Comparison of MRI properties between multimeric DOTAGA and DO3A gadolinium-dendron conjugates

The inherent lack of sensitivity of MRI needs the development of new Gd contrast agents in order to extend 20Hz,37%, the application of this technique to cellular imaging. For this purpose, two multimeric MR contrast agents obtained by peptidic coupling between an amido amine dendron and GdDOTAGA chelates (premetalation strategy, G1-4GdDOTAGA) or DO3A derivatives which then were postmetalated (G1-4GdDO-3A) have been prepared. By comparison to the monomers, an increase of longitudinal relaxivity has been observed for both structures. Especially for G1-4GdDO-3A, a marked increase is observed between 20 and 60 MHz. This structure differs from G1-4GdDOTAGA by an increased rigidity due to the aromatic linker between each chelate and the organic framework. This has the effect of limiting local rotational movements, which has a positive impact on relaxivity

The internal structure of gadolinium and perfluorocarbon-loaded polymer nanoparticles affects ¹⁹F MRI relaxation times

19F magnetic resonance imaging (19F MRI) is an emerging technique for quantitative imaging in novel therapies, such as cellular therapies and theranostic nanocarriers. Nanocarriers loaded with liquid perfluorocarbon (PFC) typically have a (single) core-shell structure with PFC in the core due to the poor miscibility of PFC with organic and inorganic solvents. Paramagnetic relaxation enhancement acts only at a distance of a few angstroms. Thus, efficient modulation of the 19F signal is possible only with fluorophilic PFC-soluble chelates. However, these chelates cannot interact with the surrounding environment and they might result in image artifacts. Conversely, chelates bound to the nanoparticle shell typically have a minimal effect on the 19F signal and a strong impact on the aqueous environment. We show that the confinement of PFC in biodegradable polymeric nanoparticles (NPs) with a multicore structure enables the modulation of longitudinal (T1) and transverse (T2) 19F relaxation, as well as proton (1H) signals, using non-fluorophilic paramagnetic chelates. We compared multicore NPs versus a conventional single core structure, where the PFC is encapsulated in the core(s) and the chelate in the surrounding polymeric matrix. This modulated relaxation also makes multicore NPs sensitive to various acidic pH environments, while preserving their stability. This effect was not observed with single core nanocapsules (NCs). Importantly, paramagnetic chelates affected both T1 and T219F relaxation in multicore NPs, but not in single core NCs. Both relaxation times of the 19F nucleus were enhanced with an increasing concentration of the paramagnetic chelate. Moreover, as the polymeric matrix remained water permeable, proton enhancement additionally was observed in MRI.</p

SYNTHESE ET APPLICATIONS DE BISPHTALOCYANINES DE LUTETIUM PORTANT DES CHAINES HYDROPHILES ET HYDROPHOBES

BREST-BU Droit-Sciences-Sports (290192103) / SudocSudocFranceF

Grey scale memory in an optically addressed spatial light modulator with a Lu(Pc)2 doped layer

International audienc

An amphiphilic lutetium bisphthalocyanine: Lu[(PEO)4Pc] [(DodO)4Pc]

International audienceThe synthesis of an amphiphilic lutetium bisphthalocyanine is described. One phthalocyanine of the sandwich complex bears four hydrophobic chains (C12H25O = DodO), and the other bears four hydrophilic polyether groups (CH3(OCH2CH2)(n)O = PEO). The molecule has been characterized by 1H NMR and ESI mass spectrometry. The mean value for n, the number of polyethyleneoxy units in the starting PEOH, is 8 with a Gaussian distribution around that value; however, for the most abundant lutetium bisphthalocyanine, 4n = 26. On the spectrum, the peak corresponding to the adduct with two Na+ is higher than the one of the singly charged ion, a result of the affinity of polyethers for alkali ions

Studies of a nickel-based single molecule magnet: resonant quantum tunnelling in an S = 12 molecule

A cyclic dodecanuclear nickel complex is the first single molecule magnet based on nickel(II) centres; the material is also the highest spin molecule to show resonant quantum tunnelling of magnetisation

Electron transfer at the liquid-liquid interface between Lu(III) bisphtalocyanines in a solvent and Fe(III)/Fe(II) in water. Studies at a micro-interface and at solvent film electrodes

Conférence du 27 avril au 2 mai 2003. Communication orale

Electron transfer at the liquid-liquid interface between Lu(III) bisphtalocyanines in a solvent and Fe(III)/Fe(II) in water. Studies at a micro-interface and at solvent film electrodes

Conférence du 27 avril au 2 mai 2003. Communication orale