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L. Tei,
G. Mazooz,
Y. Shellef,
R. Avni,
K. Vandoorne,
A. Barge,
V. Kalchenko,
M. W. Dewhirst,
L. Chaabane,
L. Miragoli,
D. Longo,
M. Neeman, S. Aime
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L. Tei,
G. Mazooz,
Y. Shellef,
R. Avni,
K. Vandoorne,
A. Barge,
V. Kalchenko,
M. W. Dewhirst,
L. Chaabane,
L. Miragoli,
D. Longo,
M. Neeman, S. Aime
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ABSTRACT: Accurate measurement of the tissue pH in vivo by MRI may be of clinical value for both diagnosis and selection/monitoring of therapy. To act as pH reporters, MRI contrast agents have to provide responsiveness to pH that does not require prior knowledge of the actual concentration of the contrast agent. This work deals with the use of a paramagnetic gadolinium(III) complex, loaded into liposomes, whose relaxometric properties are affected by the pH of the medium. In this system, the amphiphilic metal complex, which contains a moiety whose protonation changes the coordination properties of the metal chelate, experiences a different intraliposomial distribution depending on the pH conditions. The pH of the solution can be unambiguously identified by exploiting the peculiar characteristics of the resulting NMRD profiles, and a ratiometric pH-responsive method has been set up by comparing the relaxation enhancement at different magnetic field strengths.
Inorganic Chemistry 06/2012; 51(13):7210-7. · 4.60 Impact Factor
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L. Tei,
G. Mazooz,
Y. Shellef,
R. Avni,
K. Vandoorne,
A. Barge,
V. Kalchenko,
M. W. Dewhirst,
L. Chaabane,
L. Miragoli,
D. Longo,
M. Neeman, S. Aime
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ABSTRACT: Transglutaminases, including factor XIII and tissue transglutaminase, participate in multiple extracellular processes associated with remodeling of the extracellular matrix during wound repair, blood clotting, tumor progression and fibrosis of ischemic injuries. The aim of this work was to evaluate a novel substrate analog for transglutaminase optimized by molecular modeling calculations (DCCP16), which can serve for molecular imaging of transglutaminase activity by magnetic resonance imaging and by near-infrared imaging. Experimental data showed covalent binding of Gd-DCCP16 and DCCP16-IRIS Blue to human clots, to basement membrane components and to casein in purified systems as well as in three-dimensional multicellular spheroids. In vivo, DCCP16 showed enhancement with a prolonged retention in clots and tumors, demonstrating the ability to detect both factor XIII and tissue transglutaminase mediated covalent binding of the contrast material. Copyright (C) 2010 John Wiley & Sons, Ltd.
Contrast Media & Molecular Imaging. 01/2010; 5(4):213-222.
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ABSTRACT: The role of MRI in the armory of diagnostic modalities for the medicine of the forthcoming years largely depends on how chemistry will provide advanced tools to meet the medical needs. This review aims at outlining the most innovative approaches that have been undertaken in the recent history of MRI contrast agents for tackling the challenges of sensitivity and specificity required by the new generation of contrast agents that should allow the visualization of pathological processes occurring on cellular and molecular scale (the so-called Molecular Imaging). Most of the classes of MRI agents clinically approved or currently under investigation in a preclinical phase exploit peculiar magnetic properties of metals. The conventional agents acting as T(1) or T(2)/T(2)* relaxation enhancers are primarily based on the paramagnetic or the superparamagnetic properties of Gd(III)-, Mn(II)- and iron oxides systems. Recently, there has been a renewed interest towards paramagnetic lanthanide complexes with an anisotropic electronic configuration thanks to their ability to induce strong effect on the resonance frequency of the spins dipolarly coupled with them. Such systems, formerly mainly used as shift reagents, have now attracted much attention in the emerging field of Chemical Exchange Saturation Transfer (CEST) MRI agents.
Current Medicinal Chemistry 01/2010; 17(31):3684-700. · 4.86 Impact Factor
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The quarterly journal of nuclear medicine and molecular imaging: official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of... 12/2009; 53(6):563-4.
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ABSTRACT: The strong signal enhancement attainable by hyperpolarization methods has allowed the detection of heteronuclei in magnetic resonance imaging (MRI), allowing to obtain high quality images with very high signal to noise ratios in few seconds. The four methods to produce hyperpolarized molecules, i.e. the "brute force" approach, optical pumping of noble gases, parahydrogen induced polarization (PHIP) and dynamic nuclear polarization (DNP), are reported. The applications of hyperpolarized probes to MRI range from vascular imaging to interventional imaging and perfusion studies, up to the emerging and challenging field of molecular/metabolic imaging. In fact, the high signal intensities achievable by using hyperpolarized molecules make it possible to detect and image the metabolic products formed upon the administration of the hyperpolarized agent. The most striking examples are surveyed, including the use of hyperpolarized 13C-pyruvate in tumor diagnosis and stadiation, and in myocardium perfusion and activity studies, as well as the recently reported proposal of using 13C-bicarbonate as agent for pH-mapping in vivo.
The quarterly journal of nuclear medicine and molecular imaging: official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of... 12/2009; 53(6):604-17.
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ABSTRACT: Chemical exchange saturation transfer (CEST) imaging is an emerging MRI technique relying on the use of endogenous or exogenous molecules containing exchangeable proton pools. The heterogeneity of the water resonance frequency offset plays a key role in the occurrence of artifacts in CEST-MR images. To limit this drawback, a new smoothing-splines-based method for fitting and correcting Z-spectra in order to compensate for low signal-to-noise ratio (SNR) without any a priori model was developed. Global and local voxel-by-voxel Z-spectra were interpolated by smoothing splines with smoothing terms aimed at suppressing noise. Thus, a map of the water frequency offset ('zero' map) was used to correctly calculate the saturation transfer (ST) for each voxel. Simulations were performed to compare the method to polynomials and zero-only-corrected splines on the basis of SNR improvement. In vitro acquisitions of capillaries containing solutions of LIPOCEST agents at different concentrations were performed to experimentally validate the results from simulations. Additionally, ex vivo investigations of bovine muscle mass injected with LIPOCEST agents were performed as a function of increasing pulse power. The results from simulations and experiments highlighted the importance of a proper 'zero' correction (15% decrease of fictitious CEST signal in phantoms and ex vivo preparations) and proved the method to be more accurate compared with the previously published ones, often providing a SNR higher than 5 in different simulated and experimentally noisy conditions. In conclusion, the proposed method offers an accurate tool in CEST investigation.
Contrast Media & Molecular Imaging 09/2008; 3(4):136-49. · 3.33 Impact Factor
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ABSTRACT: A novel, efficient, and rapid synthesis of the 6-aminoperhydro- 1,4-diazepine scaffold is reported. It was promoted by microwave or sequential ultrasound/microwave irradiation under solvent-free conditions or in solution. Protected ethylenediamine derivatives and N-Boc-serinol dimesylate underwent rapid cyclization to give 6-aminoperhydro- 1,4-diazepine derivatives in excellent yields and with high selectivity, whereas the same reaction failed or gave negligible yields under conventional heating. Cesium or potassium ions catalyzed the ring closure by coordinating the sulfonamide groups. All relevant work reported to date in the literature mostly concern about the syntheses of either 1H-tetrahydro- 1,4-diazepine-2,5-dione or substituted 1,4-benzodiazepines, while the few published procedures for the preparation of 6-aminoperhydro-1,4-diazepines involved several steps, required long reaction times and afforded low yields. By the present method, access to 6-aminoperhydro- 1,4-diazepines becomes much easier and faster.
Synthesis-Stuttgart. 01/2008;
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ABSTRACT: C-(2-Benzyloxy)-ethyl-C'-N-tert-butoxycarbonyl-aminomethyl-o-carborane (8), a potentially useful intermediate for BNCT, has been synthesised. This intermediate can be readily functionalised with several biological vectors and MRI contrast agents. In this work intermediate 8 has been functionalised with a palmityl chain for lipophilic targeting and with Gd(III)-DOTAMA-C-6-NH2 as MRI detector. This combination yielded Gd(III)-C-palmitamidomethyl-C'-DOTAMA-C-6-o-carborane (14) as a dual MRI-BNCT agent.
Organic & Biomolecular Chemistry. 01/2008; 6(23):4460-4466.
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Polyhedron 01/2008; 27:3683-3687. · 2.06 Impact Factor
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ABSTRACT: The Gd(III) complexes of three new octadentate chelators, prepared by substitution of four, two, and one carboxylate groups of EGTA with phosphonate groups, have been investigated by H-1 and O-17 NMR relaxometric techniques in aqueous solutions. The analysis of the solvent proton relaxivity data as a function of pH, temperature, and magnetic field strength (nuclear magnetic relaxation dispersion (NMRD) profiles) in combination with the O-17 transverse relaxation rate data at variable temperature allowed assessing the hydration state of the complexes, the occurrence of pH-dependent oligomerization processes for the tetra phosphonate derivative, the presence of a well-defined second sphere of hydration that markedly contributes to the relaxivity, and the values of the structural and dynamic relaxation parameters. In addition, in the case of the monophosphonate derivative the presence of a coordinated water molecule has allowed evaluation of the kinetic parameters of the exchange process, highly relevant for the possible use of this Gd(III) complex as an MRI probe. The rate of exchange of the water molecule, (298)k(ex) = 4.2 x 10(8)s(-1), is one of the highest measured so far for a nonacoordinate Gd(III) chelate and optimal for developing contrast-enhancing probes of high efficacy at high magnetic fields. Copyright (C) 2008 John Wiley & Sons, Ltd.
Magnetic Resonance in Chemistry. 01/2008; 46:S86-S93.
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Multiple Sclerosis. 01/2007; 13:S71-S71.
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01/2007: pages 37 - 59;
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ABSTRACT: It has been shown that insoluble Gd chelates are suitable MRI contrast agents for conditional activation by intracellular lipases. The DTPA-based, insoluble, inactive contrast agent was internalized into dendritic cells by phagocytosis. Cleavage of long aliphatic side chains by intracellular lipase activity leads to the contrast agents solubility and hereby its activation depending on the enzyme expression. Uptake and activation of the contrast agent was much reduced in Flt3+ CD11b+ progenitor cells. Detectability limits in the T(1)-weighted MR images were estimated in phantoms and in vivo in the rat brain. Marginal toxic effects were only observed at very high concentrations of the contrast agent. The chelate can easily be modified to be targeted by enzymes expressed during specific change of cell status like activation or differentiation. Such a system is suitable for functional cellular in vivo MR imaging.
NeuroImage 10/2006; 32(3):1142-9. · 5.89 Impact Factor
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ABSTRACT: MR-labeling of cells may be carried out by adding a Gd-based contrast agent to the incubation media. The amount of gadolinium internalized in HTC and C6 cells upon incubation with Gd-DTPA-BMA is circa one order of magnitude higher than those found with Gd-DTPA, Gd-DOTA and Gd-HPDO3A, respectively. The comparison of relaxometric and mass spectrometry determinations allows us to establish that only a minor fraction of intact Gd-DTPA-BMA is internalized into the cells. Moreover the binding/uptake behavior shown by Gd-DTPA-BMA resembles that found when GdCl(3) is added to the incubation medium. We suggest that the lower stability of Gd-DTPA-BMA is responsible for a shift in the dissociation equilibrium that results in the net transfer of Gd(3+) ions on the cell membrane followed by a slower internalization process. The transmetallation process is mediated by components of the incubation media, among which a dominant role is represented by phosphate anions. The uptake of Gd(3+) ions is clearly reflected in the drastic decrease of cell viability observed for cells labeled with Gd-DTPA-BMA.
Contrast Media & Molecular Imaging 02/2006; 1(1):23-9. · 3.33 Impact Factor
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Ernst Schering Research Foundation workshop 02/2005;
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ABSTRACT: The low sensitivity is the major disadvantage of MRI as compared to PET. Therefore, amplification strategies are necessary for specific pathway labeling. This survey is aimed at exploring different routes to the entrapment of Gd(III) chelates in various type of cells at amounts sufficiently large to allow MRI visualization. Namely, the obtained results have been summarized in terms of internalization via i) pinocytosis; ii) phagocytosis; iii) receptors; iv) receptor mediated endocytosis; v) transporters; vi) transmembrane carrier peptides. MRI visualization of cells appears possible when the number of internalized Gd(III) chelates is of the order of 10(7)-10(8)/cell. Pinocytosis shows to be particularly useful for labeling cells that can be incubated for several hours in the presence of high concentrations of Gd-agent. This approach appears very effective for labeling stem cells. Nanoparticles filled with Gd-chelates can be used for an efficient loading of cells endowed with a good phagocytic activity. Entrapment via receptors most often results in receptor mediated endocytosis. Suitably functionalized monomeric and multimeric Gd-chelates can be considered for being internalized by this route as well as supramolecular systems such as those formed between Avidin and biotinylated Gd-complexes. Exploitation of up-regulated transporters of nutrients in tumor cells appears to be a promising route for their differentiation from healthy cells. Finally, properly designed systems entering the cells by means of penetrin-like peptides deserve great attention.
Current Pharmaceutical Biotechnology 01/2005; 5(6):509-18. · 2.81 Impact Factor
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ABSTRACT: It was early shown that the macrocyclic Ln(DOTA) complexes (DOTA = 1,4,7,10-tetra-azacyclododecane-N,N',N' ',N' "-tetraacetic acid) exists in solution as a mixture of two enantiomeric pairs of diastereoisomers differing in the ligand conformation, namely, square antiprismatic (SA) and twisted square antiprismatic (TSA) geometries, respectively. Later, extensive (1)H NMR investigations suggested that a coordination change may be superimposed on this conformational equilibrium involving two additional structures in which the metal ion possesses a coordination number of eight (CN 8). It was predicted that these two species, lacking the apical coordinated water molecule, would maintain the SA and TSA coordination geometries, and therefore, they have been labeled as SA' and TSA', respectively. In this work we report the X-ray solid-state crystal structure determination of six Ln(DOTA) complexes representative of all four coordination geometry typologies deduced from NMR solution studies. A distinctive structural feature that discriminates SA (and SA') and TSA (and TSA') structures is represented by the twist angle between the two square planes of the antiprism, the basal four nitrogen, and the apical four oxygen planes. [Ce(DOTA)(H(2)O)](-) displays a TSA structural typology with a twist angle of 25 degrees and a Ce-O(water) distance of 2.59 A. The SA-type structure has been found in the case of complexes with Pr(III), Nd(III), and Dy(III), where the twist angle is 39, 39, and 38 degrees, respectively, and the metal-water oxygen distance varies significantly (Pr-O(w) 2.529 A; Nd-O(w) 2.508 A; and Dy-O(w) 2.474 A). [Tm(DOTA)](-) displays a TSA'-type structure with a twist angle of 24 degrees. As compared with the TSA structure of the corresponding Ce(III) complex, the Tm(III) complex shows an overall marked shrinkage of all metal-nitrogen and metal-oxygen distances (ca. 0.2 A), which reflects the contraction of the metal ionic radius across the series but also the effect associated with the decrease of the CN from 9 to 8. In [Sc(DOTA)](-), the even smaller ionic radius of Sc(III) shifts the geometry of the coordination cage to the more compact SA' typology with a twist angle of 41 degrees, a value very similar to that found in the SA structures of lanthanide(III) ions with CN 9. Finally, an investigation was made into the hydration spheres of the complexes with SA and TSA geometries to account for the experimental evidence of a markedly different rate of water exchange for the two isomeric structures. This is of fundamental importance to the understanding of the corresponding Gd(III) complexes as MRI contrast agents.
Inorganic Chemistry 02/2003; 42(1):148-57. · 4.60 Impact Factor
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ABSTRACT: The aim of this work is to assess whether it is possible to control the rate of the prototropic exchange in a class of DTPA bis-amide Gd-III complexes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
European Journal of Inorganic Chemistry. 01/2003;
