Impact of agglomeration on the relaxometric properties of paramagnetic ultra-small gadolinium oxide nanoparticles

Ultra-small gadolinium oxide nanoparticles (US-Gd(2)O(3)) are used to provide 'positive' contrast effects in magnetic resonance imaging (MRI), and are being considered for molecular and cellular imaging applications. However, these nanoparticles can aggregate over time in aqueous medium, as well as when internalized into cells. This study is aimed at measuring in vitro, in aqueous medium, the impact of aggregation on the relaxometric properties of paramagnetic US-Gd(2)O(3) particles. First, the nanoparticle core size as well as aggregation behaviour was assessed by HRTEM. DLS (hydrodynamic diameter) was used to measure the hydrodynamic diameter of nanoparticles and nanoaggregates. The relaxometric properties were measured by NMRD profiling, as well as with (1)H NMR relaxometers. Then, the positive contrast enhancement effect was assessed by using magnetic resonance scanners (at 1.5 and 7 T). At every magnetic field, the longitudinal relaxivity (r(1)) decreased upon agglomeration, while remaining high enough to provide positive contrast. On the other hand, the transverse relaxivity (r(2)) slightly decreased at 0.47 and 1.41 T, but it was enhanced at higher fields (7 and 11.7 T) upon agglomeration. All NMRD profiles revealed a characteristic relaxivity peak in the range 60-100 MHz, suggesting the possibility to use US-Gd(2)O(3) as an efficient 'positive-T(1)' contrast agent at clinical magnetic fields (1-3 T), in spite of aggregation.     

Physico-chemical and NMR relaxometric characterization of gadolinium hydroxide and dysprosium oxide nanoparticles

Gadolinium hydroxide and dysprosium oxide nanoparticles, which constitute a new interesting class of magnetic nanoparticles, are characterized by different methods, using x-ray diffraction, magnetometry and NMR relaxometry at multiple fields. The rod-like particles are first shown to have a simple paramagnetic behavior, like the bulk compound, without any influence of the nanometric size of the particles. Because of their paramagnetic moment, these particles considerably shorten water relaxation times, especially the transverse relaxation time at high fields. The relaxation induced by gadolinium hydroxide particles is due to a proton exchange between the particle surface and bulk water, while the transverse relaxation caused by dysprosium oxide particles is governed by the diffusion of water protons around the magnetized particles. 1/T(2) increases linearly with the magnetic field for gadolinium hydroxide particles while a quadratic increase is observed for dysprosium oxide nanoparticles. The relaxation results are compared with those from previous studies and interpreted using different theories for the relaxation induced by magnetic particles.     

Thin film growth of epitaxial gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide by electrodeposition

Thin films of gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide were electrodeposited from non-aqueous baths. The films were on the order of 15 nm thick, and were grown epitaxially on textured nickel-tungsten substrates. The effect of deposition rate, annealing temperature and secondary metals on crystallinity and crystal orientation was investigated by X-ray diffraction and transmission electron microscopy. Slower rates, higher temperatures and low concentrations of yttrium improve the crystallinity of gadolinium oxide films, whereas the introduction of cerium induced polycrystallinity.     

Synthesis, characterization and effect of low energy Ar ion irradiation on gadolinium oxide nanoparticles

In this work, we report on the surfactant assisted synthesis of gadolinium oxide (Gd₂O₃) nanoparticles and their characterization through various microscopic and spectroscopic tools. Exhibiting a monoclinic phase, the nanoscale Gd₂O₃ particles are believed to be comprising of crystallites with an average size of ∼3.2 nm, as revealed from the X-ray diffraction analysis. The transmission electron microscopy has predicted a particle size of ∼9 nm and an interplanar spacing of ∼0.28 nm. Fourier transform infrared spectroscopy studies show that Gd-O inplane vibrations at 536.8 and 413.3 cm⁻¹ were more prominent for 80-keV Ar-ion irradiated Gd₂O₃ nanosystem than unirradiated system. The photoluminescence (PL) spectra of irradiated specimen have revealed an improvement in the symmetry factor owing to significant enhancement of surface-trap emission, compared to the band-edge counterpart. Irradiation induced creation of point defects (oxygen vacancies) were predicted both from PL and electron paramagnetic resonance (EPR) studies. Further, the Raman spectra of the irradiated sample have exhibited notable vibrational features along with the evolution of a new peak at ∼202 cm⁻¹. This can be ascribed to an additional Raman active vibrational response owing to considerable modification of the nanostructure surface as a result of ion bombardment. Probing nanoscale defects through prime spectroscopy tools would find a new avenue for precise tuning of physical properties with generation and annihilation of defects.     

Mesoporous silica nanoparticles as a delivery system of gadolinium for effective human stem cell tracking

The progress of using gadolinium (Gd)-based nanoparticles in cellular tracking lags behind that of superparamagnetic iron oxide (SPIO) nanoparticles in magnetic resonance imaging (MRI). Here, dual functional Gd-fluorescein isothiocyanate mesoporous silica nanoparticles (Gd-Dye@MSN) that possess green fluorescence and paramagnetism are developed in order to evaluate their potential as effective T1-enhancing trackers for human mesenchymal stem cells (hMSCs). hMSCs are labeled efficiently with Gd-Dye@MSN via endocytosis. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes, osteocytes, and chondrocytes, which can still be readily MRI detected. Imaging, with a clinical 1.5-T MRI system and a low incubation dosage of Gd, low detection cell numbers, and short incubation times is demonstrated on both loaded cells and hMSC-injected mouse brains. This study shows that the advantages of biocompatibility, durability, high internalizing efficiency, and pore architecture make MSNs an ideal vector of T1-agent for stem-cell tracking with MRI.     

Evaluating the effect of green synthesised copper oxide nanoparticles on oxidative stress and mitochondrial function using murine model

Green synthesis of metal nanoparticles (NPs) has now received the attention of researchers due to ease of preparation and its potential to overcome hazards of these chemicals for an eco‐friendly milieu. In this study, copper oxide (CuO) NPs were synthesised via Desmodium gangeticum aqueous root extract and standard chemical method, further characterised by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Thermogravimetric analysis and scanning electron microscopy. The nephrotoxicity of the NP obtained from two routes were compared and evaluated at subcellular level in Wistar rat, renal proximal epithelial cells (LLC PK1 cell lines) and isolated renal mitochondria. CuO NP synthesised by chemical route showed prominent nephrotoxicity measured via adverse cytotoxicity to LLC PK1 cells, elevated renal oxidative stress and damage to renal tissue (determined by impaired alanine transaminase, aspartate transaminase, urea, uric acid and creatinine in the blood). However, at the level of cell organelle, CuO NP from both routes are non‐toxic to mitochondrial functional activity. The authors’ finding suggests that CuO NP synthesised by chemical route may induce nephrotoxicity, but may be overcome by co‐administration of antioxidants, as it is not mito‐toxic.Inspec keywords: cellular biophysics, scanning electron microscopy, toxicology, nanomedicine, oxidation, nanoparticles, enzymes, blood, visible spectra, X‐ray diffraction, biochemistry, nanofabrication, antibacterial activity, ultraviolet spectra, copper compounds, Fourier transform infrared spectra, molecular biophysics, thermal analysis, biological tissuesOther keywords: green synthesised copper oxide nanoparticles, murine model, metal nanoparticles, chemicals, eco‐friendly milieu, copper oxide NPs, standard chemical method, X‐ray diffraction, scanning electron microscopy, subcellular level, renal proximal epithelial cells, LLC PK1 cell lines, renal mitochondria, renal tissue, cell organelle, mitochondrial functional activity, UV‐visible spectroscopy, Fourier transform infrared spectroscopy, nephrotoxicity, renal oxidative stress, Desmodium gangeticum aqueous root extract, thermogravimetric analysis, Wistar rat, cytotoxicity, impaired alanine transaminase, aspartate transaminase, urea, uric acid, creatinine, blood, CuO     

Effect of Sr-doping on the structural and electrical properties of gadolinium manganite oxide

The crystal structure and electrical conductivity of the perovskite oxide system Gd_1-xSr_xMnO_3± (x = 0–0.5) were investigated. The effect of the level of Sr-doping on these properties was examined. An orthorhombic GdFeO₃-type structure (space group Pbnm) was found for all oxides. The room temperature lattice parameters were determined from the XRD data. A large distortion of the unit cell was observed in the case of the undoped compound. The distortion was gradually reduced with increasing Sr content. The unit cell volume decreased on Sr-doping. The electrical conductivity of the oxides was measured from room temperature up to 800°C. The small polaron hopping conductivity model can adequately describe the electrical conductivity behavior. The activation energy decreases as x increases.     

In vitro cytotoxicity of transparent yellow iron oxide nanoparticles on human glioma cells

With rapid development of nanotechnology, concerns about the possible adverse health effects on human beings by using nanomaterials have been raised. Transparent yellow iron oxide (alpha-FeOOH) nanoparticles have been widely used in paints, plastic, rubber, building materials, papermaking, food products and pharmaceutical industry, thus the potential health implications by the exposure should be considered. The purpose of this study is to assess the cytotoxicity of transparent yellow iron oxide nanoparticles on U251 human glioma cells. The alpha-FeOOH nanoparticles are in clubbed shapes with 9 nm in diameter and 43 nm long. The specific surface area is 115.3 m2/g. After physicochemical characterization of the nanoparticles, U251 cells were exposed to a-FeOOH at the doses of 0, 3.75, 15, 60 and 120 microg/mL. The results showed that the alpha-FeOOH nanoparticles reduced the cell viability and induced necrosis and apoptosis in U251 cells. In addition, nanoparticle exposure significantly increased the levels of superoxide anion and nitric oxide in a dose-dependent fashion in the cells. Our results suggest that exposure to alpha-FeOOH nanoparticles induce significant free radical formation and cytotoxic effects. The large surface area that induced high surface reactivity may play an important role in the cytotoxic effect of alpha-FeOOH nanoparticles.     

Porous ternary complex metal oxide nanoparticles converted from core/shell nanoparticles

We demonstrate an easy and scalable low-temperature process to convert porous ternary complex metal oxide nanoparticles from solution-synthesized core/shell metal oxide nanoparticles by thermal annealing. The final products demonstrate superior electrochemical properties with a large capacity and high stability during fast charging/discharging cycles for potential applications as advanced lithium-ion battery (LIB) electrode materials. In addition, a new breakdown mechanism was observed on these novel electrode materials.

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Epitaxial growth and thermal stability of silicon layers on crystalline gadolinium oxide

In this work, an unconventional approach for epitaxial growth of Si on single-crystalline rare-earth oxide is presented using molecular beam epitaxy under ultra-high vacuum. Surface and bulk crystalline structures as well as chemical content were examined. Silicon-on-insulator layers were fabricated by encapsulated solid phase epitaxy on Si(111) substrate. The gadolinium oxide capping layer was removed by wet-chemical etching. The remaining silicon layer is single crystalline without any impurities and exhibits 7 × 7 reconstructed surface after annealing in very low silicon flux in the growth chamber. The thermal stability of the fabricated silicon-on-insulator structure was studied by step-wise heating under ultra-high vacuum conditions. The fabricated ultra-thin (10-15 nm) silicon-on-oxide layers remain structurally and chemically stable up to 900 °C.     

Effect of fluorine impurity on the oxidation of silicon oxynitride ceramics doped with gadolinium oxide

Impurities in raw Si₃N₄ powders remain in intergranular glassy phases in Si₃N₄ and Si₂N₂O ceramics and degrade their high-temperature properties. Fluorine is one of the typical impurities in the raw powders. The oxidation rate of Si₂N₂O ceramics doped with Gd₂O₃ greatly varied with a difference in impurity contents (especially F) of the raw Si₃N₄ powders used. When a high concentration of impurity existed in the intergranular glassy phase, the rate of oxidation was controlled by O^2– diffusion through the glassy phase in the partly oxidized scale and unoxidized body; outward diffusion of Gd³⁺ occurred concurrently. On the other hand, when the impurity contents in the intergranular glassy phase was very low, the diffusion rate of ions (Gd³⁺, O^2–, etc.) in the glassy phase became very low (substantially zero in the oxidation at 1300°C). Only cristobalite (SiO₂) was formed on the surface. The rate of oxidation was controlled by O₂ diffusion through the cristobalite layer, and was very low.     

钆螯合氧化钨纳米复合材料的制备及光热性能

采用溶剂热法,以氯化钨(WCl₆)为原料制备氧化钨(W₁₈O₄₉)纳米粒子,进一步利用微乳液法合成钆(Gd)螯合氧化钨(W₁₈O₄₉-DTPA/Gd)纳米复合材料。通过XRD、SEM、TEM对其结构和形貌进行表征,结果表明样品的结晶度高,分散性好,梭形形貌,长约为640 nm,宽约为160 nm左右,W和Gd元素均匀的分布于样品中。对W₁₈O₄₉-DTPA/Gd的光热性能进行测试,采用808 nm近红外光照射10 min时,样品的水溶液温度可升高到46.9℃,满足光热治疗癌症的温度要求,而对照组纯水的温度几乎无变化。样品同时具有电子计算机断层扫描(CT)成像功能,成像效果随着浓度增加而加强,与纯W₁₈O₄₉相比,成像效果无明显变化。与人正常干细胞(LO2细胞)共培养24 h,在不同的样品浓度下细胞存活率仍在85%以上。      

A biotechnological perspective on the application of iron oxide nanoparticles

In recent decades,magnetic iron nanoparticles (NPs) have attracted much attention due to properties such as superparamagnetism,high surface area,large surface-to-volume ratio,and easy separation under external magnetic fields.Therefore,magnetic iron oxides have potential for use in numerous applications,including magnetic resonance imaging contrast enhancement,tissue repair,immunoassay,detoxification of biological fluids,drug delivery,hyperthermia,and cell separation.This review provides an updated and integrated focus on the fabrication and characterization of suitable magnetic iron NPs for biotechnological applications.The possible perspective and some challenges in the further development of these NPs are also discussed.     

Biogenic silver embedded magnesium oxide nanoparticles induce the cytotoxicity in human prostate cancer cells

This work reports the synthesis, characterization, and cytotoxicity of biogenic magnesium oxide nanoparticles (MgONPs) and nanosilver embedded magnesium oxide nanoparticles (Ag-MgONPs). The formation of nanoparticles (NPs) was confirmed by the indications of color changes and precipitations. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) pattern studies showed the agglomeration colloids, porous, spherical, needle-shaped and crystal nature of MgONPs, whereas, the Ag-MgONPs was hexagonal, and spherical structured nanocrystals. Energy-dispersive X-ray fluorescence spectrometry (EDS) study indicated the existence of Ag, Mg, and O in NPs complex. The particle size analysis (PSA) revealed the mean size of 15.09?nm for Ag-MgONPs and 13.68?nm for MgONPs. Fourier transform infrared spectroscopy (FTIR) showed the peaks corresponding to amide, carboxylic acids, aromatics, alkene and esters from mycelial cell-free extract (MCFE). The absorbed and lattices oxygen of MgO was probably assigned in the formation of Ag-MgONPs as indicated by X-ray photoelectron spectroscopy (XPS). Cytotoxicity assay showed the Ag-MgONPs was stronger in inducing the prostate cancer (PC-3) cell death than the MgONPs. This work concluded that Ag-MgONPs could be potential therapeutics for cancer therapy.     

Crystalline transformation of colloidal nanoparticles on graphene oxide

Emergence of novel two-dimensional (2-D) templates, e.g., graphene oxide, has signified new intriguing opportunities to couple nanocrystals electronically to the microscopic 2-D contacts. A promising approach to uniform dispersion of inorganic nanocrystals on the 2-D interfaces is to graft them through chemical bonding. The 2-D dispersion would offer a unique opportunity to address one of the primary challenges in the field of nanotechnology: fulfilling excellent chemical and physical properties of the nanocrystals in electronic solid-state devices. In this study, we blended colloidal nanocrystals with graphene oxide in aqueous solution in attempts to bind the nanocrystals on reactive sites of the graphene oxide surface, thereby achieving uniform loading. Interestingly, the nanocrystals undergo significant crystalline transformation even under relatively moderate reaction conditions. The growth of particle size and the drastic crystalline deformation, e.g., from wurtzite CdSe to amorphous Se, appear to take place in the proximity of acidic functional groups on graphene oxide. Photocarriers also play a key role in the reaction: under room light, the transformation yielded dramatic size increase and crystalline transformation, whereas in the dark, the change was suppressed. The experimental results presented in this study provide guidelines for uniform 2-D loading of colloidal nanocrystals on graphene oxide. The findings suggest that the surface acidity be titrated for colloidal nanocrystals to deposit on the graphitic layer and to avoid unwanted changes of nanocrystal size and properties.     

Nanostructural evolution from nanosheets to one-dimensional nanoparticles for manganese oxide

This paper introduces a novel hydrothermal soft chemical synthesis process for manganese oxide nanostructured particles using two-dimensional manganese oxide nanosheets as precursor. In this process, a birnessite-type manganese oxide with a layered structure was exfoliated into its elementary layer nanosheets, and then the nanosheets were hydrothermally treated to transform the two-dimensional morphology of the nanosheets to one-dimensional nanoparticles. The manganese oxide nanofibers, nanotubes, nanobelts, nanoribbons, and fabric-ribbon-like particles constructed from nanofibers or nanobelts were obtained using this hydrothermal soft chemical process. The nanostructural evolution from the two-dimensional nanosheets to the one-dimensional nanoparticles was characterized by XRD, SEM, TEM, and TG-DTA analysis. The morphology and nanostructure of the products are strongly dependent on the molecular dimension of organic amine cations added in the reaction system. The organic amine cations act as a morphology directing agent in the nanostructural evolution process.     

Microstructural effect of gadolinium oxide nanocrystals upon annealing on electrical properties of memory devices

The microstructure evolution of sputtered gadolinium oxide nanocrystal (NC) memory devices upon annealing has been characterized in detail by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TEM results indicate that the as-deposited film is composed of metallic Gd clusters embedded in an amorphous Gd_xO_y matrix. The Gd clusters undergo phase transformation to oxide NCs upon annealing, reaching a maximum density of 7.9-9.1 × 10¹¹ cm^− 2 at 850 °C, which is consistent with the largest memory window width. Upon annealing at even higher temperature, TEM diffraction patterns and XPS composition profiles indicate apparent Si diffusion into the NC layer, probably from the SiO₂ tunneling oxide or the Si substrate, leading to the formation of gadolinium silicate NCs. The presence of silicate NCs gradually deteriorates the device performance due to the reduction of barrier confinement for stored charges, although the dot density is only marginally decreased. The results suggest that the optimum memory device performance is dominated by not only the most considered size and density of NCs, but also the composition and phase inside.     

Synthesis of magnetic nanocomposites and alloys from platinum-iron oxide core-shell nanoparticles

This paper presents a systematic study on the generation of iron platinum-containing magnetic nanocomposites and alloys from Pt@Fe(2)O(3) core-shell nanoparticle precursors. These core-shell nanoparticles were made using a sequential synthetic approach. They could form FePt alloys and alloy-containing nanocomposites through a solid-state reaction at >400?°C. The chemical compositions of FePt alloys were controllable by using Pt@Fe(2)O(3) core-shell nanoparticles that had the designed Pt core diameter and iron oxide shell thickness. We show that face-centred tetragonal (fct) FePt@Fe core-shell nanoparticles could be made from Pt@Fe(2)O(3) core-shell nanoparticles with?5% hydrogen in argon (v/v). Furthermore, various FePt alloys and alloy-containing nanocomposites including metastable intermediate phases could be obtained. The materials were characterized by high resolution scanning transmission electron microscopy (HR-STEM), energy dispersive x-ray (EDX) spectroscopy, powder x-ray diffraction (PXRD), parallel electron energy loss spectroscopy (PEELS), and superconducting quantum interference device (SQUID) magnetometry. These materials could have potential applications as permanent hard magnets and data storage media.