E.C.D. Lima

The influence of cobalt population on the structural properties of CoxFe3−xO4

CoxFe3−xO4-based (x=0.05–1.6) nanoparticles prepared by combustion reaction were investigated using x-ray diffraction, Raman spectroscopy, and Mossbauer spectroscopy. The Mossbauer data revealed Co2+ in both tetrahedral (site A) and octahedral (site B) sites of the cubic ferrite structure. For x⩽0.4 the experimental data indicated the synthesis of a core-shell structure, with hematite as the shell and cobalt ferrite as the core of the nanoparticle. Differences in crystalline structure between the two phases support the evidences we found of a highly stressed core-shell interface, leading to symmetry reduction of the tetrahedral and octahedral sites.

Stability of citrate-coated magnetite and cobalt-ferrite nanoparticles under laser irradiation: a Raman spectroscopy investigation

In this paper, Raman spectroscopy was used to investigate the chemical and structural properties of citrate-coated Fe/sub 3/O/sub 4/ and CoFe/sub 2/O/sub 4/ nanoparticles. The Raman data obtained from the two samples investigated are compared with the Raman data from the literature of bulk maghemite and bulk hematite. The Raman data are used to discuss the higher structural stability of the CoFe/sub 2/O/sub 4/-based sample in comparison to the Fe/sub 3/O/sub 4/-based sample, when submitted to optical illumination at different intensities.

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.

Preparation and electrical properties of oil-based magnetic fluids

This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%–0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7–2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%–0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7–2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

Biological investigation of a citrate-coated cobalt-ferrite-based magnetic fluid

The present study reports on several in vivo biological tests carried out with a cobalt–ferrite, citrate-coated, magnetic fluid sample developed for biomedical purposes. Systematic biological investigation was performed after endovenous injection in mice. Morphological analysis showed magnetic nanoparticle (MNP) infiltration in the parenchyma or vessels of all investigated organs. Nevertheless, at the investigated dose and period of treatment, no cell damage or inflammatory processes were observed. Cytometry alterations and genotoxic effects were not observed. Although precipitation of MNPs in tissues may be taken as undesirable, the absence of morphological alterations is very promising. The data show that the investigated sample is biocompatible and useful for biomedical applications.

The effect of bovine serum albumin on the binding constant and stoichiometry of biocompatible magnetic fluids

In this work, we investigated the interaction between different molecular-coated magnetite nanoparticles and the serum albumin protein. The investigation was based on the fluorescence quenching of the tryptophan residue of the serum albumin protein after the binding with the molecular-coated magnetite nanoparticles to specific sites. Three different biocompatible magnetic fluid samples based on magnetite nanoparticles surface-coated with carboxymethyldextran, tartrate, and polyaspartic were used. Significant differences in the values of binding constant (K/sub b/) and stoichiometry (n) were found as the surface-coating species are changed. The results obtained from the molecular-coated magnetite nanoparticles having different coatings indicate the effect of the coating material in the biological association of magnetite nanoparticles to biological macromolecules.

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.

Biodistribution and biocompatibility of DMSA-stabilized maghemite magnetic nanoparticles in nonhuman primates (Cebus spp.)

AIM This work represents the first reported investigation on the effects of magnetic nanoparticles (MNPs) in nonhuman primates. Biodistribution, biocompatibility and nanotoxicity of maghemite nanoparticles stabilized with dimercaptosuccinic acid (DMSA) were accessed. MATERIALS & METHODS A control animal was used and three other animals were intravenously injected with DMSA-MNPs and euthanized 12 h, 30 and 90 days following administration. Extracted organs were processed by histological techniques. An additional animal was used to collect blood samples to complementarily assess biocompatibility 12 h, 7, 15, 30, 60 and 90 days after DMSA-MNP injection. RESULTS DMSA-MNPs were preferentially addressed to the lungs, liver and kidneys. Hematological and serum biochemical results corroborated histological findings, supporting DMSA-MNP biocompatibility while preserving both hepatic and renal normal activity. CONCLUSION DMSA-MNPs were preferentially distributed to the lung, liver and kidneys. Furthermore, DMSA-MNPs were considered biocompatible, supporting their application as a promising nanomaterial platform for future biomedical use.

Anti-CEA loaded maghemite nanoparticles as a theragnostic device for colorectal cancer.

Nanosized maghemite particles were synthesized, precoated (with dimercaptosuccinic acid) and surface-functionalized with anticarcinoembryonic antigen (anti-CEA) and successfully used to target cell lines expressing the CEA, characteristic of colorectal cancer (CRC) cells. The as-developed nanosized material device, consisting of surface decorated maghemite nanoparticles suspended as a biocompatible magnetic fluid (MF) sample, labeled MF-anti-CEA, was characterized and tested against two cell lines: a high-CEA expressing cell line (LS174T) and a low-CEA expressing cell line (HCT116). Whereas X-ray diffraction was used to assess the average core size of the as-synthesized maghemite particles (average 8.3 nm in diameter), dynamic light scattering and electrophoretic mobility measurements were used to obtain the average hydrodynamic diameter (550 nm) and the zeta-potential (−38 mV) of the as-prepared and maghemite-based nanosized device, respectively. Additionally, surface-enhanced Raman spectroscopy (SERS) was used to track the surface decoration of the nanosized maghemite particles from the very first precoating up to the attachment of the anti-CEA moiety. The Raman peak at 1655 cm−1, absent in the free anti-CEA spectrum, is the signature of the anti-CEA binding onto the precoated magnetic nanoparticles. Whereas MTT assay was used to confirm the low cell toxicity of the MF-anti-CEA device, ELISA and Prussian blue iron staining tests performed with both cell lines (LS174T and HCT116) confirm that the as-prepared MF-anti- CEA is highly specific for CEA-expressing cells. Finally, transmission electron microscopy analyses show that the association with anti-CEA seems to increase the number of LS174T cells with internalized maghemite nanoparticles, whereas no such increase seems to occur in the HCT116 cell line. In conclusion, the MF-anti-CEA sample is a biocompatible device that can specifically target CEA, suggesting its potential use as a theragnostic tool for CEA-expressing tumors, micrometastasis, and cancer-circulating cells.

Evaluation of new complexes of biocompatible magnetic fluid and 3/sup rd/ generation of photosensitizer useful to cancer treatment

This paper introduces a new class of complex materials that combine the action of photodynamic therapy (PDT) and hyperthermia (HPT) therapies, designed to work in a synergic way, leading to an expected enhancement of the tumor damage after minimum doses of heat dissipation and/or visible light photosensitization . In this study, we evaluated comparative dark and light toxicity of the photosensitisers (PS), biocompatible magnetic fluids(BMF) and BMF/PS complex in the J774-A cell line. Maghemite nanoparticles are surface coated with phosphate (PPT) and chlorine e/sub 6/ (Chle/sub 6/) is used as a PS drug. In the dark toxicity studies, five different concentration of Chle/sub 6/ were evaluated at the lower dark toxicity concentration (5 /spl mu/M). The same studies were developed in the presence of BMFs. No change was observed upon the addition of BMFs. Light toxicity studies were performed with three different fluence of visible light irradiation (2, 5 and 10 J/cm/sup 2/). The methodology used to investigate the cell toxicity in both protocol was the classical MTT assay. All the results presented here allow the development of a new drug generation for cancer treatment extending the possibility of the use of the Chle6/PPT complex as a candidate for maximum tumor damage, acting via photoactivation and/or magnetic field exposure.