Impact of environmental conditions on the removal of Ni(II) from aqueous solution to bentonite/iron oxide magnetic composites

The sorption of radionuclide ⁶³Ni(II) on bentonite/iron oxide magnetic composites was investigated by batch technique under ambient conditions. The effect of contact time, solid content, pH, coexistent electrolyte ions, fulvic acid, and temperature on Ni(II) sorption to bentonite/iron oxide magnetic composites was examined. The results demonstrated that the sorption of Ni(II) was strongly dependent on pH and ionic strength at pH <8.0, and was independent of pH and ionic strength at high pH values. The sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange at low pH, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The experimental data were well fitted by Langmuir model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Ni(II) on bentonite/iron oxide magnetic composites was an endothermic and spontaneous processes. The results show that bentonite/iron oxide magnetic composites are promising magnetic materials for the preconcentration and separation of radionickel from aqueous solutions in environmental pollution.     

Iron hydroxide nanoparticles coated with poly(ethylene glycol)-poly(aspartic acid) block copolymer as novel magnetic resonance contrast agents for in vivo cancer imaging

PEG-coated β-FeOOH nanoparticles were prepared through electrostatic complex formation of iron oxide nanoparticles with poly(ethylene glycol)-poly(aspartic acid) block copolymer [PEG-P(Asp)] in distilled water. By dynamic light scattering (DLS) measurement, the nanopaticle size was determined to be 70 nm with narrow distribution. The FT-IR and zeta potential experimental results proved that PEG-PAsp molecules bound to the surface of the iron oxide nanoparticles via the coordination between the carboxylic acid residues in the PAsp segment of the block copolymer and the surface Fe of the β-FeOOH nanoparticles. The PEG-coated nanoparticles revealed excellent solubility and stability in aqueous solution as well as in physiological saline. In vivo MRI experiments on tumor-bearing mice demonstrated that the PEG-coated nanoparticles prepared by the current approach achieved an appreciable accumulation into solid tumor, suggesting their potential utility as tumor-selective MRI contrast agents.     

Preparation and characterization of amino-functionalized magnetic nanogels via photopolymerization for MRI applications

To design peptide-targeted iron oxide as magnetic resonance imaging (MRI) contrast agents, amino-functionalized magnetic nanogels were prepared by using N-(2-aminoethyl) methacrylamide hydrochloride (AEM·HCl) as monomer via new photochemical approach. Their chemical structure and composition were characterized by Fourier transform infrared spectra (FTIR) and thermogravimetric analyses (TGA). The core–shell structure of magnetic nanogels was confirmed by high-resolution transmission electron microscopy (HRTEM). The good storage stability, high magnetic content (88.7%), high saturation magnetizations and superparamagnetic behavior suggested their great potentials as MRI contrast agents, which were confirmed by their measurements of r₂ and coronal image of the crossing of mouse kidney.     

Diblock‐Copolymer‐Mediated Self‐Assembly of Protein‐Stabilized Iron Oxide Nanoparticle Clusters for Magnetic Resonance Imaging

Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T₂) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein–polymer double‐stabilized SPIONs for improving contrast in MRI. We used a cationic–neutral double hydrophilic poly(N‐methyl‐2‐vinyl pyridinium iodide‐block‐poly(ethylene oxide) diblock copolymer (P2QVP‐b‐PEO) to mediate the self‐assembly of protein‐cage‐encapsulated iron oxide (γ‐Fe₂O₃) nanoparticles (magnetoferritin) into stable PEO‐coated clusters. This approach relies on electrostatic interactions between the cationic N‐methyl‐2‐vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo‐TEM). DLS results indicated that the hydrodynamic diameter (D_h) of the clusters is approximately 200 nm, and cryo‐TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r₁) is decreased and the transverse relaxivity (r₂) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement.     

Isotope pattern deconvolution as a tool to study iron metabolism in plants

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP–MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using ⁵⁷Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned ⁵⁷Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP–MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low ⁵⁷Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP–MS instrument, after addition of ⁵⁷Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample.     

Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe

A new prototype consisting of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles decorated with europium(III) ions encapsulated in a DO3A organic scaffold was designed as a platform for further development of bimodal contrast agents for MRI and optical imaging. The USPIO nanoparticles act as negative MRI contrast agents, whereas the europium(III) ion is a luminophore that is suitable for use in optical imaging detection. The functionalized USPIO nanoparticles were characterized by TEM, DLS, XRD, FTIR, and TXRF analysis, and a full investigation of the relaxometric and optical properties was conducted. The typical luminescence emission of europium(III) was observed and the main red emission wavelength was found at 614 nm. The relaxometric study of these ultrasmall nanoparticles showed r₂ values of 114.8 mm ^?1_Fes^?1 at 60 MHz, which is nearly double the r₂ relaxivity of Sinerem^®.     

Flow-injection determination of total iron in freshwater samples with neutralisation chemiluminescence

A flow-injection chemiluminescence method has been established for the determination of total iron in freshwater samples. The enhanced chemiluminescence emission was caused by the iron(II) from the neutralisation reaction of hydrochloric acid and sodium hydroxide without the use of any chemiluminescent reagent. The calibration graph was linear in the concentration range of 2.8–560 µg L^?1 (r ² = 0.9983, n = 8), with relative standard deviation (RSD; n = 4) in the range of 0.8–2.6%. The limit of detection (S/N = 3) was 0.56 µg L^?1 with injection throughput of 180 h^?1. The effect of common anions and cations were studied over their environmentally relevant concentrations in freshwaters. The method was successfully applied to determine total iron in freshwater samples. Iron(III) was reduced to iron(II) by using hydroxylammonium chloride. The proposed method was compared with spectrophotometric method and there was no significant difference between the two methods at the 95% confidence level (t-test). Analysis of river water (certified reference material SLRS-4) for iron(II), after reduction of iron(III) with hydroxylammonium chloride, gave good results (2.17 ± 0.22 µM compared with the certificate value of 1.85 ± 0.1 µM).     

Electrospray-Ionization Mass Spectrometry: Detection of a radical cation present in solution: New results on the chemistry of (tetrahydropteridinone)-metal complexes

This paper marks the first reported detection of radical cations by Electrospray-Ionization Mass Spectrometry (ESI-MS). Electron Spin Resonance (ESR) measurements have proven that the detected radical cation existed already in solution and has not been generated by the electrospray ionization technique. However, we observed that the radical cation can be generated by changes in the ionization conditions. A molar mixture of 2-amino-5,6,7,8-tetrahydro-5-methylpterin-4(4H)-one dihydrochloride ( = 5,6,7,8-tetrahydro-N(5)-methylpterin-2 HCl, N(5)-MTHP-2 HCl), and tris(pentane-2,4-dionato)iron(III) in MeCN at pH 2–3 leads to the formation of a [bis(pentane-2,4-dionato)(2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (4H)-one)]iron complex ( = [bis(pentane-2,4-dionato) (5,6,7,8-tetrahydro-N(5)-methylpteridin)]iron complex) which can be detected by ESI-MS. The results suggest that this complex might be an Fe^II radical cation, which could possibly be a suitable model complex for the active center of the phenylalanine hydroxylase. In the same solution, the stable radical cation of N(5)-MTHP is identified by ESI-MS and ESR.     

Thermal Effects Associated with the Incorporation of Transition Metal Catalysts Inside Alumino-silicate Supports

Kaolinic and bentonitic-clays are selected to prepare transition metals, iron, cobalt and nickel catalysts. The metals are incorporated into two supports through new impregnation technique. The original clays and the prepared catalysts were subjected to different techniques. The crystallite size (X-ray diffraction analysis) increases from iron to cobalt then to nickel upon heating and the increase for bentonitic-catalysts is higher than that for kaolinic-ones. Infrared spectra show the appearance of bands signifying the presence of iron, cobalt and nickel bonded to OH group constituting the silica-silica tetrahedral sheets inside the clay structure. The enthalpy (ΔH) andentropy (ΔS) values (differential scanning calorimetric) are lower for bentonitic-catalysts than for kaolinic-catalysts. Thus, the incorporation of the metal hydroxide in the interlamella of the silicate-silicate bentonite clay structure facilitates the interaction between the unpaired electrons on the adjacent atoms and the support which enables the prepared catalysts to be more active for catalytic conversion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quantitative determination of the composition of nitrided layers on iron using AES

Within the framework of the study of industrial nitriding of steel, AES was chosen as the principle analysis technique. In order to characterise the nitrided layers quantitatively, reliable sensitivity factors were needed. For that purpose, different reference samples containing the pure γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases were prepared by gaseous nitriding of pure iron. The characterisation of these references by means of electron probe microanalysis (EPMA) is discussed. The first sample contained a nitrided layer with large γ′‐Fe₄N_1?x grains (～30 µm) with 19.6 at.% nitrogen on top of an iron substrate. The second one contained an ε‐Fe₂N_1?z outer layer (～6 µm) with 26 at.% nitrogen, on a γ′‐Fe₄N_1?x layer (～4 µm) with 19.8 at.% nitrogen, created on top of an iron substrate. In this study, Fe LMM and N KLL Auger electron spectral lines were acquired on the pure γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases of these two reference samples in order to calculate the sensitivity factors of iron and nitrogen. Different Auger intensities were considered and compared. It was decided to use the peak areas of the direct Auger electron spectral lines. The values of the sensitivity factors are 0.74 for iron and 0.33 for nitrogen. Finally, a set of three independent and well‐characterised samples containing the γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases was used to validate the elaborated quantification procedure. Copyright © 2007 John Wiley & Sons, Ltd.     

Determination of total iron binding capacity of serum by capillary electrophoresis

Summary A capillary electrophoresis (CE) technique for determining total iron binding capacity (TIBC) of serum has been developed. The optimum serum pretreatment involves the following major steps: at first, saturate serum transferrin with Fe⁺³; then, dissociate them completely after removing excess unbound Fe. Finally, complex the released iron with phenanthroline, a chromophore, to make suitable for the CE analysis. Ammonium acetate (pH=5.0) was used as CE background electrolyte solution. In this system, a good linear correlation coefficient was maintained over the range 0.5≈10 μM (r=0.9979,n=12). Seven adult serum samples were studied and the TIBC parameters measured. In the present system, 10≈30 μL serum is sufficient for determination. The study shows that the CE technique described is a powerful method for rapid, efficient, sensitive and reliable analysis and hence particularly suitable for clinical application.     

Spectrophotometry Determination of Iron(III) and Cobalt(II) with Salicylaldehyde Hydrazone (SH)

Iron and cobalt complexation with salicylaldehyde hydrazone (SH) has been studied spectrophotometrically employing solvent extraction technique. The Fe(III)-SH (1:3) and Co-SH (1:2) complex absorb at 510nm and 450 nm respectively. The sensitivity of the colour reactions are 0.014 and 0.005 in terms of Sandell's definition for iron and cobalt systems. Both the complexes show maximum and constant absorbance in the pH ranges 3.5 to 5.0 and 6.2 to 7.0 for Fe(III)-SH and Co(II)-SH respectively. The complexation has been used in the spectrophotometric determination of iron and cobalt in coexistence with several ions.     

QSAR Study on Binding Affinity of PATs (Rodenticides) to the [3H]-Mepyramine-Labelled H1 Receptor In Rat and Guinea Pig Brain

Abstract

The binding of a series of PAT analogues (rodenticides) to the [³H]-mepyramine-labelled H₁ receptor in rat and guinea pig brain was investigated topologically using negentropy (N), molecular redundancy (MRI), first-order molecular connectivity (¹X _v ), Wiener (W), and Szeged (Sz) indices. Multiple regression analyses showed that MRI provided excellent results upon introduction of indicator parameters. Predictive ability of the proposed models was discussed using cross-validation parameters.     

MALDI-TOF MS和电子光谱技术研究海兔肝铁蛋白亚基电离和释放铁动力学特性

选用肽质量指纹谱(peptide mass fingerprint,PMF)技术鉴定质谱纯海兔肝铁蛋白(liver ferritin ofAplysia,ALF)。来源于基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)仪中的激光和基质芥子酸协同解吸海兔肝铁蛋白(ALF)为带双电荷、单电荷[M H] 和二聚体的亚基离子,并可供质谱分析。ALF亚基的质荷比m/z分别为9784.03[M 2H]2 、19678.42[M H] 和39387.80[2M H] ,其中亚基分子量[M H] 略小于鲨鱼肝铁蛋白(liver ferritin of shark,SLF)。在弱碱介质(pH8.0)条件下,电子光谱技术研究指出,抗坏血酸以1/2级反应方式参与ALF释放铁全过程,同时又使ALF以一级反应动力学方式释放铁,呈现两种不同的速率。推测这一异常现象可能与ALF含低铁量、亚基调节能力和海兔的进化地位有关。     

Complexation of gadolinium(III) ions on top of nanometre-sized magnetoliposomes

The complex of diethylenetriaminepentaacetate (DTPA) with the paramagnetic gadolinium ion [Gd(III)] is a well-known blood pool contrast agent for magnetic resonance imaging (MRI). To obtain MRI pictures from other anatomical structures, for instance from tissues containing cells with phagocytic activity, larger colloidal complexes have to be constructed. Therefore, in view of modifying the physiological behaviour, the DTPA chelate was first hydrophobized by covalently linking it to phosphatidylethanolamine (PE), and the resulting conjugate was then incorporated into nanometre-sized, sonicated phospholipid vesicles. Qualitative information on the affinity of the PE–DTPA derivative for Gd(III) ions was derived from competition experiments using the dye Arsenazo. Furthermore, it was found that only the membranotropic adducts residing in the outer shell of the vesicle bilayer are accessible to the lanthanide ion. The vesicular particulate was also used as a vehicle to transport PE–DTPA into the coating of so-called magnetoliposomes which consist of nanometre-sized iron oxide cores onto which a phospholipid bilayer is strongly chemisorbed. After loading the resulting structures with Gd(III), this new type of magnetoliposome may offer unique potentialities as a novel bi-label MRI contrast medium.     

Development of method for the speciation of inorganic iron in wine samples

In this paper, we proposed a procedure for the determination of iron(II) and total iron in wine samples employing molecular absorption spectrophotometry. The ligand used is 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) and the chromogenic reaction in absence or presence of ascorbic acid (reducing agent) allows the determination of iron(II) or total iron, respectively. The optimization step was performed using a multivariate technique (Box Behnken design) involving the factors pH, acid ascorbic concentration and reaction time.The method allows the determination of iron(II) and iron(III) in wine samples, with limits of detection and quantification 0.22 and 0.72 μg L⁻¹, respectively. The precision expressed as relative standard deviation (R.S.D.) was 1.43 and 0.56% (both, n = 11) for content of iron(II) in wine samples of 1.68 and 4.65 mg L⁻¹, and 1.66 and 0.87% (both, n = 11) for content of total iron in wine samples of 1.72 and 5.48 mg L⁻¹.This method was applied for determination of iron(II) and total iron in six different wine samples. In these, the iron(II) content varied from 0.76 to 4.65 mg L⁻¹ and from 1.01 to 5.48 mg L⁻¹ for total iron. The results obtained in the determination of total iron by Br-PADAP method were compared with those that were performed after complete acid digestion in open system and determination of total iron employing FAAS. The method of regression linear was used for comparison of these results and demonstrated that there is no significant difference between the results obtained with these two procedures.     

Enhanced Electron Transfer Reactivity of a Nonheme Iron(IV)–Imido Complex as Compared to the Iron(IV)‐Oxo Analogue

Reactions of N,N‐dimethylaniline (DMA) with nonheme iron(IV)‐oxo and iron(IV)‐tosylimido complexes occur via different mechanisms, such as an N‐demethylation of DMA by a nonheme iron(IV)‐oxo complex or an electron transfer dimerization of DMA by a nonheme iron(IV)‐tosylimido complex. The change in the reaction mechanism results from the greatly enhanced electron transfer reactivity of the iron(IV)‐tosylimido complex, such as the much more positive one‐electron reduction potential and the smaller reorganization energy during electron transfer, as compared to the electron transfer properties of the corresponding iron(IV)‐oxo complex.     

Determination of Total Iron in Environmental Samples by Solid Phase Extraction with Dimethyl(E)‐2‐(2‐Methoxyphenoxy)‐2‐Butenedioate

A novel solid phase extraction technique for determination of total iron in environmental water samples was developed. The method is based on sorption of Fe(III) ions on octadecyl silica membrane disk modified with a new synthetic ligand dimethyl(E)‐2‐(2‐methoxyphenoxy)‐2‐butenedioate (I). Iron(III) is quantitatively retained on the disk in the pH range of 3–7 at a flow rate of 1–7 mL min⁻¹. The Fe(III) eluted with 10 mL of 0.01 M EDTA and than was measured by flame atomic absorption spectrometry (FAAS) at 248.3 nm. The maximum capacity disk modified by 7 mg of ligand was found to be 197 ± 2 μg of iron(III). The breakthrough volume was greater than 2000 mL. The iron(III) was completely recovered (> 99%) from water with a preconcentration factor of more than 200. The limit of detection of the proposed method was 1.00 ng mL⁻¹. The various cationic and anionic interferences had no effect on the recovery of iron(III) from the binary mixtures. The proposed method was successfully applied to determination of total iron from three different water samples.     

Direct Voltammetric Determination of Total Iron with a Gold Microelectrode Ensemble

The behavior of the Fe(II)/(III) redox system at a Au microelectrode ensemble (Au‐MEE) based on a solid composite by means of direct and cyclic voltammetric analysis (VA) is reported. With a simple electrode activation and sample preparation, the influence of dissolved organic substances was eliminated, providing highly sensitive results. The analytical signal was based on the maximum cathodic current (I) of the first derivative (dI/dE), and iron determination within the 0.002–0.04 mg L^?1 range was studied. A sensitive LOD (3σ) value of 0.7 µg L^?1 for total iron concentration was calculated; total iron determination in different waters was shown.     

Manganese-Zinc Ferrites: Safe and Efficient Nanolabels for Cell Imaging and Tracking In Vivo

Manganese-zinc ferrite nanoparticles were synthesized by using a hydrothermal treatment, coated with silica, and then tested as efficient cellular labels for cell tracking, using magnetic resonance imaging (MRI) in vivo. A toxicity study was performed on rat mesenchymal stem cells and C6 glioblastoma cells. Adverse effects on viability and cell proliferation were observed at the highest concentration (0.55 mM) only; cell viability was not compromised at lower concentrations. Nanoparticle internalization was confirmed by transmission electron microscopy. The particles were found in membranous vesicles inside the cytoplasm. Although the metal content (0.42 pg Fe/cell) was lower compared to commercially available iron oxide nanoparticles, labeled cells reached a comparable relaxation rate R₂, owing to higher nanoparticle relaxivity. Cells from transgenic luciferase-positive rats were used for in vivo experiments. Labeled cells were transplanted into the muscles of non-bioluminescent rats and visualized by MRI. The cells produced a distinct hypointense signal in T₂- or T₂*-weighted MR images in vivo. Cell viability in vivo was verified by bioluminescence.