title: Synthesis and characterization of magnetoliposomes for MRI contrast enhancement.
abstract: This work assesses the characteristics of magnetoliposomes of soybean phosphatidylcholine (SPC):cholesterol (Chol) loaded with superparamagnetic iron oxide nanoparticles (IONPs) stabilized with tetramethylammonium hydroxide (TMAOH) and their capacity to enhance magnetic resonance imaging (MRI) contrast. Magnetoliposomes of SPC were used for comparative studies. IONPs and magnetoliposomes were characterized using transmission electron microscopy, dynamic light scattering, SQUID magnetometry, FTIR and MRI. The saturation magnetization at 10K was ~0.06 Am(2)/kg for SPC:Chol magnetoliposomes with 7 g iron oxide/mol of lipid and ~0.05 Am(2)/kg for SPC magnetoliposomes with 21 g iron oxide/mol of lipid. As these values are associated with the number of incorporated magnetic IONPs, the saturation magnetization is 1.2 times higher for magnetoliposomes of SPC:Chol as compared with magnetoliposomes of SPC alone. The behavior of temperature dependence in both cases is typical of superparamagnetic particles. FTIR spectra evidence the increase of magnetoliposome membrane ordering with the presence of Chol. Principal component analysis (PCA) applied to FTIR spectra evidenced a clear distinction between scores for SPC:Chol, and SPC magnetoliposomes and for SPC empty liposomes. PCA applied to FTIR data differentiate magnetoliposomes from empty liposomes. MR images of aqueous phantoms obtained with and without magnetoliposomes, clearly evidence their effect on T2 image weighting.
authors: Department of Bioengineering, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal.
authors: M R
authors: MR
authors: Faria
authors: M M
authors: MM
authors: Cruz
authors: M C
authors: MC
authors: Gonçalves
authors: A
authors: A
authors: Carvalho
authors: G
authors: G
authors: Feio
authors: M B F
authors: MB
authors: Martins
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D004339:Drug Compounding; D007089:Image Enhancement; D008081:Liposomes / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D010713:Phosphatidylcholines / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D008081:Liposomes; D058185:Magnetite Nanoparticles; D010713:Phosphatidylcholines; D000644:Quaternary Ammonium Compounds; D002784:Cholesterol; C027917:tetramethylammonium