F. Pelegrini

Magnetic Resonance of a Dextran-Coated Magnetic Fluid Intravenously Administered in Mice

Magnetic resonance was used to investigate the kinetic disposition of magnetite nanoparticles (9.4 nm core diameter) from the blood circulation after intravenous injection of magnetite-based dextran-coated magnetic fluid in female Swiss mice. In the first 60 min the time-decay of the nanoparticle concentration in the blood circulation follows the one-exponential (one-compartment) model with a half-life of (6.9 +/- 0.7) min. The X-band spectra show a broad single line at g approximately 2, typical of nanomagnetic particles suspended in a nonmagnetic matrix. The resonance field shifts toward higher values as the particle concentration reduces, following two distinct regimes. At the higher concentration regime (above 10(14) cm(-3)) the particle-particle interaction responds for the nonlinear behavior, while at the lower concentration regime (below 10(14) cm(-3)) the particle-particle interaction is ruled out and the system recovers the linearity due to the demagnetizing field effect alone.

Surface and exchange anisotropy fields in MnFe2O4 nanoparticles: Size and temperature effects

Angular measurements of magnetic resonance are used to investigate the surface anisotropy field as well as the exchange anisotropy field in spherical MnFe2O4 magnetic nanoparticles as a function of temperature and particle diameter (D). The resonance field is a combination of angular dependent and angular independent fields, both affected by the surface anisotropy field, which in turn follows a D−α power law, with α very close to unity. The angular dependent component probes the surface anisotropy field while the angular independent component probes the exchange anisotropy field. In the temperature range from 100 to 250 K a negative surface anisotropy field is found, which increases as the particle size is reduced, indicating a radial orientation of the spins at the MnFe2O4 nanoparticle surface.

Electron paramagnetic resonance study of ionic water-based manganese ferrite ferrofluids

Abstract We report for the first time electron paramagnetic resonance linewidth measurements in an ionic water-based ferrofluid. The linewidth broadening is studied as a function of the particle-particle distance. We change the average particle-particle distance from 20 to 89 nm by diluting a concentrated sample with water. Magnetic and electric interactions between adjacent particles are used to explain the experimental data.

Light microscopy and magnetic resonance characterization of a DMSA-coated magnetic fluid in mice

Light microscopy and magnetic resonance were used to investigate the biodistribution of magnetite nanoparticles coated with dimercaptosuccinic acid, after intravenous injection of a single dose in mice. Morphological analysis showed a huge amount of magnetic nanoparticles (MNPs) in the lung 30 min after injection. In contrast to the lung, morphological analysis revealed lower concentration of MNPs in the liver. A progressive decrease of MNPs in both lung and liver was observed from 30 min to 4 hours after intravenous injection. MNPs were not observed in any other organs using morphological analysis. In support of the LM observations MR signals were detected in both lung and liver as early as 5 min after injection. In addition, no MR signal was observed in the blood stream as early as 5 min after injection of the single dose.

Magnetic particle–particle interaction in frozen magnetic fluids

Magnetic resonance is used to study magnetic dipole particle–particle interaction in ionic water‐based iron‐manganese magnetic fluids. A set of six samples having particle concentration running from 1.2×1016 to 6.3×1016 particles/cm3 were frozen below room temperature and analyzed in the range of 100–250 K. Average values of magnetic particle–particle interaction energy were obtained from the temperature dependence of the resonance linewidth broadening. At 1.2×1016 particles/cm3 magnetic particle–particle interaction energy is found to be of the order of 1.2 meV. However, at 6.3×1016 particles/cm3 magnetic particle–particle interaction energy goes to 32 meV. The enhancement of the magnetic particle–particle interaction energy far beyond the linearity is associated to cluster structuration. A one‐dimensional model for cluster structuration is presented.

Magnetic resonance and light microscopy investigation of a dextran coated magnetic fluid

A dextran-coated magnetite-based magnetic fluid (MF) sample (DexMF) was developed for cancer diagnostic and therapeutic purposes. In order to perform biological studies DexMF samples were endovenously injected into female Swiss mice. Magnetic resonance (MR) spectra showed a broad line around g=2, typical of magnetic nanoparticles (MNPs) suspended in a nonmagnetic matrix. The MR data showed that MNPs essentially spread in liver, spleen, and bone marrow. MNPs in blood stream were found up to 60 min after injection. Histological analysis also showed MNP agglomeration in liver, spleen, and bone marrow, from 1 h up to 28 days. No damaged cells or any other kind of alteration were observed in the investigated tissues. The data suggested that DexMF sample is biocompatible and adequate for biomedical applications.

Magnetic resonance of magnetite nanoparticles dispersed in mesoporous copolymer matrix

Magnetic resonance is used to investigate fine particles of magnetite (Fe/sub 3/O/sub 4/) synthesized as isolated nanoparticles (INPs) in a mesoporous styrene-divinylbenzene (Sty-DVB) copolymer template. The magnetite nanoparticles were obtained through alkaline precipitation of ferrous sulfate, at different iron (II) concentration (Q), in the sulfonated polymeric matrix. Analysis of the temperature (T) dependence of the resonance field (H/sub R/) and resonance linewidth (/spl Delta/H/sub R/) provide a useful way to estimate the average size of the magnetite nanoparticles. The data indicates that the nanoparticle average diameter (D) increases as Q increases, in accordance with the data reported previously.

Magnetic resonance of zinc- and copper-ferrite ionic magnetic fluids: temperature effects

Abstract Magnetic resonance was used to investigate ionic magnetic fluids based on ZnFe 2 O 4 and CuFe 2 O 4 nanoparticles. Temperature and angular variation measurements were performed with field-frozen samples, using an X-band spectrometer. The resonance line shape analysis indicates the presence of four components, irrespective of the temperature and sample orientation. Intermediate values of the anisotropy field were associated to dimers, while low and high values of the anisotropy field were associated to large- and small-sized monomers, respectively. The temperature dependence of the resonance field associated to each resonance line allowed quantitative investigation of the surface anisotropy component. Positive as well as negative surface anisotropy components, as obtained from the temperature dependence of the resonance field, are reported.

Study of particle-particle interaction in magnetic fluids using magnetic resonance

Summary form only given. A hydrocarbon-based magnetic fluid (MF) containing core magnetite nanoparticles, surface-coated by a double-layer of dodecanoic acid, is investigated in the range of 10/sup 17/ to 10/sup 13/ particle/cm/sup 3/, using an X-band CW spectrometer. The data are discussed in terms of the reduction of the particle-particle interaction upon dilution of a stock MF sample. The feature observed around 2.2 kgauss is likely due to a nanoparticle chain-like structure, but was washed away upon dilution.

Biodistribution and biocompatibility investigation in magnetoliposome treated mice

Magnetoliposomes (MLs) may be successfully applied for several purposes. A dimyristoylphosphatidyl-choline- based ML (ML-2) sample was developed as a precursor of more complex thermal cancer therapy systems. The present study reports on morphology and magnetic resonance (MR) investigations carried out with the magnetite-based ML-2 sample. For the experiments, adult female Swiss mice were endovenously treated with a bolus dose of 100 µl of ML-2. Morphology and room-temperature MR studies (X-band experiments) were performed in several organs collected from 1 hour to 28 days after ML administration. Histological data showed magnetic nanoparticle (MNP) clusters up to the 28th day in the liver and spleen tissues. In spite of the presence of MNP clusters, no morphological alterations were observed, supporting the biocompatibility of the ML-2. MR signal was detected only in the liver and spleen tissues and showed that the MNPs concentration was not altered from 48 hours to 28 days after ML injection. Using MR data, important pharmacokinetic parameters, such as the effective clearance (half-life) and peak concentration, were obtained for the liver and spleen.