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| 2. |
- Engström, Maria, et al.
(författare)
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High Proton Relaxivity for Gadolinium Oxide Nanoparticles
- 2006
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 19:4, s. 180-186
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Nanosized materials of gadolinium oxide can provide high-contrast enhancement in magnetic resonance imaging (MRI). The objective of the present study was to investigate proton relaxation enhancement by ultrasmall (5 to 10 nm) Gd2O3 nanocrystals.Materials and methods: Gd2O3 nanocrystals were synthesized by a colloidal method and capped with diethylene glycol (DEG). The oxidation state of Gd2O3 was confirmed by X-ray photoelectron spectroscopy. Proton relaxation times were measured with a 1.5-T MRI scanner. The measurements were performed in aqueous solutions and cell culture medium (RPMI).Results: Results showed a considerable relaxivity increase for the Gd2O3–DEG particles compared to Gd-DTPA. Both T 1 and T 2 relaxivities in the presence of Gd2O3–DEG particles were approximately twice the corresponding values for Gd–DTPA in aqueous solution and even larger in RPMI. Higher signal intensity at low concentrations was predicted for the nanoparticle solutions, using experimental data to simulate a T1-weighted spin echo sequence.Conclusion: The study indicates the possibility of obtaining at least doubled relaxivity compared to Gd–DTPA using Gd2O3–DEG nanocrystals as contrast agent. The high T 1 relaxation rate at low concentrations of Gd2O3 nanoparticles is very promising for future studies of contrast agents based on gadolinium-containing nanocrystals.
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| 3. |
- Fortin, Marc-André, et al.
(författare)
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Polyethylene glycol-cover ultra-small Gd2O3 nanoparticles for positive contras at 1.5 T magnetic resonance clinical scanning
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:39, s. 395501-
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Tidskriftsartikel (refereegranskat)abstract
- The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd2O3) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r1, r2) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd2O3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd2O3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd3+ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG–Gd2O3 and PEG-silane–SPGO (Gd2O3,< 40 nm diameter). The small and narrow size distribution of US-Gd2O3 was confirmed with TEM (~3 nm) and DLS. PEG-silane–US-Gd2O3 relaxation parameters were twice as high as for Gd–DTPA and the r2/r1 ratio was 1.4. PEG-silane–SPGO gave low r1 relaxivities and high r2/r1 ratios, less compatible with positive contrast agent requirements. Higher r1 were obtained with PEG-silane in comparison to DEG–Gd2O3. Treatment of DEG–US-Gd2O3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd2O3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.
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| 6. |
- Klasson, Anna, 1973-
(författare)
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MRI Contrast Enhancement using Gd2O3 Nanoparticles
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is an increasing interest for nanomaterials in biomedical applications and in this work, nanoparticles of gadolinium oxide (Gd2O3) have been investigated as a novel contrast agent for Magnetic Resonance Imaging (MRI). Relaxation properties have been studied in aqueous solutions as well as in cell culture medium and the nanoparticles have been explored as cell labeling agents. The fluorescent properties of the particles were used to visualize the internalization in cells and doped particles were also investigated as a multimodal agent that could work as a fluorescent marker for microscopy and as a contrast enhancer for MRI.Results show that in aqueous solutions, there is a twofold increase in relaxivity for Gd2O3 compared to commercial agent Gd-DTPA. In cell culture medium as well as in cells, there is a clear T1 effect and a distinct increase in signal intensity in T1-mapped images. Fluorescent studies show that the Gd2O3 nanoparticles doped with 5% terbium have interesting fluorescent properties and that these particles could work as a multimodal contrast agent.This study shows that Gd2O3 nanoparticles possess excellent relaxation properties that are retained in more biological environments. Gd2O3 particles are suitable as a T1 contrast agent, but seem also be adequate for T2 enhancement in for instance cell labeling experiments.
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| 7. |
- Klasson, Anna, et al.
(författare)
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Positive MRI Enhancement in THP-1 Cells with Gd2O3 Nanoparticles
- 2008
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Ingår i: Contrast Media and Molecular Imaging. - : Wiley. - 1555-4309 .- 1555-4317. ; 3:3, s. 106-111
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Tidskriftsartikel (refereegranskat)abstract
- There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3-labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s-1 mm-1 for cell culture medium. The r2 was 17.4 and 12.9 s-1 mm-1, respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (pr1 = 0.36), but r2 was significantly different for the two different series (pr2 = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells.
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| 8. |
- Petoral, Rodrigo M, et al.
(författare)
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Synthesis and Characterization of Tb3+-Doped Gd2O3 Nanocrystals : A Bifunctional Material with Combined Fluorescent Labeling and MRI Contrast Agent Properties
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:17, s. 6913-6920
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasmall gadolinium oxide nanoparticles doped with terbium ions were synthesized by the polyol route and characterized as a potentially bifunctional material with both fluorescent and magnetic contrast agent properties. The structural, optical, and magnetic properties of the organic-acid-capped and PEGylated Gd2O3:Tb3+ nanocrystals were studied by HR-TEM, XPS, EDX, IR, PL, and SQUID. The luminescent/fluorescent property of the particles is attributable to the Tb3+ ion located on the crystal lattice of the Gd2O3 host. The paramagnetic behavior of the particles is discussed. Pilot studies investigating the capability of the nanoparticles for fluorescent labeling of living cells and as a MRI contrast agent were also performed. Cells of two cell lines (THP-1 cells and fibroblasts) were incubated with the particles, and intracellular particle distribution was visualized by confocal microscopy. The MRI relaxivity of the PEGylated nanoparticles in water at low Gd concentration was assessed showing a higher T-1 relaxation rate compared to conventional Gd-DTPA chelates and comparable to that of undoped Gd2O3 nanoparticles.
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| 9. |
- Sjöberg, Sara, 1979, et al.
(författare)
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CD44-deficiency on hematopoietic cells limits T-cell number but does not protect against atherogenesis in LDL receptor-deficient mice
- 2009
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Ingår i: Atherosclerosis. - : Elsevier. - 0021-9150 .- 1879-1484. ; 206:2, s. 369-374
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Vascular and inflammatory cells express adhesion molecule CD44. We demonstrated previously that enhanced CD44 localizes in human atherosclerotic lesions. Apolipoprotein E/cd44 double-deficient mice and apolipoprotein E-deficient mice transplanted with CD44-deficient bone marrow (BM) exhibit reduced atherosclerosis. Since CD44 is a novel factor in atherogenesis, it is imperative that it is investigated in more than one animal model to conclusively determine its role in this particular disease pathology. To test the hypothesis that CD44 expressed by hematopoietic cells plays a critical role in atherogenesis in the low density lipoprotein (LDL) receptor-deficient mouse model, we performed BM reconstitution experiments.METHODS: Lethally irradiated LDL receptor-deficient mice were transplanted with either CD44-deficient or wild-type BM. Beginning 10 weeks after successful reconstitution, mice consumed a cholesterol-enriched atherogenic diet for 6 or 11 weeks.RESULTS: Surprisingly, CD44-deficiency on BM-derived inflammatory cells did not affect lesion size. Additionally, neither group displayed differences in smooth muscle cell, macrophage, collagen, or elastin content as well as lipoprotein levels. However, lesions in CD44-deficient BM-recipient mice contained fewer T-cells compared to wild-type BM mice. Interestingly, CD44-deficient T-cells expressed less chemokine receptor-5 mRNA. Furthermore, in vivo leukocyte adhesion decreased in CD44-deficient mice compared to wild-type mice.CONCLUSION: This study surprisingly revealed that atherogenesis does not require CD44 expression on hematopoietic cells in the LDL receptor-deficient mouse model. However, CD44 promotes T-cell recruitment, downregulates chemokine receptor-5, and participates critically in leukocyte adhesion in vivo. Consequently, the anti-atherogenic role of CD44 may require CD44-deficiency on cell types other than inflammatory cells in the LDL receptor-deficient mouse model.
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| 10. |
- Söderlind, Fredrik, et al.
(författare)
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Colloidal synthesis and characterization of ultrasmall perovskite GdFeO3 nanocrystals
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:8, s. 085608-
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of very small (about 4 nm) perovskite structured gadolinium orthoferrite nanoparticles (GdFeO3) was performed by the polyol method. The material shows promising relaxivity properties and potential as a contrast agent in magnetic resonance imaging. The perovskite nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, magnetic resonance, and magnetization measurements. Upon heating in air at 800 °C for 3 h the size of the crystals increased to about 40 nm. The crystalline structure of the heat treated compound is in good agreement with perovskite GdFeO3 as the primary product. Contributions from various secondary phases were also identified, including one hitherto unknown phase with the suggested composition 'Gd3FeO6' and isostructural with Gd3GaO6. The novel 'Gd3FeO6' phase appears to be kinetically stabilized in the nano state.
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