Search

We report a one-step synthesis protocol for obtaining polymer-coated magnetic nanoparticles (MNPs) engineered for uploading neural cells. Polyethyleneimine-coated Fe

Magnetic fluid hyperthermia (MFH), the procedure of raising the temperature of tumor cells using magnetic nanoparticles (MNPs) as heating agents, has proven successful in treating some types of cancer. However, the low heating power generated under physiological conditions makes necessary a high local concentration of MNPs at tumor sites. Here, we report how the in vitro heating power of magnetically soft MnFe$_2$O$_4$ nanoparticles can be enhanced by intracellular low-dimensional clusters through a strategy that includes: a) the design of the MNPs to retain N\'eel magnetic relaxation in high viscosity media, and b) culturing MNP-loaded cells under magnetic fields to produce elongated intracellular agglomerates. Our direct in vitro measurements demonstrated that the specific loss power (SLP) of elongated agglomerates ($SLP=576\pm33$ W/g) induced by culturing BV2 cells in situ under a dc magnetic field was increased by a factor of 2 compared to the $SLP=305\pm25$ W/g measured in aggregates freely formed within cells. A numerical mean-field model that included dipolar interactions quantitatively reproduced the SLPs of these clusters both in phantoms and in vitro, suggesting that it captures the relevant mechanisms behind power losses under high-viscosity conditions. These results indicate that in situ assembling of MNPs into low-dimensional structures is a sound possible way to improve the heating performance in MFH., Comment: 63 pages, 19 figures

Semiconductor nanoparticles (SNPs) are excellent candidates for various applications in fields like solar cells, light emitting diodes or sensors. Their size strongly determines their properties, thus characterizing their size is crucial for applications. In most cases, they are included in complex matrices which make it difficult to determine their average diameter and statistical distribution. In this work, we present a non-destructive, cheap and in situ procedure to calculate particle size distributions (PSDs) of SNPs in different media based on deconvolution of the absorbance spectrum with a database of the absorbance spectra of SNPs with different sizes. The method was validated against the SNP sizes obtained from transmission microscopy images, showing excellent agreement between both distributions. In particular, CdS SNPs embedded in mesoporous thin films were analyzed in detail. Additional composite systems were studied in order to extend the method to SNPs in polymers or bacteria, proving that it applies to several SNPs in diverse matrices. The PSDs obtained from the proposed method do not show any statistical difference with the one derived from TEM images. Finally, a web app that implements the methodology of this work has been developed. Fil: Onna, Diego Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Perez Ipiña, Ignacio Martin. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Fernández Casafuz, Agustina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Mayoral, Álvaro. Shanghai Tech University; China. Universidad de Zaragoza; España Fil: Ibarra García, M. Ricardo. Universidad de Zaragoza; España Fil: Aldabe, Sara Alfonsina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Martinez Ricci, Maria Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina

The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation. Scanning tunneling spectroscopy is used to obtain maps of the Kondo resonance intensity with sub-atomic resolution. For sufficiently small interatomic separation, the spatial distribution of Kondo screening does not coincide with the position of the adatoms. It also develops enhancements at both edges of the chains. Since we can rule out any other interaction between Kondo impurities, this is explained in terms of the indirect hybridization of the Kondo orbitals mediated by a coherent electron gas, the mechanism that causes the emergence of heavy quasiparticles in the thermodynamic limit., Financial support was provided by the Spanish Plan Nacional de I+D+i (grants MAT 2013-46593-C6-3-P, MAT2016-78293-C6-6-R, MAT2015-66888-C3-2-R, and FIS2015-64886-C5-3-P), Charles University (programme PRIMUS/Sci/09) and the European Union through programmes Interreg-POCTEFA (grant TNSI/EFA194/16) and H2020-EINFRA-5-2015 MaX Center of Excellence (grant no. 676598). M.M.-L., M.P., and D.S. acknowledge the use of SAI at Universidad de Zaragoza. R.R. acknowledges The Severo Ochoa Centers of Excellence Program (grant no. SEV-2017-0706) and Generalitat de Catalunya (grant no. 2017SGR1506 and the CERCA Programme).

The Linear Response Theory (LRT) is a widely accepted framework to analyze the power absorption of magnetic nanoparticles for magnetic fluid hyperthermia. Its validity is restricted to low applied fields and/or to highly anisotropic magnetic nanoparticles. Here, we present a systematic experimental analysis and numerical calculations of the specific power absorption for highly anisotropic cobalt ferrite (CoFe2O4) magnetic nanoparticles with different average sizes and in different viscous media. The predominance of Brownian relaxation as the origin of the magnetic losses in these particles is established, and the changes of the Specific Power Absorption (SPA) with the viscosity of the carrier liquid are consistent with the LRT approximation. The impact of viscosity on SPA is relevant for the design of MNPs to heat the intracellular medium during in vitro and in vivo experiments. The combined numerical and experimental analyses presented here shed light on the underlying mechanisms that make highly anisotropic MNPs unsuitable for magnetic hyperthermia., This work was partially supported by the Spanish Ministerio de Economia y Competitividad (MINECO) through project MAT2016-78201-P and by the Aragón Regional Government (DGA), through the Research Groups grants (E-26 and E28-17R) co-financed by the FEDER Operational Program Aragón 2014–2020 “Building Europe from Aragon”.

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La2/3Ca1/3MnO3 (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature. For different substrates and growth conditions the tetragonality of LCMO at room temperature, defined as τ = |c – a|/a, is the driving force for a phase coexistence above an approximate critical value of τC ≈ 0.024. Theoretical calculations prove that the increased tetragonality changes the energy balance of the FM and AFM ground states in strained LCMO, enabling the formation of magnetically inhomogeneous states. This work gives the key evidence that opens a new route to synthesize strain-induced exchanged-biased FM–AFM bilayers in single thin films, which could serve as building blocks of future spintronic devices., This work was supported by Spanish Ministry of Science through projects No. MAT2011-28532-C03-02 and MAT2011-27553-C02 including FEDER funding, by the Aragon Regional Government through projects E26 and CTPP4/11, by the Universidad de Zaragoza through the contract PIF-UZ-2009-CIE-02, and by the European Union under the Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2.

We show that the chemical inhomogeneity in ternary three-dimensional topological insulators preserves the topological spin texture of their surface states against a net surface magnetization. The spin texture is that of a Dirac cone with helical spin structure in the reciprocal space, which gives rise to spin-polarized and dissipation-less charge currents. Thanks to the nontrivial topology of the bulk electronic structure, this spin texture is robust against most types of surface defects. However, magnetic perturbations break the time-reversal symmetry, enabling magnetic scattering and loss of spin coherence of the charge carriers. This intrinsic incompatibility precludes the design of magnetoelectronic devices based on the coupling between magnetic materials and topological surface states. We demonstrate that the magnetization coming from individual Co atoms deposited on the surface can disrupt the spin coherence of the carriers in the archetypal topological insulator Bi2Te3, while in Bi2Se2Te the spin t...

We show here that superconductivity can be induced in bismuth nanostripes through electrical contact with an s-wave superconductor. By studying the electrical transport properties of devices containing a bismuth nanostripe with superconducting contacts, we have found that bismuth nanostripes with inner probe distance shorter than 125 nm become superconductor at temperatures above 2 K due to proximity-induced superconductivity. This finding, along with previously demonstrated large spin–orbit coupling in bismuth, opens the way to the design of bismuth-based nanostructures bearing Majorana bound states., Financial support by several projects is acknowledged: MAT2014-51982-C2-1-R, MAT2014-51982-C2-2-R and MAT2015-69725-REDT from MINECO (including FEDER funding) and Aragón Regional Government through project E26—Construyendo Europa desde Aragón.

This work reports the tailored design of novel mixed ferrite nanoparticles, CoxMn1−xFe2O4 (x = 0, 0.3, 0.7, and 1), through an optimized one-pot aqueous coprecipitation process. The influence of the substitution between Mn(II) and Co(II) and of the alkaline agent, isopropanolamine (MIPA) or NaOH, on the morphological, chemical and magnetic properties of the nanomaterials was investigated. The joint action between chemical substitution and type of alkaline agent allowed a precise tuning of the particle size, magnetic properties and inversion degree of the spinel structure. A wide range of particle dimensions (from 3 to 30 nm) and saturation magnetization (from 57 to 71 emu g−1) was achieved. The increase of Co(II) content from x = 0 to x = 1 led to a systematic decrease of the particle size, regardless of the base type, which could be modelled by an exponential decay function. For each Co:Mn composition, the use of MIPA instead of the traditional NaOH promoted a three times reduction of the particle size and simultaneously switched the magnetic state of the CoxMn1−xFe2O4 nanomaterials from ferromagnetic to superparamagnetic. These results constitute a step forward in the challenging quest for high-performance magnetic nanoprobes by an eco-friendly synthesis route.

This work aims to demonstrate the need for in silico design via numerical simulation to produce optimal Fe 3 O 4 -based magnetic nanoparticles (MNPs) for magnetic hyperthermia by minimizing the impact of intracellular environments on heating efficiency. By including the relevant magnetic parameters, such as magnetic anisotropy and dipolar interactions, into a numerical model, the heating efficiency of as prepared colloids was preserved in the intracellular environment, providing the largest in vitro specific power absorption (SPA) values yet reported. Dipolar interactions due to intracellular agglomeration, which are included in the simulated SPA, were found to be the main cause of changes in the magnetic relaxation dynamics of MNPs under in vitro conditions. These results pave the way for the magnetism-based design of MNPs that can retain their heating efficiency in vivo, thereby improving the outcome of clinical hyperthermia experiments. Fil: Sanz, Beatriz. Universidad de Zaragoza; España Fil: Calatayud, M. Pilar. Universidad de Zaragoza; España Fil: de Biasi, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Lima, Enio Junior. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Vasquez Mansilla, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Zysler, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Ibarra, M. Ricardo. Universidad de Zaragoza; España Fil: Goya, Gerardo Fabian. Universidad de Zaragoza; España

Magnetic hyperthermia is a new type of cancer treatment designed for overcoming resistance to chemotherapy during the treatment of solid, inaccessible human tumors. The main challenge of this technology is increasing the local tumoral temperature with minimal side effects on the surrounding healthy tissue. This work consists of an in vitro study that compared the effect of hyperthermia in response to the application of exogenous heating (EHT) sources with the corresponding effect produced by magnetic hyperthermia (MHT) at the same target temperatures. Human neuroblastoma SH-SY5Y cells were loaded with magnetic nanoparticles (MNPs) and packed into dense pellets to generate an environment that is crudely similar to that expected in solid micro-tumors, and the above-mentioned protocols were applied to these cells. These experiments showed that for the same target temperatures, MHT induces a decrease in cell viability that is larger than the corresponding EHT, up to a maximum difference of approximately 45\% at T = 46{\deg}C. An analysis of the data in terms of temperature efficiency demonstrated that MHT requires an average temperature that is 6{\deg}C lower than that required with EHT to produce a similar cytotoxic effect. An analysis of electron microscopy images of the cells after the EHT and MHT treatments indicated that the enhanced effectiveness observed with MHT is associated with local cell destruction triggered by the magnetic nano-heaters. The present study is an essential step toward the development of innovative adjuvant anti-cancer therapies based on local hyperthermia treatments using magnetic particles as nano-heaters., Comment: 32 pages, Biomaterials 2017

Up to now, functionalized gold nanoparticles have been optimized as an effective intracellular in vitro delivery vehicle for siRNAs to interfere with the expression of specific genes by selective targeting, and provide protection against nucleases. Few examples however of suchlike in vivo applications have been described so far. In this study, we report the use of siRNA/RGD gold nanoparticles capable of targeting tumor cells in a lung cancer syngeneic orthotopic murine model. Therapeutic RGD-nanoparticle treatment resulted in successful targeting evident from significant c-myc oncogene down-regulation followed by tumor growth inhibition and prolonged survival of lung tumor bearing mice, possibly via αvβ3 integrin interaction. Our results suggest that RGD gold nanoparticles-mediated delivery of siRNA by intratracheal instillation in mice leads to successful suppression of tumor cell proliferation and respective tumor size reduction. These results reiterate the capability of functionalized gold nanoparticles for targeted delivery of siRNA to cancer cells towards effective silencing of the specific target oncogene. What is more, we demonstrate that the gold-nanoconjugates trigger a complex inflammatory and immune response that might promote the therapeutic effect of the RNAi to reduce tumor size with low doses of siRNA.

6 páginas, 4 figuras, 1 esquema.-- Trabajo presentado como póster en el Joint European Magnetic Symposia (JEMS2012)., Superparamagnetic magnetite nanoparticles coated with an ultrathin (∼1 nm) magnesium oxide (MgO) layer have been synthesized by combining coprecipitation and sol–gel methods. A thorough chemical and structural characterization has been carried out by means of high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), dynamic light scattering (DLS), and thermogravimetric analysis (TGA). Aberration corrected HRTEM experiments with subangstrom spatial resolution have allowed us to distinguish the ultrathin MgO shell that grows epitaxially on the magnetic cores. The capability of the MgO shell to protect the magnetic nuclei from oxidation up to 600 °C has been demonstrated. The magnetic properties of the material have been studied before and after the coating procedure. The superparamagnetism of the magnetite nuclei at room temperature is preserved even after calcination. The possibility of obtaining particles of controlled size coated with an isolating layer of nanometric thickness and high thermal stability makes the combination of the two synthesis methods used in this work a starting procedure to obtain nanometric powders suitable for technological applications, such as high-frequency electronics. These particles, after the appropriated functionalization, are also potential candidates to be used in biomedical applications., This work was supported by the Spanish Ministry of Science and Innovation (MICINN) trough projects NANOBIOMED (CONSOLIDER-INGENIO 2010 Program), CTQ2008- 03739/PPQ, and EUI2008-00157. Financial support from the Autonomic Government of Aragon (DGA) is also acknowledged through ARAID Foundation and Grupos de Excelencia de la Diputación General de Aragón.

Controlled release of drugs from nanostructured functional materials, especially nanoparticles (NPs), is attracting increasing attention because of the opportunities in cancer therapy and the treatment of other ailments. The potential of magnetic NPs stems from the intrinsic properties of their magnetic cores combined with their drug loading capability and the biochemical properties that can be bestowed on them by means of a suitable coating. Here we review the problems and recent advances in the development of magnetic NPs for drug delivery, focusing particularly on the materials involved.

Magnetic nanoparticles are good candidates used for the targeted delivery of anti-tumor agents. They can be concentrated on a desired region, reducing collateral effects and improving the efficiency of the chemotherapy. We propose a method in which permanent magnets are implanted by laparoscopic technique directly in the affected organ. This method proposes the use of Fe@C nanoparticles, which are loaded with doxorubicin and injected intravenously. The particles, once attracted to the magnet, release the drug at the tumor region. This method seems to be more promising and effective than that based on the application of external magnetic fields.

A novel mechanism of ferroelectricity driven by off-centering magnetic Mn4+ ions was proposed in (Sr1–xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1–xBax)MnO3 thin films, 0.2 ≤ x ≤ 0.5, grown by pulsed laser deposition onto (001)-oriented perovskite substrates. X-ray diffraction measurements and scanning transmission electron microscopy reveal that, under appropriate deposition conditions, the perovskite phase is fully stabilized over the nonferroelectric hexagonal phase, despite the latter being increasingly favored on increasing Ba-content. Moreover, we have managed to grow epitaxial coherent cube-on-cube (Sr1–xBax)MnO3 films upon strains ranging from 0% to 4%. Our results become a milestone in further studying perovskite (Sr1–xBax)MnO3 thin films and pave the way for tailoring ferroic and magnetoelectric properties either by strain engineering or Ba-doping., This work was supported by the Spanish Ministry of Economy and Competitiveness through Projects MAT2012-38213-C02-01 and MAT2014-51982-C2 including FEDER funding, by the Aragon Regional Government through Projects E26 and CTPP4/11 and by the European Union under the Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2.

et al., We present a versatile diagram to envisage the dominant relaxation mechanism of single-domain magnetic nanoparticles (MNPs) under alternating magnetic fields, as those used in magnetic fluid hyperthermia (MFH). The diagram allows estimating the heating efficiency, measured by the Specific Power Absorption (SPA), originated in the magnetic and viscous relaxation times of single-domain MNPs for a given frequency of the ac magnetic field (AFM). The diagram has been successfully applied to different colloids, covering a wide variety of MNPs with different magnetic anisotropy and particle size, and dispersed in different viscous liquid carriers. From the general diagram, we derived a specific chart based on the Linear Response Theory in order to easily estimate the experimental condition for the optimal SPA values of most colloids currently used in MFH., The authors are grateful to the CONICET-Argentina. The authors would also like to acknowledge the use of the Servicio General de Apoyo a la Investigación–SAI, Universidad de Zaragoza. This work was supported partially from the Argentinean agencies ANPCyT (PICT2007-832), CONICET (PIP2008-1333), and UNCuyo grants. This work also was supported from Diputación General de Aragón (DGA) and Ministerio de Economia y Competitividad (MINECO, Project MAT2010-19326)-Spain.

Rispail, Nicolas et.al., For several years now, nanoscaled materials are being implemented in biotechnological applications related to animal (in particular human) cells and related pathologies. However, the use of nanomaterials in plant biology is far less widespread, although their application in this field could lead to the future development of plant biotechnology applications. For any practical use, it is crucial to elucidate the relationship between the nanomaterials and the target cells. In this work we have evaluated the behaviour of two types of nanomaterials, quantum dots and superparamagnetic nanoparticles, on Fusarium oxysporum, a fungal species that infects an enormous range of crops causing important economic losses and is also an opportunistic human pathogen. Our results indicated that both nanomaterials rapidly interacted with the fungal hypha labeling the presence of the pathogenic fungus, although they showed differential behaviour with respect to internalization. Thus, whereas magnetic nanoparticles appeared to be on the cell surface, quantum dots were significantly taken up by the fungal hyphae showing their potential for the development of novel control approaches for F. oxysporum and related pathogenic fungi following appropriate functionalization. In addition, the fungal germination and growth, accumulation of ROS, indicative of cell stress, and fungal viability have been evaluated at different nanomaterial concentrations showing the low toxicity of both types of nanomaterials to the fungus. This work represents the first study on the behavior of quantum dots and superparamagnetic particles on fungal cells, and constitutes the first and essential step to address the feasibility of new nanotechnology-based systems for early detection and eventual control of pathogenic fungi., This work was supported by the Spanish Ministry of Science and Innovation, the EuroInvestigation program [EUI2008-00157], the European Regional and Social Development Funds, the ERC-Starting Grant-NANOPUZZLE and AGR-253 funds. NR is supported by a Ramón y Cajal postdoctoral fellowship from the Ministerio de Economia y Competitividad. This study was also supported by the Fundação para a Ciência e Tecnologia-Portugal through a doctoral grant to A. S. M. (SFRH/BD/40303/2007) and by grant Pest-OE/EQB/LA0004/2011.

Superparamagnetic iron oxide nanoparticles coated with titanium dioxide have been synthesized, growing the titanium dioxide directly either on the magnetic nuclei or on magnetic nanoparticles previously coated with a semihydrophobic silica layer. Both coatings have been obtained by sol-gel. Since it is well-known that the existence of the intermediate silica layer influences the physicochemical properties of the material, a detailed characterization of both types of coatings has been carried out. The morphology, structure, and composition of the synthesized nanomatrices have been locally analyzed with subangstrom spatial resolution, by means of aberration corrected transmission electron microscopy (HRTEM and STEM-HAADF). Besides magnetization measurements, proton relaxivity experiments have been also performed on water suspensions of the as-synthesized nanoparticles to investigate the role of the silica interlayer in the relaxometric properties. The silica interlayer leads to nanoparticles with much higher water stability and to higher relaxivity of the suspensions.

Nanoparticles engineered for biomedical applications are meant to be in contact with protein-rich physiological fluids. These proteins are usually adsorbed onto the nanoparticle's surface, forming a swaddling layer that has been described as a 'protein corona', the nature of which is expected to influence not only the physicochemical properties of the particles but also the internalization into a given cell type. We have investigated the process of protein adsorption onto different magnetic nanoparticles (MNPs) when immersed in cell culture medium, and how these changes affect the cellular uptake. The role of the MNPs surface charge has been assessed by synthesizing two colloids with the same hydrodynamic size and opposite surface charge: magnetite (Fe3O4) cores of 25-30 nm were in situ functionalized with (a) positive polyethyleneimine (PEI-MNPs) and (b) negative poly(acrylic acid) (PAA-MNPs). After few minutes of incubation in cell culture medium the wrapping of the MNPs by protein adsorption resulted in a 5-fold increase of the hydrodynamic size. After 24 h of incubation large MNP-protein aggregates with hydrodynamic sizes of ≈1500 nm (PAA-MNPs) and ≈3000 nm (PEI-MNPs) were observed, each one containing an estimated number of magnetic cores between 450 and 1000. These results are consistent with the formation of large protein-MNPs aggregate units having a 'plum pudding' structure of MNPs embedded into a protein network that results in a negative surface charge, irrespective of the MNP-core charge. In spite of the similar negative ζ-potential for both MNPs within cell culture, we demonstrated that PEI-MNPs are incorporated in much larger amounts than the PAA-MNPs units. Quantitative analysis showed that SH-SY5Y cells can incorporate 100% of the added PEI-MNPs up to ≈100 pg/cell, whereas for PAA-MNPs the uptake was less than 50%. The final cellular distribution showed also notable differences regarding partial attachment to the cell membrane. These results highlight the need to characterize the final properties of MNPs after protein adsorption in biological media, and demonstrate the impact of these properties on the internalization mechanisms in neural cells.

et al., We report a two-step on-surface synthesis of Mn phthalocyanine molecules from four tetracyanobenzene (TCNB) monomers through coordinative bonding with manganese adatoms. In the first step, the coevaporation of TCNB and Mn atoms leads to a metal-organic network stabilized by a combination of coordination and hydrogen (H) bonds. In the second step, annealing the coordination networks above room temperature results in individual Mn phthalocyanine molecules. The results shown here demonstrate the viability of an on-surface chemical synthesis strategy involving the reduction of the organic reagents by metal ions to produce metal-organic molecules. © 2014 American Chemical Society., Financial support by the Spanish Ministry of Science through Plan Nacional de I+D+i grant MAT2010-19236, University of Zaragoza (JIUZ-2013-CIE-12), and the German Academic Exchange Program (DAAD) is acknowledged.

Superparamagnetic iron oxide nanoparticles coated with titanium dioxide have been synthesized, growing the titanium dioxide directly either on the magnetic nuclei or on magnetic nanoparticles previously coated with a semihydrophobic silica layer. Both coatings have been obtained by sol-gel. Since it is well-known that the existence of the intermediate silica layer influences the physicochemical properties of the material, a detailed characterization of both types of coatings has been carried out. The morphology, structure, and composition of the synthesized nanomatrices have been locally analyzed with subangstrom spatial resolution, by means of aberration corrected transmission electron microscopy (HRTEM and STEM-HAADF). Besides magnetization measurements, proton relaxivity experiments have been also performed on water suspensions of the as-synthesized nanoparticles to investigate the role of the silica interlayer in the relaxometric properties. The silica interlayer leads to nanoparticles with much higher water stability and to higher relaxivity of the suspensions. © 2014 American Chemical Society., This work has been funded by MAT2011-26851-C02-01, European Regional and Social Development Funds, Aragón Autonomous Government (DGA) through Research Groups and ARAID funds, and ERC-Starting Grant 239931-NANOPUZZLE. Authors also acknowledge the Servicio General de Apoyo a la Investigación-SAI (Universidad de Zaragoza) and B. Gaspar for their support.

et al., By means of scanning tunneling microscopy, individual Co atoms adsorbed on Ag(111) are found to behave as a model catalyst for the hydrogen oxidation reaction. The dosing of H2 in a cryogenic environment produces the otherwise unstable CoH3 molecule, which results in the complete suppression of the Kondo resonance of the host Co atom. Short voltage pulses over Co hydrides permit reversible dehydrogenation and so, the identification of the intermediate compounds. The electric polarizability of CoH3 allows controlling molecular diffusion via an external electric field, from the range of tens of nm down to the assembly of larger hydride complexes at the molecular scale. © 2014 American Chemical Society., Financial support by the Spanish Plan Nacional de I+D+i (through grant MAT2010-19236) and by the seventh F.P. of the European Union (ERG project PERG06-GA-2009-251791) is acknowledged. J.I.P. acknowledges support by DAAD.

This review analyses the advances in the field of magnetically induced cell death using intracellular magnetic nanoparticles (MNPs). Emphasis has been given to in vitro research results, discussing the action of radiofrequency (RF) waves on biological systems as well as those results of thermally induced cell death in terms of MNP cell interactions. Our main goal has been to provide a unified depiction of many recent experiments and theoretical models relevant to the effect of applied electromagnetic fields on MNPs after cellular uptake and the cytotoxicity assessment of MNPs. We have addressed the effects of RF waves used for in vitro magnetic hyperthermia on eukaryotic cells regarding physical modifications of the cellular local environment and cell viability.

Spatially resolved electron energy loss spectroscopy (SR-EELS) using scanning transmission electron microscope (STEM) allows the identification and determination of the spatial distribution of the components/elements of immuno-functionalized core-shell superparamagnetic magnetite nanoparticles. Here, we report that SR-EELS measurements allow the direct identification and study of the biological moieties (protein G and anti-HRP antibody) in complex bionanocarriers of relevance for biomedical applications. Our findings show that the biomacromolecules are located on specific areas on the nanoparticles' surface. In addition, efficiency of this functionalization was evaluated by means of biochemical techniques. © 2013 American Chemical Society., J.M.F. thanks the NANOPUZZLE project (ERC-Starting Grant) for financial support. All the authors thank the Fondo Social Europeo for funding.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.-- et al., Control of the motion of domain walls in magnetic nanowires is at the heart of various recently proposed three-dimensional (3D) memory devices. However, fabricating 3D nanostructures is extremely complicated using standard lithography techniques. Here we show that highly pure 3D magnetic nanowires with aspect-ratios of ∼100 can be grown using focused electron-beam-induced- deposition. By combining micromanipulation, Kerr magnetometry and magnetic force microscopy, we determine that the magnetisation reversal of the wires occurs via the nucleation and propagation of domain walls. In addition, we demonstrate that the magnetic switching of individual 3D nanostructures can be directly probed by magneto-optical Kerr effect., This research was supported by a Marie Curie Intra European Fellowship project No. 251698: 3DMAGNANOW, a Marie Curie International Outgoing Fellowship project no. 299376: HIGHSPIN and an ERC Advanced Grant project No. 247368: 3SPIN, all funded by the 7th European Community Framework Programme, by the MAT2011-27553-C02 project funded by the Spanish Ministry of Economy (including FEDER funding) and by the I-LINK0026 project funded by the Spanish CSIC.

The behavior of nanoparticles inside plants is gaining importance for its implications in research about putative applications and toxicology. Magnetic carbon-coated nanoparticles can be easily traced through plant tissues using simple and affordable histological techniques. Here we present a methodology for the synthesis of such nanoparticles. We also describe methods for growing plants using rhizotrons (in order to observe the roots), procedures for applying the nanoparticles, taking and processing the samples.

Radio labeled albumin microspheres with encapsulated citric acid-coated magnetite nanoparticles were developed as a targeting approach to localize both radioactivity and magnetic energy at the tumor site. We present in vitro and in vivo studies of yttrium-90 (Y-90)-labeled human scrum albumin magnetic microspheres (HSAMMS) as a multifunctional agent for possible applications in a bimodal radionuclide-hyperthermia cancer therapy. The HSAMMS were produced using a modified emulsification-heat stabilization technique and contained 11 nm magnetite nanoparticles coated with citric acid, distributed as inhomogeneous clusters within the albumin microspheres. The size, size distribution and the morphology of magnetite nanoparticles and HSAMMS were determined by FESEM, HRTEM and SEM/FIB dual beam. The average particle size of the complete HSAMMS was 20 mu m, and they exhibited superparamagnetic behavior at room temperature. The in vitro experiments (in saline and human serum) revealed the high stability of the labeled HSAMMS in saline and human serum after 72 h. Following the intravenous administration of the Y-90-HSAMMS in rats, 88.81% of the activity localizes in the lungs after 1 h, with 82.67% remaining after 72 h. These data on Y-90-HSAMMS provide good evidence for their potential use in bimodal radionuclide-hyperthermia cancer therapy.

The in vivo biodistribution of Fe@C nanoparticles (NP) was tested in mice bearing an inflammatory focus induced by injecting carrageenan into an air pouch previously formed on their back. The animals were intravenously injected NP with a high (60 mg/kg) or a low iron dose (6 mg/kg) and sacrificed 2 h later. Blood and organ samples (liver, spleen, lung, and kidney) were obtained; washed exudates were also collected. Iron concentration in plasma, blood cells, organs, and exudates was determined by flameless atomic-absorption-spectroscopy after digestion of organic material. Pouch exudate volume increased in all groups of mice with experimental inflammation. After i.v. administration of the high and low dose of NP, iron in exudate increased by 83.3% and 92.2%, respectively. A similar increase in hepatic iron appeared after the high dose (78%), but no increase appeared after the low dose. When the magnet was present, a 157% and 119% increase of iron in exudate appeared after both doses of NPs, but only the high dose of NP increased iron liver (60%). The presence of a magnetic field in the pouch favored selective biodistribution of NP in the inflammatory focus. These results indicate that mice with an inflammatory compartment are suitable for primary screening of different NP types. They also show that selective biodistribution is greater when a low dose of NP was used and that distribution in the target organ was increased by the magnetic field. © 2012 The Pharmaceutical Society of Korea and Springer Netherlands., Supported by a grant from Ministry of Education and Science, Spain (CONSOLIDER-INGENIO 2010 program, CSD2006-12).

The behavior of nanoparticles inside plants is gaining importance for its implications in research about putative applications and toxicology. Magnetic carbon-coated nanoparticles can be easily traced through plant tissues using simple and affordable histological techniques. Here we present a methodology for the synthesis of such nanoparticles. We also describe methods for growing plants using rhizotrons (in order to observe the roots), procedures for applying the nanoparticles, taking and processing the samples.

Over the past decade, the capability of double-stranded RNAs to interfere with gene expression has driven new therapeutic approaches. Since small interfering RNA (siRNAs, 21 base pair double-stranded RNA) was shown to be able to elicit RNA interference (RNAi), efforts were directed toward the development of efficient delivery systems to preserve siRNA bioactivity throughout the delivery route, from the administration site to the target cell. Here we provide evidence of RNAi triggering, specifically silencing c-myc protooncogene, via the synthesis of a library of novel multifunctional gold nanoparticles (AuNPs). The efficiency of the AuNPs is demonstrated using a hierarchical approach including three biological systems of increasing complexity: in vitro cultured human cells, in vivo invertebrate (freshwater polyp, Hydra ), and in vivo vertebrate (mouse) models. Our synthetic methodology involved fine-tuning of multiple structural and functional moieties. Selection of the most active functionalities was assisted step-by-step through functional testing that adopted this hierarchical strategy. Merging these chemical and biological approaches led to a safe, nonpathogenic, self-tracking, and universally valid nanocarrier that could be exploited for therapeutic RNAi.

Nanocomposites consisting of magnetite and FAU zeolite with a high surface area and adsorption capacity have been prepared by mechanical activation using high-energy milling at room temperature. FTIR results, as well as HRTEM, EFTEM, and XPS measurements, show that the resulting magnetic nanoparticles are covered by a thin aluminosilicate coating. A saturation magnetization as high as 16 emu g(-1) and 94.2 Oe of coercivity were observed for the obtained composites. The main advantages of this synthesis procedure are (i) simplicity of the preparation procedure, (ii) prevention of agglomeration of the magnetite nanoparticles to a large extent, and (iii) absence of free magnetite outside the zeolitic matrix. In addition, in vitro experiments revealed that the nanoparticles prepared were able to store and release substantial amounts of doxorubicin. In view of these advantages, these magnetic nanoparticles can be considered as potential candidates for drug-delivery applications.

In this article, we review our recent research on Fe3O4 epitaxial thin films and Fe3O4/MgO/Fe epitaxial heterostructures. More specifically, we report on the magnetotransport properties of Fe3O4 epitaxial films in a wide range of film thicknesses and temperatures, focusing on the anomalous, planar and ordinary Hall effects. We also summarize our insight on the origin of the enhanced magnetic moment found in ultra-thin magnetite films (thickness t < 5 nm). Finally, our work on the growth, and structural and magnetic characterization of heteroepitaxial Fe3O4/MgO/Fe trilayers is presented.

This chapter is a brief description of the state of the art of the field of targeted drug delivery using magnetic implants. It describes the advantages and drawbacks of the use of internal magnets to concentrate magnetic nanoparticles near tumor locations, and the different approaches to this task performed in vitro and in vivo reviewed in literature are presented.

We report a single-step chemical synthesis of iron oxide hollow nanospheres with 9.3 nm in diameter. The sample presents a narrow particle diameter distribution and chemical homogeneity. The hollow nature of the particles is confirmed by HRTEM and HAADF STEM analysis. Electron and x-ray diffraction show that the outer material component is constituted by 2 nm ferrite crystals. Mossbauer data provide further evidence for the formation of iron oxide with high structural disorder, magnetically ordered at 4.2 K and superparamagnetism at room temperature. An unusual magnetic behavior under an applied field is reported, which can be explained by the large fraction of atoms existing at both inner and outer surfaces.

This chapter is a brief description of the state of the art of the field of targeted drug delivery using magnetic implants. It describes the advantages and drawbacks of the use of internal magnets to concentrate magnetic nanoparticles near tumor locations, and the different approaches to this task performed in vitro and in vivo reviewed in literature are presented.

Inorganic nanoparticles (NPs) show great potential for medicinal therapy. However, biocompatibility studies are essential to determine if they are safe. Here, five different NPs are compared for their cytotoxicity, internalization, aggregation in medium, and reactive oxygen species (ROS) production, using tumoral and normal human blood cells. Differences depending on the cell type are analyzed, and no direct correlation between ROS production and cell toxicity is found. Results are discussed with the aim of standardizing the procedures for the evaluation of the toxicity.

The rare earth intermetallic compounds R5(SixGe1−x )4 exhibit an extraordinary magnetostructural coupling which gives rise to an unprecedented variety of magnetoresponsive properties. The most exceptional is the discovery in Gd5(SixGe1−x )4 of the giant magnetocaloric effect, an extremely large magnetic-field-induced temperature and entropy change, which has promoted great advances in the field of the room temperature magnetic refrigeration based on these and other materials. Additionally, this potent coupling between the magnetic and crystallographic lattices opens the prospect of the modification of the physical properties of these alloys by externally modifying their volume cell/atomic distances, and thus the crystal structure and magnetic properties. Recent investigations have confirmed the strong impact of a moderate hydrostatic pressure on the magnetic and crystallographic properties of R5(SixGe1−x )4. In this work, we emphasize the newly discovered significance of pressure as a new control parameter of the physical properties of the 5:4 alloys by reviewing the most outstanding findings arising from the effect of pressure on the strong interplay between the crystallographic structure and magnetism in the compounds with R = Gd, Tb and Er.

4 tables, 5 figures.-- et al., The ferromagnetic shape memory (MSM) alloy Ni2MnGa undergoes a martensitic transformation (MT) at T=220 K on cooling. The structure of this phase is studied by powder X-ray diffraction experiment. The analysis of the experimental data combined with the huge information reported in literature allowed to conclude that the Ni2MnGa martensite shows an incommensurate modulated structure closely related to a five-fold layered superstructure. The symmetry of the basic structure is found to be orthorhombic. The structure is refined by Rietveld method with superspace group Immm(00γ)s00 having a=4.2187(1) Å, b=5.5534(1) Å and c=4.1899(1) Å and modulation vector q=0.4248(3)c*. The results show that the modulation is mainly related to the periodic shuffling of the atomic layers perpendicular to the c-axis of the orthorhombic basic structure.

We report a one-step synthesis protocol for obtaining polymer-coated magnetic nanoparticles (MNPs) engineered for uploading neural cells. Polyethyleneimine-coated Fe3O4 nanoparticles (PEI-MNPs) with sizes of 25 ± 5 nm were prepared by oxidation of Fe(OH)2 by nitrate in basic aqueous media and adding PEI in situ during synthesis. The obtained PEI-MNP cores displayed a neat octahedral morphology and high crystallinity. The resulting nanoparticles were coated with a thin polymer layer of about 0.7–0.9 nm, and displayed a saturation magnetization value MS = 58 A m2 kg−1 at 250 K (64 A m2 kg−1 for T = 10 K). Cell uptake experiments on a neuroblastoma-derived SH-SY5Y cell line were undertaken over a wide time and MNP concentration range. The results showed a small decrease in cell viability for 24 h incubation (down to 70% viability for 100 μg ml−1), increasing the toxic effects with incubation time (30% cell survival at 100 μg ml−1 for 7 days of incubation). On the other hand, primary neuronal cells displayed higher sensitivity to PEI-MNPs, with a cell viability reduction of 44% of the control cells after 3 days of incubation with 50 μg ml−1. The amount of PEI-MNPs uploaded by SH-SY5Y cells was found to have a linear dependence on concentration. The intracellular distribution of the PEI-MNPs analyzed at the single-cell level by the dual-beam (FIB/SEM) technique revealed the coexistence of both fully incorporated PEI-MNPs and partially internalized PEI-MNP-clusters crossing the cell membrane. The resulting MNP-cluster distributions open the possibility of using these PEI-MNPs for magnetically driven axonal re-growth in neural cells.