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Nanoparticles in magnetic resonance imaging: from simple to dual contrast agents.

Estelrich J, Sánchez-Martín MJ, Busquets MA - Int J Nanomedicine (2015)

Bottom Line: Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements.They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively.Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

View Article: PubMed Central - PubMed

Affiliation: Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalonia, Spain ; Institut de Nanociència I Nanotecnologia (IN UB), Barcelona, Catalonia, Spain.

ABSTRACT
Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T 1, spin-lattice relaxation and T 2, spin-spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T 1 and T 2 increases the corresponding relaxation rates, 1/T 1 and 1/T 2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T 2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T 1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

No MeSH data available.


Related in: MedlinePlus

Scheme of multifunctional liposome for molecular imaging, drug delivery, and therapy.Abbreviations: RGD, arginine-glycine-aspartic acid; PEG, poly(ethyelene) glycol.
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f5-ijn-10-1727: Scheme of multifunctional liposome for molecular imaging, drug delivery, and therapy.Abbreviations: RGD, arginine-glycine-aspartic acid; PEG, poly(ethyelene) glycol.

Mentions: Figure 5 is a scheme of a multimodal particle based on a liposomal structure that allows theranostic applications. This liposome contains several individual cores (or a cluster of cores) of SPIONs, and, moreover, it can enclose a drug. The presence of magnetic nanoparticles makes bioimaging possible or the generation of heat in therapeutic hyperthermia, and also magnetic targeting. Optionally, the liposome can also encapsulate a drug. The shell material is responsible for its surface properties, because of the presence of reactive moieties on the surface. In this way, PEG is attached covalently to the surface of phospholipids in order to prevent aggregation and opsonization. The shell can be tuned to provide binding to molecules; as an example, the peptide RGD is bound at the distal end of some PEG chains for the purpose of targeted drug delivery. Such peptides facilitate the interaction of the liposome with integrins: proteins present on the cellular surface that recognize the peptide RGD. This biological targeting promotes the internalization of liposomes into cells. Moreover, the liposomal bilayer can contain a fluorescent probe, which permits its interaction with cells to be visualized by confocal microscopy.


Nanoparticles in magnetic resonance imaging: from simple to dual contrast agents.

Estelrich J, Sánchez-Martín MJ, Busquets MA - Int J Nanomedicine (2015)

Scheme of multifunctional liposome for molecular imaging, drug delivery, and therapy.Abbreviations: RGD, arginine-glycine-aspartic acid; PEG, poly(ethyelene) glycol.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4358688&req=5

f5-ijn-10-1727: Scheme of multifunctional liposome for molecular imaging, drug delivery, and therapy.Abbreviations: RGD, arginine-glycine-aspartic acid; PEG, poly(ethyelene) glycol.
Mentions: Figure 5 is a scheme of a multimodal particle based on a liposomal structure that allows theranostic applications. This liposome contains several individual cores (or a cluster of cores) of SPIONs, and, moreover, it can enclose a drug. The presence of magnetic nanoparticles makes bioimaging possible or the generation of heat in therapeutic hyperthermia, and also magnetic targeting. Optionally, the liposome can also encapsulate a drug. The shell material is responsible for its surface properties, because of the presence of reactive moieties on the surface. In this way, PEG is attached covalently to the surface of phospholipids in order to prevent aggregation and opsonization. The shell can be tuned to provide binding to molecules; as an example, the peptide RGD is bound at the distal end of some PEG chains for the purpose of targeted drug delivery. Such peptides facilitate the interaction of the liposome with integrins: proteins present on the cellular surface that recognize the peptide RGD. This biological targeting promotes the internalization of liposomes into cells. Moreover, the liposomal bilayer can contain a fluorescent probe, which permits its interaction with cells to be visualized by confocal microscopy.

Bottom Line: Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements.They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively.Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

View Article: PubMed Central - PubMed

Affiliation: Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalonia, Spain ; Institut de Nanociència I Nanotecnologia (IN UB), Barcelona, Catalonia, Spain.

ABSTRACT
Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T 1, spin-lattice relaxation and T 2, spin-spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T 1 and T 2 increases the corresponding relaxation rates, 1/T 1 and 1/T 2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T 2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T 1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

No MeSH data available.


Related in: MedlinePlus