 to 5.0 × 10−7 mol L−1 with a limit of detection of 5.0 × 10−9 mol L−1 were obtained. The prepared electrode exhibited the successful ability for the determination of ciprofloxacin in real samples such as human serum and commercial tablets with recoveries 99.85% and 101.5%, respectively.

Synthesis, characterization, crystal structure, electrochemical, solvatochromic and biological investigation of novel N4 and N3 type Cu(II) Schiff base complexes

In the present study, three novel Cu(II) Schiff base complexes [CuL](ClO4)2, [CuL′Cl2] and [CuL′(NO3)2] (L: N,N′-bis(2-pyridinylmethylene)-1,2-diphenylethylenediamine and L′: N-(2-pyridinylmethylene)-1,2-diphenylethylenediamine) were synthesized and characterized using infrared spectroscopy, elemental analysis, conductivity measurements and X-ray crystallography. The crystal structure of the [CuL′(NO3)2] and [CuL′Cl2] complexes were determined by X-ray crystallography. However, suitable single crystals for [CuL](ClO4)2 could not be obtained. The complexes were assessed to determine their thermal, electrochemical and biological behaviors and electronic absorption. Among the complexes, only the [CuL](ClO4)2 complex showed solvatochromic properties in various solvents. The antibacterial activities of these complexes were evaluated in Muller-Hinton broth against Staphylococcus aureus, Escherichia coli and Enterococcus faecalis using the serial dilution technique at concentrations ranging from 2 to 0.0625 mg mL−1. The data demonstrates that the complexes were bacteriostatic agents that inhibit bacterial growth, but had no bactericidal properties.

Entrapment of uropathogenic E. coli cells into ultra-thin sol-gel matrices on gold thin films: A low cost alternative for impedimetric bacteria sensing

Bacterial infections are causing worldwide morbidity and mortality. One way to limit infectious outbreaks and optimize clinical management of infections is through the development of fast and sensitive sensing of bacteria. Most sensing approaches are currently based on immunological detection principles. We report here on an impedimetric sensor to selectively and sensitive detect uropathogenic E. coli cells (E. coli UTI89) using artificial recognition sites. We show here the possibility to imprint the rod-shape structure of E. coli UTI 89 into ultra-thin inorganic silica coatings on gold electrodes in a reproducible manner. A linear range from to 1 × 100 -1 × 104 cfu mL-1 is obtained. With a detection limit for E. coli UTI89 below 1 cfu mL-1 from five blank signals (95% confidence level) and excellent selective binding capabilities, these bacterial cell imprinted electrodes brings us closer to a low cost specific bacterial recognition surfaces.

Palladium nanoparticles in electrochemical sensing of trace terazosin in human serum and pharmaceutical preparations

In this approach, palladium nanoparticle film was simply fabricated on the surface of carbon paste electrode by electrochemical deposition method. The film was characterized using scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The prepared electrode exhibited an excellent electrocatalytic activity toward detection of trace amounts of terazosin, which is an antihypertensive drug. Under the optimum experimental conditions, a linear range of 1.0×10-8-1.0×10-3molL-1 with a detection limit of 1.9×10-9molL-1 was obtained for determination of terazosin using differential pulse voltammetry as a sensitive method. The efficiency of palladium nanoparticle film on the surface of carbon paste electrode successfully proved for determination of terazosin in pharmaceutical sample and human serum sample with promising recovery results. The effect of some foreign species has been studied.