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Magnetotactic bacteria (MTB) have the remarkable capability of producing intracellularly membrane-enveloped magnetic nanocrystals (i.e. magnetosomes) and swimming along geomagnetic field lines. Despite more than 50 years of research, bacterial diversity and magnetosome biomineralization within MTB are relatively less known in the Gammaproteobacteria class than other groups. This is incompatible with the status of Gammaproteobacteria as the most diverse class of gram-negative bacteria with a number of ecologically important bacteria. Here, we identify a novel MTB strain YYHR-1 affiliated with the Gammaproteobacteria class of the Pseudomonadota phylum from a freshwater lake. In YYHR-1, most magnetosome crystals are organized into a long chain aligned along the cell long axis; unusually, a few small superparamagnetic crystals are located at the side of the chain, off the main chain axis. Micromagnetic simulations indicate that magnetostatic interactions among adjacent crystals within a chain reduce the Gibbs energy to enhance chain stability. Genomic analysis suggests that duplication of magnetosome gene clusters may result in off-chain magnetosomes formation. By integrating available genomic data from Gammaproteobacteria, the phylogenetic position of MTB in this class is reassigned here. Our new findings expand knowledge about MTB diversity and magnetosome biomineralization, and deepen understanding of the phylogenetics of the Gammaproteobacteria., (© The Author(s) 2023. Published by Oxford University Press on behalf of FEMS.)

Magnetotactic bacteria (MTB) ubiquitously inhabit the oxic-anoxic interface or anaerobic areas of aquatic environments. MTB biomineralize magnetite or greigite crystals and synthesize an organelle known as magnetosome. This intrinsic ability of MTB allows them to accumulate iron to levels 100-1000 times higher than those in non-magnetotactic bacteria (non-MTB). Therefore, MTB considerably contributes to the global iron cycle as primary iron suppliers in the aquatic environmental food chain. However, to the best of our knowledge, there have been no reports describing the effects of trophic interactions between MTB and their protist grazers on the iron distributions in MTB grazers and the extracellular milieu. Herein, we evaluated the effects of MTB grazing using a model species of protist (Tetrahymena pyriformis) and a model species of MTB (Magnetospirillum magneticum AMB-1). MTB-fed T. pyriformis exhibited a magnetic response and contained magnetite crystals in their vacuoles. Fluorescence imaging using a ferrous ion-specific fluorescent dye revealed that the cellular ferrous ion content was five times higher in MTB-fed T. pyriformis than in non-MTB grazers. Moreover, soluble iron concentrations in the spent media increased with time during MTB predation. This study provides experimental evidence to delineate the importance of trophic interactions of MTB on iron distributions., (© 2023 The Authors. Environmental Microbiology Reports published by Applied Microbiology International and John Wiley & Sons Ltd.)

In this work, a novel surface-modified, green-based wheat straw-supported magnetite nanoparticles (Fe 3 O 4 -NPs) were synthesized via the green synthesis method, and the adsorption of mercury (Hg(II)) ion from aqueous solutions was methodically investigated. The synthesized wheat straw-supported magnetite (Fe 3 O 4 -WSS) NPs were characterized using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopic (SEM) methods. FT-IR and TGA confirmed that the surface of Fe 3 O 4 -NPs was functionalized well. The XRD analysis revealed the existence of magnetite in the synthesized wheat straw-supported Fe 3 O 4 -NPs of 19.83 nm average crystalline size. SEM analysis showed Fe 3 O 4 -NPs were almost spherical, with an average particle size of 22.48 nm. Adsorption studies were carried out to investigate the adsorption of Hg(II) ions onto Fe 3 O 4 -WSS NPs and the effect of various adsorption parameters such as pH, time, adsorbent dosage, and Hg(II) ion concentration. The optimum adsorption conditions were obtained: pH of 6, contact time of 45 min, adsorbate of 40 mg/L, and adsorbent of 1 g. A maximum of 98.04% Hg(II) ion removal efficiency was obtained at these optimum conditions. FT-IR analysis also indicated that surface functional groups such as C = C,-OH, and C-C of the newly produced Fe 3 O 4 -NPs led to the more efficient removal of Hg(II) from aqueous solution. The synthesized nano-adsorbent showed an excellent adsorption capability of 101.01 mg/g. Hg(II) ions adsorption onto Fe 3 O 4 -WSS NPs fitted well with the Langmuir adsorption isotherm model. Therefore, these reasonable findings reveal that Fe 3 O 4 -WSS NPs are an efficient and promising adsorbent for Hg(II) removal from aqueous water environments., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: One of the most complex prokaryotic organelles are magnetosomes, which are formed by magnetotactic bacteria as sensors for navigation in the Earth's magnetic field. In the alphaproteobacterium Magnetospirillum gryphiswaldense magnetosomes consist of chains of magnetite crystals (Fe 3 O 4 ) that under microoxic to anoxic conditions are biomineralized within membrane vesicles. To form such an intricate structure, the transcription of > 30 specific structural genes clustered within the genomic magnetosome island (MAI) has to be coordinated with the expression of an as-yet unknown number of auxiliary genes encoding several generic metabolic functions. However, their global regulation and transcriptional organization in response to anoxic conditions most favorable for magnetite biomineralization are still unclear., Results: Here, we compared transcriptional profiles of anaerobically grown magnetosome forming cells with those in which magnetosome biosynthesis has been suppressed by aerobic condition. Using whole transcriptome shotgun sequencing, we found that transcription of about 300 of the > 4300 genes was significantly enhanced during magnetosome formation. About 40 of the top upregulated genes are directly or indirectly linked to aerobic and anaerobic respiration (denitrification) or unknown functions. The mam and mms gene clusters, specifically controlling magnetosome biosynthesis, were highly transcribed, but constitutively expressed irrespective of the growth condition. By Cappable-sequencing, we show that the transcriptional complexity of both the MAI and the entire genome decreased under anaerobic conditions optimal for magnetosome formation. In addition, predominant promoter structures were highly similar to sigma factor σ 70 dependent promoters in other Alphaproteobacteria., Conclusions: Our transcriptome-wide analysis revealed that magnetite biomineralization relies on a complex interplay between generic metabolic processes such as aerobic and anaerobic respiration, cellular redox control, and the biosynthesis of specific magnetosome structures. In addition, we provide insights into global regulatory features that have remained uncharacterized in the widely studied model organism M. gryphiswaldense, including a comprehensive dataset of newly annotated transcription start sites and genome-wide operon detection as a community resource (GEO Series accession number GSE197098)., (© 2022. The Author(s).)

Metal sulfides are a common group of extracellular bacterial biominerals. However, only a few cases of intracellular biomineralization are reported in this group, mostly limited to greigite (Fe 3 S 4 ) in magnetotactic bacteria. Here, a previously unknown periplasmic biomineralization of copper sulfide produced by the magnetotactic bacterium Desulfamplus magnetovallimortis strain BW-1, a species known to mineralize greigite (Fe 3 S 4 ) and magnetite (Fe 3 O 4 ) in the cytoplasm is reported. BW-1 produces hundreds of spherical nanoparticles, composed of 1-2 nm substructures of a poorly crystalline hexagonal copper sulfide structure that remains in a thermodynamically unstable state. The particles appear to be surrounded by an organic matrix as found from staining and electron microscopy inspection. Differential proteomics suggests that periplasmic proteins, such as a DegP-like protein and a heavy metal-binding protein, could be involved in this biomineralization process. The unexpected periplasmic formation of copper sulfide nanoparticles in BW-1 reveals previously unknown possibilities for intracellular biomineralization that involves intriguing biological control and holds promise for biological metal recovery in times of copper shortage., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Molecular machines, as exemplified by the kinesin and microtubule system, are responsible for molecular transport in cells. The monitoring of the cellular machinery has attracted much attention in recent years, requiring sophisticated techniques such as optical tweezers, and dark field hyperspectral and fluorescence microscopies. It also demands suitable procedures for immobilization and labeling with functional agents such as dyes, plasmonic nanoparticles and quantum dots. In this work, microtubules were co-polymerized by incubating a tubulin mix consisting of 7 biotinylated tubulin to 3 rhodamine tubulin. Rhodamine provided the fluorescent tag, while biotin was the anchoring group for receiving streptavidin containing species. To control the microtubule alignment and consequently, the molecular gliding directions, functionalized iron oxide nanoparticles were employed in the presence of an external magnet field. Such iron oxide nanoparticles, (MagNPs) were previously coated with silica and (3-aminopro-pyl)triethoxysilane (APTS) and then modified with streptavidin (SA) for linking to the biotin-functionalized microtubules. In this way, the binding has been successfully performed, and the magnetic alignment probed by Inverted Fluorescence Microscopy. The proposed strategy has proved promising, as tested with one of the most important biological structures of the cellular machinery.

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V-Ti magnetite mine tailings. In the present work, we first examined the native plants' potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16 S rRNA-based metagenomics. It was found that in V-Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF = 1.212), while T. angustifolia was an accumulator of Mn (TF = 2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background and Purpose: Glioblastoma-associated macrophages are a major constituent of the immune response to therapy and are known to engulf the iron-based MR imaging contrast agent, ferumoxytol. Current ferumoxytol MR imaging techniques for localizing macrophages are confounded by contaminating intravascular signal. The aim of this study was to assess the utility of a newly developed MR imaging technique, segregation and extravascular localization of ferumoxytol imaging, for differentiating extravascular-from-intravascular ferumoxytol contrast signal at a delayed 24-hour imaging time point., Materials and Methods: Twenty-three patients with suspected post-chemoradiotherapy glioblastoma progression underwent ferumoxytol-enhanced SWI. Segregation and extravascular localization of ferumoxytol imaging maps were generated as the voxelwise difference of the delayed (24 hours) from the early (immediately after administration) time point SWI maps. Continuous segregation and extravascular localization of ferumoxytol imaging map values were separated into positive and negative components. Image-guided biologic correlation was performed., Results: Negative segregation and extravascular localization of ferumoxytol imaging values correlated with early and delayed time point SWI values, demonstrating that intravascular signal detected in the early time point persists into the delayed time point. Positive segregation and extravascular localization of ferumoxytol imaging values correlated only with delayed time point SWI values, suggesting successful detection of the newly developed extravascular signal., Conclusions: Segregation and extravascular localization of ferumoxytol MR imaging improves on current techniques by eliminating intrinsic tissue and intravascular ferumoxytol signal and may inform glioblastoma outcomes by serving as a more specific metric of macrophage content compared with uncorrected T1 and SWI techniques., (© 2020 by American Journal of Neuroradiology.)

The use of magnetic fluid hyperthermia (MFH) for cancer therapy has shown promise but lacks suitable methods for quantifying exogenous irons such as superparamagnetic iron oxide (SPIO) nanoparticles as a source of heat generation under an alternating magnetic field (AMF). Application of quantitative susceptibility mapping (QSM) technique to prediction of SPIO in preclinical models has been challenging due to a large variation of susceptibility values, chemical shift from tissue fat, and noisier data arising from the higher resolution required to visualize the anatomy of small animals. In this study, we developed a robust QSM for the SPIO ferumoxytol in live mice to examine its potential application in MFH for cancer therapy. We demonstrated that QSM was able to simultaneously detect high level ferumoxytol accumulation in the liver and low level localization near the periphery of tumors. Detection of ferumoxytol distribution in the body by QSM, however, required imaging prior to and post ferumoxytol injection to discriminate exogenous iron susceptibility from other endogenous sources. Intratumoral injection of ferumoxytol combined with AMF produced a ferumoxytol-dose dependent tumor killing. Histology of tumor sections corroborated QSM visualization of ferumoxytol distribution near the tumor periphery, and confirmed the spatial correlation of cell death with ferumoxytol distribution. Due to the dissipation of SPIOs from the injection site, quantitative mapping of SPIO distribution will aid in estimating a change in temperature in tissues, thereby maximizing MFH effects on tumors and minimizing side-effects by avoiding unwanted tissue heating.

The long-term survival of osteosarcoma patients with metastatic or recurrent disease remains dismal, and new therapeutic options are urgently needed. The purpose of our study was to compare the efficacy of CD47 mAb plus doxorubicin combination therapy in mouse models of osteosarcoma with CD47 mAb and doxorubicin monotherapy. Forty-eight NOD scid gamma (NSG) mice with intratibial MNNG/HOS tumors received CD47 mAb, doxorubicin, combination therapy, or control IgG treatment. Twenty-four mice (n = 6 per group) underwent pre- and post-treatment magnetic resonance imaging (MRI) scans with the macrophage marker ferumoxytol, bioluminescence imaging, and histological analysis. Tumor ferumoxytol enhancement, tumor flux, and tumor-associated macrophages (TAM) density were compared between different groups using a one-way ANOVA. Twenty-four additional NSG mice underwent survival analyses with Kaplan-Meier curves and a log-rank (Mantel-Cox) test. Intratibial osteosarcomas demonstrated significantly stronger ferumoxytol enhancement and significantly increased TAM quantities after CD47 mAb plus doxorubicin combination therapy compared to CD47 mAb (P = 0.02) and doxorubicin monotherapy (P = 0.001). Tumor-bearing mice treated with CD47 mAb plus doxorubicin combination therapy demonstrated significantly reduced tumor size and prolonged survival compared to control groups that received CD47 mAb (P = 0.03), doxorubicin monotherapy (P = 0.01), and control IgG (P = 0.001). In conclusion, CD47 mAb plus doxorubicin therapy demonstrates an additive therapeutic effect in mouse models of osteosarcomas, which can be monitored with an immediately clinically applicable MRI technique., (© 2019 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.)

During the past several decades there has been much interest in the existence of magnetite particles in the human brain and their accumulation with age. These particles also appear to play an important role in neurodegenerative diseases of the brain. However, up to now the amount and distribution of these particles has been measured only in post-mortem brain tissue. Although in-vivo MRI measurements do show iron compounds generally, MRI cannot separate them according to their magnetic phases, which are associated with their chemical interactions. In contrast, we here offer a new noninvasive, in-vivo method which is selectively sensitive only to particles which can be strongly magnetized. We magnetize these particles with a strong magnetic field through the head, and then measure the resulting magnetic fields, using the dcMagnetoencephalogram (dcMEG). From these data, the mass and locations of the particles can be estimated, using a distributed inverse solution. To test the method, we measured 11 healthy male subjects (ages 19-89 year). Accumulation of magnetite, in the hippocampal formation or nearby structures, was observed in the older men. These in-vivo findings agree with reports of post-mortem measurements of their locations, and of their accumulation with age. Thus, our findings allow in-vivo measurement of magnetite in the human brain, and possibly open the door for new studies of neurodegenerative diseases of the brain., (© 2018 The Authors. Human Brain Mapping published by Wiley Periodicals, Inc.)

Recently it has been shown that there are two types of magnetite particles in the human brain, some, which occur naturally and are jagged in appearance, and others that arise from industrial sources, such as coal fired power plants, and are spherical. In order to confirm the latter, the magnetic component of coal ash is first purified and characterized by XRD, showing that it is magnetite with an average particle size of 211 nm. Studies confirm the coal ash magnetic behavior, and that the magnetite is not bound to the other components of coal ash but exist as an isolatable component. SEM studies confirm that in the process of burning coal at very high temperatures for industrial uses, the magnetite formed is spherically shaped, as recent studies of brain tissues of highly exposed urban residents have found. As such, the use of coal for industrial applications such as coking in the production of steel and in power plants is indicated to be a major source of the spherical magnetic combustion-associated magnetite fine particle and nanoparticle environmental pollution. The capacity of these magnetic particles to penetrate and damage the blood-brain-barrier and the early development of Alzheimer's disease hallmarks in exposed populations calls for detail analysis of magnetic fine and nanoparticle distribution across the world. Summation: Industrial coal usage produces spherical magnetic particles and nanoparticles, identical to those associated with neurological disorders., (Published by Elsevier Ltd.)

Understanding marine environmental change and associated biological turnover across the Palaeocene-Eocene Thermal Maximum (PETM; ~56 Ma)-the most pronounced Cenozoic short-term global warming event-is important because of the potential role of the ocean in atmospheric CO 2 drawdown, yet proxies for tracing marine productivity and oxygenation across the PETM are limited and results remain controversial. Here we show that a high-resolution record of South Atlantic Ocean bottom water oxygenation can be extracted from exceptionally preserved magnetofossils-the bioinorganic magnetite nanocrystals produced by magnetotactic bacteria (MTB) using a new multiscale environmental magnetic approach. Our results suggest that a transient MTB bloom occurred due to increased nutrient supply. Bottom water oxygenation decreased gradually from the onset to the peak PETM. These observations provide a record of microbial response to the PETM and establish the value of magnetofossils as palaeoenvironmental indicators.

Using Artemia salina cysts (capsulated and decapsulated) and larvae (instar I, II and III) as experimental models, the potential effects of Fe 3 O 4 nanoparticles (Fe 3 O 4 -NPs) on marine ecosystems were investigated. Hatchability, mortality and a number of ethological, morphological and biochemical parameters were selected as end-points to define the toxic responses. Data showed that the hatching rates of capsulated and decapsulated cysts were significantly decreased (p < 0.01) following exposure to 600 mg/L for 24 and 36 h. The LC 50 values for instar II and III were 482 and 561 mg/L (could not be measured for instar I), and the EC 50 values for swimming inhibition of instar I, II and III were 474, 365 and 421 mg/L, respectively. Effects on hatchability, mortality and swimming were accounted for Fe 3 O 4 -NPs rather than iron ion released from the NPs. Instar II larvae showed the greatest sensitivity to Fe 3 O 4 -NPs, and followed by instar III, instar I, decapsulated cysts and capsulated cysts. Body lengths of instar I, II and III larvae were decreased in dose-dependent manners. Fe 3 O 4 -NPs attached onto the gills and body surface, resulting in irreversible damages. Reactive oxygen species, malondialdehyde content, total antioxidant capacity and antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) activities were substantially increased following exposure, indicating that toxic effects were related to oxidative stress. Mitochondrial malformation, cristae rupturing and membranous structure disruption were clearly observed after Fe 3 O 4 -NPs exposure. Fe 3 O 4 -NPs were ingested and well distributed in the gut, yolk and primary body cavity. Uptake kinetics data showed that the maximum Fe 3 O 4 -NPs content (16.4 mg/g) was reached at 30 h. The combined results so far indicate that Fe 3 O 4 -NPs have the potential to affect aquatic organisms when released into the marine ecosystems., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) or greigite (Fe3S4) particles in the cells. Recently, several studies have shown some possibilities of controlling the biomineralization process and altering the magnetic properties of magnetosomes by adding some transition metals to the culture media under various environmental conditions. Here, we successfully grow Magnetospirillum magneticum strain RSS-1, which are isolated from a freshwater environment, and find that synthesis of magnetosomes are encouraged in RSS-1 in the presence of samarium and that each core magnetic crystal composed of magnetite is covered with a thin layer of samarium oxide (Sm2O3). The present results show some possibilities of magnetic recovery of transition metals and synthesis of some novel structures composed of magnetic particles and transition metals utilizing MTB., Competing Interests: The authors have declared that no competing interests exist.

The unique electrocoagulator proposed in this study is highly efficient at removing Ni-EDTA, providing a potential remediation option for wastewater containing lower concentrations of Ni-EDTA (Ni ≤ 10 mg L -1 ). In the electrocoagulation (EC) system, cylindrical graphite was used as a cathode, and a packed-bed formed from iron scraps was used as an anode. The results showed that the removal of Ni-EDTA increased with the application of current and favoured acidic conditions. We also found that the iron scrap packed-bed anode was superior in its treatment ability and specific energy consumption (SECS) compared with the iron rod anode. In addition, the packed density and temperature had a large influence on the energy consumption (ECS). Over 94.3% of Ni and 95.8% of TOC were removed when conducting the EC treatment at an applied current of 0.5 A, initial pH of 3, air-purged rate 0.2 L min -1 , anode packed density of 400 kg m -3 temperature of 313 K and time of 30 min. SEM analysis of the iron scraps indicated that the specific area of the anode increased after the EC. The XRD analysis of flocs produced during EC revealed that hematite (α-Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) were the main by-products under aerobic and anoxic conditions, respectively. A kinetic study demonstrated that the removal of Ni-EDTA followed a first-order model with the current parameters. Moreover, the removal efficiency of real wastewater was essentially consistent with that of synthetic wastewater., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Abnormal accumulation of brain metals is a key feature of Alzheimer's disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

Aim: To test the hypothesis that MRI can monitor intraportal vein (IPV) transcatheter delivery of clinically applicable heparin-protamine-ferumoxytol (HPF) nanocomplex-labeled natural killer (NK) cells to liver tumor., Materials & Methods: Liver tumor rat models underwent catheterization for IPV infusion of HPF-labeled NK cells (NK-92MI cell line). MRI measurements within tumor and adjacent liver tissues were compared pre- and post-NK cell infusion. Histology studies were used to identify NK cells in the target tumors., Results: For first time, we demonstrated that MRI tracks HPF-labeled NK cells migration within liver following IPV delivery., Conclusion: IPV transcatheter infusion permitted selective delivery of NK cells to liver tissues and MRI allowed tracking NK cell biodistributions within the tumors.

The environmental risk of exposure to six heavy metals (Cu, Pb, Zn, Cr, Ni, and Cd) found in fly ashes from waste filter bags obtained from a steel plant was estimated based on the mineralogical compositions, total concentrations and speciation of the metals in the fly ashes. The results indicated that the fly ashes mainly consisted of hematite, magnetite, cyanite, spinel, coesite and amorphous materials. The concentrations of Zn and Pb were much higher than that of other materials. After Zn and Pb, Ni was present in the highest concentration, followed by Cu, Cr and Cd. Each heavy metal was distributed differently in fly ashes. The levels of Zn, Cd and Pb in the active fraction were very high, and ranged from 64.83 to 81.96%, 34.48 to 82.4% and 6.92 to 79.65% respectively, while Cu, Cr and Ni were mainly present in the residual fraction. The risk assessment code (RAC) values of fly ashes showed that the Zn and Cd present in the H3 sample presented a very high risk, with RAC values greater than 50%. The Cu present in the H3 sample, Cd in the H2 sample and Zn in the H4 and H5 samples presented a high risk. The Pb present in the H2 sample, Cd in the H4 sample, Ni in the H1 and H5 samples, and Zn in the H1 sample presented a medium risk. A low risk was presented by the Cu present in the H1, H2, H4 and H5 samples, the Pb in the H1, H3 and H5 samples, the Cd in the H1 and H5 samples, and the Ni in the H2 sample. No risk was presented by Cr in any sample., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This letter describes an ultrasound imaging assessment of novel contrast agents that are detectable by both medical ultrasound and magnetic resonance imaging. Such agents are created by including superparamagnetic particles in polymer-shelled microbubbles through two different approaches. The reduced echogenicity and nonlinearity of the microbubbles are observed, depending on the strategy used to include the particles and the resulting density. The best results are obtained using imaging techniques that exploit the third-order nonlinear term, which is especially true when the microbubbles are excited by means of chirp pulses.

Magnetotactic bacteria contain magnetosomes--intracellular, membrane-bounded, magnetic nanocrystals of magnetite (Fe(3)O(4)) or greigite (Fe(3)S(4))--that cause the bacteria to swim along geomagnetic field lines. We isolated a greigite-producing magnetotactic bacterium from a brackish spring in Death Valley National Park, California, USA, strain BW-1, that is able to biomineralize greigite and magnetite depending on culture conditions. A phylogenetic comparison of BW-1 and similar uncultured greigite- and/or magnetite-producing magnetotactic bacteria from freshwater to hypersaline habitats shows that these organisms represent a previously unknown group of sulfate-reducing bacteria in the Deltaproteobacteria. Genomic analysis of BW-1 reveals the presence of two different magnetosome gene clusters, suggesting that one may be responsible for greigite biomineralization and the other for magnetite.

Superparamagnetic iron-oxide particles (SPIO) are used in different ways as contrast agents for magnetic resonance imaging (MRI): Particles with high nonspecific uptake are required for unspecific labeling of phagocytic cells whereas those that target specific molecules need to have very low unspecific cellular uptake. We compared iron-oxide particles with different core materials (magnetite, maghemite), different coatings (none, dextran, carboxydextran, polystyrene) and different hydrodynamic diameters (20-850 nm) for internalization kinetics, release of internalized particles, toxicity, localization of particles and ability to generate contrast in MRI. Particle uptake was investigated with U118 glioma cells und human umbilical vein endothelial cells (HUVEC), which exhibit different phagocytic properties. In both cell types, the contrast agents Resovist, B102, non-coated Fe(3)O(4) particles and microspheres were better internalized than dextran-coated Nanomag particles. SPIO uptake into the cells increased with particle/iron concentrations. Maximum intracellular accumulation of iron particles was observed between 24 h to 36 h of exposure. Most particles were retained in the cells for at least two weeks, were deeply internalized, and only few remained adsorbed at the cell surface. Internalized particles clustered in the cytosol of the cells. Furthermore, all particles showed a low toxicity. By MRI, monolayers consisting of 5000 Resovist-labeled cells could easily be visualized. Thus, for unspecific cell labeling, Resovist and microspheres show the highest potential, whereas Nanomag particles are promising contrast agents for target-specific labeling.

The magnetotactic bacterium Magnetospirillum sp. has been cultured and the properties of its endogenous magnetic nanoparticles characterized. Electron-microscopic analyses indicate that the endogenous magnetite nanoparticles in Magnetospirillum sp. are coated with a 3-4 nm thick transparent shell, forming a magnetosome. These magnetite nanoparticles had diameters of 50.9+/-13.3 nm, in good agreement with the diameter of 40.6+/-1.2 nm extracted from magnetometry. Each Magnetospirillum sp. bacterium contained chains of 5-25 magnetosomes. Superconducting quantum interference device magnetometry results indicate that the extrinsic superparamagnetic response of the bacterial solution at room temperature can be attributed to the reversal of the magnetization by physical rotation of the nanoparticles. The intrinsic blocking temperature of a sample of freeze-dried bacteria was estimated to be 282+/-13 K. A tunnelling magneto resistance sensor was used to detect the stray fields of endogenous magnetic nanoparticles in static and quasi-dynamic modes. Based on the tunnelling magneto resistance sensor results, the magnetic moment per bacterium was estimated to be approximately 2.6 x 10(-13) emu. The feasibility of this detection method either as a mass-coverage device or as part of an integrated microfluidic circuit for detection and sorting of magnetosome-containing cells was demonstrated.

The behavior of four types of untreated metal oxide nanoparticles in saturated porous media was studied. The transport of Fe(3)O(4), TiO(2), CuO, and ZnO was measured in a series of column experiments. Vertical columns were packed with uniform, spherical glass beads. The particles were introduced as a pulse suspended in aqueous solutions and breakthrough curves at the outlet were measured using UV-vis spectrometry. Different factors affecting the mobility of the nanoparticles such as ionic strength, addition of organic matter (humic acid), flow rate and pH were investigated. The experiments showed that mobility varies strongly among the nanoparticles, with TiO(2) demonstrating the highest mobility. The mobility is also strongly affected by the experimental conditions. Increasing the ionic strength enhances the deposition of the nanoparticles. On the other hand, addition of humic acid increases the nanoparticle mobility significantly. Lower flow rates again led to reduced mobility, while changes in pH had little effect. Overall, in natural systems, it is expected that the presence of humic acid in soil and aquifer materials, and the ionic strength of the resident water, will be key factors determining nanoparticle mobility., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Magnetotactic bacteria (MTB), Magnetospirillum magnetotacticum (MS-1) were successfully grown in modified magnetic spirillum growth medium (MSGM) at normal laboratory environment. About five-time increase in the bacterial yield was achieved in the modified MSGM medium without compromising their magnetosomes properties. Transmission electron and scanning electron microscopy (TEM & SEM) were used for morphological study of MTB. Energy dispersive analysis of X-rays (EDAX) and vibrating sample magnetometer (VSM) techniques, respectively, were used to elucidate the phase and magnetization in the bacterially synthesized magnetosomes. These studies were important to cross-check the morphology of magnetosomes, as the formation of magnetosomes was highly sensitive to environmental conditions.

The use of nanometer-sized iron oxide nanoparticles and micron-sized iron oxide particles as magnetic resonance (MR) contrast agents has garnered a high degree of interest in diverse areas of biology and medicine. Applications such as cell tracking, molecular imaging, gene detection, and lymphography are being explored to provide insight into disease mechanisms, monitor therapeutic efficacy, and facilitate diagnostic imaging. What makes iron oxide so appealing is a number of favorable properties including high detectability by MR, biodegradability and low toxicity. Here we describe the recent progress on the use of magnetic nanoparticles in imaging circulating cells and lymphoid tissues. The study of the lymph system and the biodistribution of various circulating immune cells is important in the diagnosis, prognosis, and treatment of a wide range of diseases and is expected to have a profound effect on patient outcome.

A suite of rock magnetic experiments and intensive microscopic observations were carried out on Asian dust deposits in Seoul, Korea, collected on 19 and 23 March 2002, 9 April 2002 and 12 April 2003. Desert-sand and loess from the dust source regions in China were also analyzed as a comparison. Asian dust showed a higher magnetic concentration than the source region samples, indicating a significant influx of magnetic particles into Asian dust had occurred during its transportation. Electron microscopy identified carbon-bearing iron-oxides as the added material. These iron-oxides were likely to have been produced by anthropogenic pollution (fossil fuel combustion) while the wind-blown dusts passing across the industrial areas of eastern China and western Korea. Such wind-paths were confirmed by a simulation of the air-mass trajectories. The magnetic technique appears to be useful for determining the anthropogenic pollution of Asian dust.

Magnetosomes are magnetite nanoparticles formed by biomineralization within magnetotactic bacteria. Although there have been numerous genetic and proteomic studies of the magnetosome-formation process, there have been only limited and inconclusive studies of mineral-phase evolution during the formation process, and no real-time studies of such processes have yet been performed. Thus, suggested formation mechanisms still need substantiating with data. Here we report the examination of the magnetosome material throughout the formation process in a real-time in vivo study of Magnetospirillum gryphiswaldense, strain MSR-1. Transmission EM and x-ray absorption spectroscopy studies reveal that full-sized magnetosomes are seen 15 min after formation is initiated. These immature magnetosomes contain a surface layer of the nonmagnetic iron oxide-phase hematite. Mature magnetite is found after another 15 min, concurrent with a dramatic increase in magnetization. This rapid formation result is contrary to previously reported studies and discounts the previously proposed slow, multistep formation mechanisms. Thus, we conclude that the biomineralization of magnetite occurs rapidly in magnetotactic bacteria on a similar time scale to high-temperature chemical precipitation reactions, and we suggest that this finding is caused by a biological catalysis of the process.

Background: In this study, we report on the use of a new, bolus-injectable, carboxymethyl dextran-based magnetic nanoparticle (MNP), ferumoxytol, to improve detection in loco-regional lymph nodes by magnetic resonance imaging (MRI)., Methods: This preliminary study was performed as a prospective, single-center, open label pilot study to determine the magnitude of nodal MRI signal changes and to determine the optimal time points for imaging following intravenous (IV) bolus injection of the MNP. The study group consisted of 10 patients, all of whom were diagnosed with prostate cancer before any systemic therapy., Results: All 10 patients had lymph nodes evaluated by histopathology. Of the evaluated 26 lymph nodes, 20 were benign and 6 were malignant. The mean short-axis diameter of benign lymph nodes was 6 mm and the mean short-axis diameter of malignant lymph nodes was 7 mm. Following IV administration, there was a significant change in mean signal-to-noise ratio (SNR) of benign lymph nodes (P < .0001) whereas there was little change in the mean SNR of malignant nodes (P = .1624). No adverse events were encountered., Conclusion: Ferumoxytol is safe and, at the appropriate circulation interval, modulates nodal signal intensity, allowing for identification of malignant nodal involvement by MRI.

Polyethylene glycol (PEG)ylated and rhodamine-labeled liposomes loaded with maghemite nanocrystals provide a novel nanoscaled hybrid system for magnetic targeting to solid tumors in possible combination with double in vivo imaging by fluorescence microscopy and magnetic resonance imaging (MRI). Human prostate adenocarcinoma tumors implanted in mice were used as a system model. A magnetic field gradient was produced at the tumor level by external apposition of a magnet. Noninvasive fibered confocal fluorescence microscopy was successfully used to track the liposomes in vivo within organs and tumor blood vessels. Active targeting to the magnet-exposed tumors was clearly shown, in agreement with previous MRI studies. The liposomes were driven and accumulated within the microvasculature through a process that preserved vesicle structure and content.

Some vertebrates can navigate over long distances using the Earth's magnetic field, but the sensory system that they use to do so has remained a mystery. Here we describe the key components of a magnetic sense underpinning this navigational ability in a single species, the rainbow trout (Oncorhynchus mykiss). We report behavioural and electrophysiological responses to magnetic fields and identify an area in the nose of the trout where candidate magnetoreceptor cells are located. We have tracked the sensory pathway from these newly identified candidate magnetoreceptor cells to the brain and associated the system with a learned response to magnetic fields.