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PubMed1986

Trace element interactions affecting pulmonary macrophage cytotoxicity.

Effluents from the smokestacks of powerplants contain respirable particles that are enriched with a variety of biologically active trace elements. To determine the relative toxicity of trace elements in coal fly ash, the effects of selected compounds, alone and in combination, were evaluated in cultures of pulmonary alveolar macrophages. The inorganic compounds studied were ZnO, Na2SeO3, V2O5, NaAsO2, Mn3O4, and Ni3S2. Vanadium pentoxide was the most cytotoxic compound while selenium was the least toxic (approximately 100-fold less toxic than vanadium). After dose-response curves for each element were established, interactions between various compounds were studied by coexposure to trace elements at different concentrations. Selenium was completely antagonistic to the toxic effects of vanadium and slightly antagonistic to arsenic. In contrast to selenite, sulfite, a moiety with a similar redox potential, was not antagonistic to vanadium toxicity. Zinc was weakly antagonistic to the in vitro effects of nickel. No other chemical combinations displayed antagonistic, synergistic or additive effects on the function of the cultured macrophages.

Air Pollutants↗
PubMed2005

Study on interaction between poly(amidoamine) dendrimer and CdSe nanocrystal in chloroform.

The binding of different categories of molecules to quantum dot has been studied for many years through different spectroscopic techniques to elucidate details of binding mechanism. In this work we present the results of the study of the interactions between CdSe and poly(amidoamine) dendrimer monitored by photoluminescence spectroscopy of CdSe in chloroform. Dendrimers with different terminal groups and different generations were used to bind with CdSe nanocrystal of different size. Significant differences in the values of binding constant Kb(n) and K(SV) were found in these experiments. The binding constant for poly(amidoamine) dendrimer of generation 4.0 is higher as compared to generation 3.5. The interaction of CdSe with poly(amidoamine) dendrimer shows an increase of binding constants with increasing dendrimer generation from 2.0 to 4.0, as well as with decreasing CdSe diameter. From HRTEM and FTIR analysis, we suggest that dendrimer/CdSe interactions are primarily hydrogen-bonding.

Cadmium Compounds↗
PubMed2006

Preparation of colloidal CdSe and CdS/CdSe nanoparticles from sodium selenosulfate in aqueous polymers solutions.

Cadmium selenide nanoparticles formation at the interaction between CdCl2 and Na2SeSO3 in aqueous solutions of sodium polyphosphate and gelatin has been studied. Structural and optical properties of CdSe nanoparticles have been characterized. It has been shown that the temperature and the ratio of reagents concentrations are the basic parameters, controlling the size of CdSe nanoparticles. Photocatalytic activity of CdS nanoparticles in Na2SeSO3 reduction has been found and investigated; structural and optical properties of binary CdS/CdSe nanoparticles have been characterized. This photoreaction, when carried out in the presence of CdCl2, results in the formation of composite CdS/CdSe nanoparticles. It has been shown that slow interaction of adsorbed selenosulfate with surface-trapped CdS conduction band electrons is the limiting stage of the photocatalytic reaction.

Cadmium Compounds↗
PubMed2005

Incorporating lanthanide cations with cadmium selenide nanocrystals: a strategy to sensitize and protect Tb(III).

The electronic structure of CdSe semiconductor nanocrystals has been used to sensitize Tb3+ in solution by incorporation of Tb3+ cations into the nanocrystals during synthesis. Doping of luminescent Tb3+ metal ions in semiconductor nanocrystals utilizes the positive attributes of both species' photophysical properties, resulting in a final product with long luminescence lifetimes, sharp emission bands, high absorptivities, and strong resistance to decomposition. This strategy also helps protect the lanthanide cations from nonradiative deactivation from C-H, N-H, and O-H oscillators of solvent molecules or traditional organic lanthanide ligands, leading to long Tb3+ luminescence lifetimes. This new type of nanomaterial synergistically combines the photophysical properties of nanocrystals and Tb3+.

Cadmium Compounds↗
PubMed2004

Effect of reaction media on the growth and photoluminescence of colloidal CdSe nanocrystals.

Using cadium oxide (CdO) as the Cd precursor and tri-n-octylphosphine selenide (TOPSe) as the Se source, TOP-capped and TOP/tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals were synthesized without the use of an acid. The synthetic approach involved the addition of a TOPSe/TOP solution into a CdO/TOP solution with or without TOPO at one temperature and subsequent growth at a lower temperature. The temporal evolution of the optical properties, namely, absorption and luminescence, of the growing nanocrystals was monitored in detail. A comprehensive examination on the control of the photoluminescence (PL) properties was performed by systematically varying the TOP/TOPO weight ratio of the reaction media. Surprisingly, a rational choice of 100% TOP or 80% TOP was found to produce "quality" nanocrystals when monitored under the present experimental conditions and growth-time scale. The term "quality" is mainly based on the sharp features and rich substructure exhibited in the absorption spectra of the growing nanocrystals, as well as the sharp features in the emission spectra with narrow full width at half-maximum (fwhm). There are two distinguishable stages of growth: an early stage (<5 min) and a later stage. TOP plays a major role in the control of a slow growth rate in the early stage, while TOPO controls slow growth in the later stage. The optical sensitivity of the growing nanocrystals when dispersed in nonpolar or polar solvents was studied, including two size-dependent parameters, namely, the solvent sensitivity (PL intensity) and nonresonant Stokes shift (NRSS). The insights gained from the present study enable a synthetic approach in which high-quality CdSe nanocrystals are achieved with high synthetic reproducibility.

Cadmium Compounds↗
PubMed2006

Photo-gated charge transfer of organized assemblies of CdSe quantum dots.

The electronic conductivity of tri-n-octylphosphineoxide (TOPO)-protected CdSe quantum dots (QDs) was studied at the air-water interface using the Langmuir technique within the context of photochemical and photophysical excitation. It was found that, upon photoirradiation with photon energies higher than that of the absorption threshold, the voltammetric currents increased rather substantially with a pair of voltammetric peaks at positive potentials. However, the photoconductivity profiles exhibited a dynamic transition, which was ascribed to the strong affinity of oxygen onto the CdSe surface and the consequent trapping of the photogenerated electrons. The resulting excess of holes led to photocorrosion of the particle cores. The oxygen adsorption and photoetching processes were found to be reversible upon cessation of the photoexcitation. In contrast, only featureless voltammetric responses were observed when the particle monolayers were deposited onto the electrode surface and the film conductance was measured in a vacuum (the overall profiles were analogous to that of a Coulomb blockade). A comparative study was also carried out with a CdSe dropcast thick film immersed in acetonitrile, where the photoconductivity profiles were reversible and almost linear. The latter was attributed to the separation of photogenerated electrons and holes which were subsequently collected at the electrodes under voltammetric control. In the dropcast system, the oxygen effects were minimal which was ascribed to the acetontrile medium that limited the access to oxygen and thus the particles were chemically intact. These studies suggest that chemical environment plays an important role in the determination of the chemical stability and electronic conductivity of CdSe QD thin films.

Absorption↗
PubMed2006

Zero-phonon linewidth in CdSe/ZnS core/shell nanorods.

High-resolution spectral hole-burning studies of CdSe/ZnS core/shell nanorods reveal a sharp zero-phonon line, with a line width dependent on the measurement time scale. The zero-phonon line width is attributed to contributions from radiative decay, spectral diffusion induced by surface electric field fluctuations, and phonon-assisted migration of excitons localized in the nanorods. A decoherence rate as small as 4.5 GHz has been observed, when the effects of spectral diffusion are suppressed in the spectral hole-burning measurement. Comparison between zero-phonon line widths in nanorods and spherical nanocrystals also elucidates important differences in the decoherence process between the one- and zero-dimensional nanostructures.

Cadmium Compounds↗
PubMed2004

Ultra-stable nanoparticles of CdSe revealed from mass spectrometry.

Nanoparticles under a few nanometres in size have structures and material functions that differ from the bulk because of their distinct geometrical shapes and strong quantum confinement. These qualities could lead to unique device applications. Our mass spectral analysis of CdSe nanoparticles reveals that (CdSe)(33) and (CdSe)(34) are extremely stable: with a simple solution method, they grow in preference to any other chemical compositions to produce macroscopic quantities. First-principles calculations predict that these are puckered (CdSe)(28)-cages, with four- and six-membered rings based on the highly symmetric octahedral analogues of fullerenes, accommodating either (CdSe)(5) or (CdSe)(6) inside to form a three-dimensional network with essentially heteropolar sp(3)-bonding. This is in accordance with our X-ray and optical analyses. We have found similar mass spectra and atomic structures in CdS, CdTe, ZnS and ZnSe, demonstrating that mass-specified and macroscopically produced nanoparticles, which have been practically limited so far to elemental carbon, can now be extended to a vast variety of compound systems.

Cadmium Compounds↗
PubMed2006

Practicalities of selenium supplementation in critically ill patients.

PURPOSE OF REVIEW: To review the reason for and clinical effects of selenium supplementation in critically ill patients. RECENT FINDINGS: Selenium-dependent enzymes and selenoprotein P regulate immune and endothelial cell function. Obviously not the anorganic compounds of selenium but the activity of selenium-dependent enzymes is the most important factor modulating the immune system and the clinical outcome of patients. Despite low selenium levels in severely ill patients and low glutathione peroxidase activity associated with the extent of multiorgan dysfunction, only a few trials have investigated the effect of selenium supplementation on clinical outcome. A metaanalysis did not reveal a statistically significant survival rate with selenium supplementation, but suggested a dose-dependent trend. The recently completed multicentre trial on high-dose selenium supplementation in septic patients also did not reveal a significant overall reduction in mortality. SUMMARY: The available evidence suggests that selenoproteins play an important role in the immunomodulation of critically ill patients and a sodium selenite supplementation upregulates these selenoenzymes. The intervention trials with sodium selenite performed to date are small and therefore only a tendency in reduction of morbidity and mortality could be demonstrated. Larger trials are necessary to show the supposed benefits and risks of selenite supplementation in critically ill patients.

Antioxidants↗
PubMed2006

Bioavailability of selenium from the selenotrisulphide derivative of lipoic acid.

BACKGROUND/PURPOSE: Selenium is a required micronutrient in mammals, needed for the activity of enzymes that contain selenocysteine at their active site. Several isoenzymes of glutathione peroxidase and thioredoxin reductase contain selenocysteine and thus the nutritional status of selenium in tissues can have significant impact on the steady state level of reactive oxygen species. The aims of this study were to evaluate the bioavailability of selenium derived from the selenotrisulfide derivative of lipoic acid (LASe) and determine the ability of this compound to be absorbed into skin. METHODS: Bioavailability of selenium derived from LASe was determined using a keratinocyte cell model (HaCat). Efficiency of utilization of selenium was assessed by following the decrease in the incorporation of radiolabeled selenite (75Se) in the presence of increasing concentration of selenium compounds. Percutaneous absorption of LASe was measured by determining selenium levels in full thickness biopsy of skin using a Yorkshire pig model. RESULTS: LASe was efficiently absorbed topically into pig skin, a good model of human skin. In a keratinocyte cell line LASe was an efficient source of selenium for selenoprotein synthesis, demonstrating that LASe is a good candidate as a topical selenium micronutrient. Both L-selenomethionine and selenate were found to be poor sources of selenium for selenoprotein synthesis in the skin cell model and L-selenomethionine was poorly absorbed into pig skin. CONCLUSION: These results indicate that stable selenotrisulfides, such as LASe, are good candidates for testing as topical selenium supplements.

Administration, Cutaneous↗
PubMed1999

Autometallographic mercury correlates with degenerative changes in dorsal root ganglia of rats intoxicated with organic mercury.

Organic mercury intoxication in rats produces degenerative changes in the dorsal root ganglia and dorsal nerve roots. In a previous study of rats treated with organic mercury (2 mg/kg ) for 19 days, significant losses of ganglion cells (especially A-cells) and myelinated axons were observed in dorsal nerve roots and there was qualitative evidence of glial cell proliferation and the formation of Nageotte bodies (1). In the present study, the autometallographic silver-enhancement technique, for tracing inorganic mercury bound to sulphide or selenide (AMG-Hg), was applied to tissue sections of dorsal root ganglia and dorsal nerve roots of the same rats used in the earlier study. Satellite cells and macrophages that surrounded ganglion cells and formed Nageotte bodies were heavily labelled by coarse deposits of AMG-Hg, while the labelling of ganglion cells was less pronounced. A-cells were consistently labelled, while B-cells were only occasionally labelled. In the dorsal nerve roots, only a few AMG-Hg deposits could be seen in macrophages. At the ultrastructural level, AMG-Hg was observed within lysosomes of target cells. It is concluded that AMG-Hg is primarily located in glial cells and that the pattern of deposition of AMG-Hg is the same as that for the morphological changes observed in rats intoxicated with organic mercury.

Animals↗
PubMed2002

A Raman study of CdSe and ZnSe nanostructures.

Raman studies have been carried out on CdSe nanotubes and ZnSe nanorods produced by surfactant-assisted synthesis. The Raman spectrum of CdSe nanotubes shows modes at 207.5 and 198 cm-1; the former arises from the longitudinal optic phonon mode red-shifted with respect to the bulk mode because of phonon confinement, and the latter is the l = 1 surface phonon. Analysis based on the phonon confinement model demonstrates that the size of the nanoparticle responsible for the red-shift is about 4 nm, close to the estimate from the blue-shift of the photoluminescence. The Raman spectrum of ZnSe nanorods shows modes at 257 and 213 cm-1, assigned to longitudinal and transverse optic phonons, blue-shifted with respect to the bulk ZnSe modes because of compressive strain. The mode at 237 cm-1 is the surface phonon.

Cadmium Compounds↗
PubMed2001

Conformational search of antisense nucleotides.

A preliminary MMFF implementation of selenium atom parameters necessary to model the nucleoside 1 is reported. X-ray structures of two compounds 1 and 2 have been used as references. Ab initio methods have been adopted for checking torsional energy profile and charge distribution. Monte Carlo calculations and energy minimization in solvation complete the conformational search.

Antisense Elements (Genetics)↗
PubMed1989

Determination of selenium in drugs by oxygen flask combustion and ion chromatography.

A method is described for the determination of trace selenium (impurities in medicinal organic compounds) by ion chromatography (IC) after oxygen flask combustion. All selenium compounds formed by oxygen flask combustion are converted to selenate ion by heating with nitric acid and potassium permanganate. The selenate ion is then determined by IC, using a simple recycle system to eliminate interfering ions. The detection limit of selenium is 0.4 nmol in 50 mg of sample. The recoveries of selenium added to seven drugs are ca. 95-103% with relative standard deviations of 1-6%.

Chromatography↗