NP Solution Research Articles

Enhancing the performance of electro-peroxone by incorporation of UV irradiation and BDD anodes

ABSTRACTIn this work, the treatment of 4-nitrophenol (NP) in water by ozonation, electrolysis, electro-peroxone (EP), and photo-electro-peroxone (PEP) processes was investigated. PEP process is based on the combination of ozonation, UV irradiation, and electrolysis using a carbon felt cathode and a boron-doped diamond (BDD) anode. In this process, H2O2 is electrochemically generated from reduction of O2 in the ozone generator effluent at a carbon felt cathode. The in situ generated H2O2 is simultaneously decomposed by UV-photolysis and by reaction with O3 to form HO• radicals that can rapidly and non-selectively oxidize organic pollutants. The results showed that PEP is the most efficient process for a rapid NP degradation in water than the other individual and combined methods. In addition, PEP process was able to completely remove total organic carbon (TOC) from NP solution after consumption of 4.1 kWh/kg TOC removed. Hydroquinone, 1,2,4-trihydroxybenzene, oxalic and maleic acids were identified as the main intermediates of NP degradation. The addition of iron to NP solution did not significantly affect the efficiency of PEP process. The results demonstrated that the incorporation of BDD anodes and UV light in PEP process can significantly enhance the kinetics and minimize energy requirements.

Bismuth Sulfide Nanoparticles as a Complement to Traditional Iodinated Contrast Agents at Various X-Ray Computed Tomography Tube Potentials

Background: Investigation of the contrast enhancement effects on the CT images of the conventional iodinated contrast media (CM) or bismuth sulfide nanoparticles (Bi2S3 NPs) with increasing x-ray tube potentials. Materials and methods: A phantom was filled with iodinated CM or Bi2S3 NP solutions at concentrations ranging from 0 to 65 mM and the phantom was scanned with a CT scanner using tube potentials of 80, 100, 120 and 140 kVp at a fixed current of 200 mA. The CT contrast enhancement and contrast-to-noise ratios (CNR) of all scanned images were calculated. Results: This study demonstrated that greater image contrast was observed with Bi2S3 NPs compared to the iodinated CM at all concentrations and energies (80-140 kVp) tested. For example, at a concentration of 65 mM and tube potential of 140 kVp, a CNR enhancement of three to four times was observed for Bi2S3 NPs compared to iodinated CM. Even at a conventional tube potential of 80 KVp, one to two-fold increase in CNR was noted for Bi2S3 NPs. Results are also demonstrated that CNR increased with increasing concentration of Bi2S3 NPs at a fixed tube potential. Conclusion: These results highlight the effects of the different physical densities and atomic numbers of the two elements (I versus Bi), and their role in enhancing the probability of Compton scattering (CS) and photoelectric effects (PEs). As tube potential was increased, the CT numbers for both Bi2S3 NPs and iodinated CM decreased, consistent with a decrease in the probability of CS and PEs with increasing beam energy. However, the rate of decrease for iodinated CM was larger than Bi2S3 NPs. A good correlation was observed between the experimental results and the theoretical spectra based on linear attenuation coefficients .

Speciation of neptunium during sorption and diffusion in natural clay

In argillaceous rocks, which are considered as a potential host rock for nuclear waste repositories, sorption and diffusion processes govern the migration behaviour of actinides like neptunium. For the safety analysis of such a repository, a molecular-level understanding of the transport and retardation phenomena of radioactive contaminants in the host rock is mandatory. The speciation of Np during sorption and diffusion in Opalinus Clay was studied at near neutral pH using a combination of spatially resolved synchrotron radiation techniques. During the sorption and diffusion experiments, the interaction of 8 μM Np(V) solutions with the clay lead to the formation of spots at the clay-water interface with increased Np concentrations as determined by μ-XRF. Several of these spots are correlated with areas of increased Fe concentration. Np L3-edge μ-XANES spectra revealed that up to 85% of the initial Np(V) was reduced to Np(IV). Pyrite could be identified by μ-XRD as a redox-active mineral phase responsible for the formation of Np(IV). The analysis of the diffusion profile within the clay matrix after an in-diffusion experiment for two months showed that Np(V) is progressively reduced with diffusion distance, i.e. Np(IV) amounted to ≈12% and ≈26% at 30 μm and 525 μm, respectively.

Lifetime-resolved Photoacoustic (LPA) Spectroscopy for monitoring Oxygen change and Photodynamic Therapy (PDT).

The Methylene Blue loaded Polyacrylamide Nanoparticles (MB-PAA NPs) are used for oxygen sensing and Photodynamic therapy (PDT), a promising therapeutic modality employed for various tumors, with distinct advantages of delivery of biomedical agents and protection from other bio-molecules overcoming inherent limitations of molecular dyes. Lifetime-resolved photoacoustic spectroscopy using quenched-phosphorescence method is applied with MB-PAA NPs so as to sense oxygen, while the same light source is used for PDT. The dye is excited by absorbing 650 nm wavelength light from a pump laser to reach triplet state. The probe laser at 810 nm wavelength is used to excite the first triplet state at certain delayed time to measure the dye lifetime which indicates oxygen concentration. The 9L cells (106 cells/ml) incubated with MB-PAA NP solution are used for monitoring oxygen level change during PDT in situ test. The oxygen level and PDT efficacy are confirmed with a commercial oximeter, and fluorescence microscope imaging and flow cytometry results. This technique with the MB-PAA NPs allowed us to demonstrate a potential non-invasive theragnostic operation, by monitoring oxygen depletion during PDT in situ, without the addition of secondary probes. Here, we demonstrate this theragnostic operation, in vitro, performing PDT while monitoring oxygen depletion. We also show the correlation between O2 depletion and cell death.

The behaviour of selected fission products and actinides on UTEVA® resin

The behaviour of selected fission product elements and actinides on UTEVA® resin in HCl and HNO3 media was determined by loading a mixed solution of Sr, Y, Zr, Mo, Ag, Cd, Cs, Ba, Ce, Eu, Tb, U, Np and Pu on to UTEVA® resin. The columns were eluted with decreasing concentrations of each acid. This investigation used stable elemental standards for the fission product elements and radioactive tracers for the actinide elements. The eluted fractions were analysed using ICP-OES and ICP-MS to determine the recovery of the elements across the fractions. A comparison using valency adjustment for the separation of Pu and Np is also reported.

Synthesis of radioactive gold nanoparticles for brachytherapy treatments using plasma electrochemistry

Event Abstract Back to Event Synthesis of radioactive gold nanoparticles for brachytherapy treatments using plasma electrochemistry Mathieu Bouchard1, 2, 3, Myriam Laprise-Pelletier1, 2, 3, Stéphane Turgeon2 and Marc-André Fortin1, 2, 3 1 Université Laval, Génie des mines, de la métallurgie et des matériaux, Canada 2 Université Laval, Centre hospitalier universitaire de Québec, Canada 3 Université Laval, Centre de recherche sur les matériaux avancés (CERMA), Canada Gold nanoparticles (Au NPs) are increasingly considered for use as biocompatible radioactive sources (198Au) for prostate brachytherapy procedures[1],[2]. The range of the 198Au β-particle (0.96 MeV, ~ 11 mm in soft tissue, ~ 1100 cell diameters) is sufficiently long to provide cross-fire effects of a radiation dose delivered to cells within the prostate gland, and short enough to minimize the dose to healthy peripheral tissues. The integration of 198Au NPs into brachytherapy procedures requires the development of more efficient, safer, and more compact Au NP synthesis methods. Indeed, because of their relatively short half-life (2.7 days), 198Au NPs should ideally be synthesized on-site (directly in hospitals) and upon request. However, the current NP colloidal synthesis methods invariably rely on the expertise of skilled chemists, and require several manipulation steps (ligand and solvent exchange, purification procedures), which represent critical radioprotection challenges. Here we report on a novel bench-top technology based on plasma-liquid electrochemistry that facilitates the automated production of 198Au NPs directly in water. Plasma consists of an ionized gas: it contains electrons, positive ions, UV photons and excited chemical species. The reactor we developed allowed the generation of large-area atmospheric pressure argon plasma at the surface of a liquid containing 1 mM of gold salts (Fig.1)[3]. Radioactive 198Au salts were added with an initial activity of 500 µCi. We used dextran, a biocompatible polymer widely used in vascular injection media, to stabilise the NPs with specific sizes and shapes. A UV-vis spectrometer allowed the in situ monitoring of the NP solution throughout the synthesis (Fig.2: plasmon peak, usually between 530 and 570 nm depending on NP sizes), which is necessary for quality control. The plasma treatment was followed by a rapid purification procedure involving centrifugation and filtration to separate the NPs according to their size. The highly reactive species in the plasma allowed the reduction of gold ions into very stable NPs at the plasma-liquid interface. Within 30 minutes, a 20 mL solution of Au NPs was produced. Two different size distributions were obtained and efficiently separated, with mean diameters of 26 and 44 nm (Fig.3). SPECT imaging showed the internalization of 198Au atoms into the NP matrices. A "ripening" period of 16 hours after plasma treatment led to the reduction of the remaining gold salts through seed-mediated growth, up to a reduction yield over 99.9%. The size distribution was also shifted toward more uniform and larger diameters (> 50 nm). Overall, plasma electrochemistry could enable the rapid, efficient and on-site production of quality-controlled 198Au NPs for a next generation of brachytherapy procedures. Further work is required to understand the exact electrochemical mechanisms responsible for the synthesis, which will surely open the way to new applications of atmospheric plasma reactors in the biomaterials field. Julie-Christine Lévesque

Morfologia radicular de Zantedeschia influenciada pela deficiência múltipla de nitrogênio e fósforo

The knowledge of the phenomena that occur in root systems developed under nutritional deficiency is still limited. Among the factors that may raise doubt in the identification of nutritional state, multiple deficiencies stand out. This study aimed to evaluate the effect of multiple and single omission of nitrogen and phosphorus in nutrient solution on roots development in Zantedeschia aethiopica. For that, plants were cultivated over a period of eight months in treatments with complete Hoagland and Arnon solution (1950), with the omission of N (Nitrogen), omission of P (Phosphorus), omission of NP and nutrient solution with NP at concentrations of 25%, 50% and 75%, totaling seven treatments with four replications, in a completely randomized design. At the end of the experiment period, length, root volume, root dry mass and density were evaluated. Plants grown in solution with omission of P and with 25NP were those that most exploited space with their roots. The diameter of roots was influenced by multiple deficiencies of macronutrients. The mineral composition of the plant roots is influenced by multiple deficiencies of N and P.

A facile and general route to synthesize silica-coated SERS tags with the enhanced signal intensity.

Silica-coated SERS tags have been attracting greater attention in recent years. However, the reported methods to synthesize these tags are tedious, and often subjected to the limited signal intensity. Here, we report a facile and general method to prepare the silica-coated Ag SERS tags with the enhanced signal intensity by no introducing the primers. This approach mainly depends on the colloidal stability of the Ag NPs in alcohol solution. By decreasing the concentration of salt in Ag NP solution, the citrate-stabilized Ag NPs can be well dispersed in alcohol solution. Based on this, the Ag SERS tags can be directly coated with thickness-controlled and homogeneous silica shells. This approach is highly reproducible for silica shell growth and signal intensity, not depending on the properties of Raman molecules, proved by 7 kinds of the Raman molecules. Moreover, this kind of SERS tags coated with silica hold the stronger SERS signals than the traditional method due to no interference from the priming molecules.

Abstract 3681: Facile fabrication of MRI-capable and NIR-resonant core-satellite nanomediators for photothermal therapy

Abstract Although many techniques exist for fabricating near-infrared (NIR)-resonant and magnetic resonance imaging (MRI)-capable nanomediators for photothermal cancer therapy, preparing them in an efficient and scalable process remains a significant challenge. In this report, we develop two facile methods to fabricate both NIR-resonant and MRI-capable nanomediators utilizing well developed polysiloxane-containing polymer-coated iron oxide nanoparticles (IONPs). One of the methods is to attach multiple NIR-resonant nanoparticles onto a thiol-modified IONP core through one-step mixing with gold sulfide nanoparticles (Au2S NPs) to fabricate a core-satellite nanomediator. The other strategy is to covalently attach a NIR organic dye onto intact polysiloxane-containing polymer-coated IONPs through facile mixing with siloxane-modified IR820. The successful decoration with either Au2S NPs or IR820 is demonstrated for the resultant nanomediators by absorption spectra and transmission electron microscopy (TEM) images. It is estimated that 10 Au2S NPs and 2×104 dye molecules (loading capacity: 4.5 mg IR820/mg Fe) are attached onto the polymer-coated IONPs, respectively. The hydrodynamic sizes of these novel multifunctional nanomediators are ∼57.5 nm for IONP-Au2S NP and 28.2 nm for IONP-IR820, which are much smaller than traditional gold nanoshell-based designs. The photothermal efficiency of the IONP-Au2S NP and IONP-IR820 nanocomposite solutions under the irradiation of 885 nm NIR laser light is significantly enhanced compared to IONPs alone. The enhancement in photothermal efficiency by the newly developed nanomediators is also investigated in nude mice bearing SUM-159 tumor xenografts. The biodistribution data measured by inductively coupled plasma optical emission spectrometry (ICP-OES) reveal that ∼1% injection dose (ID) of IONP-Au2S NPs and ∼9% ID of IONP-IR820 accumulate into tumor tissue 24 h post intravenous injection at a dose of 20 mg Fe/Kg mouse body weight. The average tumor surface temperature recorded by an infrared camera is increased by 10.8 ± 1.2 °C for the mice administered with IONP-Au2S NPs and 25.7 ± 3.6 °C for the group injected with IONP-IR820, compared to 4.8 ± 0.5 °C for the PBS-injected control mice after laser irradiation with a power of 0.5 W for 10 min. Furthermore, our data reveal that the fabrication will not compromise the IONP core capability as an MRI contrast agent. Taken together, we demonstrate a facile technique to generate NIR-resonant and MRI-capable nanomediators from a polysiloxane-containing polymer-coated IONP platform. The as-developed dual functional nanomediators hold great promise for translatable MRI-guided photothermal cancer therapy. Citation Format: Hongwei Chen, Xiaoqing Ren, Hayley Paholak, Joseph Burnett, Feng Ni, Duxin Sun. Facile fabrication of MRI-capable and NIR-resonant core-satellite nanomediators for photothermal therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3681. doi:10.1158/1538-7445.AM2015-3681

Electrochemical sensor for dimetridazole based on novel gold nanoparticles@molecularly imprinted polymer

Herein, we reported a facile method for preparing gold nanoparticles@molecularly imprinted polymer (Au NPs@MIP), which was coated on mesoporous carbon (CKM-3) and porous graphene (P-r-GO) modified glassy carbon electrode to construct an electrochemical sensor for the determination of dimetridazole. Firstly, Au NP was prepared by reducing HAuCl4 with sodium citrate. Then, an ionic liquid (IL, i.e. 3-propyl-1-vinylimidazolium bromide) was added into Au NP solution to achieve Au NPs@IL by self-assembling. In succession, the Au NPs@IL was used as monomer to synthesize Au NPs@MIP. After that, the resultant Au NPs@MIP was coated on CKM-3 and P-r-GO modified electrode. Experimental conditions were carefully optimized for this assay strategy. In this case, the electrochemical sensor presented good response for dimetridazole, and its linear ranges were 2.0×10−9 to 2.5×10−7molL−1 and 2.5×10−7 to 3.0×10−6molL−1, and its detection limit was 5.0×10−10molL−1. The electrochemical sensor was applied to determine dimetridazole in food samples with satisfactory results.

Corrosion properties of Inconel-600 and 304 stainless steel in new oxidative and reductive decontamination reagent

to minimize the damage of base metals by the corrosion in this study. Type 304 stainless steel (304SS) and Inconel-600 (I-600) that are major components of the primary coolant system in pressurized water reactor were tested. To improve the integrity of base metal to the corrosion, we tested Ni2+, Fe3+, Cr6+, or Cu2+ by adding in NP solutions as a corrosion inhibitor and found that general and local corrosions were suppressed by the addition of Cu2+ ion. Decontamination performance and corrosion tests for NP(Cu) process with HYBRID (HYdrazine Base Reductive metal Ion Decontamination) process as a multi-step process were carried out and compared with existing processes such as citric-oxalic acid and oxalic acid. Our tests revealed that NP(Cu)-HYBRID process greatly inhibited local corrosions such as pits and Intergranular Attack. Moreover the proposed process was assured by the decontamination performance equivalent to other conventional processes.

Investigation of Structural, Chemical, and Electrical Properties of CdTe/Back Contact Interface by TEM and XPS

CdTe solar cell back contact preparation usually includes a chemical etching process which helps to obtain a Te-rich p-doped CdTe surface. In this work we compared the influence of two different etching solutions [nitric–phosphoric (NP) and nitric–acetic acid (NA)] on the CdTe surface. Transmission electron microscopy indicated that a Te-rich layer was formed on the surface of polycrystalline CdTe films after the etching process. The layer thickness was 80 nm and 10 nm for NP and NA etching solutions, respectively. In addition, the images showed that the influence of the etching solution was preferentially along the grain boundaries. The chemical properties of the etched CdTe surface were studied by using x-ray photoelectron spectroscopy. The nitric–phosphoric acid yielded a relatively thicker Te-rich layer on the CdTe surface. On the other hand, the J–V properties of the solar cells prepared using nitric–acetic acid showed no rollover behavior, indicating improved back contact. The solar cells prepared with the NA and NP etching processes yielded >10% solar cell efficiency. The CdTe solar cell homogeneity was improved by the NA etching method.

In vitro studies of the toxic effects of silver nanoparticles on HeLa and U937 cells.

In the last decade, much attention has been paid to studies of the effect of silver nanoparticles (Ag NPs) on tumor cells. Apart from elucidation of the mechanism of NPs’ interaction with mammalian cells, these studies are aimed at discovering new effective antitumor drugs. In this work, we report about the toxic effects of Ag NPs observed on two types of tumor cells: HeLa (adhesive cells) and U937 (suspension cells). The Ag NPs were obtained by an original method of biochemical synthesis. Particle size was 13.2±4.72 nm, and zeta potential was −61.9±3.2 mV. The toxicity of Ag NPs in the concentration range 0.5–8.0 μg Ag/mL was determined by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cytofluorometry after 4 and 24 hours’ incubation. It was found that Ag NPs had high toxicity toward both cell types. The minimal concentrations where a toxicity effect was registered (toxicity thresholds) lied in the range 0.5–2.0 μg Ag/mL. In parallel with the Ag NP solution, cells were incubated with water solutions of the NP stabilizer (aerosol-OT) and Ag+ ions (as silver nitrate). It was shown that aerosol-OT had no effect on the viability on HeLa cells, but was moderately toxic toward U937, though less dangerous for these cells than Ag NPs. With Ag+ ions, for HeLa no toxic effect was observed, while for U937 they were as toxic as the Ag NPs. The data obtained indicate that Ag NPs as used in this study may prove to be useful for the creation of medicines for cancer therapy.

Exploring the Stability of Gold Nanoparticles by Experimenting with Adsorption Interactions of Nanomaterials in an Undergraduate Lab

The proposed experiment can help students to understand the factors involved in the stability of gold nanoparticles (Au NPs) by exploring the adsorption interaction between Au NPs and various substances. The students in this study found that the surface plasmon resonance band of Au NP solutions underwent a red shift (i.e., from 520 to 650 nm) because of NaCl-induced aggregation caused by the elimination of the repulsive electrostatic force. In addition, a sufficient amount of bovine serum albumin molecules (29.4 nM) adsorbed on the surface of Au NPs (1.8 nM) through electrostatic interactions provides steric barriers that hinder electrolyte-induced aggregation. This experiment was performed in the fall 2014 semester to improve the recognition of nanoscale science and engineering concepts of undergraduates.

Effect of hydration repulsion on nanoparticle agglomeration evaluated via a constant number Monte–Carlo simulation

The effect of hydration repulsion on the agglomeration of nanoparticles in aqueous suspensions was investigated via the description of agglomeration by the Smoluchowski coagulation equation using constant number Monte–Carlo simulation making use of the classical DLVO theory extended to include the hydration repulsion energy. Evaluation of experimental DLS measurements for TiO2, CeO2, SiO2, and α-Fe2O3 (hematite) at high IS (up to 900 mM) or low |ζ-potential| (≥1.35 mV) demonstrated that hydration repulsion energy can be above electrostatic repulsion energy such that the increased overall repulsion energy can significantly lower the agglomerate diameter relative to the classical DLVO prediction. While the classical DLVO theory, which is reasonably applicable for agglomeration of NPs of high |ζ-potential| (∼>35 mV) in suspensions of low IS (∼<1 mM), it can overpredict agglomerate sizes by up to a factor of 5 at high IS or low |ζ-potential|. Given the potential important role of hydration repulsion over a range of relevant conditions, there is merit in quantifying this repulsion energy over a wide range of conditions as part of overall characterization of NP suspensions. Such information would be of relevance to improved understanding of NP agglomeration in aqueous suspensions and its correlation with NP physicochemical and solution properties.

Acute effect of nano-copper on liver tissue and function in rat

Objective(s): This paper reports on the toxicity of CuO NPs on hepatic enzymes and liver and lung histology. Materials and Methods: To assess the toxicity of copper nanoparticles (10-15 nm) in vivo, pathological examinations and blood biochemical indexes including serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) at various time points (2, 7 and 14 days) were studied. Thirty two Wistar rats were randomly divided into four groups. Treatment groups (group 1, 2, 3) received CuO NP solution containing 5, 10 and 100 mg/kg, respectively. Control group received 0.5 mL of normal saline via ip injection for 7 consecutive days. After 14 days, the tissue of liver and lung were collected and investigated for their histological problems. Results: The histology of the hepatic tissues showed vasculature in central veins and portal triad vessels in all three treatment groups. Histology of lungs showed air sac wall thickening and increased fibrous tissue in all three groups. Biochemical results of the hepatic enzymes showed that the SGOT levels in groups 1 and 2 were significantly higher than the control group two days after the intervention. Conclusion: Results of this study indicated that all concentration of copper nanoparticles [with 10-15 nm diameters, spherical shape, purity of 99.9%, mineral in nature, and wet synthesis method in liquid phase (alternation)] induce toxicity and changes of histopathological changes in liver and lung tissues of rats. It is evident that these nanoparticles cannot be used for human purposes because of their toxicity.

Dynamic analysis of DNA nanoparticle immobilization to model biomaterial substrates using combinatorial spectroscopic ellipsometry and quartz crystal microbalance with dissipation

Gene expression within cells can be altered through gene delivery approaches, which have tremendous potential for gene therapy, tissue engineering, and diagnostics. Substrate-mediated gene delivery describes the delivery of plasmid DNA or DNA complexed with nonviral vectors to cells from a surface, with the DNA immobilized to a substrate through specific or nonspecific interactions. In this work, DNA-nanoparticle (DNA–NP) adsorption to substrates is evaluated using combinatorial, in situ spectroscopic ellipsometry and quartz crystal microbalance with dissipation (SE/QCM-D), to evaluate the basic dynamic processes involved in the adsorption and immobilization of DNA–NP complexes to substrates. The concentration of DNA–NP solutions influences the adsorbed DNA–NP surface mass, which increases by a factor of approximately 6 (detected by SE) and approximately 4.5-fold (detected by QCM-D), as the DNA concentration increases from 1.5μg/mL to 15μg/mL, with an increase in layer porosity. In addition, SE/QCM-D analysis indicates that DNA–NP adsorption rates, surface coverage densities, and volume fractions are dependent on the type of substrate: gold (Au) and silicon dioxide substrates, protein-coated and uncoated substrates, and surfaces modified with alkanethiol self assembled monolayers (SAMs). These studies also demonstrate that the influence of an adsorbed protein layer on resulting DNA–NP immobilization efficiency is substrate dependent. For example, Au surfaces coated with fetal bovine serum (FBS) resulted in two-fold greater mass of adsorbed DNA–NPs, compared to DNA–NP adsorption to FBS-coated SAM substrates. This investigation offers insights into dynamic DNA–NP surface adsorption processes, characteristics of the immobilized DNA–NP layer, and demonstrates substrate-dependent DNA–NP adsorption.

Determination of neptunium in a reprocessing plant by an on-line solid-phase extraction/electrochemical detection system

In this study, a flow-based electrochemical detection system coupled to a solid-phase extraction column was developed for the determination of neptunium in the presence of Pu(IV). Np(V) in the sample solution was completely oxidized to Np(VI) via electrolysis using a column electrode composed of carbon fibers. The column electrode effluent was then loaded onto a TEVA® column, and subsequently onto a UTEVA® column using 3 mol L−1 HNO3. Pu(IV) was retained on the TEVA column and separated from Np(VI), while Np(VI) was retained on the UTEVA column. Np(VI) was eluted from the UTEVA column with 0.01 mol L−1 HNO3 and then introduced directly into a flow-through electrolysis cell. An electrochemical amperometric method with a working potential of +0.1 V (vs. Ag/AgCl) was used to detect Np(VI). The current produced due to the reduction of Np(VI) was continuously monitored and recorded, and the Np concentration was calculated from the peak area. The relative standard deviation of 10 analyses was 2.4 % for an Np solution (0.50 mg L−1) containing 1.0 μg Np. The detection limit, which was determined to be three times the standard deviation, was 35 μg L−1 (70 ng Np).

Effects of Functionalized Gold Nanoparticle Size on X-ray Attenuation and Substrate Binding Affinity

Gold nanoparticles (Au NPs) have attracted interest as an X-ray contrast agent due to exhibiting high X-ray attenuation, colloidal stability, vascular retention, and facile surface functionalization for targeted delivery to cells and tissues. However, the effects of Au NP size on X-ray attenuation and binding affinity to a targeted surface are not well-understood. Therefore, the effect of Au NP size on X-ray attenuation was investigated by preparing mercaptosuccinic acid functionalized Au NPs exhibiting a mean particle diameter of 5, 13, 35, or 76 nm, as well as chloroauric acid control, at gold concentrations up to ∼50 mM (∼10 g/L). The X-ray attenuation of Au NP and chloroauric acid solutions increased with decreased photon energy and increased linearly with increased gold concentration, but was independent of the particle diameter. The effects of Au NP size on substrate binding affinity were investigated by preparing bisphosphonate functionalized Au NPs exhibiting a mean particle diameter of 5, 13, 35,...

Short- and long-term effects of silver nanoparticles on human microvascular endothelial cells.

To study the response to silver nanoparticles (Ag NP) of human microvascular endothelial cells, protagonists of angiogenesis. We cultured human microvascular endothelial cells and endothelial colony-forming cells in their corresponding growth medium. Stock solutions of Ag NP were prepared in culture medium and sonicated before use. They were added at different concentrations and for different times to culture media. The toxicity of Ag NP was investigated by measuring the reduction of yellow tetrazolium salt to dark purple formazan (MTT assay) at 575 nm. After staining with trypan blue, cell proliferation was assessed by counting viable cells. The lactate dehydrogenase leakage assay was performed on culture media by following the oxidation of NADH to NAD+ and monitoring the reaction kinetically at 340 nm. Reactive oxygen species production was quantified using 2'-7'-dichlorofluorescein diacetate. The alkaline comet assay was performed after mixing the cells with low melting-point agarose. Electrophoresis was then conducted and the samples were stained with ethidium bromide and analyzed with a fluorescence microscope. Ag NP are cytotoxic in a dose and time dependent fashion for HMEC. At high concentrations, Ag NP determine loss of membrane integrity as demonstrated by the increased activity of lactate dehydrogenase in the culture medium. Ag NP rapidly stimulate the formation of free radicals. However, pre-incubation with Trolox, apocynin, or N-acetyl-L-cysteine, antioxidants which have different structure and act through different mechanisms, is not sufficient to prevent cytotoxicity. Ag NP also induce DNA damage dose-dependently, as shown by comet assay. When exposed to sublethal concentrations of Ag NP for long times, the cells remain viable but are growth retarded. Interestingly, removal of Ag NP partially rescues cell growth. Also genotoxicity is reversible upon removal of Ag NP from culture medium, suggesting that no permanent modifications occur. It is noteworthy that Ag NP are cytotoxic and genotoxic also for endothelial progenitors, in particular for endothelial colony-forming cells, which participate to angiogenesis. Silver nanoparticles are cytotoxic and genotoxic for human microvascular endothelial cells and might become a useful tool to control excessive angiogenesis.