Molecular sieve based MRI contrast agents

Balkus, Kenneth J.; Bresinska, I.

doi:10.1016/0925-8388(94)90170-8

Cited by 20 publications

(9 citation statements)

References 5 publications

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“…[14][15][16] For R 1 -weighted images of the gastrointestinal tract, gadolinium-loaded NaY zeolites (Gd-NaY) have been developed. [17][18][19][20][21][22][23][24] 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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“…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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“…Additionally, the contrast agent should evenly coat the bowel walls and not become diluted or absorbed as it passes through the intestines. Microporous metal oxides such as zeolites − and clays modified with paramagnetic metal ions or complexes have proven effective as positive contrast or brightening agents. In particular, the oral diagnostic pharmaceutical GADOLITE, which is based on a gadolinium(III) ( S = 7 / 2 ) modified synthetic faujasite type zeolite, exhibited excellent contrast with no toxicity or side effects during clinical trials …”

Section: Introductionmentioning

confidence: 99%

Studies of Gadolinium(III)-Modified Hectorite Clays as Potential Oral MRI Contrast Agents

Balkus

Shi

1996

J. Phys. Chem.

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Hectorite type clays modified with gadolinium(III) were prepared by ion-exchange of natural (SHCa) hectorite and synthetic (SLH) hectorite. Results show that Gd(III) content in the clay increases with increasing gadolinium(III) in the exchange solution within the range between 0 and 25% of the Gd/clay weight ratio. Studies relevant to the in vivo stability and efficacy of Gd(III) ion-exchanged hectorite as an oral MRI contrast agent are detailed. The stability of Gd(III) ion-exchanged hectorite at low pH as well as in the presence of sodium ion at concentrations relevant to the gastrointestinal tract has been evaluated. The room-temperature relaxivities (1/T 1 vs [Gd]) of aqueous Gd(III)-exchanged hectorite suspensions at different stirring time, concentration, and pH were measured at 40 MHz and room-temperature. The type of clay and the gadolinium loading as well as the amount of clay in suspension and the stirring time were found to have a profound effect on the relaxivity.

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Molecular sieve based MRI contrast agents

Cited by 20 publications

References 5 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

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

Studies of Gadolinium(III)-Modified Hectorite Clays as Potential Oral MRI Contrast Agents

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Molecular sieve based MRI contrast agents

Cited by 20 publications

References 5 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

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

Studies of Gadolinium(III)-Modified Hectorite Clays as Potential Oral MRI Contrast Agents

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Product

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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