The design of liposomal paramagnetic mr agents: effect of vesicle size upon the relaxivity of surface‐incorporated lipophilic chelates

Tilcock, Colin; Ahkong, Quet F.; Koenig, Seymour H.; Brown, Rodney D.; Davis, M.A.F.; Kabalka, George W.

doi:10.1002/mrm.1910270106

Cited by 63 publications

(27 citation statements)

References 27 publications

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“…Liposomes are vesicles which can carry paramagnetic complexes for magnetic resonance applications either by encapsulating them into the interior aqueous volume or by incorporating paramagnetic moieties into the membranes of liposomal vesicles (Fossheim et al 1999;Tilcock et al 1992). In the latter case the paramagnetic amphiphilic gadolinium(III) complex becomes an integral part of the liposomal lamella.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2005

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

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Section: Resultsmentioning

confidence: 99%

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

et al. 2005

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“…The amphiphiles used can consist of Gd-DTPA as the hydrophilic part attached to a hydrophobic part. DTPA-stearate (131,132) or DTPA attached to alkyl chains via amide linkers are examples of such molecules (133,134). Phosphatidylethanolamine (PE) has been linked to DTPA to obtain PE-DTPA, which can form vesicles when mixed with natural phospholipids (135).…”

Section: Lipid-based Mri Contrast Agents: Applications Liposomal Contmentioning

confidence: 99%

Lipid-based nanoparticles for contrast-enhanced MRI and molecular imaging

et al. 2006

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In the field of MR imaging and especially in the emerging field of cellular and molecular MR imaging, flexible strategies to synthesize contrast agents that can be manipulated in terms of size and composition and that can be easily conjugated with targeting ligands are required. Furthermore, the relaxivity of the contrast agents, especially for molecular imaging applications, should be very high to deal with the low sensitivity of MRI. Lipid-based nanoparticles, such as liposomes or micelles, have been used extensively in recent decades as drug carrier vehicles. A relatively new and promising application of lipidic nanoparticles is their use as multimodal MR contrast agents. Lipids are amphiphilic molecules with both a hydrophobic and a hydrophilic part, which spontaneously assemble into aggregates in an aqueous environment. In these aggregates, the amphiphiles are arranged such that the hydrophobic parts cluster together and the hydrophilic parts face the water. In the low concentration regime, a wide variety of structures can be formed, ranging from spherical micelles to disks or liposomes. Furthermore, a monolayer of lipids can serve as a shell to enclose a hydrophobic core. Hydrophobic iron oxide particles, quantum dots or perfluorocarbon emulsions can be solubilized using this approach. MR-detectable and fluorescent amphiphilic molecules can easily be incorporated in lipidic nanoparticles. Furthermore, targeting ligands can be conjugated to lipidic particles by incorporating lipids with a functional moiety to allow a specific interaction with molecular markers and to achieve accumulation of the particles at disease sites. In this review, an overview of different lipidic nanoparticles for use in MRI is given, with the main emphasis on Gd-based contrast agents. The mechanisms of particle formation, conjugation strategies and applications in the field of contrast-enhanced, cellular and molecular MRI are discussed.

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“…Considering that the liposome lumen must be used to encapsulate large amounts of drug molecules, the membrane moiety might be suitable for the incorporation of MRI probes. Therefore, lipid-based MRI contrast agents, such as amphiphilic Gd-DTPA derivatives [32,33] have been used for this purpose. Because these molecules contain single Gd-chelate moiety per molecule, inclusion of a high content of these amphiphilic Gd-chelate molecules might be necessary in the liposomes to gain high detectability with MRI, which should affect performance of the liposomes.…”

Section: Introductionmentioning

confidence: 99%

Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy

Kono

Nakashima

Kokuryo³

et al. 2011

Biomaterials

111

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The design of liposomal paramagnetic mr agents: effect of vesicle size upon the relaxivity of surface‐incorporated lipophilic chelates

Cited by 63 publications

References 27 publications

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

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

Lipid-based nanoparticles for contrast-enhanced MRI and molecular imaging

Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy

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