Toxicological evaluation of MnAl based permanent magnets using different in vitro models.

Due to economic, environmental and geopolitical issues, the development of permanent magnets with a composition free of rare earth elements and with acceptable magnetic properties has been considered a priority by the international community, being MnAl based alloys amongst the most promising candidates. The aim of this work was to evaluate the toxicity of powders of two forms of newly developed MnAl(C) permanent magnets through exposure experiments applying three model organisms, using as a benchmark powders of a commercial rare-earth-containing magnet (Nd2Fe14B). For this purpose, the direct exposure to the different particles suspensions as well as to magnets leachates was evaluated. Both viability and oxidative stress assays were applied in an adenocarcinomic human alveolar basal epithelial cell line (A549) and in the yeast Saccharomyces cerevisiae, together with the bioluminescent inhibition assay in the Gram negative bacterium Vibrio fischeri. The obtained results indicate that MnAl(C) permanent magnets, in general terms, presented similar toxicity than the Nd magnet for the selected biological models under the studied conditions. Overall, the presented data provide, for the first time, an in vitro toxicity analysis of MnAl based magnets.

Carbon Nanotubes Filled with Different Ferromagnetic Alloys Affect the Growth and Development of Rice Seedlings by Changing the C:N Ratio and Plant Hormones Concentrations.

The aim of this study was to investigate the phytotoxicity of thin-walled carbon nanotubes (CNTs) to rice (Oryza sativa L.) seedlings. Three different CNTs, including hollow multi-walled carbon nanotubes (MWCNTs), Fe-filled carbon nanotubes (Fe-CNTs), and Fe-Co-filled carbon nanotubes (FeCo-CNTs), were evaluated. The CNTs significantly inhibited rice growth by decreasing the concentrations of endogenous plant hormones. The carbon to nitrogen ratio (C:N ratio) significantly increased in rice roots after treatments with CNTs, and all three types of CNTs had the same effects on the C:N ratio. Interestingly, the increase in the C:N ratio in roots was largely because of decreased N content, indicating that the CNTs significantly decreased N assimilation. Analyses of the Fe and Co contents in plant tissues, transmission electron microscope (TEM) observations and energy dispersive X-ray spectroscopy (EDS) analysis proved that the CNTs could penetrate the cell wall and the cell membrane, and then enter the root cells. According to the author's knowledge, this is the first time to study the relationship between carbon nanotubes and carbon nitrogen ratio and plant hormones.

A cheap and facile route to synthesize monodisperse magnetic nanocrystals and their application as MRI agents.

A facile solution-based thermal decomposition strategy, using very cheap polyisobutylene succimide (PIBSI) and paraffin oil as a surfactant and solvent, respectively, has been developed for the controllable synthesis of magnetic MnFe2O4 and CoFe2O4 nanocrystals (NCs) with high dispersibility, uniform shape, and high yield. By fine-tuning the reaction temperature and growth time, the morphology and size of MnFe2O4 and CoFe2O4 NCs can be simply regulated. It is found that the surfactant PIBSI plays a key role in the final shape of the products due to its long chain with non-polar groups, which can markedly hinder the aggregation of the NCs and thus greatly improve the stability and dispersibility of the products. The results reveal that MnFe2O4 and CoFe2O4 NCs have good biocompatibility and obvious T2 contrast enhancement effects have been achieved with the increase of iron concentration. MnFe2O4 and CoFe2O4 NCs show high longitudinal relaxivity of 165.6 and 65.143 mM(-1) S(-1) in aqueous solutions due to the positive signal enhancement ability of Fe(3+) ions, indicating the highly potential to be used as effective T2 contrast agents for magnetic resonance imaging (MRI).

Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells.

Superparamagnetic iron-oxide nanoparticles (SPIONs) show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells). We evaluated the effect of particle diameter (50 and 100 nm) and polyethylene glycol (PEG) chain length (2k, 5k and 20k Da) on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS). Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications.

Magnetic PEGylated Pt3Co nanoparticles as a novel MR contrast agent: in vivo MR imaging and long-term toxicity study.

Magnetic resonance (MR) imaging using magnetic nanoparticles as the contrast agent has been extensively explored in biomedical imaging and disease diagnosis. Herein, we develop biocompatible polymer coated ultra-small Pt3Co magnetic nanoparticles as a new T2-weighted MR imaging contrast agent. A unique class of alloy Pt3Co nanoparticles is synthesized through a thermal decomposition method. After being modified with polyethylene glycol (PEG), the obtained Pt3Co-PEG nanoparticles exhibit an extremely high T2-weighted relaxivity rate (r2) up to 451.2 mM s(-1), which is much higher than that of Resovist®, a commercial T2-MR contrast agent used in the clinic. In vitro experiments indicate no obvious cytotoxicity of Pt3Co-PEG nanoparticles to various cell lines. After intravenous injection of Pt3Co-PEG nanoparticles, in vivo T2-weighted MR imaging of tumor-bearing mice reveals strong tumor contrast, which is much higher than that offered by injecting Resovist®. We further study the long-term biodistribution and toxicology of this new type of MR contrast nanoparticles after intravenous injection into healthy mice. Despite the significant retention of Pt3Co-PEG nanoparticles in the mouse liver and spleen, no appreciable toxicity of these nanoparticles to the treated animals has been noted in our detailed histological and hematological analysis over a course of 60 days. Our work demonstrates that functionalized Pt3Co nanoparticles may be a promising new type of T2-weighted MR contrast agent potentially useful in biomedical imaging and diagnosis.

Short-term in vitro responses of human peripheral blood monocytes to ferritic stainless steel fiber networks.

Beneficial effects on bone-implant bonding may accrue from ferromagnetic fiber networks on implants which can deform in vivo inducing controlled levels of mechanical strain directly in growing bone. This approach requires ferromagnetic fibers that can be implanted in vivo without stimulating undue inflammatory cell responses or cytotoxicity. This study examines the short-term in vitro responses, including attachment, viability, and inflammatory stimulation, of human peripheral blood monocytes to 444 ferritic stainless steel fiber networks. Two types of 444 networks, differing in fiber cross section and thus surface area, were considered alongside austenitic stainless steel fiber networks, made of 316L, a widely established implant material. Similar high percent seeding efficiencies were measured by CyQuant® on all fiber networks after 48 h of cell culture. Extensive cell attachment was confirmed by fluorescence and scanning electron microscopy, which showed round monocytes attached at various depths into the fiber networks. Medium concentrations of lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-α) were determined as indicators of viability and inflammatory responses, respectively. Percent LDH concentrations were similar for both 444 fiber networks at all time points, whereas significantly lower than those of 316L control networks at 24 h. All networks elicited low-level secretions of TNF-α, which were significantly lower than that of the positive control wells containing zymosan. Collectively, the results indicate that 444 networks produce comparable responses to medical implant grade 316L networks and are able to support human peripheral blood monocytes in short-term in vitro cultures without inducing significant inflammatory or cytotoxic effects.

Prevalence, clinical features and management of pediatric magnetic foreign body ingestions.

BACKGROUND: Foreign body (FB) ingestions are frequent in children. Whereas the majority of FBs pass spontaneously through the gastrointestinal tract, ingestion of magnetic FBs pose a particular risk for obstruction due to proximate attraction through the intestinal wall. STUDY OBJECTIVES: We aimed to identify the prevalence, clinical presentation, and management of magnetic FB ingestions at our tertiary care institution. METHODS: We performed a retrospective chart review of medical records of patients presenting to the pediatric Emergency Department (ED) or admitted to the hospital with FB ingestions from June 2003-July 2009. From those cases, patients with magnetic FB ingestions were identified. RESULTS: During the study period, 337,839 patients presented to the ED; 38 cases of magnetic FB ingestion were identified (prevalence 0.01%). Abdominal radiography was obtained in all cases. Ingestion of a single magnet occurred in 30 of 38 cases (79%). Of those, 4 patients underwent endoscopic removal due to signs of FB impaction in the esophagus or pylorus; no complications were noted. Ingestion of multiple magnets (range 2-6) occurred in 8 of 38 cases. Four of the 8 patients with multiple magnetic FBs (50%) presented with signs of peritonitis and required operative repair of multiple intestinal perforations. No deaths were identified. CONCLUSION: Although ingestion of a single magnetic FB may, in most cases, be managed as a simple FB ingestion, the ingestion of multiple magnetic FB is associated with a high risk of complication and requires aggressive management. We propose an algorithm for management of children with magnetic FB ingestions.

Surface design of core-shell superparamagnetic iron oxide nanoparticles drives record relaxivity values in functional MRI contrast agents.

Core-shell hydrophilic superparamagnetic iron oxide (SPIO) nanoparticles, surface functionalized with either terephthalic acid or 2-amino terephthalic acid, showed large negative MRI contrast ability, validating the advantage of using low molecular weight and π-conjugated canopies for engineering functional nanostructures with superior performances.

Magnetic nanovectors for drug delivery.

Nanotechnology holds the promise of novel and more effective treatments for vexing human health issues. Among these are the use of nanoparticle platforms for site-specific delivery of therapeutics to tumors, both by passive and active mechanisms; the latter includes magnetic vectoring of magnetically responsive nanoparticles (MNP) that are functionalized to carry a drug payload that is released at the tumor. The conceptual basis, which actually dates back a number of decades, resides in physical (magnetic) enhancement, with magnetic field gradients aligned non-parallel to the direction of flow in the tumor vasculature, of existing passive mechanisms for extravasation and accumulation of MNP in the tumor interstitial fluid, followed by MNP internalization. In this review, we will assess the most recent developments and current status of this approach, considering MNP that are composed of one or more of the three elements that are ferromagnetic at physiological temperature: nickel, cobalt and iron. The effects on cellular functions in vitro, the ability to successfully vector the platform in vivo, the anti-tumor effects of such localized nano-vectors, and any associated toxicities for these MNP will be presented. The merits and shortcomings of nanomaterials made of each of the three elements will be highlighted, and a roadmap for moving this long-established approach forward to clinical evaluation will be put forth.

Properties of nanoparticles prepared from NdFeB-based compound for magnetic hyperthermia application.

Nanoparticles were prepared from a NdFeB-based alloy using the hydrogen decrepitation process together with high-energy ball milling and tested as heating agent for magnetic hyperthermia. In the milling time range evaluated (up to 10 h), the magnetic moment per mass at H = 1.59 MA m(-1) is superior than 70 A m(2) kg(-1); however, the intrinsic coercivity might be inferior than 20 kA m(-1). The material presents both ferromagnetic and superparamagnetic particles constituted by a mixture of phases due to the incomplete disproportionation reaction of Nd(2)Fe(14)BH(x) during milling. Solutions prepared with deionized water and magnetic particles exposed to an AC magnetic field (H(max) ~ 3.7 kA m(-1) and f = 228 kHz) exhibited 26 K ≤ ΔT(max) ≤ 44 K with a maximum estimated specific absorption rate (SAR) of 225 W kg(-1). For the pure magnetic material milled for the longest period of time (10 h), the SAR was estimated as ~2500 W kg(-1). In vitro tests indicated that the powders have acceptable cytotoxicity over a wide range of concentration (0.1-100 µg ml(-1)) due to the coating applied during milling.

Magnetic Fe3O4@mesoporous silica composites for drug delivery and bioadsorption.

Magnetic Fe(3)O(4)@mesoporous silica (MS) composites were synthesized by generating Fe(3)O(4) nanoparticles in the mesoporous silica matrix using the sol-gel method in nitrogen atmosphere. The mesoporous silica hosts include SBA-15 particles owning highly ordered p6mm mesostructure, siliceous mesostructured cellular foams (MCFs), and fiber-like mesoporous silica (FMS) with unique pore structures. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and N(2) adsorption/desorption results show that Fe(3)O(4) functionalized MCFs and FMS possess suitable mesoporous structure for the adsorption of both small-molecular drug and large biomolecules. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of these systems. These Fe(3)O(4)@mesoporous silica composites show sustained release properties for aspirin in vitro. The release of the aspirin molecules from the pores of the Fe(3)O(4)@mesoporous silica composites is basically a diffusive process. Fe(3)O(4)@MCFs and Fe(3)O(4)@FMS owning larger pore size are good candidates for the adsorption of bovine serum albumin (BSA). These magnetic composites can be potential vectors for drug delivery and bioadsorption.