Structure and dynamics of lanthanide(III) complexes of the bis(propylamide) of diethylenetriaminepentaacetic acid in aqueous solution

Geraldes, Carlos F. G. C.; Urbano, Ana M.; Alpoím, Maria C.; Hoefnagel, M. A.; Peters, Joop A.

doi:10.1039/c39910000656

Cited by 26 publications

(26 citation statements)

References 9 publications

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“…60 cm À1 to lower energy were observed for the carbonyl stretching frequencies upon complexation, indicating amide oxygen coordination to gadolinium(III) ion. These findings are consistent with previous studies which have shown that DTPA bisamide derivatives coordinate to lanthanide(III) ions via three acetate oxygens, three nitrogen atoms and two carbonyl oxygens of the amide group, while the ninth coordination site is occupied by a water molecule (Geraldes et al 1991;Ehnebom et al 1992;Bligh et al 1995;Aime et al 1997;Wang et al 1999).…”

Section: Resultssupporting

confidence: 93%

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

et al. 2005

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Three amphiphilic DTPA bisamide derivatives containing long-chain phenylalanine esters (with 14, 16 and 18 carbon atoms in the alkyl chain) were synthesized and their corresponding gadolinium(III) complexes were prepared. The attempts to form paramagnetic micelles carrying the gadolinium(III) complexes yielded unstable or polydisperse micelles implying that the presence of the bulky aromatic side groups in the amphiphilic Gd-DTPA bisamide complexes results in an inefficient packing of the paramagnetic complex into micelles. All complexes were efficiently incorporated into liposomes consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), yielding stable and monodisperse paramagnetic liposomes. All liposomes had a comparable size, typically between 120 and 160 nm. As a result of the reduced mobility of the gadolinium(III) complexes, solutions of these supramolecular structures show a higher relaxivity than solutions of Gd-DTPA. However, the relaxivity gain is lower compared to compounds consisting of purely aliphatic chains of the same length, most likely due to the less efficient packing or increased local mobility of the gadolinium(III) complex. In the case of the Gd-DTPA bisamide complex with 18 carbon atoms, the immobilization inside the liposomal structure is less effective, probably because the aliphatic chains of the complex are longer than the alkyl chains of the DPPC host, resulting in a relatively high local mobility. The paramagnetic liposomes containing the Gd-DTPA bisamide complexes with 14 carbon atoms showed the highest relaxivity because the optimal length match between the hydrophobic chains of the DPPC and the ligand allowed very efficient packing of the paramagnetic complex into the liposome.

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Section: Resultssupporting

confidence: 93%

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

et al. 2005

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“…The number of resonances in NMR spectra at low temperature shows that all of these isomers are populated in aqueous solution (see Figure 5.5) [197,198,210]. On an increase in temperature, coalescence of pairs of resonances has been observed due to the isomerization processes through the wagging and decoordination-coordination mechanisms.…”

Section: The Parent System Dtpa and Dtpa-bisamidesmentioning

confidence: 95%

Structure, Dynamics, and Computational Studies of Lanthanide‐Based Contrast Agents

Peters

Djanashvili

Geraldes

et al. 2013

The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging

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“…Experimental settings: spectral width 10000 Hz, 90°pulse (7 µs), acquisition time 10 ms, 1000 scans and no sample spinning. Aqueous solutions containing 2.6% of 17 O isotope (Yeda, Israel) were used. The observed transverse relaxation rates (R O 2obs ) were calculated from the signal width at half-height (∆ν 1/2 ): R O 2obs ϭ π ∆ν 1/2 .…”

Section: Synthesis Of Gdmentioning

confidence: 99%

“…Variable temperature 17 O NMR measurements were recorded at 2.1 T on a JEOL EX-90 spectrometer, equipped with a 5 mm probe, by using a D 2 O external lock. Experimental settings: spectral width 10000 Hz, 90°pulse (7 µs), acquisition time 10 ms, 1000 scans and no sample spinning.…”

Section: Synthesis Of Gdmentioning

confidence: 99%

Modulation of the Prototropic Exchange Rate at the Water Molecule Coordinated to a Gd^III Ion

et al. 2003

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The aim of this work is to assess whether it is possible to control the rate of the prototropic exchange in a class of DTPA bis-amide Gd III complexes.In the last decade much attention has been devoted to the understanding of the determinants of the water-exchange process in Gd III complexes because their successful application as MRI contrast agents is related to the occurrence of a suitable exchange lifetime (τ M ) of the coordinated water.[1Ϫ4] The latter parameter inversely affects the innersphere relaxation term (R 1p is ) and is often the main determinant of the overall relaxivity of a paramagnetic Gd III complex. The R 1p is contribution is given by Equation (1):(1)where [C] is the molar concentration of the paramagnetic agent, q is the number of coordinated water molecules and T 1M is the relaxation time of their protons. Thus, as long as τ M is shorter than T 1M the paramagnetic relaxation effect can be efficiently transferred to the bulk water solvent.Bis-amide derivatives of Gd-DTPA (DTPA ϭ diethylenetriamine pentaacetic acid) display relatively long exchange lifetimes of the coordinated water,[5Ϫ8] therefore their relaxivity is usually smaller than expected. However, such a drawback has been exploited in order to assess the rate of prototropic exchange at the coordinated water molecule. The latter process is pH-dependent and becomes significantly high either at acidic or basic pH, to overcome the ''quenching'' effect of the slow exchanging water, thus allowing the system to raise the relaxivity expected on the basis of its T 1M value.[a] Dipartimento di Chimica IFM, Università di Torino, Via P. Thus, τ M in Equation (1) can be replaced by Equation (2): (2) where k ex is the prototropic exchange rate. Although the prototropic exchange is either acid or base catalysed, its assessment, in the case of bis-amide derivatives of Gd-DTPA, is preferentially pursued under basic conditions because the limited thermodynamic stability of these complexes may cause some release of Gd III ions upon protonation of the acetic arms at acidic pH. Typically the determination of k ex is then carried out by fitting the pH-dependent curve of the relaxivity in the pH range between 3 and 10.The aim of this work is to assess whether it is possible to control the rate of the prototropic exchange in this class of Gd III complexes. Six novel bis-amide derivatives of Gd-DTPA have been synthesised (Scheme 1). These ligands were obtained according to the previously reported procedure [9] based on the reaction of DTPA bis-anhydride with the amine group of the entering R substituent. Compounds 1 and 2 were obtained by hydrolyzing the ester functionalities of 3 and 4, respectively.The corresponding Gd III complexes were obtained by reacting equimolar amounts of any given ligand and GdCl 3 at pH 6. The eventual excess of uncomplexed Gd III ions was precipitated as the hydroxide as the pH of the solution was brought to basic values, and separated by ultracentrifugation.At neutral pH and 298 K, the relaxivity (measured at 20 MHz) shown by...

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Structure and dynamics of lanthanide(III) complexes of the bis(propylamide) of diethylenetriaminepentaacetic acid in aqueous solution

Abstract: NMR shift and relaxation measurements show that the lanthanide(iii) complexes of the bis(propy1amide) of diethylenetriaminepentaacetic acid (H3L) occur in at least eight isomeric forms, in which the metal ion is coordinated

Cited by 26 publications

References 9 publications

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

Structure, Dynamics, and Computational Studies of Lanthanide‐Based Contrast Agents

Modulation of the Prototropic Exchange Rate at the Water Molecule Coordinated to a Gd^III Ion

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Structure and dynamics of lanthanide(III) complexes of the bis(propylamide) of diethylenetriaminepentaacetic acid in aqueous solution

Abstract: NMR shift and relaxation measurements show that the lanthanide(iii) complexes of the bis(propy1amide) of diethylenetriaminepentaacetic acid (H3L) occur in at least eight isomeric forms, in which the metal ion is coordinated

Cited by 26 publications

References 9 publications

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging

Structure, Dynamics, and Computational Studies of Lanthanide‐Based Contrast Agents

Modulation of the Prototropic Exchange Rate at the Water Molecule Coordinated to a GdIII Ion

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Modulation of the Prototropic Exchange Rate at the Water Molecule Coordinated to a Gd^III Ion