title: Relaxivities of magnetoliposomes: the effect of cholesterol.
abstract: We present relaxivities measurements for both the longitudinal and transverse relaxations of two types of liposomes loaded with ultra small superparamagnetic iron oxide nanoparticles. The magnetoliposome systems presented are soybean phosphatidylcholine liposomes, with and without cholesterol, in the phospholipid bilayer with different molar ratios lipid:cholesterol. In fact, cholesterol is needed to obtain stable liposomes for intravenous administration. The longitudinal and transverse relaxivities were measured with a NMR spectrometer in a 7T magnetic field. For the studied concentrations, the liposomes show a negligible effect on the longitudinal relaxation time T1 of the medium, but they are very efficient on decreasing the transverse relaxation time T2, the behaviour one expects for a negative CA. We observed a lower transverse relaxivity for the magnetoliposome nanosystem with cholesterol, which strongly decreases with the cholesterol content in the liposome bilayer.
authors: CENIMAT-I3N/DCM/FCT/UNL, Campus da Caparica, 2829-516 Caparica, Portugal. amfc.carvalho@fct.unl.pt
authors: Alexandra
authors: A
authors: Carvalho
authors: M Clara
authors: MC
authors: Gonçalves
authors: M Bárbara F
authors: MB
authors: Martins
authors: Diana
authors: D
authors: Meixedo
authors: Gabriel
authors: G
authors: Feio
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D003287:Contrast Media / Q000737:chemistry*; D003911:Dextrans / Q000737:chemistry*; D004553:Electric Conductivity; D008081:Liposomes / Q000737:chemistry*; D060526:Magnetic Fields; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008422:Materials Testing
chemical_list: D003287:Contrast Media; D003911:Dextrans; D008081:Liposomes; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; D002784:Cholesterol