Superparamagnetic iron oxide particles: contrast media for magnetic resonance imaging

Abstract

The mainstream magnetic iron oxide particles used as contrast media for magnetic resonance (MR) imaging are composed of a magnetic iron oxide core surrounded by a dextran or carboxydextran coat. The core size ranges from 2 nm to less than 10 nm, and the hydrodynamic diameter ranges from 20 nm to about 120 nm. The coat prevents aggregation and sedimentation of the particles in aqueous solutions, achieves high biological tolerance, and prevents toxic side effects.Two kinds of particles are considered: (i) large particles (>30 nm), called superparamagnetic iron oxide particles (SPIOs) for liver imaging; (ii) smaller particles (<30 nm hydrodynamic diameter), called ultrasmall SPIOs (USPIOs), e.g. for MR angiography.To characterize the particles, Mössbauer spectra are presented for the two particle ensembles. These spectra allow insight into the magnetic coupling, the valency of the iron ions and a rough estimate of the core size to be deduced. On the basis of the concentration dependence of the MR signal intensities, two applications are discussed together with two representative clinical examples.Future indications for MR diagnostics, e.g. the labeling and tracking of stem cells during stem-cell therapy control, are outlined.

Impact of Biohybrid Magnetite Nanoparticles and Moroccan Propolis on Adherence of Methicillin Resistant Strains of Staphylococcus aureus

“…The morphology and particle size of nanoparticles were similar to those reported by Anghel et al [15] for functionalized magnetite (Fe 3 O 4 /C 18 ), that is, the same type of functionalization (oleic acid) done in the present work. In the Mössbauer spectroscopy, and at room temperature, spectra showed a gradual passage from bulk-like to superparamagnetic (SPM) behavior, as the average size of the particles decrease, a striking characteristic of the superparamagnetic nature of nanoparticles [28]. by Anghel et al [15] for functionalized magnetite (Fe3O4/C18), that is, the same type of functionalization (oleic acid) done in the present work.…”

“…by Anghel et al [15] for functionalized magnetite (Fe3O4/C18), that is, the same type of functionalization (oleic acid) done in the present work. In the Mössbauer spectroscopy, and at room temperature, spectra showed a gradual passage from bulk-like to superparamagnetic (SPM) behavior, as the average size of the particles decrease, a striking characteristic of the superparamagnetic nature of nanoparticles [28]. FTIR spectroscopy contributes to provide a fast way of identification of MNPs.…”

Nanocompósitos magnéticos: potencialidades de aplicações em Biomedicina

“…Este tempo é uma das propriedades mais importantes para aplicações de agentes de contraste para IMR; 50 ii) partículas menores (<30 nm de diâmetro hidrodinâmico), chamadas de ultrapequenas SPIOs (USPIOs), que apresentam longo T 1/2 , sendo usadas, por exemplo, para angiografia por ressonância magnética (angio-RM) e imagens IRM de macrófagos e linfonodos, bem como agentes de marcação celular. 53,54 As USPIOs têm um menor contraste negativo que as SPIOs, devido à baixa relaxação de T 2 .…”

Superparamagnetic iron oxide as an efficient and recoverable catalyst for rapid and selective trimethylsilyl protection of hydroxyl groups

“…In this context, magnetic particles have emerged as one the most useful heterogeneous catalysts due to their numerous applications in nanocatalysis, [9] biotechnology, [10,11] and medicine. [12,13] Additionally, the magnetic property of such particles provides the opportunity for quantitative recovery of the catalyst by the use of an external magnetic field. [14] Protection of hydroxyl groups is a common practice in synthetic organic [15] and analytical chemistry.…”