Investigations into the Physicochemical Properties of Dextran Small Particulate Gadolinium Oxide Nanoparticles

McDonald, Michael; Watkin, Kenneth L.

doi:10.1016/j.acra.2005.11.005

Cited by 98 publications

(60 citation statements)

References 11 publications

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“…As previously reported by McDonald and Watkin, it can be difficult to produce contrast agents of sufficiently fine and narrow particle size distributions by using 20-40 nm Gd 2 O 3 nanopowders [26,34]. In the present study, despite careful elimination of larger size aggregates from PEG-SPGO suspensions prior to DLS and MRI measurement, the broader DLS particle size distributions and possible particle aggregation present in this compound seem to strongly affect the T 1 -reducing capacity of the contrast agent.…”

Section: Discussionmentioning

confidence: 99%

“…However r 2 /r 1 ratios were still in the 3-4 range [34], limiting applications of the contrast agent in T 1 -weighted images. The first studies with US-Gd 2 O 3 obtained from colloidal synthesis in DEG revealed signal enhancement properties at low Gd concentrations which could allow advanced applications in positively contrasted MRI procedures [23].…”

Section: Discussionmentioning

confidence: 99%

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Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

et al. 2007

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The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd 2 O 3 ) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r 1 , r 2 ) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd 2 O 3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd 2 O 3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd 3+ 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-Gd 2 O 3 and PEG-silane-SPGO (Gd 2 O 3 , < 40 nm diameter). The small and narrow size distribution of US-Gd 2 O 3 was confirmed with TEM (∼3nm)andDLS.PEG-silane-US-Gd 2 O 3 relaxation parameters were twice as high as for Gd-DTPA and the r 2 /r 1 ratio was 1.4. PEG-silane-SPGO gave low r 1 relaxivities and high r 2 /r 1 ratios, less compatible with positive contrast agent requirements. Higher r 1 were obtained with PEG-silane in comparison to DEG-Gd 2 O 3 . Treatment of DEG-US-Gd 2 O 3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd 2 O 3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

et al. 2007

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“…The crystals preferably are kept small enough to give a large surface to bulk ratio and thereby an efficient interaction between Gd 3+ and water molecules; i.e a high water exchange. Small or ultrasmall Gd 2 O 3 nanoparticles synthesized according to the polyol route have been extensively studied, by our group and others (Bridot et al 2007;Fortin et al 2007;McDonald and Watkin 2006;Park et al 2009;Petoral Jr et al 2009;Söderlind et al 2005). The yield of the polyol synthesis is rather low though, and a severe drawback is the necessity to apply lengthy dialysis times to purify the nanoparticle solutions from free Gd 3+ .…”

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confidence: 99%

“…; Fortin et al 2007;McDonald and Watkin 2006;Park et al 2009;Söderlind et al 2005;Petoral Jr et al 2009;Kim et al 2010), gadolinium fluoride (GdF 3 ) (Evanics et al 2006;Chaput et al 2011) or gadolinium phosphate (GdPO 4 ) (Hifumi et al 2006;Yan et al 2010;Lai et al 2008). The crystals preferably are kept small enough to give a large surface to bulk ratio and thereby an efficient interaction between Gd 3+ and water molecules; i.e a high water exchange.…”

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confidence: 99%

A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study

et al. 2012

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In all kinds of gadolinium based contrast agents, the presence of free gadolinium ions have to be avoided due to the cytotoxicity. The conventional way of producing a gadolinium based contrast agent is to form a chelate, i.e. stabilizing the metal ion using a chelating agent (for example DTPA or DOTA) but recently nanoparticles is an initial step towards biocompatible and directed nanoparticles.The main focus is on a material that in the nearby future will be the core of an The experimental results are supported by theoretical modeling studies.Theoretical IR spectra of three different Gd acetate complexes are presented as well as calculated NEXAFS spectra of one of the Gd acetate complexes and an isolated acetate group. These calculations were performed to elucidate the molecular capping of the synthesized particles. 5 EXPERIMENTAL DETAILS ChemicalsAll chemicals were used as received. Gadolinium(III) acetate hydrate (SigmaAldrich, 99.9 %), tetramethylammonium hydroxide (Sigma-Aldrich, >97 % ), ethyl acetate (Fisher Scientific, 99.99 %), dimethyl sulfoxide (Merck, 99.9 %), ammonium acetate (Merck, >96%), ethanol (Kemetyl, 99.5 %). For preparation of water based solutions, Milli-Q water (ρ > 18.2 MΩ) was used. A commercial gadolinium oxide nanopowder (Aldrich, < 100 nm, 99.8 %) was used as a reference. Preparation of Gd 2 O 3 nanoparticlesThe preparation of Gd 2 O 3 nanoparticles was based on a method previously used for producing nanocrystalline ZnO (Schwartz et al. 2003). As Zn 2+ is divalent and Ethyl acetate was added and the mixture was centrifuge washed (3500 rpm) at least three times with ethyl acetate before it was diluted in deionized water. A total amount of 0.28 g ammonium acetate was added to one whole batch to increase the water solubility. Powder samples were air dried. The yield of the sample is dependent on the washing procedure. The gadolinium content after three times of centrifuge washing with ethyl acetate is roughly 60-65 % of the initial amount added in the synthesis.6 Instrumentation X-ray diffraction XRD measurements were carried out with a Philips XRD powder diffractometer using Cu Kα radiation (λ = 1.5418 Å, 40kV, 40 mA). The 2θ step-size was 0.025° and the time per step 4 s. Air dried powder samples were used in the preparation.High-resolution transmission electron microscopy TEM measurements were performed on a FEI Tecnai G 2 electron microscope operated at 200 kV. Sample preparation was done by letting 1-2 drops of Gd 2 O 3 in water dry on an amorphous carbon-covered copper grid.Dynamic light scattering DLS measurements were carried out on an ALV/DLS/SLS-5022F system from ALV-GmbH, Langen Germany, using a HeNe laser at 632.8 nm with 22 mW output power. Prior to the measurements, the samples were temperature stabilized in a thermostat bath at 22.1 °C for at least 10 minutes. The scattering angle was 90°. 15 Gd 2 O 3 samples dispersed in MilliQ water were studied in DLS, and the long term stability of the suspensions were studied by repeated measurements during a period of 6 weeks.ζ Pot...

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“…For the purpose to decrease the toxicity of Gd 2 O 3 nanoparticles and their aggregation in aqueous sus pensions, as well as to enhance contrasting properties, extensive investigations have been performed on Gd 2 O 3 nanoparticles covered with shells of various organic (polyethylene glycol [23], dextran [24], pol ysiloxane [25], diethylene glycol [26]) and inorganic (Gd 2 O 3 /SiO 2 [15]) substances. In particular, McDonald and Watkin [27] observed that small Gd 2 O 3 nanoparticles encapsulated in spherical albumin par ticles provided a better contrast than free Gd 2 O 3 parti cles and, in strong magnetic fields, retained their con trasting properties despite the observations of weaken ing these properties in other contrast agents [28].…”

Section: Introductionmentioning

confidence: 99%

Properties of the amorphous-nanocrystalline Gd2O3 powder prepared by pulsed electron beam evaporation

et al. 2013

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Abstract-An amorphous-nanocrystalline Gd 2 O 3 powder with a specific surface area of 155 m 2 /g has been prepared using pulsed electron beam evaporation in vacuum. The nanopowder consists of 20 to 500 nm agglomerates formed by crystalline nanoparticles (3-12 nm in diameter) connected by amorphous-nanoc rystalline strands. At room temperature, the Gd 2 O 3 nanopowder exhibits a paramagnetic behavior. The phase transformations occurring in the powder have been investigated using differential scanning calorimetry and thermogravimetry (40-1400°C). The amorphous phase of the nanopowder is thermally stable up to a tem perature of 1080°C. It has been found that the amorphous phase has an inhibitory effect on the temperature of the polymorphic transformation from the cubic phase into the monoclinic phase. It has been revealed that, compared with the microcrystalline powder, the Gd 2 O 3 nanopowder is characterized by a complete quench ing of photoluminescence.

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Investigations into the Physicochemical Properties of Dextran Small Particulate Gadolinium Oxide Nanoparticles

Cited by 98 publications

References 11 publications

Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study

Properties of the amorphous-nanocrystalline Gd2O3 powder prepared by pulsed electron beam evaporation

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Investigations into the Physicochemical Properties of Dextran Small Particulate Gadolinium Oxide Nanoparticles

Cited by 98 publications

References 11 publications

Polyethylene glycol-covered ultra-small Gd2O3nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

Polyethylene glycol-covered ultra-small Gd2O3nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study

Properties of the amorphous-nanocrystalline Gd2O3 powder prepared by pulsed electron beam evaporation

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Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

Polyethylene glycol-covered ultra-small Gd₂O₃nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning