Zeolite Encapsulated Gadolinium(iii) Chelate Complexes

Balkus, Kenneth J.; Bresinska, I.; Young, Stuart W.

doi:10.1016/b978-1-4832-8383-8.50107-0

Cited by 7 publications

(4 citation statements)

References 7 publications

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“…For R 1 -weighted images of the gastrointestinal tract, gadolinium-loaded NaY zeolites (Gd−NaY) have been developed. − Later, the synthesis of Gd 3+ -loaded nanosized NaY zeolites opened the way for the application of this material in the imaging of the intravascular system as well. Gd 3+ exchanged NaY nanoparticles of an average size of 80 nm, contain about 40 000 Gd 3+ ions per particle.…”

Section: Introductionmentioning

confidence: 99%

¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

2007

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The results of a 1H nuclear magnetic relaxation dispersion (NMRD) and EPR study on aqueous suspensions of Gd3+-loaded NaY nanozeolites and AlTUD-1 mesoporous material are described. Upon increase of the Si/Al ratio from 1.7 to 4.0 in the Gd3+-loaded zeolites, the relaxation rate per mM Gd3+ (r 1) at 40 MHz and 25 °C increases from 14 to 27 s-1 mM-1. The NMRD and EPR data were fitted with a previously developed two-step model that considers the system as a concentrated aqueous solution of Gd3+ in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results show that the observed increase in relaxivity can mainly be attributed to the residence lifetime of the water protons in the interior of the material, which decreased from 0.3 to 0.2 μs, upon the increase of the Si/Al ratio. This can be explained by the decreased interaction of water with the zeolite walls as a result of the increased hydrophobicity. The importance of the exchange rate of water between the inside and the outside of the material was further demonstrated by the relatively high relaxivity (33 s-1 mM-1 at 40 MHz, 25 °C) observed for a suspension of the Gd3+-loaded mesoporous material AlTUD-1. Unfortunately, Gd3+ leaches rather easily from that material, but not from the Gd3+-loaded NaY zeolites, which may have potential as contrast agents for magnetic resonance imaging.

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Section: Introductionmentioning

confidence: 99%

¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

2007

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“…It was the first extra-large-pore silicate-based zeolite ever synthesized. Earlier studies with the smaller cobalticinium ([(Cp) 2 Co] + ) ion as a structure-directing agent had produced clathrasil phases with the NON , AST , and DOH topologies, , but no silicate-based materials with an accessible pore system (though more recently, UTD-12, which does have accessible channels, has been prepared with use of the cobalticinium ion). Structural characterization of the calcined form of UTD-1 indicated that it was disordered along the one-dimensional 14-ring channel, but this did not affect the size of the pores, just the topology of the channel walls …”

Section: Introductionmentioning

confidence: 99%

An Ordered Form of the Extra-Large-Pore Zeolite UTD-1: Synthesis and Structure Analysis from Powder Diffraction Data

et al. 1999

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A highly crystalline sample of the extra-large-pore, high-silica zeolite UTD-1 has been prepared in fluoride medium. The resulting product (UTD-1F) has a powder diffraction pattern remarkably different from that published for the calcined form of conventionally prepared UTD-1, and it could only be indexed on a monoclinic unit cell. The crystal structure was determined ab initio in the space group P2 1 /c from synchrotron powder diffraction data collected on a textured sample. The resulting structure, with 69 non-H atoms in the asymmetric unit, is by far the largest structure solved directly from powder diffraction data to date. Subsequent Rietveld refinement of the structure in Pc, with 349 positional parameters and 464 geometric restraints, proved to be surprisingly stable and converged with R F ) 0.041 and R wp ) 0.134 (R exp ) 0.101). In contrast to the structure reported for calcined UTD-1, no evidence of disorder was found in the UTD-1F framework (structure type code DON). There is a strict up-down alternation of the orientation of the Si tetrahedra in the 14-rings, and double crankshaft chains link adjacent 14-ring channels. Not only the framework, but also the (Cp*) 2 Co complex, which appeared very clearly on the difference electron density map, was found to be fully ordered in the channels with the 5-fold axis parallel to the channel direction.

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“…Until recently, the application of MRI to the gastrointestinal (GI) tract has been hindered by the lack of suitable contrast media. We have found that microporous metal oxides such as zeolite molecular sieves − and clays , modified with paramagnetic metal complexes are effective MRI contrast agents. Zeolites are crystalline aluminosilicates having well-defined pore and channel systems of molecular dimensions.…”

Section: Introductionmentioning

confidence: 99%

A Study of Suspending Agents for Gadolinium(III)-Exchanged Hectorite. An Oral Magnetic Resonance Imaging Contrast Agent

Balkus

Shi

1996

Langmuir

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Clays modified with paramagnetic ions have been shown to be effective magnetic resonance imaging contrast agents. The efficacy in part relies on the suspension of the small clay particles in aqueous solution. In this study a series of macromolecules were evaluated as suspending agents for Gd(III) ion exchanged hectorite clay in water. The room temperature relaxivities for the Gd-hectorite clays were enhanced by the addition of poly(ethylene oxide), poly(ethylene glycol), cyclodextrins, and cholic acid to aqueous suspensions. Additionally, there was no evidence of free Gd(III) in solution in the presence of these suspending agents. In contrast the combination of alginic acid or poly(sodium 4-styrenesulfonate) with the clays resulted in release of the Gd(III) into solution. Xanthan gum, which is often used as an emulsifier and stabilizer in food products, forms a viscous suspension but also reacts with free Gd(III) ions.

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Zeolite Encapsulated Gadolinium(iii) Chelate Complexes

Cited by 7 publications

References 7 publications

¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

An Ordered Form of the Extra-Large-Pore Zeolite UTD-1: Synthesis and Structure Analysis from Powder Diffraction Data

A Study of Suspending Agents for Gadolinium(III)-Exchanged Hectorite. An Oral Magnetic Resonance Imaging Contrast Agent

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Zeolite Encapsulated Gadolinium(iii) Chelate Complexes

Cited by 7 publications

References 7 publications

1H Relaxivity of Water in Aqueous Suspensions of Gd3+-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

1H Relaxivity of Water in Aqueous Suspensions of Gd3+-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

An Ordered Form of the Extra-Large-Pore Zeolite UTD-1: Synthesis and Structure Analysis from Powder Diffraction Data

A Study of Suspending Agents for Gadolinium(III)-Exchanged Hectorite. An Oral Magnetic Resonance Imaging Contrast Agent

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¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size

¹H Relaxivity of Water in Aqueous Suspensions of Gd³⁺-Loaded NaY Nanozeolites and AlTUD-1 Mesoporous Material: the Influence of Si/Al Ratio and Pore Size