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Oliveira AC, Filipe HAL, Geraldes CF, Voth GA, Moreno MJ, Loura LMS. Interaction of MRI Contrast Agent [Gd(DOTA)] - with Lipid Membranes: A Molecular Dynamics Study. Inorg Chem 2024; 63:10897-10914. [PMID: 38795015 PMCID: PMC11186012 DOI: 10.1021/acs.inorgchem.4c00972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/16/2024] [Accepted: 04/30/2024] [Indexed: 05/27/2024]
Abstract
Contrast agents are important imaging probes in clinical MRI, allowing the identification of anatomic changes that otherwise would not be possible. Intensive research on the development of new contrast agents is being made to image specific pathological markers or sense local biochemical changes. The most widely used MRI contrast agents are based on gadolinium(III) complexes. Due to their very high charge density, they have low permeability through tight biological barriers such as the blood-brain barrier, hampering their application in the diagnosis of neurological disorders. In this study, we explore the interaction between the widely used contrast agent [Gd(DOTA)]- (Dotarem) and POPC lipid bilayers by means of molecular dynamics simulations. This metal complex is a standard reference where several chemical modifications have been introduced to improve key properties such as bioavailability and targeting. The simulations unveil detailed insights into the agent's interaction with the lipid bilayer, offering perspectives beyond experimental methods. Various properties, including the impact on global and local bilayer properties, were analyzed. As expected, the results indicate a low partition coefficient (KP) and high permeation barrier for this reference compound. Nevertheless, favorable interactions are established with the membrane leading to moderately long residence times. While coordination of one inner-sphere water molecule is maintained for the membrane-associated chelate, the physical-chemical attributes of [Gd(DOTA)]- as a MRI contrast agent are affected. Namely, increases in the rotational correlation times and in the residence time of the inner-sphere water are observed, with the former expected to significantly increase the water proton relaxivity. This work establishes a reference framework for the use of simulations to guide the rational design of new contrast agents with improved relaxivity and bioavailability and for the development of liposome-based formulations for use as imaging probes or theranostic agents.
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Affiliation(s)
- Alexandre C. Oliveira
- Coimbra
Chemistry Centre, Institute of Molecular
Sciences (CQC-IMS), 3004-535 Coimbra, Portugal
- Department
of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Hugo A. L. Filipe
- Coimbra
Chemistry Centre, Institute of Molecular
Sciences (CQC-IMS), 3004-535 Coimbra, Portugal
- CPIRN-IPG—Center
of Potential and Innovation of Natural Resources, Polytechnic Institute of Guarda, 6300-559 Guarda, Portugal
| | - Carlos F.G.C. Geraldes
- Coimbra
Chemistry Centre, Institute of Molecular
Sciences (CQC-IMS), 3004-535 Coimbra, Portugal
- Department
of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-393 Coimbra, Portugal
- CIBIT/ICNAS
- Instituto de Ciências Nucleares Aplicadas à Saúde, Pólo das Ciências
da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal
| | - Gregory A. Voth
- Department
of Chemistry, Chicago Center for Theoretical Chemistry, James Franck
Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, United States
| | - Maria João Moreno
- Coimbra
Chemistry Centre, Institute of Molecular
Sciences (CQC-IMS), 3004-535 Coimbra, Portugal
- Department
of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- CNC−Center
for Neuroscience and Cell Biology, University
of Coimbra, 3004-517 Coimbra, Portugal
| | - Luís M. S. Loura
- Coimbra
Chemistry Centre, Institute of Molecular
Sciences (CQC-IMS), 3004-535 Coimbra, Portugal
- Faculty
of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
- CNC−Center
for Neuroscience and Cell Biology, University
of Coimbra, 3004-517 Coimbra, Portugal
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2
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Nucera A, Platas-Iglesias C, Carniato F, Botta M. Effect of hydration equilibria on the relaxometric properties of Gd(III) complexes: new insights into old systems. Dalton Trans 2023; 52:17229-17241. [PMID: 37955945 DOI: 10.1039/d3dt03413e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
We present a detailed relaxometric and computational investigation of three Gd(III) complexes that exist in solution as an equilibrium of two species with a different number of coordinated water molecules: [Gd(H2O)q]3+ (q = 8, 9), [Gd(EDTA)(H2O)q]- and [Gd(CDTA)(H2O)q]- (q = 2, 3). 1H nuclear magnetic relaxation dispersion (NMRD) data were recorded from aqueous solutions of these complexes using a wide Larmor frequency range (0.01-500 MHz). These data were complemented with 17O transverse relaxation rates and chemical shifts recorded at different temperatures. The simultaneous fit of the NMRD and 17O NMR data was guided by computational studies performed at the DFT and CASSCF/NEVPT2 levels, which provided information on Gd⋯H distances, 17O hyperfine coupling constants and the zero-field splitting (ZFS) energy, which affects electronic relaxation. The hydration equilibrium did not have a very important effect in the fits of the experimental data for [Gd(H2O)q]3+ and [Gd(CDTA)(H2O)q]-, as the hydration equilibrium is largely shifted to the species with the lowest hydration number (q = 8 and 2, respectively). The quality of the analysis improves however considerably for [Gd(EDTA)(H2O)q]- upon considering the effect of the hydration equilibrium. As a result, this study provides for the first time an analysis of the relaxation properties of this important model system, as well as accurate parameters for [Gd(H2O)q]3+ and [Gd(CDTA)(H2O)q]-.
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Affiliation(s)
- Alessandro Nucera
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
| | - Carlos Platas-Iglesias
- Universidade da Coruña, Centro de Interdisciplinar de Química e Bioloxía (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Fabio Carniato
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
| | - Mauro Botta
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
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3
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Harriswangler C, Lucio-Martínez F, Godec L, Soro LK, Fernández-Fariña S, Valencia L, Rodríguez-Rodríguez A, Esteban-Gómez D, Charbonnière LJ, Platas-Iglesias C. Effect of Magnetic Anisotropy on the 1H NMR Paramagnetic Shifts and Relaxation Rates of Small Dysprosium(III) Complexes. Inorg Chem 2023; 62:14326-14338. [PMID: 37602400 PMCID: PMC10481378 DOI: 10.1021/acs.inorgchem.3c01959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Indexed: 08/22/2023]
Abstract
We present a detailed analysis of the 1H NMR chemical shifts and transverse relaxation rates of three small Dy(III) complexes having different symmetries (C3, D2 or C2). The complexes show sizeable emission in the visible region due to 4F9/2 → 6HJ transitions (J = 15/2 to 11/2). Additionally, NIR emission is observed at ca. 850 (4F9/2 → 6H7/2), 930 (4F9/2 → 6H5/2), 1010 (4F9/2 → 6F9/2), and 1175 nm (4F9/2 → 6F7/2). Emission quantum yields of 1-2% were determined in aqueous solutions. The emission lifetimes indicate that no water molecules are present in the inner coordination sphere of Dy(III), which in the case of [Dy(CB-TE2PA)]+ was confirmed through the X-ray crystal structure. The 1H NMR paramagnetic shifts induced by Dy(III) were found to be dominated by the pseudocontact mechanism, though, for some protons, contact shifts are not negligible. The analysis of the pseudocontact shifts provided the magnetic susceptibility tensors of the three complexes, which were also investigated using CASSCF calculations. The transverse 1H relaxation data follow a good linear correlation with 1/r6, where r is the distance between the Dy(III) ion and the observed proton. This indicates that magnetic anisotropy is not significantly affecting the relaxation of 1H nuclei in the family of complexes investigated here.
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Affiliation(s)
- Charlene Harriswangler
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - Fátima Lucio-Martínez
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - Léna Godec
- Equipe
de Synthèse Pour l′Analyse (SynPA), Institut Pluridisciplinaire
Hubert Curien (IPHC), UMR 7178, CNRS, Université
de Strasbourg, ECPM, 25 rue Becquerel, 67087 Strasbourg Cedex, France
| | - Lohona Kevin Soro
- Equipe
de Synthèse Pour l′Analyse (SynPA), Institut Pluridisciplinaire
Hubert Curien (IPHC), UMR 7178, CNRS, Université
de Strasbourg, ECPM, 25 rue Becquerel, 67087 Strasbourg Cedex, France
| | - Sandra Fernández-Fariña
- Departamento
de Química Inorgánica, Facultade de Química,
Campus Vida, Universidade de Santiago de
Compostela, 15782 Santiago de Compostela, Spain
| | - Laura Valencia
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidade de Vigo, As Lagoas, Marcosende, 36310 Pontevedra, Spain
| | - Aurora Rodríguez-Rodríguez
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - David Esteban-Gómez
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - Loïc J. Charbonnière
- Equipe
de Synthèse Pour l′Analyse (SynPA), Institut Pluridisciplinaire
Hubert Curien (IPHC), UMR 7178, CNRS, Université
de Strasbourg, ECPM, 25 rue Becquerel, 67087 Strasbourg Cedex, France
| | - Carlos Platas-Iglesias
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
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4
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Oliveira A, Filipe HAL, Ramalho JP, Salvador A, Geraldes CFGC, Moreno MJ, Loura LMS. Modeling Gd 3+ Complexes for Molecular Dynamics Simulations: Toward a Rational Optimization of MRI Contrast Agents. Inorg Chem 2022; 61:11837-11858. [PMID: 35849762 PMCID: PMC9775472 DOI: 10.1021/acs.inorgchem.2c01597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The correct parametrization of lanthanide complexes is of the utmost importance for their characterization using computational tools such as molecular dynamics simulations. This allows the optimization of their properties for a wide range of applications, including medical imaging. Here we present a systematic study to establish the best strategies for the correct parametrization of lanthanide complexes using [Gd(DOTA)]- as a reference, which is used as a contrast agent in MRI. We chose the bonded model to parametrize the lanthanide complexes, which is especially important when considering the study of the complex as a whole (e.g., for the study of the dynamics of its interaction with proteins or membranes). We followed two strategies: a so-called heuristic approach employing strategies already published by other authors and another based on the more recent MCPB.py tool. Adjustment of the Lennard-Jones parameters of the metal was required. The final topologies obtained with both strategies were able to reproduce the experimental ion to oxygen distance, vibrational frequencies, and other structural properties. We report a new strategy to adjust the Lennard-Jones parameters of the metal ion in order to capture dynamic properties such as the residence time of the capping water (τm). For the first time, the correct assessment of the τm value for Gd-based complexes was possible by recording the dissociative events over up to 10 μs all-atom simulations. The MCPB.py tool allowed the accurate parametrization of [Gd(DOTA)]- in a simpler procedure, and in this case, the dynamics of the water molecules in the outer hydration sphere was also characterized. This sphere was divided into the first hydration layer, an intermediate region, and an outer hydration layer, with a residence time of 18, 10 and 19 ps, respectively, independent of the nonbonded parameters chosen for Gd3+. The Lennard-Jones parameters of Gd3+ obtained here for [Gd(DOTA)]- may be used with similarly structured gadolinium MRI contrast agents. This allows the use of molecular dynamics simulations to characterize and optimize the contrast agent properties. The characterization of their interaction with membranes and proteins will permit the design of new targeted contrast agents with improved pharmacokinetics.
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Affiliation(s)
- Alexandre
C. Oliveira
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,Department
of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Hugo A. L. Filipe
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,CPIRN-IPG-Center
of Potential and Innovation of Natural Resources, Polytechnic Institute of Guarda, 6300-559 Guarda, Portugal
| | - João P.
Prates Ramalho
- Hercules
Laboratory, LAQV, REQUIMTE, Department of Chemistry, School of Science
and Technology, University of Évora, 7000-671 Évora, Portugal
| | - Armindo Salvador
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,CNC−Center
for Neuroscience and Cell Biology, University
of Coimbra, P-3004-517 Coimbra, Portugal,Institute
for Interdisciplinary Research - University of Coimbra, Casa Costa Alemão- Polo II, Rua D. Francisco de Lemos, 3030-789 Coimbra, Portugal
| | - Carlos F. G. C. Geraldes
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,Department
of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-393 Coimbra, Portugal,CIBIT/ICNAS
- Instituto de Ciências Nucleares Aplicadas à Saúde, Pólo das Ciências
da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal
| | - Maria João Moreno
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,Department
of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal,
| | - Luís M. S. Loura
- Coimbra
Chemistry Center - Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal,Faculty
of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal,
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5
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Lucio-Martínez F, Garda Z, Váradi B, Kálmán FK, Esteban-Gómez D, Tóth É, Tircsó G, Platas-Iglesias C. Rigidified Derivative of the Non-macrocyclic Ligand H 4OCTAPA for Stable Lanthanide(III) Complexation. Inorg Chem 2022; 61:5157-5171. [PMID: 35275621 PMCID: PMC8965877 DOI: 10.1021/acs.inorgchem.2c00501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
![]()
The stability constants
of lanthanide complexes with the potentially
octadentate ligand CHXOCTAPA4–,
which contains a rigid 1,2-diaminocyclohexane scaffold functionalized
with two acetate and two picolinate pendant arms, reveal the formation
of stable complexes [log KLaL = 17.82(1)
and log KYbL = 19.65(1)]. Luminescence
studies on the Eu3+ and Tb3+ analogues evidenced
rather high emission quantum yields of 3.4 and 11%, respectively.
The emission lifetimes recorded in H2O and D2O solutions indicate the presence of a water molecule coordinated
to the metal ion. 1H nuclear magnetic relaxation dispersion
profiles and 17O NMR chemical shift and relaxation measurements
point to a rather low water exchange rate of the coordinated water
molecule (kex298 = 1.58 ×
106 s–1) and relatively high relaxivities
of 5.6 and 4.5 mM–1 s–1 at 20
MHz and 25 and 37 °C, respectively. Density functional theory
calculations and analysis of the paramagnetic shifts induced by Yb3+ indicate that the complexes adopt an unprecedented cis geometry
with the two picolinate groups situated on the same side of the coordination
sphere. Dissociation kinetics experiments were conducted by investigating
the exchange reactions of LuL occurring with Cu2+. The
results confirmed the beneficial effect of the rigid cyclohexyl group
on the inertness of the Lu3+ complex. Complex dissociation
occurs following proton- and metal-assisted pathways. The latter is
relatively efficient at neutral pH, thanks to the formation of a heterodinuclear
hydroxo complex. A
non-macrocyclic ligand containing a rigid cyclohexyl spacer
forms thermodynamically stable complexes with the lanthanide(III)
ions in aqueous solution. The complexes also show remarkable kinetic
inertness, though a structural change facilitates dissociation through
the metal-assisted mechanism for the small lanthanides. The Gd(III)
complex displays a relatively high relaxivity due to the presence
of a water molecule coordinated to the metal ion, while the Eu(III)
and Tb(III) analogues display strong metal-centered luminescence.
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Affiliation(s)
- Fátima Lucio-Martínez
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - Zoltán Garda
- Department of Physical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary
| | - Balázs Váradi
- Department of Physical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary.,Doctoral School of Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary
| | - Ferenc Krisztián Kálmán
- Department of Physical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary
| | - David Esteban-Gómez
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
| | - Éva Tóth
- Centre de Biophysique Moléculaire, CNRS UPR 4301, Université d'Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
| | - Gyula Tircsó
- Department of Physical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary
| | - Carlos Platas-Iglesias
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, Universidade da Coruña, 15071 A Coruña, Galicia, Spain
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6
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Uzal-Varela R, Lalli D, Brandariz I, Rodríguez-Rodríguez A, Platas-Iglesias C, Botta M, Esteban-Gómez D. Rigid versions of PDTA 4- incorporating a 1,3-diaminocyclobutyl spacer for Mn 2+ complexation: stability, water exchange dynamics and relaxivity. Dalton Trans 2021; 50:16290-16303. [PMID: 34730583 DOI: 10.1039/d1dt02498a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Rigid derivatives of the acyclic ligand PDTA4- (H4PDTA = propylenediamine-N,N,N',N'-tetraacetic acid) were prepared by functionalization of a 1,3-diaminocyclobutyl spacer. The new ligands contain either four acetate groups attached to the central scaffold (H4L1) or incorporate pyridyl (H2L2) or propylamide (H2L3) units replacing two of the carboxylate groups. The ligand protonation constants and the stability constants of their Mn2+ complexes were determined using potentiometric and spectrophotometric titrations. The stability of the [Mn(L1)]2- complex was found to be significantly higher than that of the flexible [Mn(PDTA)]2- derivative (log KMnL = 10.78 and 10.01, respectively). A detailed study of the 1H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles and 17O NMR measurements evidence that the [Mn(L1)]2- and [Mn(L2)] complexes display a hydration equilibrium in solution involving a seven-coordinate species with an inner-sphere water molecule and a six-coordinate species that lacks a coordinated water molecule. As a result the 1H relaxivities of these complexes are somewhat lower than that of [Mn(EDTA)]2- and related systems. The introduction of propylamide groups in [Mn(L3)] shifts the hydration equilibrium to the seven-coordinate species, which results in a 1H relaxivity (r1p = 3.7 mM-1 s-1 at 22 MHz and 25 °C) exceeding that of [Mn(EDTA)]2- (r1p = 3.3 mM-1 s-1 at 22 MHz and 25 °C). The parameters that control the relaxivities in this family of complexes were determined by simultaneous fitting of the experimental 1H NMRD and 17O NMR data (transverse relaxation rates and chemical shifts), with the aid of computational studies performed at the DFT and CASSCF/NEVPT2 levels. These studies provide detailed insight of the parameters that control the efficiency of these relaxation agents at the molecular level.
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Affiliation(s)
- Rocío Uzal-Varela
- Universidade da Coruña, Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Daniela Lalli
- Magnetic Resonance Platform (PRISMA-UPO), Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale "A. Avogadro", Viale T. Michel 11, 15121 Alessandria, Italy
| | - Isabel Brandariz
- Universidade da Coruña, Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Aurora Rodríguez-Rodríguez
- Universidade da Coruña, Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Carlos Platas-Iglesias
- Universidade da Coruña, Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Mauro Botta
- Magnetic Resonance Platform (PRISMA-UPO), Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale "A. Avogadro", Viale T. Michel 11, 15121 Alessandria, Italy
| | - David Esteban-Gómez
- Universidade da Coruña, Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
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7
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Webber BC, Payne KM, Rust LN, Cassino C, Carniato F, McCormick T, Botta M, Woods M. Analysis of the Relaxometric Properties of Extremely Rapidly Exchanging Gd 3+ Chelates: Lessons from a Comparison of Four Isomeric Chelates. Inorg Chem 2020; 59:9037-9046. [PMID: 32536158 DOI: 10.1021/acs.inorgchem.0c00905] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Relaxometric analyses and in particular the use of fast-field cycling techniques have become routine in the study of paramagnetic metal complexes. The field dependence of the solvent proton relaxation properties (nuclear magnetic relaxation dispersion, NMRD) can provide unparalleled insights into the chemistry of these complexes. However, analyzing NMRD data is a multiparametric problem, and some sets of variables are mutually compensatory. Specifically, when fitting NMRD profiles, the metal-proton distance and the rotational correlation time constant have a push-pull relationship in which a change to one causes a predictable compensation in the other. A relaxometric analysis of four isomeric chelates highlights the pitfalls that await when fitting the NMRD profiles of chelates for which dissociative water exchange is extremely rapid. In the absence of independently verified values for one of these parameters, NMRD profiles can be fitted to multiple parameter sets. This means that NMRD fitting can inadvertently be used to buttress a preconceived notion of how the complex should behave when a different parameter set may more accurately describe the actual behavior. These findings explain why the effect of very rapid dissociative exchange on the hydration state of Gd3+ has remained obscured until only recently.
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Affiliation(s)
- Benjamin C Webber
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, Oregon 97201, United States
| | - Katherine M Payne
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, Oregon 97201, United States
| | - Lauren N Rust
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, Oregon 97201, United States
| | - Claudio Cassino
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale "Amedeo Avogadro″, Viale T. Michel 11, I-15121 Alessandria, Italy
| | - Fabio Carniato
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale "Amedeo Avogadro″, Viale T. Michel 11, I-15121 Alessandria, Italy
| | - Theresa McCormick
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, Oregon 97201, United States
| | - Mauro Botta
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale "Amedeo Avogadro″, Viale T. Michel 11, I-15121 Alessandria, Italy
| | - Mark Woods
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, Oregon 97201, United States.,Advanced Imaging Research Center, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
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8
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Morse SV, Boltersdorf T, Harriss BI, Chan TG, Baxan N, Jung HS, Pouliopoulos AN, Choi JJ, Long NJ. Neuron labeling with rhodamine-conjugated Gd-based MRI contrast agents delivered to the brain via focused ultrasound. Am J Cancer Res 2020; 10:2659-2674. [PMID: 32194827 PMCID: PMC7052893 DOI: 10.7150/thno.42665] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/01/2020] [Indexed: 12/14/2022] Open
Abstract
Gadolinium-based magnetic resonance imaging contrast agents can provide information regarding neuronal function, provided that these agents can cross the neuronal cell membrane. Such contrast agents are normally restricted to extracellular domains, however, by attaching cationic fluorescent dyes, they can be made cell-permeable and allow for both optical and magnetic resonance detection. To reach neurons, these agents also need to cross the blood-brain barrier. Focused ultrasound combined with microbubbles has been shown to enhance the permeability of this barrier, allowing molecules into the brain non-invasively, locally and transiently. The goal of this study was to investigate whether combining fluorescent rhodamine with a gadolinium complex would form a dual-modal contrast agent that could label neurons in vivo when delivered to the mouse brain with focused ultrasound and microbubbles. Methods: Gadolinium complexes were combined with a fluorescent, cationic rhodamine unit to form probes with fluorescence and relaxivity properties suitable for in vivo applications. The left hemisphere of female C57bl/6 mice (8-10 weeks old; 19.07 ± 1.56 g; n = 16) was treated with ultrasound (centre frequency: 1 MHz, peak-negative pressure: 0.35 MPa, pulse length: 10 ms, repetition frequency: 0.5 Hz) while intravenously injecting SonoVue microbubbles and either the 1 kDa Gd(rhodamine-pip-DO3A) complex or a conventionally-used lysine-fixable Texas Red® 3 kDa dextran. The opposite right hemisphere was used as a non-treated control region. Brains were then extracted and either sectioned and imaged via fluorescence or confocal microscopy or imaged using a 9.4 T magnetic resonance imaging scanner. Brain slices were stained for neurons (NeuN), microglia (Iba1) and astrocytes (GFAP) to investigate the cellular localization of the probes. Results: Rhodamine fluorescence was detected in the left hemisphere of all ultrasound treated mice, while none was detected in the right control hemisphere. Cellular uptake of Gd(rhodamine-pip-DO3A) was observed in all the treated regions with a uniform distribution (coefficient of variation = 0.4 ± 0.05). Uptake was confirmed within neurons, whereas the probe did not co-localize with microglia and astrocytes. Compared to the dextran molecule, Gd(rhodamine-pip-DO3A) distributed more homogeneously and was less concentrated around blood vessels. Furthermore, the dextran molecule was found to accumulate unselectively in microglia as well as neurons, whereas our probe was only taken up by neurons. Gd(rhodamine-pip-DO3A) was detected via magnetic resonance imaging ex vivo in similar regions to where fluorescence was detected. Conclusion: We have introduced a method to image neurons with a dual-modal imaging agent delivered non-invasively and locally to the brain using focused ultrasound and microbubbles. When delivered to the mouse brain, the agent distributed homogeneously and was only uptaken by neurons; in contrast, conventionally used dextran distributed heterogeneously and was uptaken by microglia as well as neurons. This result indicates that our probe labels neurons without microglial involvement and in addition the probe was found to be detectable via both ex vivo MRI and fluorescence. Labeling neurons with such dual-modal agents could facilitate the study of neuronal morphology and physiology using the advantages of both imaging modalities.
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9
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Pujales‐Paradela R, Savić T, Esteban‐Gómez D, Angelovski G, Carniato F, Botta M, Platas‐Iglesias C. Gadolinium(III)‐Based Dual1H/19F Magnetic Resonance Imaging Probes. Chemistry 2019; 25:4782-4792. [DOI: 10.1002/chem.201806192] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Indexed: 12/28/2022]
Affiliation(s)
- Rosa Pujales‐Paradela
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento, de QuímicaFacultade de CienciasUniversidade da Coruña 15071 A Coruña Galicia Spain
| | - Tanja Savić
- MR Neuroimaging AgentsMax Planck Institute for Biological Cybernetics Tübingen Germany
| | - David Esteban‐Gómez
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento, de QuímicaFacultade de CienciasUniversidade da Coruña 15071 A Coruña Galicia Spain
| | - Goran Angelovski
- MR Neuroimaging AgentsMax Planck Institute for Biological Cybernetics Tübingen Germany
| | - Fabio Carniato
- Dipartimento di Scienze e Innovazione TecnologicaUniversità del Piemonte Orientale “A. Avogadro” Viale T. Michel 11 15121 Alessandria Italy
| | - Mauro Botta
- Dipartimento di Scienze e Innovazione TecnologicaUniversità del Piemonte Orientale “A. Avogadro” Viale T. Michel 11 15121 Alessandria Italy
| | - Carlos Platas‐Iglesias
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento, de QuímicaFacultade de CienciasUniversidade da Coruña 15071 A Coruña Galicia Spain
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10
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Wahsner J, Gale EM, Rodríguez-Rodríguez A, Caravan P. Chemistry of MRI Contrast Agents: Current Challenges and New Frontiers. Chem Rev 2019; 119:957-1057. [PMID: 30350585 PMCID: PMC6516866 DOI: 10.1021/acs.chemrev.8b00363] [Citation(s) in RCA: 832] [Impact Index Per Article: 166.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tens of millions of contrast-enhanced magnetic resonance imaging (MRI) exams are performed annually around the world. The contrast agents, which improve diagnostic accuracy, are almost exclusively small, hydrophilic gadolinium(III) based chelates. In recent years concerns have arisen surrounding the long-term safety of these compounds, and this has spurred research into alternatives. There has also been a push to develop new molecularly targeted contrast agents or agents that can sense pathological changes in the local environment. This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety. From there we describe different mechanisms of generating MR image contrast such as relaxation, chemical exchange saturation transfer, and direct detection and the types of molecules that are effective for these purposes. Next we describe efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives. Finally we survey approaches to make contrast agents more specific for pathology either by direct biochemical targeting or by the design of responsive or activatable contrast agents.
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Affiliation(s)
- Jessica Wahsner
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Eric M. Gale
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Aurora Rodríguez-Rodríguez
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Peter Caravan
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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11
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Bombieri G, Artali R, Mason SA, McIntyre GJ, Mortillaro A, Aime S. Inner-sphere water and hydrogen bonds in lanthanide DOTAM complexes. A neutron diffraction study. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.09.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Mousavi B, Chauvin A, Moriggi L, Helm L. Carbazole as Linker for Dinuclear Gadolinium‐Based MRI Contrast Agents. Eur J Inorg Chem 2017. [DOI: 10.1002/ejic.201700847] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Bibimaryam Mousavi
- Institut des Sciences et Ingénieries Chimiques Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
- State Key Laboratory of Advanced Technology fort Materials Synthesis and Processing Wuhan University of Technology 430070 Wuhan P.R. China
| | - Anne‐Sophie Chauvin
- Institut des Sciences et Ingénieries Chimiques Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Loïck Moriggi
- Institut des Sciences et Ingénieries Chimiques Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Lothar Helm
- Institut des Sciences et Ingénieries Chimiques Ecole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
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13
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Boros E, Srinivas R, Kim H, Raitsimring AM, Astashkin AV, Poluektov OG, Niklas J, Horning AD, Tidor B, Caravan P. Intramolecular Hydrogen Bonding Restricts Gd–Aqua‐Ligand Dynamics. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201702274] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Eszter Boros
- A. A. Martinos Center for Biomedical Imaging Massachusetts General Hospital Harvard Medical School 149 13th Street, Suite 2301 Charlestown MA 02129 USA
| | - Raja Srinivas
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Hee‐Kyung Kim
- A. A. Martinos Center for Biomedical Imaging Massachusetts General Hospital Harvard Medical School 149 13th Street, Suite 2301 Charlestown MA 02129 USA
| | - Arnold M. Raitsimring
- Department of Chemistry and Biochemistry The University of Arizona 1306 E. University Boulevard Tucson AZ 85721-0041 USA
| | - Andrei V. Astashkin
- Department of Chemistry and Biochemistry The University of Arizona 1306 E. University Boulevard Tucson AZ 85721-0041 USA
| | - Oleg G. Poluektov
- Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA
| | - Andrew D. Horning
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Bruce Tidor
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Peter Caravan
- A. A. Martinos Center for Biomedical Imaging Massachusetts General Hospital Harvard Medical School 149 13th Street, Suite 2301 Charlestown MA 02129 USA
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14
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Boros E, Srinivas R, Kim HK, Raitsimring AM, Astashkin AV, Poluektov OG, Niklas J, Horning AD, Tidor B, Caravan P. Intramolecular Hydrogen Bonding Restricts Gd-Aqua-Ligand Dynamics. Angew Chem Int Ed Engl 2017; 56:5603-5606. [PMID: 28398613 DOI: 10.1002/anie.201702274] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Indexed: 11/11/2022]
Abstract
Aqua ligands can undergo rapid internal rotation about the M-O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivity were systematically ruled out. Intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes.
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Affiliation(s)
- Eszter Boros
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Suite 2301, Charlestown, MA, 02129, USA
| | - Raja Srinivas
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Hee-Kyung Kim
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Suite 2301, Charlestown, MA, 02129, USA
| | - Arnold M Raitsimring
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Boulevard, Tucson, AZ, 85721-0041, USA
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Boulevard, Tucson, AZ, 85721-0041, USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Andrew D Horning
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Bruce Tidor
- Department of Biological Engineering and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Peter Caravan
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Suite 2301, Charlestown, MA, 02129, USA
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15
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Karimi S, Helm L. Water Exchange on [Ln(DO3A)(H2O)2] and [Ln(DTTA–Me)(H2O)2]− Studied by Variable Temperature, Pressure, and Magnetic Field NMR. Inorg Chem 2016; 55:4555-63. [DOI: 10.1021/acs.inorgchem.6b00363] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shima Karimi
- Laboratoire
de Chimie Inorganique
et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
| | - Lothar Helm
- Laboratoire
de Chimie Inorganique
et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
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16
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Peters JA. The reliability of parameters obtained by fitting of1H NMRD profiles and17O NMR data of potential Gd3+-based MRI contrast agents. CONTRAST MEDIA & MOLECULAR IMAGING 2015; 11:160-8. [DOI: 10.1002/cmmi.1677] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 11/02/2015] [Accepted: 11/09/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Joop A. Peters
- Department of Biotechnology; Delft University of Technology; Julianalaan 136 2628 BL Delft The Netherlands
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17
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Oukhatar F, Meudal H, Landon C, Logothetis NK, Platas-Iglesias C, Angelovski G, Tóth É. Macrocyclic Gd3+Complexes with Pendant Crown Ethers Designed for Binding Zwitterionic Neurotransmitters. Chemistry 2015; 21:11226-37. [DOI: 10.1002/chem.201500542] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 12/23/2022]
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18
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De León-Rodríguez LM, Martins AF, Pinho MC, Rofsky NM, Sherry AD. Basic MR relaxation mechanisms and contrast agent design. J Magn Reson Imaging 2015; 42:545-65. [PMID: 25975847 DOI: 10.1002/jmri.24787] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 10/11/2014] [Indexed: 12/22/2022] Open
Abstract
The diagnostic capabilities of magnetic resonance imaging (MRI) have undergone continuous and substantial evolution by virtue of hardware and software innovations and the development and implementation of exogenous contrast media. Thirty years since the first MRI contrast agent was approved for clinical use, a reliance on MR contrast media persists, largely to improve image quality with higher contrast resolution and to provide additional functional characterization of normal and abnormal tissues. Further development of MR contrast media is an important component in the quest for continued augmentation of diagnostic capabilities. In this review we detail the many important considerations when pursuing the design and use of MR contrast media. We offer a perspective on the importance of chemical stability, particularly kinetic stability, and how this influences one's thinking about the safety of metal-ligand-based contrast agents. We discuss the mechanisms involved in MR relaxation in the context of probe design strategies. A brief description of currently available contrast agents is accompanied by an in-depth discussion that highlights promising MRI contrast agents in the development of future clinical and research applications. Our intention is to give a diverse audience an improved understanding of the factors involved in developing new types of safe and highly efficient MR contrast agents and, at the same time, provide an appreciation of the insights into physiology and disease that newer types of responsive agents can provide.
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Affiliation(s)
| | - André F Martins
- Department of Chemistry, University of Texas at Dallas, Richardson, Texas, USA
| | - Marco C Pinho
- Department of Radiology and the Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Neil M Rofsky
- Department of Radiology and the Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - A Dean Sherry
- Department of Chemistry, University of Texas at Dallas, Richardson, Texas, USA.,Department of Radiology and the Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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19
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Abstract
This perspective outlines strategies towards the development of MR imaging probes that our lab has explored over the last 15 years. Namely, we discuss methods to enhance the signal generating capacity of MR probes and how to achieve tissue specificity through protein targeting or probe activation within the tissue microenvironment.
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Affiliation(s)
- Eszter Boros
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Eric M Gale
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Peter Caravan
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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20
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Webber BC, Woods M. The confluence of structure and dynamics in lanthanide(III) chelates: how dynamics help define structure in solution. Dalton Trans 2014; 43:251-8. [PMID: 24100299 DOI: 10.1039/c3dt52143e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Coordination exchange processes tend to dominate the solution state behaviour of lanthanide chelates and generally prohibit the study of small conformational changes. In this article we take advantage of coordinatively rigid Eu(3+) chelates to examine the small conformational changes that occur in these chelates as water dissociatively exchanges in and out of the inner coordination sphere. The results show that the time-averaged conformation of the chelate alters as the water exchange rate increases. This conformational change reflects a change in the hydration state (q/r(LnH)(6)) of the chelate. The hydration state has recently come to be expressed as two separate parameters q and r(LnH). However, these two parameters simultaneously describe the same structural considerations which in solution are indistinguishable and intrinsically related to, and dependent upon, the dissociative water exchange rate. This realization leads to the broader understanding that a solution state structure can only be appreciated with reference to the dynamics of the system.
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Affiliation(s)
- Benjamin C Webber
- Department of Chemistry, Portland State University, 1719 SW 10th Ave, Portland, OR 97201, USA.
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21
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Kotková Z, Helm L, Kotek J, Hermann P, Lukeš I. Gadolinium complexes of monophosphinic acid DOTA derivatives conjugated to cyclodextrin scaffolds: efficient MRI contrast agents for higher magnetic fields. Dalton Trans 2013; 41:13509-19. [PMID: 23018269 DOI: 10.1039/c2dt30858d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Middle-molecular-weight MRI contrast agents based on conjugates of a phosphinic acid DOTA analogue, 1,4,7,10-tetraazacyclododecane-4,7,10-triacetic-1-{methyl[(4-aminophenyl)methyl]phosphinic acid} (DO3AP(ABn)), with amino-substituted cyclodextrins were prepared and studied by a variety of physico-chemical methods. The conjugates were formed by reaction of the corresponding isothiocyanate with per-6-amino-α/β-cyclodextrin and were complexed with the Ln(III) ion to get the final complexes, (LnL)(6)-α-CD and (LnL)(7)-β-CD. Solution structure of the complexes was estimated by investigation of the Eu(III) complexes. The Gd(III) conjugate complexes are endowed with a short water residence time (τ(M) ∼ 10-15 ns at 298 K) and a high abundance of the twisted-square antiprismatic diastereoisomer. They show a high (1)H relaxivity at high fields due to a convenient combination of the fast water exchange rate and the slow rate of the molecular tumbling given by their macromolecular nature. The (1)H relaxation enhancements per molecule of a contrast agent (CA) are very high reaching for a larger (GdL)(7)-β-CD conjugate ∼140 s(-1) mM(-1) and ∼100 s(-1) mM(-1) at 25 °C and magnetic fields 1.5 T and 3 T, respectively, which is the highest reported longitudinal relaxivity for kinetically stable contrast agents of an intermediate molecular mass (<10 kDa) with one water molecule in the first coordination sphere.
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Affiliation(s)
- Zuzana Kotková
- Department of Inorganic Chemistry, Charles University in Prague, Hlavova 2030, 128 40 Prague 2, Czech Republic
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22
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Dynamic aggregation of the mid-sized gadolinium complex {Ph4[Gd(DTTA)(H2O)2]− 3}. J Biol Inorg Chem 2013; 19:145-59. [DOI: 10.1007/s00775-013-1036-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 08/14/2013] [Indexed: 12/28/2022]
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23
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Elmehriki AA, Milne M, Suchý M, Bartha R, Hudson RH. Complexes of selected late period lanthanide(III) cations with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid amide (DOTAM)-alkyl ligands — A new platform for the development of paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) contrast agents. CAN J CHEM 2013. [DOI: 10.1139/cjc-2012-0358] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A series of 18 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid amide (DOTAM)-alkyl derived complexes with selected late lanthanide(III) cations (Dy3+, Tb3+, and Tm3+) has been synthesized; their magnetic properties have been evaluated and compared to those derived from DOTAM. Peralkylation of cyclen with corresponding N-iodoacetyl amines was utilized as the key step in the synthesis. Chemical exchange saturation transfer (CEST) spectra of the complexes have been acquired at 37 °C, revealing that Tm3+-derived DOTAM-alkyl complexes possess the most favorable properties as potential paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) contrast agents.
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Affiliation(s)
- Adam A.H. Elmehriki
- Department of Chemistry, The University of Western Ontario, London ON N6A5B7, Canada
| | - Mark Milne
- Department of Chemistry, The University of Western Ontario, London ON N6A5B7, Canada
| | - Mojmír Suchý
- Department of Chemistry, The University of Western Ontario, London ON N6A5B7, Canada
- Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London ON N6A 5K8, Canada
| | - Robert Bartha
- Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London ON N6A 5K8, Canada
| | - Robert H.E. Hudson
- Department of Chemistry, The University of Western Ontario, London ON N6A5B7, Canada
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Esteban-Gómez D, de Blas A, Rodríguez-Blas T, Helm L, Platas-Iglesias C. Hyperfine Coupling Constants on Inner-Sphere Water Molecules of GdIII-Based MRI Contrast Agents. Chemphyschem 2012; 13:3640-50. [DOI: 10.1002/cphc.201200417] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Indexed: 01/02/2023]
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25
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Rodríguez-Rodríguez A, Esteban-Gómez D, de Blas A, Rodríguez-Blas T, Fekete M, Botta M, Tripier R, Platas-Iglesias C. Lanthanide(III) Complexes with Ligands Derived from a Cyclen Framework Containing Pyridinecarboxylate Pendants. The Effect of Steric Hindrance on the Hydration Number. Inorg Chem 2012; 51:2509-21. [DOI: 10.1021/ic202436j] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Aurora Rodríguez-Rodríguez
- Departamento de Química
Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña,
Spain
| | - David Esteban-Gómez
- Departamento de Química
Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña,
Spain
| | - Andrés de Blas
- Departamento de Química
Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña,
Spain
| | - Teresa Rodríguez-Blas
- Departamento de Química
Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña,
Spain
| | - Marianna Fekete
- Dipartimento di Scienze
dell’
Ambiente e della Vita, Università del Piemonte Orientale “Amedeo Avogadro”, Alessandria,
Italy
| | - Mauro Botta
- Dipartimento di Scienze
dell’
Ambiente e della Vita, Università del Piemonte Orientale “Amedeo Avogadro”, Alessandria,
Italy
| | - Raphaël Tripier
- Université de Bretagne Occidentale, UMR-CNRS 6521, UFR des Sciences
et Techniques, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 BREST
Cedex 3, France
| | - Carlos Platas-Iglesias
- Departamento de Química
Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña,
Spain
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Bonnet CS, Buron F, Caillé F, Shade CM, Drahoš B, Pellegatti L, Zhang J, Villette S, Helm L, Pichon C, Suzenet F, Petoud S, Tóth É. Pyridine-Based Lanthanide Complexes Combining MRI and NIR Luminescence Activities. Chemistry 2011; 18:1419-31. [DOI: 10.1002/chem.201102310] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Indexed: 11/07/2022]
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High relaxivity magnetic resonance imaging contrast agents. Part 1. Impact of single donor atom substitution on relaxivity of serum albumin-bound gadolinium complexes. Invest Radiol 2011; 45:600-12. [PMID: 20808235 DOI: 10.1097/rli.0b013e3181ee5a9e] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
RATIONALE AND OBJECTIVES The donor atoms that bind to gadolinium in contrast agents influence inner-sphere water exchange and electronic relaxation, both of which determine observed relaxivity. The effect of these molecular parameters on relaxivity is greatest when the contrast agent is protein bound. We sought to determine an optimal donor atom set to yield high relaxivity compounds. METHODS A total of 38 gadolinium-1,4,7,10-tetraazacyclo-dodecane-N,N',N'',N'''-tetraacetato derivatives were prepared and relaxivity was determined in the presence and absence of human serum albumin as a function of temperature and magnetic field. Each compound had a common albumin-binding group and differed only by substitution of different donor groups at one of the macrocycle nitrogens. Oxygen-17 isotope relaxometry at 7.05 T was performed to estimate water exchange rates. RESULTS Changing a single donor atom resulted in changes in water exchange rates ranging across 3 orders of magnitude. Donor groups increased water exchange rate in the order: phosphonate ∼ phenolate > α-substituted acetate > acetate > hydroxamate ∼ sulfonamide > amide ∼ pyridyl ∼ imidazole. Relaxivites at 0.47 and 1.4 T, 37°C, ranged from 12.3 to 55.6 mM(-1)s(-1) and from 8.3 to 32.6 mM(-1)s(-1) respectively. Optimal relaxivities were observed when the donor group was an α-substituted acetate. Electronic relaxation was slowest for the acetate derivatives as well. CONCLUSIONS Water exchange dynamics and relaxivity can be predictably tuned by choice of donor atoms.
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Bonnet CS, Fries PH, Crouzy S, Delangle P. Outer-Sphere Investigation of MRI Relaxation Contrast Agents. Example of a Cyclodecapeptide Gadolinium Complex with Second-Sphere Water. J Phys Chem B 2010; 114:8770-81. [DOI: 10.1021/jp101443v] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Célia S. Bonnet
- CEA, INAC, Service de Chimie Inorganique et Biologique (UMR_E 3 CEA UJF, FRE 3200 CNRS), 38054 Grenoble, France and CEA, iRTSV, Laboratoire Chimie et Biologie des Métaux (UMR 5249 CEA CNRS UJF), F-38054 Grenoble, France
| | - Pascal H. Fries
- CEA, INAC, Service de Chimie Inorganique et Biologique (UMR_E 3 CEA UJF, FRE 3200 CNRS), 38054 Grenoble, France and CEA, iRTSV, Laboratoire Chimie et Biologie des Métaux (UMR 5249 CEA CNRS UJF), F-38054 Grenoble, France
| | - Serge Crouzy
- CEA, INAC, Service de Chimie Inorganique et Biologique (UMR_E 3 CEA UJF, FRE 3200 CNRS), 38054 Grenoble, France and CEA, iRTSV, Laboratoire Chimie et Biologie des Métaux (UMR 5249 CEA CNRS UJF), F-38054 Grenoble, France
| | - Pascale Delangle
- CEA, INAC, Service de Chimie Inorganique et Biologique (UMR_E 3 CEA UJF, FRE 3200 CNRS), 38054 Grenoble, France and CEA, iRTSV, Laboratoire Chimie et Biologie des Métaux (UMR 5249 CEA CNRS UJF), F-38054 Grenoble, France
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Henig J, Tóth É, Engelmann J, Gottschalk S, Mayer HA. Macrocyclic Gd3+ Chelates Attached to a Silsesquioxane Core as Potential Magnetic Resonance Imaging Contrast Agents: Synthesis, Physicochemical Characterization, and Stability Studies. Inorg Chem 2010; 49:6124-38. [DOI: 10.1021/ic1007395] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jörg Henig
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Éva Tóth
- Le Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans, France
| | - Jörn Engelmann
- Hochfeld-Magnetresonanz-Zentrum, Max-Planck-Institut für Biologische Kybernetik, Spemannstrasse 41, 72076 Tübingen, Germany
| | - Sven Gottschalk
- Hochfeld-Magnetresonanz-Zentrum, Max-Planck-Institut für Biologische Kybernetik, Spemannstrasse 41, 72076 Tübingen, Germany
| | - Hermann A. Mayer
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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Polášek M, Hermann P, Peters JA, Geraldes CFGC, Lukeš I. PAMAM Dendrimers Conjugated with an Uncharged Gadolinium(III) Chelate with a Fast Water Exchange: The Influence of Chelate Charge on Rotational Dynamics. Bioconjug Chem 2009; 20:2142-53. [DOI: 10.1021/bc900288q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Miloslav Polášek
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40 Prague 2, Czech Republic, Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Department of Biochemistry, Faculty of Science and Technology, Center of Neurosciences and Cell Biology, University of Coimbra, 3001-401 Coimbra, Portugal
| | - Petr Hermann
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40 Prague 2, Czech Republic, Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Department of Biochemistry, Faculty of Science and Technology, Center of Neurosciences and Cell Biology, University of Coimbra, 3001-401 Coimbra, Portugal
| | - Joop A. Peters
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40 Prague 2, Czech Republic, Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Department of Biochemistry, Faculty of Science and Technology, Center of Neurosciences and Cell Biology, University of Coimbra, 3001-401 Coimbra, Portugal
| | - Carlos F. G. C. Geraldes
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40 Prague 2, Czech Republic, Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Department of Biochemistry, Faculty of Science and Technology, Center of Neurosciences and Cell Biology, University of Coimbra, 3001-401 Coimbra, Portugal
| | - Ivan Lukeš
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40 Prague 2, Czech Republic, Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Department of Biochemistry, Faculty of Science and Technology, Center of Neurosciences and Cell Biology, University of Coimbra, 3001-401 Coimbra, Portugal
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Caravan P. Protein-targeted gadolinium-based magnetic resonance imaging (MRI) contrast agents: design and mechanism of action. Acc Chem Res 2009; 42:851-62. [PMID: 19222207 DOI: 10.1021/ar800220p] [Citation(s) in RCA: 288] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnetic resonance imaging (MRI) is a powerful medical diagnostic technique: it can penetrate deep into tissue, provide excellent soft tissue contrast with sub-millimeter resolution, and does not employ ionizing radiation. Targeted contrast agents provide an additional layer of molecular specificity to the wealth of anatomical and functional information already attainable by MRI. However, the major challenge for molecular MR imaging is sensitivity: micromolar concentrations of Gd(III) are required to cause a detectable signal change, which makes detecting proteins by MRI a challenge. Protein-targeted MRI contrast agents are bifunctional molecules comprising a protein-targeting moiety and typically one or more gadolinium chelates for detection by MRI. The ability of the contrast agent to enhance the MR image is termed relaxivity, and it depends upon many molecular factors, including protein binding itself. As in other imaging modalities, protein binding provides the pharmacokinetic effect of concentrating the agent at the region of interest. Unique to MRI, protein binding provides the pharmacodynamic effect of increasing the relaxivity of the contrast agent, thereby increasing the MR signal. In designing new agents, optimization of both the targeting function and the relaxivity is critical. In this Account, we focus on optimization of the relaxivity of targeted agents. Relaxivity depends upon speciation, chemical structure, and dynamic processes, such as water exchange kinetics and rotational tumbling rates. We describe mechanistic studies that relate these factors to the observed relaxivities and use these findings as the basis of rational design of improved agents. In addition to traditional biochemical methods to characterize ligand-protein interactions, the presence of the metal ion enables more obscure biophysical techniques, such as relaxometry and electron nuclear double resonance, to be used to elucidate the mechanism of relaxivity differences. As a case study, we explore the mechanism of action of the serum-albumin-targeted angiography agent MS-325 and closely related compounds and show how small changes in the metal chelate can impact relaxivity. We found that, while protein binding generally improves relaxivity by slowing the tumbling rate of the complex, in some cases, the protein itself can also negatively affect hydration of the metal complex and/or inner-sphere water exchange. Drawing on these findings, we designed next-generation agents targeting albumin, fibrin, or collagen and incorporating up to four gadolinium chelates. Through judicious molecular design, we show that high-relaxivity complexes with high target affinity can be realized.
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Affiliation(s)
- Peter Caravan
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, 149 Thirteenth Street, Suite 2301, Charlestown, Massachusetts 02129
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Lindgren M, Laaksonen A, Westlund PO. A theoretical spin relaxation and molecular dynamics simulation study of the Gd(H2O)93+ complex. Phys Chem Chem Phys 2009; 11:10368-76. [DOI: 10.1039/b907099k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Řehoř I, Kubíček V, Kotek J, Hermann P, Lukeš I, Száková J, Vander Elst L, Muller RN, Peters JA. 1H NMR relaxivity of aqueous suspensions of titanium dioxide nanoparticles coated with a gadolinium(III) chelate of a DOTA-monoamide with a phenylphosphonate pendant arm. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b817065g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Kubíček V, Hamplová A, Maribé L, Mameri S, Ziessel R, Tóth É, Charbonnière L. Relaxation and luminescence studies on hydrated bipyridyl- and terpyridyl-based lanthanide complexes. Dalton Trans 2009:9466-74. [DOI: 10.1039/b913084e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Dhingra K, Fousková P, Angelovski G, Maier ME, Logothetis NK, Tóth É. Towards extracellular Ca2+ sensing by MRI: synthesis and calcium-dependent 1H and 17O relaxation studies of two novel bismacrocyclic Gd3+ complexes. J Biol Inorg Chem 2008; 13:35-46. [PMID: 17874148 PMCID: PMC2757613 DOI: 10.1007/s00775-007-0296-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 08/29/2007] [Indexed: 11/08/2022]
Abstract
Two new bismacrocyclic Gd3+ chelates containing a specific Ca2+ binding site were synthesized as potential MRI contrast agents for the detection of Ca2+ concentration changes at the millimolar level in the extracellular space. In the ligands, the Ca2+-sensitive BAPTA-bisamide central part is separated from the DO3A macrocycles either by an ethylene (L1) or by a propylene (L2) unit [H4BAPTA is 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; H3DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid]. The sensitivity of the Gd3+ complexes towards Ca2+ and Mg2+ was studied by (1)H relaxometric titrations. A maximum relaxivity increase of 15 and 10% was observed upon Ca2+ binding to Gd2L1 and Gd2L2, respectively, with a distinct selectivity of Gd2L1 towards Ca2+ compared with Mg2+. For Ca2+ binding, association constants of log K = 1.9 (Gd2L1) and log K = 2.7 (Gd2L2) were determined by relaxometry. Luminescence lifetime measurements and UV-vis spectrophotometry on the corresponding Eu3+ analogues proved that the complexes exist in the form of monohydrated and nonhydrated species; Ca2+ binding in the central part of the ligand induces the formation of the monohydrated state. The increasing hydration number accounts for the relaxivity increase observed on Ca2+ addition. A 1H nuclear magnetic relaxation dispersion and 17O NMR study on Gd2L1 in the absence and in the presence of Ca2+ was performed to assess the microscopic parameters influencing relaxivity. On Ca2+ binding, the water exchange is slightly accelerated, which is likely related to the increased steric demand of the central part leading to a destabilization of the Ln-water binding interaction.
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Affiliation(s)
- Kirti Dhingra
- Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Petra Fousková
- Centre de Biophysique Moléculaire, CNRS, rue Charles Sadron, 45071 Orléans Cedex 2, France
| | - Goran Angelovski
- Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Martin E. Maier
- Institut für Organische Chemie, Universität Tübingen, Tübingen, Germany
| | - Nikos K. Logothetis
- Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Imaging Science and Biomedical Engineering, University of Manchester, Manchester, UK
| | - Éva Tóth
- Centre de Biophysique Moléculaire, CNRS, rue Charles Sadron, 45071 Orléans Cedex 2, France
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Borel A, Bean JF, Clarkson RB, Helm L, Moriggi L, Sherry AD, Woods M. Towards the rational design of MRI contrast agents: electron spin relaxation is largely unaffected by the coordination geometry of gadolinium(III)-DOTA-type complexes. Chemistry 2008; 14:2658-67. [PMID: 18283704 PMCID: PMC2750028 DOI: 10.1002/chem.200701747] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Electron-spin relaxation is one of the determining factors in the efficacy of MRI contrast agents. Of all the parameters involved in determining relaxivity it remains the least well understood, particularly as it relates to the structure of the complex. One of the reasons for the poor understanding of electron-spin relaxation is that it is closely related to the ligand-field parameters of the Gd(3+) ion that forms the basis of MRI contrast agents and these complexes generally exhibit a structural isomerism that inherently complicates the study of electron spin relaxation. We have recently shown that two DOTA-type ligands could be synthesised that, when coordinated to Gd(3+), would adopt well defined coordination geometries and are not subject to the problems of intramolecular motion of other complexes. The EPR properties of these two chelates were studied and the results examined with theory to probe their electron-spin relaxation properties.
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Affiliation(s)
- Alain Borel
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland)
- Illinois EPR Research Center, University of Illinois at Urbana-Champaign, Urbana IL 61801 (USA)
| | - Jonathan F. Bean
- Illinois EPR Research Center, University of Illinois at Urbana-Champaign, Urbana IL 61801 (USA)
| | - Robert B. Clarkson
- Illinois EPR Research Center, University of Illinois at Urbana-Champaign, Urbana IL 61801 (USA)
| | - Lothar Helm
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland)
| | - Loïck Moriggi
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland)
| | - A. Dean Sherry
- Department of Chemistry, University of Texas at Dallas, 2601 N. Floyd Road, Richardson, TX 75080 (USA), Fax: (+1) 972-883-2925
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, NE 4.2, Dallas TX 75390 (USA)
| | - Mark Woods
- Department of Chemistry, University of Texas at Dallas, 2601 N. Floyd Road, Richardson, TX 75080 (USA), Fax: (+1) 972-883-2925
- Macrocyclics, 2110 Research Row, Suite 425, Dallas, TX 75252 (USA)
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Livramento JB, Helm L, Sour A, O'Neil C, Merbach AE, Tóth É. A benzene-core trinuclear GdIIIcomplex: towards the optimization of relaxivity for MRI contrast agent applications at high magnetic field. Dalton Trans 2008:1195-202. [DOI: 10.1039/b717390c] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yazyev OV, Helm L. Nuclear Spin Relaxation Parameters of MRI Contrast Agents – Insight from Quantum Mechanical Calculations. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200701013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Oleg V. Yazyev
- Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne, and Institut Romand de Recherche Numérique en Physique des Matériaux (IRRMA), EPFL‐PPH, 1015 Lausanne, Switzerland, Fax: +41‐21‐693‐9875
| | - Lothar Helm
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, EPFL‐BCH, 1015 Lausanne, Switzerland, Fax: +41‐21‐693‐9875
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Torres S, Martins JA, André JP, Pereira GA, Kiraly R, Brücher E, Helm L, Tóth É, Geraldes CFGC. H5EPTPACH2OH: Synthesis, Relaxometric Characterization and1H NMR Spectroscopic Studies on the Solution Dynamics of Its LnIII Complexes. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200700435] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Yazyev OV, Helm L. Gadolinium (III) ion in liquid water: Structure, dynamics, and magnetic interactions from first principles. J Chem Phys 2007; 127:084506. [PMID: 17764268 DOI: 10.1063/1.2759919] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We applied first principles molecular dynamics (MD) technique to study structure, dynamics, and magnetic interactions of the Gd(3+) aqua ion dissolved in liquid water, a prototypical system for Gd-based complexes used as contrast agents for magnetic resonance imaging. The first coordination sphere contains eight water molecules with an average Gd-O distance of 2.37 A and an average geometric arrangement close to a square antiprism. The mean tilt angle of the electric dipole vector of these water molecules is theta=145 degrees . In our picosecond time scale simulation we observe no exchange event from the first coordination sphere but only fast "wagging" motions. The second coordination sphere is well pronounced though water molecules in this sphere are subjected to large amplitude dynamic motions. The isotropic hyperfine coupling constants for the inner sphere water molecules [A(iso)((17)O(I))=0.65+/-0.03 MHz, A(iso)((1)H(I))=0.085+/-0.005 MHz] are in good agreement with experimental data and with an earlier study using classical MD. Second sphere Fermi contact hyperfine coupling constants calculated are more than one order of magnitude smaller and of opposite sign as those of the first coordination sphere. The effect of spin polarization induced by the paramagnetic Gd(3+) ion on the dipolar hyperfine interaction was found to be sizable only for the (17)O nuclei of inner sphere water molecules and has a screening character.
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Affiliation(s)
- Oleg V Yazyev
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
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Gianolio E, Giovenzana GB, Longo D, Longo I, Menegotto I, Aime S. Relaxometric and Modelling Studies of the Binding of a Lipophilic Gd-AAZTA Complex to Fatted and Defatted Human Serum Albumin. Chemistry 2007; 13:5785-97. [PMID: 17407109 DOI: 10.1002/chem.200601277] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A new lipophilic gadolinium chelate consisting of a long aliphatic chain bound to the AAZTA coordination cage (Gd-AAZTAC17) has been synthesised. It possesses two coordinated water molecules (q=2) in fast exchange with the solvent (tau298(M) = 67 ns), which yields a relaxivity of 10.2 mM(-1) s(-1). At concentrations greater than 0.1 mM, it forms micelles (average diameter 5.5 nm) characterised by a relaxivity of approximately 30 mM(-1) s(-1) at 20 MHz and 298 K. The latter value appears to be "quenched" by magnetic interactions among the Gd(III) ions on the surface of the micelle that cause a decrease in the electronic relaxation time. A relaxivity of 41 mM(-1) s(-1) was recorded for this micellar system when 98 % of the Gd(III) ions were replaced by diamagnetic Y(III). Gd-AAZTAC17 exhibits a better affinity for fatted human serum albumin (HSA) than for defatted HSA, whereas the relaxivities of the supramolecular adducts are reversed. The relaxivity shown by Gd-AAZTAC17/defatted HSA ({r b(1) (20 MHz, 298 K)=84 mM(-1) s(-1)) is by far the highest relaxivity reported so far for non-covalent paramagnetic adducts with slow-moving substrates. As shown by molecular docking calculations, the gadolinium complex enters a hydrophobic pocket present in fatted HSA more extensively than the corresponding adduct with defatted HSA. Interestingly, no marked difference was observed in either the relaxation enhancement or the binding affinity between fatted and defatted HSA when the binding titrations were carried out at a Gd-AAZTAC17 concentration higher than its critical micellar concentration (cmc). This behaviour has been attributed to the formation of an association between the negatively charged micelle of the lipophilic metal complexes and the positive residues on the surface of the protein.
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Affiliation(s)
- Eliana Gianolio
- Dipartimento di Chimica I.F.M. e Centro di eccellenza per l'Imaging Molecolare, Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino, Italy
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Lebdusková P, Hermann P, Helm L, Tóth E, Kotek J, Binnemans K, Rudovský J, Lukes I, Merbach AE. Gadolinium(III) complexes of mono- and diethyl esters of monophosphonic acid analogue of DOTA as potential MRI contrast agents: solution structures and relaxometric studies. Dalton Trans 2006:493-501. [PMID: 17213936 DOI: 10.1039/b612876a] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two new macrocyclic DOTA-like chelates containing one phosphonate pendant arm were synthesised as potential contrast agents for MRI (magnetic resonance imaging). The chelates bind to the lanthanide(III) in an octadentate manner, via four nitrogen atoms, three carboxylate and one phosphonate oxygen atoms. Solution structures of [Ln(do3ap(OEt2))(H(2)O)] and [Ln(do3ap(OEt))(H(2)O)](-) were studied using (31)P and (1)H NMR spectroscopy and SAP (square-antiprismatic)/TSAP (twisted square-antiprismatic) isomerism was observed. Depending on the nature of the lanthanide(III) ion, the lanthanide(III) complexes of H(4)do3ap(OEt) are present in solution as up to four different diastereoisomers observable with NMR. The TSAP isomer is the most abundant at the beginning of the lanthanide series and, with a decrease of the ionic radius of lanthanide(III) ions, both TSAP and SAP forms were observed. A second interconversion (SAP<-->TSAP') becomes important at the end of the series (TSAP' means the TSAP species without a coordinated water molecule). The remaining axial coordination site is occupied by one water molecule for the Gd(3+)-complex. The calculated fraction of the TSAP isomer in the gadolinium(III) complexes increases in the order [Gd(DOTA)(H(2)O)](-) < [Gd(do3ap(OEt2))(H(2)O)] < [Gd(do3ap(OEt))(H(2)O)](-) < [Gd(do3ap)(H(2)O)](2-). Gadolinium(III) complexes of phosphorus-containing chelates, generally, have the advantage of a relatively fast water exchange rate due to a greater sterical demand of the phosphorus acid moiety and of the presence of the second-sphere water shell, which also contributes to the overall relaxivity. The [Gd(do3ap(OEt2))(H(2)O)] and [Gd(do3ap(OEt))(H(2)O)](-) complexes were studied by variable-temperature (17)O NMR and (1)H NMRD. The experimental data were evaluated simultaneously with commonly used equations based on Solomon-Bloembergen-Morgan approximation, extended by a contribution of the second coordination sphere. The water exchange rates were found to be strongly dependent on the TSAP/SAP isomeric ratio and the overall charge of the complex: the monoanionic [Gd(do3ap(OEt))(H(2)O)](-) complex with TSAP molar fraction equal to 0.36 has the water exchange rate of 20 x 10(6) s(-1) (tau(M) = 50 ns) while neutral [Gd(do3ap(OEt2))(H(2)O)] complex with TSAP molar fraction 0.28 has an exchange rate equal to 4.4 x 10(6) s(-1) (tau(M) = 227 ns).
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Affiliation(s)
- Petra Lebdusková
- Department of Inorganic Chemistry, Charles University, Hlavova 2030, 12840, Prague, Czech Republic
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Balogh E, Mato-Iglesias M, Platas-Iglesias C, Tóth E, Djanashvili K, Peters JA, de Blas A, Rodríguez-Blas T. Pyridine- and Phosphonate-Containing Ligands for Stable Ln Complexation. Extremely Fast Water Exchange on the GdIII Chelates. Inorg Chem 2006; 45:8719-28. [PMID: 17029383 DOI: 10.1021/ic0604157] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two novel ligands containing pyridine units and phosphonate pendant arms, with ethane-1,2-diamine (L2) or cyclohexane-1,2-diamine (L3) backbones, have been synthesized for Ln complexation. The hydration numbers obtained from luminescence lifetime measurements in aqueous solutions of the Eu(III) and Tb(III) complexes are q = 0.6 (EuL2), 0.7 (TbL2), 0.8 (EuL3), and 0.4 (TbL3). To further assess the hydration equilibrium, we have performed a variable-temperature and -pressure UV-vis spectrophotometric study on the Eu(III) complexes. The reaction enthalpy, entropy, and volume for the hydration equilibrium EuL <--> EuL(H2O) were calculated to be DeltaH degrees = -(11.6 +/- 2) kJ mol(-1), DeltaS degrees = -(34.2 +/- 5) J mol(-1) K(-1), and = 1.8 +/- 0.3 for EuL2 and DeltaH degrees = -(13.5 +/- 1) kJ mol(-1), DeltaS degrees = -(41 +/- 4) J mol(-1) K(-1), and = 1.7 +/- 0.3 for EuL3, respectively. We have carried out variable-temperature 17O NMR and nuclear magnetic relaxation dispersion (NMRD) measurements on the GdL2(H2O)q and GdL3(H2O)q systems. Given the presence of phosphonate groups in the ligand backbone, a second-sphere relaxation mechanism has been included for the analysis of the longitudinal (17)O and (1)H NMR relaxation rates. The water exchange rate on GdL2(H2O)q, = (7.0 +/- 0.8) x 10(8) s(-1), is extremely high and comparable to that on the Gd(III) aqua ion, while it is slightly reduced for GdL3(H2O)q, = (1.5 +/- 0.1) x 10(8) s(-1). This fast exchange can be rationalized in terms of a very flexible inner coordination sphere, which is slightly rigidified for L3 by the introduction of the cyclohexyl group on the amine backbone. The water exchange proceeds via a dissociative interchange mechanism, evidenced by the positive activation volumes obtained from variable-pressure 17O NMR for both GdL2(H2O)q and GdL3(H2O)q (DeltaV = +8.3 +/- 1.0 and 8.7 +/- 1.0 cm(3) mol(-1), respectively).
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Affiliation(s)
- Edina Balogh
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, BCH, CH-1015 Lausanne, Switzerland
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44
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Yazyev OV, Helm L. O17 nuclear quadrupole coupling constants of water bound to a metal ion: A gadolinium(III) case study. J Chem Phys 2006; 125:054503. [PMID: 16942222 DOI: 10.1063/1.2217950] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Rotational correlation times of metal ion aqua complexes can be determined from 17O NMR relaxation rates if the quadrupole coupling constant of the bound water oxygen-17 nucleus is known. The rotational correlation time is an important parameter for the efficiency of Gd3+ complexes as magnetic resonance imaging contrast agents. Using a combination of density functional theory with classical and Car-Parrinello molecular dynamics simulations we performed a computational study of the 17O quadrupole coupling constants in model aqua ions and the [Gd(DOTA)(H2O)]- complex used in clinical diagnostics. For the inner sphere water molecule in the [Gd(DOTA)(H2O)]- complex the determined quadrupole coupling parameter chi square root of (1 + eta2/3) of 8.7 MHz is very similar to that of the liquid water (9.0 MHz). Very close values were also predicted for the the homoleptic aqua ions of Gd3+ and Ca2+. We conclude that the 17O quadrupole coupling parameters of water molecules coordinated to closed shell and lanthanide metal ions are similar to water molecules in the liquid state.
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Affiliation(s)
- Oleg V Yazyev
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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45
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Lebdusková P, Sour A, Helm L, Tóth E, Kotek J, Lukes I, Merbach AE. Phosphinic derivative of DTPA conjugated to a G5 PAMAM dendrimer: an 17O and 1H relaxation study of its Gd(III) complex. Dalton Trans 2006:3399-406. [PMID: 16832488 DOI: 10.1039/b517847a] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A DTPA-based chelate containing one phosphinate group was conjugated to a generation 5 polyamidoamine (PAMAM) dendrimer via a benzylthiourea linkage. The Gd(III) complex of this novel conjugate has potential as a contrast agent for magnetic resonance imaging (MRI). The chelates bind Gd3+via three nitrogen atoms, four carboxylates and one phosphinate oxygen, and one water molecule completes the inner coordination sphere. The monomer Gd(III) chelates bearing nitrobenzyl and aminobenzyl groups ([Gd(DTTAP-bz-NO2)(H2O)]2- and [Gd(DTTAP-bz-NH2)(H2O)]2-) as well as the dendrimeric Gd(III) complex G5-(Gd(DTTAP))63) were studied by multiple-field, variable temperature 17O and 1H NMR. The rate of water exchange is faster than that of [Gd(DTPA)(H2O)]2- and very similar on the two monomeric complexes (8.9 and 8.3 x 10(6) s-1 for [Gd(DTTAP-bz-NO2)(H2O)]2- and [Gd(DTTAP-bz-NH2)(H2O)]2-, respectively), while it is decreased on the dendrimeric conjugate (5.0 x 10(6) s-1). The Gd(III) complex of the dendrimer conjugate has a relaxivity of 26.8 mM-1 s-1 at 37 degrees C and 0.47 T (corresponding to 1H Larmor frequency of 20 MHz). Given the contribution of the second sphere water molecules to the overall relaxivity, this value is slightly higher than those reported for similar size dendrimers. The experimental 17O and 1H NMR data were fitted to the Solomon-Bloembergen-Morgan equations extended with a contribution from second coordination sphere water molecules. The rotational dynamics of the dendrimeric conjugate was described in terms of global and local motions with the Lipari-Szabo approach.
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Affiliation(s)
- Petra Lebdusková
- Department of Inorganic Chemistry, Charles University, Hlavova 2030, 12840 Prague, Czech Republic
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46
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Livramento JB, Sour A, Borel A, Merbach AE, Tóth E. A Starburst-Shaped Heterometallic Compound Incorporating Six Densely Packed Gd3+ Ions. Chemistry 2006; 12:989-1003. [PMID: 16311990 DOI: 10.1002/chem.200500969] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The heterotritopic ligand [bpy(DTTA)2]8- has two diethylenediamine-tetraacetate units for selective lanthanide(III) coordination and one bipyridine function for selective Fe(II) coordination. In aqueous solution and in the presence of these metals, the ligand is capable of self-assembly to form a rigid supramolecular metallostar structure, [Fe[Gd2bpy(DTTA)2(H2O)4]3]4-. We report here the physicochemical characterization of the dinuclear complex [Gd2bpy(DTTA)2(H2O)4]2- and the metallostar [Fe[Gd2bpy(DTTA)2(H2O)4]3]4- with regard to potential MRI contrast agent applications. A combination of pH potentiometry and 1H NMR spectroscopy has been used to determine protonation constants for the ligand [bpy(DTTA)2]8- and for the complexes [Fe[bpy(DTTA)2]3]22- and [Y2bpy(DTTA)2]2-. In addition, stability constants have been measured for the dinuclear chelates [M2bpy(DTTA)2]n- formed with M = Gd3+ and Zn2+ (log K(GdL) = 18.2; log K(ZnL) = 18.0; log K(ZnHL) = 3.4). A multiple field, variable-temperature 17O NMR and proton relaxivity study on [Gd2bpy(DTTA)2(H2O)4]2- and [Fe[Gd2bpy(DTTA)2(H2O)4]3](4-) yielded the parameters for water exchange and the rotational dynamics. The 17O chemical shifts are indicative of bishydration of the lanthanide ion. The exchange rates of the two inner-sphere water molecules are very similar in the dinuclear [Gd2bpy(DTTA)2(H2O)(4)]2- and in the metallostar (k(ex)298 = 8.1 +/- 0.3 x 10(6) and 7.4 +/- 0.2 x 10(6) s(-1), respectively), and are comparable to k(ex)298 for similar Gd(III) poly(amino carboxylates). The rotational dynamics of the metallostar has been described by means of the Lipari-Szabo approach, which involves separating global and local motions. The difference between the local and global rotational correlation times, tau(lO)298 = 190 +/- 15 ps and tau(gO)298 = 930 +/- 50 ps, respectively, shows that the metallostar is not completely rigid. However, the relatively high value of S2 = 0.60 +/- 0.04, describing the restriction of the local motions with regard to the global one, points to a limited flexibility compared with previously reported macromolecules such as dendrimers. As a result of the two inner-sphere water molecules, with their near-optimal exchange rate, and the limited flexibility, the metallostar has a remarkable molar proton relaxivity, particularly at high magnetic fields (r1 = 33.2 and 16.4 mM(-1) s(-1) at 60 and 200 MHz, respectively, at 25 degrees C). It packs six efficiently relaxing Gd(III) ions into a small molecular space, which leads, to the best of our knowledge, to the highest relaxivity per molecular mass ever reported for a Gd(III) complex. The [bpy(DTTA)2]8- ligand is also a prime candidate as a terminal ligand for constructing larger sized, Fe(II) (or Ru(II))-based metallostars or metallodendrimers loaded with Gd(III) on the surface.
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Affiliation(s)
- João Bruno Livramento
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, 1015 Lausanne, Switzerland
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47
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Torres S, Martins JA, André JP, Geraldes CFGC, Merbach AE, Tóth E. Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate. Chemistry 2006; 12:940-8. [PMID: 16224764 DOI: 10.1002/chem.200500551] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report the synthesis and characterization of the novel ligand H(5)EPTPA-C(16) ((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the Gd(III) ion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kappa(ex)) on the Gd(III) complex owing to steric compression around the water-binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles with a long tumbling time (tau(R)) in aqueous solution. The critical micelle concentration (cmc = 0.34 mM) of the amphiphilic [Gd(eptpa-C(16))(H(2)O)](2-) chelate was determined by variable-concentration proton relaxivity measurements. A global analysis of the data obtained in variable-temperature and multiple-field (17)O NMR and (1)H NMRD measurements allowed for the determination of parameters governing relaxivity for [Gd(eptpa-C(16))(H(2)O)](2-); this is the first time that paramagnetic micelles with optimized water exchange have been investigated. The water exchange rate was found to be kappa(298)(ex) = 1.7 x 10(8) s(-1), very similar to that previously reported for the nitrobenzyl derivative [Gd(eptpa-bz-NO(2))(H(2)O)](2-) kappa(298)(ex) = 1.5 x 10(8) s(-1)). The rotational dynamics of the micelles were analysed by using the Lipari-Szabo approach. The micelles formed in aqueous solution show considerable flexibility, with a local rotational correlation time of tau(298)(l0) = 330 ps for the Gd(III) segments, which is much shorter than the global rotational correlation time of the supramolecular aggregates, tau(298)(g0) = 2100 ps. This internal flexibility of the micelles is responsible for the limited increase of the proton relaxivity observed on micelle formation (r(1) = 22.59 mM(-1) s(-1) for the micelles versus 9.11 mM(-1) s(-1) for the monomer chelate (20 MHz; 25 degrees C)).
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Affiliation(s)
- Susana Torres
- Centro de Química, Campus de Gualtar, Universidade do Minho, Braga, Portugal
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48
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Burai L, Tóth E, Bazin H, Benmelouka M, Jászberényi Z, Helm L, Merbach AE. Positively charged GdIIIcryptates: slow, associative water exchange. Dalton Trans 2006:629-34. [PMID: 16402151 DOI: 10.1039/b506700f] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combined variable-temperature and multiple field 17O NMR, EPR and NMRD study has been performed for the first time on gadolinium(III) complexes of cryptand ligands, L1 and L2, where L1 contains three 2,2'-bipyridine units ([bpy.bpy.bpy]) and L2 is the disubstituted methyl ester derivative of L1. The experimental data have been analysed in a simultaneous fit in order to determine parameters for water exchange, rotational dynamics and electronic relaxation for both complexes. The cryptates have three water molecules in the inner sphere which exchange with a rate of k(ex)298 = 1.8 x 10(6) s(-1) and 0.97 x 10(6) s(-1) for [GdL1(H2O)3]3+ and [GdL2(H2O)3)]3+, respectively. The k(ex)298 values obtained for these positively charged cryptates are smaller than those of the negatively charged Gd-poly(amino carboxylate) complexes. The water exchange mechanism was assessed for [GdL2(H2O)3]3+ by variable-pressure 17O NMR relaxation measurements. Based on the activation volume, DeltaV++ = -2.5 cm3 mol(-1), the water exchange is an associative interchange process. The proton relaxivities, r1, of the cryptate complexes are 9.79 mM(-1) s(-1) for [GdL1(H2O)3]3+ and 11.18 mM(-1) s(-1) for [GdL2(H2O)3]3+ (298 K, 20 MHz), which, due to the presence of three inner sphere water molecules, represent much higher values than those obtained for Gd3+ poly(amino carboxylate) complexes of similar molecular weight.
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Affiliation(s)
- László Burai
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, ISIC, BCH, CH-1015, Lausanne, Switzerland
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49
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Costa J, Ruloff R, Burai L, Helm L, Merbach AE. Rigid MIIL2Gd2III (M = Fe, Ru) complexes of a terpyridine-based heteroditopic chelate: a class of candidates for MRI contrast agents. J Am Chem Soc 2005; 127:5147-57. [PMID: 15810849 DOI: 10.1021/ja0424169] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rigid chelates of high-molecular weight, [M(tpy-DTTA)2]6- (M = Fe, Ru), are obtained upon self-assembly around one M(II) ion of two terpyridine-based molecules substituted in the 4'-position with the polyaminocarboxylate diethylenetriamine-N,N,N'',N''-tetraacetate, tpy-DTTA4-. The protonation constants of tpy-DTTA4- (log K1 = 8.65(4), log K2 = 7.63(4), log K3 = 5.25(6), log K4 = 3.30(7)) and [Fe(tpy-DTTA)2]6- (log K1 = 8.40(4), log K2 = 7.26(4)) have been determined by potentiometry, 1H NMR and UV-vis titrations. The thermodynamic stability constant log K(GdL) of [Fe(tpy-DTTA)2Gd2(H2O)4] measured at 25 degrees C by potentiometry is 10.87. This relatively low value is due to the direct linkage of the polyaminocarboxylate part to the electron-withdrawing terpyridine. UV-vis absorbance spectra of [M(tpy-DTTA)2Gd2(H2O)4] and 1H NMR spectra of [M(tpy-DTTA)2Eu2(H2O)4] revealed similar solution behavior of the Fe and Ru complexes. An I(d) water-exchange mechanism (DeltaV++ = +6.8 +/- 1 cm3 mol(-1)) with a rate constant of k(ex)298 = (5.1 +/- 0.3) x 10(6) s(-1) has been found for [Fe(tpy-DTTA)2Gd2(H2O)4] by 17O NMR. A slow rotational correlation time (tau(RO) = 410 +/- 10 ps) and the presence of two water molecules (q = 2) in the coordination inner-sphere of each Gd(III) ion have also been determined for this complex. A remarkably high relaxivity has been observed for both [M(tpy-DTTA)2Gd2(H2O)4] complexes (at 20 MHz and 37 degrees C, r(1) = 15.7 mM(-1) s(-1) for the Fe complex, and r(1) = 15.6 mM(-1) s(-1) for the Ru complex).
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Affiliation(s)
- Jérôme Costa
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Chimie Inorganique et Bioinorganique, EPFL-BCH, CH-1015 Lausanne, Switzerland
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50
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Costa J, Tóth E, Helm L, Merbach AE. Dinuclear, Bishydrated GdIII Polyaminocarboxylates with a Rigid Xylene Core Display Remarkable Proton Relaxivities. Inorg Chem 2005; 44:4747-55. [PMID: 15962983 DOI: 10.1021/ic0500309] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two novel dinuclear Gd(III) complexes have been synthesized, based on a xylene core substituted with diethylenetriamine-N,N,N'',N''-tetraacetate (DTTA) chelators in para or meta position. The complexes [Gd2(pX(DTTA)2)(H2O)4]2- and [Gd2(mX(DTTA)2)(H2O)4]2- both exhibit high complex stability (log K(GdL) = 19.1 and 17.0, respectively), and a good selectivity for Gd(III) against Zn(II), the most abundant endogenous metal ion (log K(ZnL) = 17.94 and 16.19). The water exchange rate is identical within experimental error for the two isomers: k(ex)298 = (9.0 +/- 0.4) x 10(6) s(-1) for [Gd2(pX(DTTA)2)(H2O)4]2- and (8.9 +/- 0.5) x 10(6) s(-1) for [Gd2(mX(DTTA)2)(H2O)4]2-. It is very similar to the k(ex)298 of the structural analogue, bishydrated [Gd(TTAHA)(H2O)2]3-, and about twice as high as that of the monohydrated [Gd(DTPA)(H2O)]2- (TTAHA(6-) = N-tris(2-aminoethyl)amine-N',N',N'',N'',N''',N'''-hexaacetate; DTPA(5-) = diethylenetriamine-N,N,N',N'',N''-pentaacetate). This relatively fast water exchange can be related to the presence of two inner sphere water molecules which decrease the stereorigidity of the inner sphere thus facilitating the water exchange process. At all frequencies, the water proton relaxivities (r1 = 16.79 and 15.84 mM(-1) s(-1) for the para and meta isomers, respectively; 25 degrees C and 20 MHz) are remarkably higher for the two dinuclear chelates than those of mononuclear commercial contrast agents or previously reported dinuclear Gd(III) complexes. This is mainly the consequence of the two inner-sphere water molecules. In addition, the increased molecular size as compared to monomeric compounds associated with the rigid xylene linker between the two Gd(III) chelating subunits also contributes to an increased relaxivity. However, proton relaxivity is still limited by fast molecular motions which also hinder any beneficial effect of the increased water exchange rate.
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Affiliation(s)
- Jérôme Costa
- Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Chimie Inorganique et Bioinorganique, EPFL-BCH, CH-1015 Lausanne, Switzerland
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