Formation Mechanism of Maghemite Nanoflowers Synthesized by a Polyol-Mediated Process.

Magnetic nanoparticles are being developed as structural and functional materials for use in diverse areas, including biomedical applications. Here, we report the synthesis of maghemite (γ-Fe2O3) nanoparticles with distinct morphologies: single-core and multicore, including hollow spheres and nanoflowers, prepared by the polyol process. We have used sodium acetate to control the nucleation and assembly process to obtain the different particle morphologies. Moreover, from samples obtained at different time steps during the synthesis, we have elucidated the formation mechanism of the nanoflowers: the initial phases of the reaction present a lepidocrocite (γ-FeOOH) structure, which suffers a fast dehydroxylation, transforming to an intermediate "undescribed" phase, possibly a partly dehydroxylated lepidocrocite, which after some incubation time evolves to maghemite nanoflowers. Once the nanoflowers have been formed, a crystallization process takes place, where the γ-Fe2O3 crystallites within the nanoflowers grow in size (from ∼11 to 23 nm), but the particle size of the flower remains essentially unchanged (∼60 nm). Samples with different morphologies were coated with citric acid and their heating capacity in an alternating magnetic field was evaluated. We observe that nanoflowers with large cores (23 nm, controlled by annealing) densely packed (tuned by low NaAc concentration) offer 5 times enhanced heating capacity compared to that of the nanoflowers with smaller core sizes (15 nm), 4 times enhanced heating effect compared to that of the hollow spheres, and 1.5 times enhanced heating effect compared to that of single-core nanoparticles (36 nm) used in this work.

Manipulating directional cell motility using intracellular superparamagnetic nanoparticles.

This study investigated the ability for magnetic nanoparticles to influence cellular migration in the presence of an external magnetic field. We found that the direction of migrating keratinocytes can be controlled and the migration speed of fibroblasts can be increased with the internalisation of these nanoparticles in the presence of a magnetic field. The possibility of shepherding cells towards a region of interest through the use of internalized nanoparticles is an attractive prospect for cell tracking, cell therapies, and tissue engineering applications.

Long term biotransformation and toxicity of dimercaptosuccinic acid-coated magnetic nanoparticles support their use in biomedical applications.

Although iron oxide magnetic nanoparticles (MNP) have been proposed for numerous biomedical applications, little is known about their biotransformation and long-term toxicity in the body. Dimercaptosuccinic acid (DMSA)-coated magnetic nanoparticles have been proven efficient for in vivo drug delivery, but these results must nonetheless be sustained by comprehensive studies of long-term distribution, degradation and toxicity. We studied DMSA-coated magnetic nanoparticle effects in vitro on NCTC 1469 non-parenchymal hepatocytes, and analyzed their biodistribution and biotransformation in vivo in C57BL/6 mice. Our results indicate that DMSA-coated magnetic nanoparticles have little effect on cell viability, oxidative stress, cell cycle or apoptosis on NCTC 1469 cells in vitro. In vivo distribution and transformation were studied by alternating current magnetic susceptibility measurements, a technique that permits distinction of MNP from other iron species. Our results show that DMSA-coated MNP accumulate in spleen, liver and lung tissues for extended periods of time, in which nanoparticles undergo a process of conversion from superparamagnetic iron oxide nanoparticles to other non-superparamagnetic iron forms, with no significant signs of toxicity. This work provides the first evidence of DMSA-coated magnetite nanoparticle biotransformation in vivo.

Biophysical and genetic analysis of iron partitioning and ferritin function in Drosophila melanogaster.

Metals have vital functions as prosthetic groups in enzymes, but in labile form they can propagate oxidative stress. The primary function of ferritin is to store bioavailable iron in the form of ferrihydrite. In animals, ferritin is also used to traffic and recycle iron, and to modulate intestinal iron absorption. However, the effect of ferritin accumulation on cellular iron bioavailability remains poorly understood. Moreover, putative in vivo interactions of ferritin with other metal ions have been proposed, but their physiological relevance remains unclear. Here, heterozygous mutant and overexpression ferritin strains of Drosophila melanogaster were subjected to dietary iron manipulations to study the dynamics of iron partition between ferritin and other proteins. Quantitative magnetic analysis of whole fly samples indicated that iron loading of the ferritin core varied in the different genotypes. Total paramagnetic iron content, a likely correlate of bioavailable iron, was reduced in flies overexpressing ferritin when compared with control white flies. Further, three-dimensional maps of the ferritin protein shell and iron core were obtained from single particle transmission electron microscopy imaging and confirmed the similarity between Drosophila and Trichoplusia ferritin structures. Purified Drosophila ferritin also contained small amounts of zinc and manganese. Flies that overexpressed ferritin accumulated in their bodies half the amount of manganese compared to their respective controls. Our results indicate that ferritin may be involved in the homeostasis of other divalent metals, besides iron, and that overexpression of ferritin, sometimes employed to rescue neurodegenerative models of disease, serves to limit divalent metal bio-availability in cells.

Bilateral anterior dislocation of the shoulder: review of seventy cases and proposal of a new etiological-mechanical classification.

BACKGROUND: Although anterior shoulder dislocation is common in everyday practice in Emergency Departments, bilateral presentation is a rare entity. OBJECTIVES: The aim of this article is to report two additional cases of this rare injury and to introduce a new mechanism that can produce it. We made an exhaustive review of the literature and found 68 cases in printed publications. Also, we analyzed the mechanism of injury and the presence of predisposing factors, and propose a new etiological-mechanical classification. CASE REPORT: One case occurred after a trivial fall, and the other was produced by a mechanism not previously reported: the patient pushed strongly forward, expecting a resistance and finding none, his arms kept the forward movement and the shoulders dislocated. DISCUSSION: This lesion has a bimodal distribution, affecting mainly men (70%) with a mean age of 33.5 years, whereas in women, the average age is 57 years. The most common cause is trauma (50%), followed by muscle contractions (37%) due to seizures of different causes (epileptic, hypoglycemia, toxic, or hypoxic) or electrocution. In 15.7% of the cases, the diagnosis of bilateral anterior dislocation was not acute (<3 weeks), and in virtually all of these cases it was not traumatic. CONCLUSION: The bilateral anterior shoulder dislocation may not be as rare as previously thought and must be taken into account in emergency services. The authors propose a new etiological-mechanical classification. Also, the importance of radiologic diagnosis must be highlighted.

Identification of nonferritin mitochondrial iron deposits in a mouse model of Friedreich ataxia.

There is no effective treatment for the cardiomyopathy of the most common autosomal recessive ataxia, Friedreich ataxia (FA). This disease is due to decreased expression of the mitochondrial protein, frataxin, which leads to alterations in mitochondrial iron (Fe) metabolism. The identification of potentially toxic mitochondrial Fe deposits in FA suggests Fe plays a role in its pathogenesis. Studies using the muscle creatine kinase (MCK) conditional frataxin knockout mouse that mirrors the disease have demonstrated frataxin deletion alters cardiac Fe metabolism. Indeed, there are pronounced changes in Fe trafficking away from the cytosol to the mitochondrion, leading to a cytosolic Fe deficiency. Considering Fe deficiency can induce apoptosis and cell death, we examined the effect of dietary Fe supplementation, which led to body Fe loading and limited the cardiac hypertrophy in MCK mutants. Furthermore, this study indicates a unique effect of heart and skeletal muscle-specific frataxin deletion on systemic Fe metabolism. Namely, frataxin deletion induces a signaling mechanism to increase systemic Fe levels and Fe loading in tissues where frataxin expression is intact (i.e., liver, kidney, and spleen). Examining the mutant heart, native size-exclusion chromatography, transmission electron microscopy, Mössbauer spectroscopy, and magnetic susceptibility measurements demonstrated that in the absence of frataxin, mitochondria contained biomineral Fe aggregates, which were distinctly different from isolated mammalian ferritin molecules. These mitochondrial aggregates of Fe, phosphorus, and sulfur, probably contribute to the oxidative stress and pathology observed in the absence of frataxin.

Quantitative magnetic analysis reveals ferritin-like iron as the most predominant iron-containing species in the murine Hfe-haemochromatosis.

Quantitative analysis of the temperature dependent AC magnetic susceptibility of freeze-dried mouse tissues from an Hfe hereditary haemochromatosis disease model indicates that iron predominantly appears biomineralised, like in the ferritin cores, in the liver, the spleen and duodenum. The distribution of the amount of ferritin-like iron between genders and genotypes coincides with that of elemental iron and nonheme iron. Importantly, the so-called paramagnetic iron, a quantity also determined from the magnetic data and indicative of nonmineralised iron forms, appears only marginally increased when iron overload takes place.

Dimercaptosuccinic acid-coated magnetite nanoparticles for magnetically guided in vivo delivery of interferon gamma for cancer immunotherapy.

As radio- and chemotherapy-based cancer treatments affect both tumors and healthy tissue, cancer immunotherapy attempts to specifically enhance the natural immune response to tumor cells. In mouse models of cancer, we tested uniform dimercaptosuccinic acid (DMSA)-coated monodisperse magnetic nanoparticles as a delivery system for the anti-tumorigenic cytokine IFN-γ. IFN-γ-adsorbed DMSA-coated magnetic nanoparticles were targeted to the tumor site by application of an external magnetic field. We analyzed nanoparticle biodistribution before and after IFN-γ conjugation, as well as the efficiency of nanoparticle accumulation in tumors, IFN-γ release in the area of interest, and the effects of both on tumor development. At the tumor site, we observed a high degree of nanoparticle accumulation and of cytokine delivery, which led to increased T cell and macrophage infiltration and promoted an anti-angiogenic effect. The combined action led to a notable reduction in tumor size. Our findings indicate that IFN-γ-adsorbed DMSA-coated magnetite nanoparticles can be used as an efficient in vivo drug delivery system for tumor immunotherapy.

Serum ferritin is derived primarily from macrophages through a nonclassical secretory pathway.

The serum ferritin concentration is a clinical parameter measured widely for the differential diagnosis of anemia. Its levels increase with elevations of tissue iron stores and with inflammation, but studies on cellular sources of serum ferritin as well as its subunit composition, degree of iron loading and glycosylation have given rise to conflicting results. To gain further understanding of serum ferritin, we have used traditional and modern methodologies to characterize mouse serum ferritin. We find that both splenic macrophages and proximal tubule cells of the kidney are possible cellular sources for serum ferritin and that serum ferritin is secreted by cells rather than being the product of a cytosolic leak from damaged cells. Mouse serum ferritin is composed mostly of L-subunits, whereas it contains few H-subunits and iron content is low. L-subunits of serum ferritin are frequently truncated at the C-terminus, giving rise to a characteristic 17-kD band that has been previously observed in lysosomal ferritin. Taken together with the fact that mouse serum ferritin is not detectably glycosylated, we propose that mouse serum ferritin is secreted through the nonclassical lysosomal secretory pathway.

Iron speciation study in Hfe knockout mice tissues: magnetic and ultrastructural characterisation.

Liver, spleen and heart tissues of DBA/2 Hfe knockout mice have been characterised by low temperature AC magnetic susceptibility measurements together with Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction in order to investigate the chemical iron speciation in a murine model of iron overload diseases. With emphasis on ferritin-like species, the temperature dependent in-phase and out-of-phase susceptibility profiles agree with the elemental analysis in that, in this model, iron accumulation takes place in the hepatic tissue while in the spleen and heart tissues no differences have been observed between knockout and wild type animals. The comparison of the magnetic properties between perfused and non-perfused liver tissues has made it possible to estimate the magnetic contribution of usually present blood remains. The TEM observations reveal that, besides the isolated ferritins and ferritin-containing lysosomes-siderosomes present in the hepatocytes, other iron deposits, of heterogeneous size, morphology and crystalline structure (haematite and/or goethite), are present in the cytoplasm, near the membrane, and in extracellular spaces.

Bioinorganic transformations of liver iron deposits observed by tissue magnetic characterisation in a rat model.

The magnetic properties and the ultrastructure, with special emphasis on the nanometric range, of liver tissues in an iron overload rat model have been investigated. The tissues of the animals, sacrificed at different times after a single iron dextran injection, have been characterised by magnetic AC susceptibility measurements together with transmission electron microscopy (TEM) and selected area electron diffraction (SAED) as helping techniques. It has been observed that few days after the iron administration the liver contains at least two iron species: (i) akaganéite nanoparticles, coming from iron dextran and (ii) ferrihydrite nanoparticles corresponding to ferritin. The magnetic susceptibility of the tissues depends not only on the elemental iron content but also on its distribution among chemical species, and varies in a remarkable regular manner as a function of the elapsed time since the iron administration. The results are of relevance with respect to non-invasive techniques for liver iron determination, directly or indirectly based on the magnetic susceptibility of the tissues, as biomagnetic liver susceptometry (BLS) and magnetic resonance (MRI) image treatment.

Synoviocyte-derived CXCL12 is displayed on endothelium and induces angiogenesis in rheumatoid arthritis.

CXCL12 (stromal cell-derived factor-1) is a potent CXC chemokine that is constitutively expressed by stromal resident cells. Although it is considered a homeostatic rather than an inflammatory chemokine, CXCL12 has been immunodetected in different inflammatory diseases, but also in normal tissues, ant its potential functions and regulation in inflammation are not well known. In this study, we examined the cellular sources of CXCL12 gene expression and the mechanism and effects of its interactions with endothelial cells in rheumatoid arthritis synovium. We show that CXCL12 mRNA was not overexpressed nor induced in cultured rheumatoid synoviocytes, but it specifically accumulated in the rheumatoid hyperplastic lining layer and endothelium. CXCL12 gene expression was restricted to fibroblast-like synoviocytes, whereas endothelial cells did not express CXCL12 mRNA, but displayed the protein on heparitinase-sensitive factors. CXCL12 colocalized with the angiogenesis marker alpha(v)beta(3) integrin in rheumatoid endothelium and induced angiogenesis in s.c. Matrigel plugs in mice. The angiogenic activity of rheumatoid synovial fluid in vivo was abrogated by specific immunodepletion of CXCL12. Our results indicate that synoviocyte-derived CXCL12 accumulates and it is immobilized on heparan sulfate molecules of endothelial cells, where it can promote angiogenesis and inflammatory cell infiltration, supporting a multifaceted function for this chemokine in the pathogenesis of rheumatoid arthritis.