Structures of MRI Contrast Agents in Solution

Frullano, Luca; Rohovec, Jan; Peters, Joop A.; Geraldes, Carlos F. G. C.

doi:10.1007/3-540-45733-x_2

Cited by 22 publications

(27 citation statements)

References 176 publications

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“…From the coalescence temperature of the carboxylate resonances (9 8C), the free enthalpy of activation of the exchange process concerned (DG 282 ) can be estimated to be 56 AE 3 kJmol À1 . The value is in the range of DG values generally found for the racemisa- [32,33] this suggests that the exchange process observed here can be assigned to such a racemisation. The racemisation at the phosphorus atom has a considerably lower barrier, as at 0 8C the exchange between the corresponding two enantiomeric forms is already rapid on the NMR timescale.…”

Section: Interconversion Between Isomers Of Thementioning

confidence: 72%

“…complexes of DTPA derivatives has shown that the two ethylene moieties can adopt either a ll or a dd conformation. [32,33] Therefore, this is most likely to also be the case for the presently studied ligands. Then, four enantiomers (two diastereomeric pairs) are possible: llR, llS, ddR and ddS, where R and S denote the chirality of the phosphorus atom.…”

Section: àmentioning

confidence: 92%

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Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Kotek

Lebdušková

Hermann

et al. 2003

Chemistry A European J

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Three novel phosphorus-containing analogues of H(5)DTPA (DTPA = diethylenetriaminepentaacetate) were synthesised (H6L1, H5L2, H5L3). These compounds have a -CH2-P(O)(OH)-R function (R = OH, Ph, CH2NBn2) attached to the central nitrogen atom of the diethylenetriamine backbone. An NMR study reveals that these ligands bind to lanthanide(III) ions in an octadentate fashion through the three nitrogen atoms, a P-O oxygen atom and four carboxylate oxygen atoms. The complexed ligand occurs in several enantiomeric forms due to the chirality of the central nitrogen atom and the phosphorus atom upon coordination. All lanthanide complexes studied have one coordinated water molecule. The residence times (tau(M)298) of the coordinated water molecules in the gadolinium(III) complexes of H6L1 and H5L2 are 88 and 92 ns, respectively, which are close to the optimum. This is particularly important upon covalent and noncovalent attachment of these Gd(3+) chelates to polymers. The relaxivity of the complexes studied is further enhanced by the presence of at least two water molecules in the second coordination sphere of the Gd(3+) ion, which are probably bound to the phosphonate/phosphinate moiety by hydrogen bonds. The complex [Gd(L3)(H2O)](2-) shows strong binding ability to HSA, and the adduct has a relaxivity comparable to MS-325 (40 s(-1) mM(-1) at 40 MHz, 37 degrees C) even though it has a less favourable tau(M) value (685 ns). Transmetallation experiments with Zn(2+) indicate that the complexes have a kinetic stability that is comparable to-or better than-those of [Gd(dtpa)(H2O)](2-) and [Gd(dtpa-bma)(H2O)].

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Section: Interconversion Between Isomers Of Thementioning

confidence: 72%

Section: àmentioning

confidence: 92%

Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Kotek

Lebdušková

Hermann

et al. 2003

Chemistry A European J

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“…3 There are now known various types of GBCAs currently employed for clinical uses and may be classified into several groups according to their structural features as well as the charge of the complex. [4][5][6][7] As a whole, four types of Gdchelate may be recognized. They are (1) Each type of these MRI CAs possesses its own merits and drawbacks.…”

Section: Introductionmentioning

confidence: 98%

Gd-Complexes of 1,4,7,10-Tetraazacyclododecane-N,N′,N′′,N′′′-1,4,7,10-tetraacetic Acid (DOTA) Conjugates of Tranexamates as a New Class of Blood-Pool Magnetic Resonance Imaging Contrast Agents

Kim²,

Lee³

et al. 2010

J. Med. Chem.

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Gd-complexes of the type [Gd(L)(H(2)O)]·xH(2)O (5a-c), where L is DOTA conjugates of tranexamic acid (4a) and tranexamic esters (4b,c), have been prepared as a new class of MRI blood-pool contrast agents (BPCAs). Thermodynamic stability (K(GdL)) and pharmacokinetic inertness of 5 compare well with or better than those of analogous MRI contrasting agents (CAs) such as Gd-DOTA and Gd-DTPA-BMA. Their R(1)-relaxivities are significantly higher than those of any of the clinically used MRI CAs. T(1)-weighted MR images of mice administered by 5c demonstrate high blood-pool effect with simultaneous contrast enhancement in liver. The structural uniqueness of 5c lies in the fact that it adopts macrocyclic DOTA instead of acyclic DTPA. In addition, 5c is nonionic and makes no resort to aromatic substituent(s) in the chelate backbone for the blood-pool enhancement. The nature of hepatobiliary uptake demonstrated by 5c may be explained in terms of lipophilicity of tranexamate in the chelate (4c). The cell cytotoxicity test shows no toxicity found with 5, suggesting their use as a practical MRI BPCAs.

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“…[3,4] Delivery of higher doses of CA at the target site, by exploiting receptors or molecular determinants, would improve the visualization of abnormalities. A major problem encountered in imaging of receptors is their low concentration (typically 10 À9 -…”

Section: Introductionmentioning

confidence: 99%

Gadolinium(III)‐Loaded Nanoparticulate Zeolites as Potential High‐Field MRI Contrast Agents: Relationship Between Structure and Relaxivity

Csajbók

Bányai

Elst

et al. 2005

Chemistry A European J

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The effects of dealumination, pore size, and calcination on the efficiency (as expressed in the relaxivity) of Gd3+-loaded zeolites for potential application as magnetic resonance imaging (MRI) contrast agents were studied. Partial dealumination of zeolites NaY or NaA by treatment with (NH4)2SiF6 or diluted HCl resulted in materials that, upon loading with Gd3+, had a much higher relaxivity than the corresponding non-dealuminated materials. Analysis of the 1H NMR dispersion profiles of the various zeolites showed that this can be mainly ascribed to an increase of the amount of water inside the zeolite cavities as a result of the destruction of walls between cavities. However, the average residence time of water inside the Gd3+-loaded cavities did not change significantly, which suggests that the windows of the Gd3+-loaded cavities are not affected by the dealumination. Upon calcination, the Gd3+ ions moved to the small sodalite cavities and became less accessible for water, resulting in a decrease in relaxivity. The important role of diffusion for the relaxivity was demonstrated by a comparison of the relaxivity of Gd3+-loaded zeolite NaY and NaA samples. NaA had much lower relaxivities due to the smaller pore sizes. The transversal relaxivities of the Gd3+-doped zeolites are comparable in magnitude to the longitudinal ones at low magnetic fields (<60 MHz). However at higher fields, the transversal relaxivities steeply increased, whereas the longitudinal relaxivities decreased as field strength increased. Therefore, these materials have potential as T1 MRI contrast agents at low field, and as T2 agents at higher fields.

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Structures of MRI Contrast Agents in Solution

Cited by 22 publications

References 176 publications

Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Gd-Complexes of 1,4,7,10-Tetraazacyclododecane-N,N′,N′′,N′′′-1,4,7,10-tetraacetic Acid (DOTA) Conjugates of Tranexamates as a New Class of Blood-Pool Magnetic Resonance Imaging Contrast Agents

Gadolinium(III)‐Loaded Nanoparticulate Zeolites as Potential High‐Field MRI Contrast Agents: Relationship Between Structure and Relaxivity

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