title: Enhanced contrast efficiency in MRI by PEGylated magnetoliposomes loaded with PEGylated SPION: effect of SPION coating and micro-environment.
abstract: Magnetic core coatings modify the efficiency of nanoparticles used as contrast agents for MRI. In studies of these phenomena, care should be given to take into account possible effects of the specific micro-environment where coated nanoparticles are embedded. In the present work, the longitudinal and transverse relaxivities of superparamagnetic iron oxide nanoparticles stabilized with short-chain polyethylene glycol molecules (PEGylated SPIONs) were measured in a 7T magnetic field. PEGylated SPIONs with two different diameters (5 and 10nm) were studied. Two different PEGylated magnetoliposomes having liposome bilayer membranes composed of egg-phosphatidylcholine, cholesterol and 1,2-distearoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy PEG-2000] were also studied for their relaxivities, after being loaded with the PEGylated SPION of 5 or 10nm. This type of liposomes is known to have long residence time in bloodstream that leads to an attractive option for therapeutic applications. The influence of the magnetic core coating on the efficiency of the nanosystem as a negative contrast agent for MRI was then compared to the cumulative effect of the coating plus the specific micro-environment components. As a result, it was found that the PEGylated magnetoliposomes present a 4-fold higher efficiency as negative contrast agents for MRI than the PEGylated SPION.
authors.affiliation: CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal. Electronic address: amfc.carvalho@fct.unl.pt.
authors.forename: A
authors.initials: A
authors.lastname: Carvalho
authors.affiliation: iMed.UL, Faculdade de Farmácia da Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal.
authors.forename: M B F
authors.initials: MB
authors.lastname: Martins
authors.affiliation: iMed.UL, Faculdade de Farmácia da Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal.
authors.forename: M L
authors.initials: ML
authors.lastname: Corvo
authors.affiliation: CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal.
authors.forename: G
authors.initials: G
authors.lastname: Feio
mesh_terms: D003287:Contrast Media; D008081:Liposomes; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D008081:Liposomes; D011092:Polyethylene Glycols
keywords: Contrast agents; MRI; Magnetoliposomes; Relaxivities; SPION