N. Buske

Novel polyelectrolyte multilayer micro- and nanocapsules as magnetic carriers.

Polyelectrolyte multilayer (PEM) capsules are introduced as versatile magnetic carrier systems. Superparamagnetic magnetite is mounted to the multilayer shell itself or is a component of the capsule interior. The PEM is formed at different (decomposable) colloidal templates, e.g. melamine formaldehyde resin, glutaraldehyde fixed red blood cells, emulsion oil droplets. The results are illustrated by transmission electron microscopy and confocal laser scanning microscopy.

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.

Determination of binding constant Kb of biocompatible, ferrite-based magnetic fluids to serum albumin

In this work, we investigated the interaction between molecular-coated magnetic nanoparticles (MC-MNPs) and serum albumin proteins (BSA) through the fluorescence quenching of the tryptophan residue present in BSA after the binding of MC-MNPs to specific sites. Three different biocompatible magnetic fluid (BMF) samples based on magnetite or cobalt–ferrite MNPs coated with citric acid or dextran were used. The binding constant and the stoichiometry of the investigated MNPs indicate that the BMF based on cobalt–ferrite is more site specific and more strongly bound to the BSA than the BMFs based on magnetite. The results may direct the design of new magnetic drug-carriers based on BMFs.In this work, we investigated the interaction between molecular-coated magnetic nanoparticles (MC-MNPs) and serum albumin proteins (BSA) through the fluorescence quenching of the tryptophan residue present in BSA after the binding of MC-MNPs to specific sites. Three different biocompatible magnetic fluid (BMF) samples based on magnetite or cobalt–ferrite MNPs coated with citric acid or dextran were used. The binding constant and the stoichiometry of the investigated MNPs indicate that the BMF based on cobalt–ferrite is more site specific and more strongly bound to the BSA than the BMFs based on magnetite. The results may direct the design of new magnetic drug-carriers based on BMFs.

Nanoparticle sizing: a comparative study using atomic force microscopy, transmission electron microscopy, and ferromagnetic resonance

Abstract Atomic force microscopy (AFM), transmission electron microscopy (TEM), and ferromagnetic resonance (FMR) were used to unfold the nanoparticle size of a ferrofluid sample. Compared to TEM, the AFM method showed a nanoparticle diameter (Dm) reduction of 20% and standard deviation (σ) increase of 15%. The differences in Dm and σ were associated with the AFM tip and the nanoparticle concentration on the substrate.

A double-coated magnetite-based magnetic fluid evaluation by cytometry and genetic tests

Abstract Magnetite nanoparticles pre-coated with dodecanoic acid and ethoxylated alcohol (DE) were used to obtain a physiologically stable magnetic fluid (DE–MF) sample. Three different doses of DE–MF were intraperitoneally applied to mice. Blood and peritoneum cytometry and micronucleus test were performed for 1–21 days after injection to investigate the DE–MF toxicity. Changes in cell population, peritoneum inflammation, and potential DE–MF genotoxic action were all time and dose dependent. At the lowest dose (5×1015 particles/kg), DE–MF seems to be useful as a drug precursor with both diagnostic and therapeutic values.

Raman spectroscopy in magnetic fluids.

In this work Raman spectroscopy was used to investigate uncoated magnetic fluids (UMFs) and coated magnetic fluids (CMFs). The coating agents were N-oleoylsarcosine, dodecanoic acid, and ethoxylated polyalcohol. The Raman probe is the hydroxyl (OH) group chemisorbed at the magnetic nanoparticle surface and the measurements were performed in the typical OH bending and OH stretching regions. The room temperature Raman data obtained from the UMFs and CMFs are compared to each other and with the data obtained from liquid water. Suppression of Raman modes from the MFs are discussed in terms of symmetry reduction and in terms of the interaction between the chemisorbed OH-group and the surrounding medium. The relative grafting coefficient associated to different coatings are estimated from the Raman data. The highest grafting coefficient is achieved with a single coating of dodecanoic acid in the hydrocarbon-based MF. The surface-grafting coefficient of the N-oleoylsarcosine-coated MF reduces when the polar liquid carrier replaces the non-polar liquid carrier. In comparison to liquid water, it was found that the hydrogen bonding between the chemisorbed OH-group and the solvent was enhanced in UMFs and reduced in CMFs.

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.

Photoacoustic spectroscopy: a promising technique to investigate magnetic fluids

In the present study, we investigate biocompatible magnetic fluids (BMFs) by photoacoustic spectroscopy and the investigation are based on magnetic nanoparticles surface-coated with citric acid and dispersed in physiological media (pH8 and 0.9 salinity).

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.

Magnetic resonance study of zero-field-frozen magnetite-based biocompatible magnetic fluid

In this paper, a biocompatible MF sample was investigated using X-band MR. The resonance linewidth broadening (/spl Delta/H/sub R/) and the resonance field (H/sub R/) was investigated as a function of temperature (T), at different nonparticle concentration. The biocompatible MF sample used in this study is based on magnetic nanoparticle (9.4 nm is average diameter) coated with dextran. After precipitation in alkaline medium, magnetite nanoparticles were surface coated to produce stable biocompatible MF samples at physiological pH and salinity.