Z.G.M. Lacava

Regulation of antioxidant enzyme activities in male and female rat macrophages by sex steroids

Human and animal immune functions present sex dimorphism that seems to be mainly regulated by sex hormones. In the present study, the activities of the antioxidant enzymes total superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were measured in intraperitoneal resident macrophages from adult male and female rats. In addition to comparing males and females, we also examined the regulation of these enzyme activities in macrophages by sex steroids. GSH-Px activity did not differ between male and female macrophages. However, both total SOD and CAT activities were markedly higher in females than in males (83 and 180%). Removal of the gonads in both males and females (comparison between castrated groups) increased the difference in SOD activity from 83 to 138% and reduced the difference in CAT activity from 180 to 86%. Castration and testosterone administration did not significantly modify the activities of the antioxidant enzymes in male macrophages. Ovariectomy did not affect SOD or GSH-Px activity but markedly reduced (48%) CAT activity. This latter change was fully reversed by estrogen administration, whereas progesterone had a smaller effect. These results led us to conclude that differences in the SOD and CAT activities may partially explain some of the differences in immune function reported for males and females. Also, estrogen is a potent regulator of CAT in macrophages and therefore this enzyme activity in macrophages may vary considerably during the menstrual cycle.

Particle sizing of magnetite-based magnetic fluid using atomic force microscopy: A comparative study with electron microscopy and birefringence

Atomic force microscopy (AFM), transmission electron microscopy (TEM), and static magnetic birefringence (SMB) were used to unfold the particle size polydispersity profile of a magnetite-based magnetic fluid sample. The data obtained from different techniques were curve fitted using the lognormal distribution function, from which the mean particle diameter (Dm) and the standard deviation (σ) were obtained. In comparison to the TEM data, the AFM data show a reduction of Dm (about 20%) and an increase of σ (about 15%). In contrast, close agreement between the TEM and SMB data was found.

The influence of aggregates and relative permeability on the magnetic birefringence in ionic magnetic fluids

The static magnetic birefringence (SMB) of nickel-ferrite ionic magnetic fluid was investigated within the oscillating dipole-interaction anisotropy concept proposed by Xu and Ridler [J. Appl. Phys. 82, 326 (1997)]. The model was extended to include the magnetic texture of particle agglomerates and the field dependence of the magnetic permeability. The SMB data of samples subjected or not to a magnetic aging process and presenting particle concentration in the range of 2×1016 to 8×1016 particle/cm3 were successfully described. The particle size distribution obtained from the fit of the SMB data was discussed in comparison with the data obtained from transmission electron 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.

In vitro photodynamic therapy on human oral keratinocytes using chloroaluminum-phthalocyanine

In this study, oral carcinoma cells were used to evaluate chloroaluminum-phthalocyanine encapsulated in liposomes as the photosensitizer agent in support of photodynamic therapy (PDT). The genotoxicity and cytotoxicity behavior of the encapsulated photosensitizer in both dark and under irradiation using the 670-nm laser were investigated with the classical trypan blue cell viability test, the acridine orange/ethidium bromide staining organelles test, micronucleus formation frequency, DNA fragmentation, and cell morphology. The cell morphology investigation was carried out using light and electronic microscopes. Our findings after PDT include reduction in cell viability (95%) associated with morphologic alterations. The neoplastic cell destruction was predominantly started by a necrotic process, according to the assay with acridine orange and ethidium bromide, and this was confirmed by electronic microscopy analysis. Neither the PDT agent nor laser irradiation alone showed cytotoxicity, genotoxicity, or even morphologic alterations. Our results reinforce the efficiency of light-irradiated chloroaluminum-phthalocyanine in inducing a positive effect of PDT.

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.

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.

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.

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.

Quantitative approach to skin field cancerization using a nanoencapsulated photodynamic therapy agent: a pilot study

Background This paper introduces a new nanoformulation of 5-aminolevulinic acid (nano-ALA) as well as a novel quantitative approach towards evaluating field cancerization for actinic keratosis and/or skin photodamage. In this pilot study, we evaluated field cancerization using nano-ALA and methyl aminolevulinate (MAL), the latter being commercialized as Metvix®. Methods and results Photodynamic therapy was used for the treatment of patients with selected skin lesions, whereas the fluorescence of the corresponding photosensitizer was used to evaluate the time evolution of field cancerization in a quantitative way. Field cancerization was quantified using newly developed color image segmentation software. Using photodynamic therapy as the precancer skin treatment and the approach introduced herein for evaluation of fluorescent area, we found that the half-life of field cancerization reduction was 43.3 days and 34.3 days for nano-ALA and MAL, respectively. We also found that nano-ALA targeted about 45% more skin lesion areas than MAL. Further, we found the mean reduction in area of skin field cancerization was about 10% greater for nano-ALA than for MAL. Conclusion Although preliminary, our findings indicate that the efficacy of nano-ALA in treating skin field cancerization is higher than that of MAL.