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  • 1.
    Ahrentorp, Fredrik
    et al.
    RISE, Swedish ICT, Acreo.
    Astalan, Andrea
    RISE, Swedish ICT, Acreo.
    Blomgren, Jakob
    RISE, Swedish ICT, Acreo.
    Jonasson, Christian
    RISE, Swedish ICT, Acreo.
    Wetterskog, Erik
    Uppsala University, Sweden.
    Svedlindh, Peter
    Uppsala University, Sweden.
    Lak, Aidin
    Technical University of Braunschweig, Germany.
    Ludwig, Frank
    Technical University of Braunschweig, Germany.
    van Ijzendoorn, Leo J.
    Eindhoven University of Technology, Netherlands.
    Westphal, Fritz
    Micromod Partikeltechnologie GmbH, Germany.
    Gruttner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Gehrke, Nicole
    nanoPET Pharma GmbH, Germany.
    Gustafsson, Stefan
    Chalmers University of Technology, Sweden.
    Olsson, Eva
    Chalmers University of Technology, Sweden.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Effective particle magnetic moment of multi-core particles2015In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 380, p. 221-226Article in journal (Refereed)
    Abstract [en]

    In this study we investigate the magnetic behavior of magnetic multi-core particles and the differences in the magnetic properties of multi-core and single-core nanoparticles and correlate the results with the nanostructure of the different particles as determined from transmission electron microscopy(TEM). We also investigate how the effective particle magnetic moment is coupled to the individual moments of the single-domain nanocrystals by using different measurement techniques: DC magnetometry, AC susceptometry, dynamic light scattering and TEM. We have studied two magnetic multi-core particle systems – BNF Starch from Micromod with a median particle diameter of 100 nm and FeraSpin R from nanoPET with a median particle diameter of 70 nm – and one single-core particle system – SHP25 from Ocean NanoTech with a median particle core diameter of 25 nm.

  • 2.
    Ahrentorp, Fredrik
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Blomgren, Jakob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sarwe, Anna
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sepehri, Sobhan
    Chalmers University of Technology, Sweden.
    Eriksson, Emil
    Chalmers University of Technology, Sweden.
    Kalaboukhov, Alexei
    Chalmers University of Technology, Sweden.
    Jesorka, Aldo
    Chalmers University of Technology, Sweden.
    Winkler, Dag
    Chalmers University of Technology, Sweden.
    Schneiderman, Justin F.
    University of Gothenburg, Sweden.
    Nilsson, Mats
    Stockholm University, Sweden.
    Albert, Jan
    Karolinska University Hospital, Sweden; Karolinska Institute, Sweden.
    de la Torre, Theresa Z. G.
    Uppsala University, Sweden.
    Strømme, Maria
    Uppsala University, Sweden.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 427, p. 14-18Article in journal (Refereed)
    Abstract [en]

    We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 µm. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 µL) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.

  • 3.
    Bender, P.
    et al.
    University of Cantabria, Spain .
    Bogart, L. K.
    University College London, UK .
    Posth, O.
    Physikalisch-Technische Bundesanstalt, Germany .
    Szczerba, W.
    BAM Bundesanstalt für Materialforschung Und-prüfung, Germany ; AGH University of Science and Technology, Poland .
    Rogers, S. E.
    ISIS-STFC Neutron Scattering Facility, UK.
    Castro, A.
    SOLVE Research and Consultancy AB, Sweden .
    Nilsson, L.
    SOLVE Research and Consultancy AB, Sweden; Lund University, Sweden.
    Zeng, L. J.
    Chalmers University of Technology, Sweden.
    Sugunan, Abhilash
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Sommertune, Jens
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Fornara, A.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    González-Alonso, D.
    University of Cantabria, Spain .
    Fernández Barquín, L.
    University of Cantabria, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 45990Article in journal (Refereed)
    Abstract [en]

    The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions.

  • 4.
    Bender, P.
    et al.
    University of Cantabria, Spain.
    Fock, J.
    DTU Technical University of Denmark, Denmark.
    Hansen, M. F.
    DTU Technical University of Denmark, Denmark.
    Bogart, L. K.
    UCL University College London, UK.
    Southern, P.
    UCL University College London, UK.
    Ludwig, F.
    Technische Universität Braunschweig, Germany.
    Wiekhorst, F.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Szczerba, W.
    Bundesanstalt für Materialforschung und -prüfung, Germany; AGH University of Science and Technology, Poland.
    Zeng, L. J.
    Chalmers University of Technology, Sweden.
    Heinke, D.
    nanoPET Pharma GmbH, Germany.
    Gehrke, N.
    nanoPET Pharma GmbH, Germany.
    Díaz, M. T. F.
    Institut Laue Langevin, France.
    González-Alonso, D.
    University of Cantabria, Spain.
    Espeso, J. I.
    University of Cantabria, Spain.
    Fernández, J. R.
    University of Cantabria, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Influence of clustering on the magnetic properties and hyperthermia performance of iron oxide nanoparticles2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 42, article id 425705Article in journal (Refereed)
    Abstract [en]

    Clustering of magnetic nanoparticles can drastically change their collective magnetic properties, which in turn may influence their performance in technological or biomedical applications. Here, we investigate a commercial colloidal dispersion (FeraSpin™R), which contains dense clusters of iron oxide cores (mean size around 9 nm according to neutron diffraction) with varying cluster size (about 18-56 nm according to small angle x-ray diffraction), and its individual size fractions (FeraSpin™XS, S, M, L, XL, XXL). The magnetic properties of the colloids were characterized by isothermal magnetization, as well as frequency-dependent optomagnetic and AC susceptibility measurements. From these measurements we derive the underlying moment and relaxation frequency distributions, respectively. Analysis of the distributions shows that the clustering of the initially superparamagnetic cores leads to remanent magnetic moments within the large clusters. At frequencies below 105 rad s-1, the relaxation of the clusters is dominated by Brownian (rotation) relaxation. At higher frequencies, where Brownian relaxation is inhibited due to viscous friction, the clusters still show an appreciable magnetic relaxation due to internal moment relaxation within the clusters. As a result of the internal moment relaxation, the colloids with the large clusters (FS-L, XL, XXL) excel in magnetic hyperthermia experiments.

  • 5.
    Bender, P.
    et al.
    University of Cantabria, Spain.
    Wetterskog, E.
    Uppsala University, Sweden.
    Honecker, D.
    Institut Laue-Langevin, France.
    Fock, J.
    DTU Technical University of Denmark,, Denmark.
    Frandsen, C.
    DTU Technical University of Denmark, Denmark.
    Moerland, C.
    Technische Universiteit Eindhoven, The Netherlands.
    Bogart, L. K.
    University College London, UK.
    Posth, O.
    Physikalisch-Technische Bundesanstalt, Germany.
    Szczerba, W.
    Bundesanstalt für Materialforschung und-prüfung,Germany; AGH University of Science and Technology, Poland.
    Gavilán, H.
    Instituto de Ciencia de Materiales de Madrid, Spain.
    Costo, R.
    Fernández-Díaz, M. T.
    Institut Laue-Langevin, France.
    González-Alonso, D.
    University of Cantabria, Spain.
    Fernández Barquín, L.
    University of Cantabria, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Dipolar-coupled moment correlations in clusters of magnetic nanoparticles2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 22, article id 224420Article in journal (Refereed)
    Abstract [en]

    Here, we resolve the nature of the moment coupling between 10-nm dimercaptosuccinic acid-coated magnetic nanoparticles. The individual iron oxide cores were composed of >95% maghemite and agglomerated to clusters. At room temperature the ensemble behaved as a superparamagnet according to Mössbauer and magnetization measurements, however, with clear signs of dipolar interactions. Analysis of temperature-dependent ac susceptibility data in the superparamagnetic regime indicates a tendency for dipolar-coupled anticorrelations of the core moments within the clusters. To resolve the directional correlations between the particle moments we performed polarized small-angle neutron scattering and determined the magnetic spin-flip cross section of the powder in low magnetic field at 300 K. We extract the underlying magnetic correlation function of the magnetization vector field by an indirect Fourier transform of the cross section. The correlation function suggests nonstochastic preferential alignment between neighboring moments despite thermal fluctuations, with anticorrelations clearly dominating for next-nearest moments. These tendencies are confirmed by Monte Carlo simulations of such core clusters.

  • 6.
    Blomgren, Jakob
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ahrentorp, Fredrik
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ilver, Dag
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sepehri, Sobhan
    Chalmers University of Technology, Sweden.
    Kalaboukhov, Alexei
    Chalmers University of Technology, Sweden.
    Winkler, Dag
    Chalmers University of Technology, Sweden.
    de la Torre, Tereza
    Uppsala University, Sweden.
    Strømme, Maria
    Uppsala University, Sweden.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Development of a sensitive induction-based magnetic nanoparticle biodetection method2018In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 11, article id 887Article in journal (Refereed)
    Abstract [en]

    We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility measurement techniques (the DynoMag induction technique) together with functionalized multi-core magnetic nanoparticles. The sample consisting of an incubated mixture of magnetic nanoparticles and rolling circle amplified DNA coils is injected into a tube by a peristaltic pump. The sample is moved as a plug to the two well-balanced detection coils and the dynamic magnetic moment in each position is read over a range of excitation frequencies. The time for making a complete frequency sweep over the relaxation peak is about 5 minutes (10 Hz–10 kHz with 20 data points). The obtained standard deviation of the magnetic signal at the relaxation frequency (around 100 Hz) is equal to about 10−5 (volume susceptibility SI units), which is in the same range obtained with the DynoMag system. The limit of detection with this method is found to be in the range of 1 pM. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

  • 7.
    Bogren, Sara
    et al.
    RISE, Swedish ICT, Acreo.
    Fornara, Andrea
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Ludwig, Frank
    Technical University of Braunschweig, Germany.
    Del Puerto Morales, Maria
    Instituto de Ciencia de Materiales de Madrid, Spain.
    Steinhoff, Uwe
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Fougt Hansen, Mikkel
    DTU Technical University of Denmark, Denmark.
    Kazakova, Olga
    NPL National Physical Laboratory, UK.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Classification of Magnetic Nanoparticle Systems—Synthesis, Standardization and Analysis Methods in the NanoMag Project2015In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 16, no 9, p. 20308-20325Article in journal (Refereed)
    Abstract [en]

    This study presents classification of different magnetic single- and multi-core particle systems using their measured dynamic magnetic properties together with their nanocrystal and particle sizes. The dynamic magnetic properties are measured with AC (dynamical) susceptometry and magnetorelaxometry and the size parameters are determined from electron microscopy and dynamic light scattering. Using these methods, we also show that the nanocrystal size and particle morphology determines the dynamic magnetic properties for both single- and multi-core particles. The presented results are obtained from the four year EU NMP FP7 project, NanoMag, which is focused on standardization of analysis methods for magnetic nanoparticles.

  • 8.
    Carlsson, Raul
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SWECAST.
    Elmquist, Lennart
    RISE - Research Institutes of Sweden, Materials and Production, SWECAST.
    Thore, Andreas
    RISE - Research Institutes of Sweden, Materials and Production, SWECAST.
    Ahrentorp, Fredrik
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Israelsson, Björn
    SKF Mekan AB, Sweden.
    Connecting sensors inside smart castings2018Conference paper (Refereed)
    Abstract [en]

    The paper presents ongoing research on smart metal castings, meaning the technologicalinnovation of elevating cast metal components into metal components with integratedsensor functionality. Since the innovation targets aim straight at low cost industrial serialproduction, specific high cost and high-end solutions like inclusion of advancedelectronic equipment and after mounted sensors are not part of this innovationdevelopment. Integrating signal carriers inside metal castings to achieve metal castingswith sensor functionality requires robust solutions for connecting the sensor signal to thesensor interrogator and interpreter. The actual transmission of the signal may be donewirelessly or by wire. However, for several reasons there is a challenge with establishingan isolated and distinct connection between the sensor contact, and the contact at theexternal connection, regardless of whether it is to an antenna for wireless transmission orto a wire. This paper presents metallurgical challenges associated with choices ofmaterials, and combinations of metallurgical challenges and production process relatedchallenges, including the high melting temperatures. Aims are to find the rightcombinations of metal alloys, production simplicity, signal stability and robustness. Thepaper will present some of the tests made in the project so far. The project is run in aconsortium of the two Sweden-based industrial companies Husqvarna and SKF, and thetwo Swedish research institutes Swerea SWECAST and RISE Acreo.

  • 9.
    Chakkarapani, Prabu
    et al.
    Anna University, India.
    Subbiah, Latha
    Anna University, India.
    Palanisamy, Selvamani
    Anna University, India.
    Bibiana, Arputha
    Anna University, India.
    Ahrentorp, Fredrik
    RISE, Swedish ICT, Acreo.
    Jonasson, Christian
    RISE, Swedish ICT, Acreo.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Encapsulation of methotrexate loaded magnetic microcapsules for magnetic drug targeting and controlled drug release2015In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 380, p. 285-294Article in journal (Refereed)
    Abstract [en]

    We report on the development and evaluation of methotrexate magnetic microcapsules (MMC) for targeted rheumatoid arthritis therapy. Methotrexate was loaded into CaCO3-PSS (poly (sodium 4-styrenesulfonate)) doped microparticles that were coated successively with poly (allylamine hydrochloride) and poly (sodium 4-styrenesulfonate) by layer-by-layer technique. Ferrofluid was incorporated between the polyelectrolyte layers. CaCO3-PSS core was etched by incubation with EDTA yielding spherical MMC. The MMC were evaluated for various physicochemical, pharmaceutical parameters and magnetic properties. Surface morphology, crystallinity, particle size, zeta potential, encapsulation efficiency, loading capacity, drug release pattern, release kinetics and AC susceptibility studies revealed spherical particles of ~3 µm size were obtained with a net zeta potential of +24.5 mV, 56% encapsulation and 18.6% drug loading capacity, 96% of cumulative drug release obeyed Hixson-Crowell model release kinetics. Drug excipient interaction, surface area, thermal and storage stability studies for the prepared MMC was also evaluated. The developed MMC offer a promising mode of targeted and sustained release drug delivery for rheumatoid arthritis therapy.

  • 10.
    Elmquist, Lennart
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SWECAST.
    Carlsson, Raul
    RISE - Research Institutes of Sweden, Materials and Production, SWECAST.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Cast iron components with intelligence2018Conference paper (Refereed)
    Abstract [en]

    The paper describes a project with the aim to develop communicating and functional cast iron components in smart systems. The concept is based on sensors integrated into cast iron components; this will influence not only the component but also the casting process. Among the technical challenges is how to choose a sensor solution that cost-efficiently and with minimal environmental impact can be integrated into the component during the casting process, and especially without being damaged during mold filling and the high pouring temperature. Another challenge is how the iron will interact and interfere with sensor signals and whether an insulating intermediate material is needed or not. Integrating the sensors into the casting makes sensors a natural part of the component, which in turn can lead to more resource efficient designs, increased value added for the casting sector, and a general access to different possibilities of digitalization. The integrated sensors can be used for effective control and monitoring of components when in service and give information about for example how the component is used and what conditions it is exposed to. In other words, the component can tell when maintenance is needed or in worst cases, indicate that something is wrong before a failure will happen. Important measurands can e.g. be elongation, shear, temperature and vibration. Different combinations of sensor materials and insulating materials and their interaction with the cast iron have been investigated. It is shown how the interaction at the interface affects the microstructure and consequently the properties of the cast iron. In the case of insulating materials it is e.g. shown how air gaps are formed and in the case of sensor materials it is shown how a diffusion zone is formed and how this zone depends on the sensor material. How this diffusion zone affects the microstructure is discussed.

  • 11.
    Fock, Jeppe
    et al.
    DTU Technical University of Denmark, Denmark .
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Hansen, Mikkel F.
    DTU Technical University of Denmark, Denmark .
    Characterization of fine particles using optomagnetic measurements2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 13, p. 8802-8814Article in journal (Refereed)
    Abstract [en]

    The remanent magnetic moment and the hydrodynamic size are important parameters for the synthesis and applications of magnetic nanoparticles (MNPs). We present the theoretical basis for the determination of the remanent magnetic moment and the hydrodynamic size of MNPs with a narrow size distribution using optomagnetic measurements. In these, the 2nd harmonic variation of the intensity of light transmitted through an MNP suspension is measured as a function of an applied axial oscillating magnetic field. We first show how the measurements of the optomagnetic signal magnitude at a low frequency vs. magnetic field amplitude can be used to determine the MNP moment. Subsequently, we use linear response theory to describe the dynamic non-equilibrium response of the MNP suspension at low magnetic field amplitudes and derive a link between optomagnetic measurements and magnetic AC susceptibility measurements. We demonstrate the presented methodology on two samples of commercially available multi-core MNPs. The results compare well with those obtained by dynamic light scattering, AC susceptibility and vibrating sample magnetometry measurements on the same samples when the different weighting of the particle size in the techniques is taken into account. The optomagnetic technique is simple, fast and does not require prior knowledge of the concentration of MNPs and it thus has the potential to be used as a routine tool for quality control of MNPs.

  • 12.
    Fortes Brollo, Maria Eugenia
    et al.
    CSIC Institute of Material Science of Madrid, Spain.
    Hernández Flores, Patricia
    CSIC Centro Nacional de Biotecnología, Spain.
    Gutiérrez, Lucía
    INA Instituto Universitario de Nanociencia de Aragón, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Barber, Domingo Francisco
    CSIC Centro Nacional de Biotecnología, Spain.
    Morales, María Del Puerto
    CSIC Institute of Material Science of Madrid, Spain.
    Magnetic properties of nanoparticles as a function of their spatial distribution on liposomes and cells2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 26, p. 17829-17838Article in journal (Refereed)
    Abstract [en]

    The aggregation processes of magnetic nanoparticles in biosystems are analysed by comparing the magnetic properties of three systems with different spatial distributions of the nanoparticles. The first one is iron oxide nanoparticles (NPs) of 14 nm synthesized by coprecipitation with two coatings, (3-aminopropyl)trimethoxysilane (APS) and dimercaptosuccinic acid (DMSA). The second one is liposomes with encapsulated nanoparticles, which have different configurations depending on the NP coating (NPs attached to the liposome surface or encapsulated in its aqueous volume). The last system consists of two cell lines (Pan02 and Jurkat) incubated with the NPs. Dynamic magnetic behaviour (AC) was analysed in liquid samples, maintaining their colloidal properties, while quasi-static (DC) magnetic measurements were performed on lyophilised samples. AC measurements provide a direct method for determining the effect of the environment on the magnetization relaxation of nanoparticles. Thus, the imaginary (χ'') component shifts to lower frequencies as the aggregation state increases from free nanoparticles to those attached or embedded into liposomes in cell culture media and more pronounced when internalized by the cells. DC magnetization curves show no degradation of the NPs after interaction with biosystems in the analysed timescale. However, the blocking temperature is shifted to higher temperatures for the nanoparticles in contact with the cells, regardless of the location, the incubation time, the cell line and the nanoparticle coating, supporting AC susceptibility data. These results indicate that the simple fact of being in contact with the cells makes the nanoparticles aggregate in a non-controlled way, which is not the same kind of aggregation caused by the contact with the cell medium nor inside liposomes.

  • 13.
    Gao, Shang
    et al.
    Paul Scherrer Institut, Switzerland; University of Geneva, Switzerland.
    Zaharko, Oksana
    Paul Scherrer Institut, Switzerland.
    Tsurkan, Vladimir
    University of Augsburg, Germany; Academy of Sciences of Moldova, Moldova.
    Prodan, Lilian
    Academy of Sciences of Moldova, Moldova.
    Riordan, Edvard
    Cardiff University, UK.
    Lago, Jorge
    University of the Basque Country, Spain.
    Fak, Björn
    Institut Laue-Langevin, France.
    Wildes, Andrew R.
    Institut Laue-Langevin, France.
    Koza, Marek M.
    Institut Laue-Langevin, France.
    Ritter, Clemens
    Institut Laue-Langevin, France.
    Fouquet, Peter
    Institut Laue-Langevin, France.
    Keller, Lukas
    Paul Scherrer Institut, Switzerland.
    Canevet, Emmanuel
    Paul Scherrer Institut, Switzerland; DTU Technical University of Denmark, Denmark.
    Medarde, Marisa
    Paul Scherrer Institut, Switzerland.
    Blomgren, Jakob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Giblin, Sean R.
    Cardiff University, UK.
    Vrtnik, Stanislav
    Jozef Stefan Institute, Slovenia.
    Luzar, Jose
    Jozef Stefan Institute, Slovenia.
    Loidl, Alois
    University of Augsburg, Germany.
    Ruegg, Christina
    Paul Scherrer Institut, Switzerland; University of Geneva, Switzerland.
    Fennell, Tom
    Paul Scherrer Institut, Switzerland.
    Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr2X4 (X = Se, S)2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 13, article id 130201Article in journal (Refereed)
    Abstract [en]

    Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr2Se4 is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy2Ti2O7. In this Letter we use diffuse neutron scattering to show that both CdEr2Se4 and CdEr2S4 support a dipolar spin ice state-the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy2Ti2O7, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er3+ ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr2X4 (X = Se, S) are primarily due to much faster monopole hopping. Our work suggests that CdEr2X4 offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.

  • 14.
    Gavilán, Helena
    et al.
    CSIC Instituto de Ciencia de Materiales de Madrid, Spain.
    Kowalski, Anja
    Micromod Partikeltechnologie GmbH, Germany.
    Heinke, David
    NanoPET Pharma GmbH, Germany.
    Sugunan, Abhilash
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Sommertune, Jens
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Varón, Miriam
    DTU Technical University of Denmark, Denmark.
    Bogart, Lara K.
    UCL University College London, UK.
    Posth, Oliver
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Zeng, Lunjie
    Chalmers University of Technology, Sweden.
    González-Alonso, David
    University of Cantabria, Spain.
    Balceris, Chrsitoph
    TU Braunschweig, Germany.
    Fock, Jeppe
    DTU Technical University of Denmark, Denmark.
    Wetterskog, Erik
    Uppsala University, Sweden.
    Frandsen, Cathrine
    DTU Technical University of Denmark, Denmark.
    Gehrke, Nicole
    NanoPET Pharma GmbH, Germany.
    Grüttner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Fornara, Andrea
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Ludwig, Frank
    TU Braunschweig, Germany.
    Veintemillas-Verdaguer, Sabino
    CSIC Instituto de Ciencia de Materiales de Madrid, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Morales, M. Puerto
    CSIC Instituto de Ciencia de Materiales de Madrid, Spain.
    Colloidal Flower-Shaped Iron Oxide Nanoparticles: Synthesis Strategies and Coatings2017In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 34, no 7, article id 1700094Article in journal (Refereed)
    Abstract [en]

    The assembly of magnetic cores into regular structures may notably influence the properties displayed by a magnetic colloid. Here, key synthesis parameters driving the self-assembly process capable of organizing colloidal magnetic cores into highly regular and reproducible multi-core nanoparticles are determined. In addition, a self-consistent picture that explains the collective magnetic properties exhibited by these complex assemblies is achieved through structural, colloidal, and magnetic means. For this purpose, different strategies to obtain flower-shaped iron oxide assemblies in the size range 25–100 nm are examined. The routes are based on the partial oxidation of Fe(OH)2, polyol-mediated synthesis or the reduction of iron acetylacetonate. The nanoparticles are functionalized either with dextran, citric acid, or alternatively embedded in polystyrene and their long-term stability is assessed. The core size is measured, calculated, and modeled using both structural and magnetic means, while the Debye model and multi-core extended model are used to study interparticle interactions. This is the first step toward standardized protocols of synthesis and characterization of flower-shaped nanoparticles.

  • 15.
    Gutiérrez, Lucía
    et al.
    CSIC Spanish National Research Council, Spain.
    Costo, Rocio
    CSIC Spanish National Research Council, Spain.
    Grüttner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Westphal, Fritz
    Micromod Partikeltechnologie GmbH, Germany.
    Gehrke, Nicole
    NanoPET Pharma GmbH, Germany.
    Heinke, David
    NanoPET Pharma GmbH, Germany.
    Fornara, Andrea
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Pankhurst, Quentin A.
    University College of London, UK.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Veintemillas-Verdaguer, Sabino
    CSIC Spanish National Research Council, Spain.
    Morales, Maria del Puerto
    CSIC Spanish National Research Council, Spain.
    Synthesis methods to prepare single- and multi-core iron oxide nanoparticles for biomedical applications2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 7, p. 2943-2952Article in journal (Refereed)
    Abstract [en]

    We review current synthetic routes to magnetic iron oxide nanoparticles for biomedical applications. We classify the different approaches used depending on their ability to generate magnetic particles that are either single-core (containing only one magnetic core, i.e. a single domain nanocrystal) or multi-core (containing several magnetic cores, i.e. single domain nanocrystals). The synthesis of single-core magnetic nanoparticles requires the use of surfactants during the particle generation, and careful control of the particle coating to prevent aggregation. Special attention has to be paid to avoid the presence of any toxic reagents after the synthesis if biomedical applications are intended. Several approaches exist to obtain multi-core particles based on the coating of particle aggregates; nevertheless, the production of multi-core particles with good control of the number of magnetic cores per particle, and of the degree of polydispersity of the core sizes, is still a difficult task. The control of the structure of the particles is of great relevance for biomedical applications as it has a major influence on the magnetic properties of the materials.

  • 16.
    Johansson, Christer
    et al.
    RISE, Swedish ICT, Acreo, Sensor Systems.
    Ahrentorp, Fredrik
    Metod och anordning för detektering av förändringar av magnetisk respons hos magnetiska partiklar försedda med yttre skikt i bärarvätska2002Patent (Other (popular science, discussion, etc.))
  • 17.
    Jonasson, Christian
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Schaller, Vincent
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zeng, Lunjie
    Chalmers University of Technology, Sweden.
    Olsson, Eva
    Chalmers University of Technology, Sweden.
    Frandsen, Cathrine
    DTU Technical University of Denmark, Denmark.
    Castro, Alejandra
    Solve AB, Sweden.
    Nilsson, Lars
    Solve AB, Sweden.
    Bogart, Lara
    University College London, UK.
    Southern, Paul
    University College London, UK.
    Pankhurst, Quentin
    University College London, UK.
    Morales, Puerto
    Institute of Material Science of Madrid, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Modelling the effect of different core sizes and magnetic interactions inside magnetic nanoparticles on hyperthermia performance2019In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 477, p. 198-202Article in journal (Refereed)
    Abstract [en]

    We present experimental intrinsic loss power (ILP) values, measured at an excitation frequency of 1 MHz and at relatively low field amplitudes of 3.4 to 9.9 kA/m, as a function of the mean core diameter, for selected magnetic nanoparticle (MNP). The mean core sizes ranged from ca. 8 nm to 31 nm. Transmission electron microscopy indicated that those with smaller core sizes (less than ca. 22 nm) were single-core MNPs, while those with larger core sizes (ca. 29 nm to 31 nm) were multi-core MNPs. The ILP data showed a peak at ca. 20 nm. We show here that this behaviour correlates well with the predicted ILP values obtained using either a non-interacting Debye model, or via dynamic Monte-Carlo simulations, the latter including core-core magnetic interactions for the multi-core particles. This alignment of the models is a consequence of the low field amplitudes used. We also present interesting results showing that the core-core interactions affect the ILP value differently depending on the mean core size.

  • 18.
    Kumari, Monika
    et al.
    ETH Zurich, Switzerland.
    Hirt, Ann
    ETH Zurich, Switzerland.
    Uebe, Rene
    Ludwig Maximilian University of Munich, Germany; University of Bayreuth, Germany.
    Schuler, Dirk
    Ludwig Maximilian University of Munich, Germany; University of Bayreuth, Germany.
    Tompa, Eva
    University of Pannonia, Hungary.
    Mihaly Posfai, Mihaly
    University of Pannonia, Hungary.
    Lorenz, Wolfram
    ETH Zurich, Switzerland.
    Ahrentorp, Fredrik
    RISE, Swedish ICT, Acreo.
    Jonasson, Christian
    RISE, Swedish ICT, Acreo.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Experimental mixtures of superparamagnetic single domain magnetite with respect to Day-Dunlop plots2015In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 16, no 6, p. 1739-1752Article in journal (Refereed)
    Abstract [en]

    Day‐Dunlop plots are widely used in paleomagnetic and environmental studies as a tool to determine the magnetic domain state of magnetite, i.e., superparamagnetic (SP), stable single‐domain (SD), pseudosingle‐domain (PSD), multidomain (MD), and their mixtures. The few experimental studies that have examined hysteresis properties of SD‐SP mixtures of magnetite found that the ratios of saturation remanent magnetization to saturation magnetization and the coercivity of remanence to coercivity are low, when compared to expected theoretical mixing trends based on Langevin theory. This study reexamines Day‐Dunlop plots using experimentally controlled mixtures of SD and SP magnetite grains. End‐members include magnetotactic bacteria (MSR‐1) as the SD source, and a commercial ferrofluid or magnetotactic bacteria (ΔA12) as the SP source. Each SP‐component was added incrementally to a SD sample. Experimental results from these mixing series show that the magnetization and coercivity ratios are lower than the theoretical prediction for bulk SP magnetic size. Although steric repulsion was present between the particles, we cannot rule out interaction in the ferrofluid for higher concentrations. The SP bacteria are noninteracting as the magnetite was enclosed by an organic bilipid membrane. Our results demonstrate that the magnetization and coercivity ratios of SD‐SP mixtures can lie in the PSD range, and that an unambiguous interpretation of particle size can only be made with information about the magnetic properties of the end‐members.

  • 19.
    Ludwig, Frank
    et al.
    TU Braunschweig, Germany.
    Balceris, Christoph
    TU Braunschweig, Germany.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    The Anisotropy of the AC Susceptibility of Immobilized Magnetic Nanoparticles-the Influence of Intra-Potential-Well Contribution on the AC Susceptibility Spectrum2017In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 53, no 11, article id 7894242Article in journal (Refereed)
    Abstract [en]

    We have experimentally verified the ac susceptibility model by Shliomis and Stepanov which accounts for the anisotropy caused by the different directions of the easy axes of the magnetic nanoparticle (MNP) cores with respect to the applied ac magnetic field. To experimentally access the anisotropy, single-core MNPs were immobilized in the absence of a magnetic field, thus causing random orientations of easy axes, and in a static magnetic field of 170 mT, thus orienting the nanoparticles' easy axes either parallel or perpendicular to the ac field. In agreement with theory, the real part of the sample with easy axes aligned perpendicularly to the ac field is constant while the imaginary part is zero. In contrast, the real part of the sample with parallel-oriented easy axes decays with increasing frequency. The susceptibility spectra of the sample with random orientation of easy axes are in between the other two cases according to χω= χIIω+ 2χω/3. This anisotropic behavior also explains why the real part of suspensions of thermally blocked MNPs does not drop down to zero at high frequencies but to a finite value. This value allows one to independently estimate the effective anisotropy constant of MNPs.

  • 20.
    Ludwig, Frank
    et al.
    TU Braunschweig, Germany.
    Balceris, Christoph
    TU Braunschweig, Germany.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Analysis of AC Susceptibility Spectra for the Characterization of Magnetic Nanoparticles2017In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 53, no 11, article id 7898860Article in journal (Refereed)
    Abstract [en]

    Measurements of the ac susceptibility (ACS) as a function of frequency have been widely applied for the determination of structure parameters of magnetic nanoparticles (MNP). The analysis of spectra of real and imaginary parts measured on suspensions of MNP is generally based on the Debye model, extended by distributions of size parameters. Here, we compare different modifications of the Debye model with experimental data recorded on suspensions of single-core and multi-core iron-oxide nanoparticles. The applied models also depend on whether the nanoparticle's magnetic moments are thermally blocked and whether both Brownian and Néel relaxation have to be taken into account. The obtained core and hydrodynamic size parameters are compared with those from transmission electron microscopy and dynamic light scattering. Whereas structure parameters can be reliably determined for single-core nanoparticles, the interpretation of ACS spectra measured on multi-core nanoparticles is more complicated, especially regarding the contribution of particles relaxing via the Néel mechanism. Depending on the packing density and thus the interaction between cores in a particle, the effective core parameters derived from the spectrum must be interpreted with care.

  • 21.
    Ludwig, Frank
    et al.
    Technische Universität Braunschweig, Germany.
    Balceris, Christoph
    Technische Universität Braunschweig, Germany.
    Viereck, Thilo
    Technische Universität Braunschweig, Germany.
    Posth, Oliver
    Physikalisch-Technische Bundesanstalt, Germany.
    Steinhoff, Uwe
    Physikalisch-Technische Bundesanstalt, Germany.
    Gavilan, Helena
    CSIC Instituto de Ciencia de Materiales de Madrid, Spain.
    Costo, Rocio
    CSIC Instituto de Ciencia de Materiales de Madrid, Spain.
    Zeng, Lunjie
    Chalmers University of Technology, Sweden.
    Olsson, Eva
    Chalmers University of Technology, Sweden.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Size analysis of single-core magnetic nanoparticles2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 427, p. 19-24Article in journal (Refereed)
    Abstract [en]

    Single-core iron-oxide nanoparticles with nominal core diameters of 14 nm and 19 nm were analyzed with a variety of non-magnetic and magnetic analysis techniques, including transmission electron microscopy (TEM), dynamic light scattering (DLS), static magnetization vs. magnetic field (M-H) measurements, ac susceptibility (ACS) and magnetorelaxometry (MRX). From the experimental data, distributions of core and hydrodynamic sizes are derived. Except for TEM where a number-weighted distribution is directly obtained, models have to be applied in order to determine size distributions from the measurand. It was found that the mean core diameters determined from TEM, M-H, ACS and MRX measurements agree well although they are based on different models (Langevin function, Brownian and Néel relaxation times). Especially for the sample with large cores, particle interaction effects come into play, causing agglomerates which were detected in DLS, ACS and MRX measurements. We observed that the number and size of agglomerates can be minimized by sufficiently strong diluting the suspension.

  • 22.
    Löfström, Roland
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Energiteknik (ET).
    Johansson, Christer
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Energiteknik (ET).
    Lösfyllnadsisolering på bjälklag - Bestämning av värmemotstånd.1992Report (Refereed)
  • 23. Nilsson, Erik
    et al.
    Lund, Anja
    Jonasson, Christian
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Hagström, Bengt
    Poling characterization of piezoelectric polymer fibers for use in textile sensors2013In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 201, p. 477-486Article in journal (Refereed)
  • 24.
    Posth, Oliver
    et al.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Hansen, Mikkel Fougt
    DTU Technical University of Denmark, Denmark.
    Steinhoff, Uwe
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Bogart, Lara
    University College London, UK.
    Southern, Paul
    University College London, UK.
    Svedlindh, Peter
    Uppsala University, Sweden.
    Grüttner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Barquin, Luis Fernández
    University of Cantabria, Spain.
    Szczerba, Wojciech
    BAM Federal Institute for Materials Research and Testing, Germany.
    Ludwig, Frank
    Technical University of Braunschweig, Germany.
    Gehrke, Nicole
    NanoPET Pharma GmbH, Germany.
    Kazakova, Olga
    NPL National Physical Laboratory, UK.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Classification of analysis methods for characterization of magnetic nanoparticle properties2015In: 21st IMEKO World Congress 2015: Measurement in Research and Industry, 2015, Vol. 2, p. 1310-1315Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to provide a roadmap for the standardization of magnetic nanoparticle (MNP) characterization. We have assessed common MNP analysis techniques under various criteria in order to define the methods that can be used as either standard techniques for magnetic particle characterization or those that can be used to obtain a comprehensive picture of a MNP system. This classification is the first step on the way to develop standards for nanoparticle characterization.

  • 25.
    Prabu, Chakkarapani
    et al.
    Anna University, India.
    Latha, Subbiah
    Anna University, India.
    Selvamani, Palanisamy
    Anna University, India.
    Ahrentorp, Fredrik
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Takeda, Ryoji
    Yokohama National University, Japan.
    Takemura, Yasushi
    Yokohama National University, Japan.
    Ota, Satoshi
    Shizuoka University, Japan.
    Layer-by-layer assembled magnetic prednisolone microcapsules (MPC) for controlled and targeted drug release at rheumatoid arthritic joints2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 427, p. 258-267Article in journal (Refereed)
    Abstract [en]

    We report here in about the formulation and evaluation of Magnetic Prednisolone Microcapsules (MPC) developed in order to improve the therapeutic efficacy relatively at a low dose than the conventional dosage formulations by means of magnetic drug targeting and thus enhancing bioavailability at the arthritic joints. Prednisolone was loaded to poly (sodium 4-styrenesulfonate) (PSS) doped calcium carbonate microspheres confirmed by the decrease in surface area from 97.48 m2/g to 12.05 of m2/g by BET analysis. Adsorption with oppositely charged polyelectrolytes incorporated with iron oxide nanoparticles was confirmed through zeta analysis. Removal of calcium carbonate core yielded MPC with particle size of ~3.48 µm, zeta potential of +29.7 mV was evaluated for its magnetic properties. Functional integrity of MPC was confirmed through FT-IR spectrum. Stability studies were performed at 25 °C±65% relative humidity for 60 days showed no considerable changes. Further the encapsulation efficiency of 63%, loading capacity of 18.2% and drug release of 88.3% for 36 h and its kinetics were also reported. The observed results justify the suitability of MPC for possible applications in the magnetic drug targeting for efficient therapy of rheumatoid arthritis.

  • 26.
    Riordan, E
    et al.
    Cardiff University, UK.
    Blomgren, Jakob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ahrentorp, Fredrik
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Margineda, D
    Cardiff University, UK.
    Elfassi, A
    INSA Institut National des Sciences Appliques, France.
    Michel, S
    INSA Institut National des Sciences Appliques, France.
    Dell'ova, F
    INSA Institut National des Sciences Appliques, France.
    Klemencic, G M
    Cardiff University, UK.
    Giblin, S R
    Cardiff University, UK.
    Design and implementation of a low temperature, inductance based high frequency alternating current susceptometer.2019In: Review of Scientific Instruments, Vol. 90, no 7Article in journal (Refereed)
    Abstract [en]

    We report on the implementation of an induction based, low temperature, high frequency ac susceptometer capable of measuring at frequencies up to 3.5 MHz and at temperatures between 2 K and 300 K. Careful balancing of the detection coils and calibration allow a sample magnetic moment resolution of 5 × 10−10 Am2 at 1 MHz. We discuss the design and characterization of the susceptometer and explain the calibration process. We also include some example measurements on the spin ice material CdEr2S4 and iron oxide based nanoparticles to illustrate functionality.

  • 27.
    Schanzenbach, Christoph
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ilver, Dag
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Blomgren, Jacob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Krozer, Aanatol
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ye, Lei
    Lund University, Sweden.
    Rustas, Bengt-Ove
    SLU Swedish University of Agricultural Science, Sweden.
    Preparation and characterisation of a sensing system for wireless pH measurements in vivo, in a rumen of a cow2017In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 242, p. 637-644Article in journal (Refereed)
    Abstract [en]

    We describe a sensing system that is able to measure pH in-vivo, in the rumen of a cow, in real time. The sensing principle is based on gravimetric transduction using a magnetoelastic ribbon functionalized by pH-sensitive nanobeads that is placed in the rumen where it is actuated and read-out wirelessly. We describe a generic procedure that enables one to deposit monolayers or multilayers of nano- and micro beads onto virtually any substrate. The topography of the resulting layers as well as interlayer coverages were characterised using optical microscopy and scanning profilometry. First we determined performance of the system in-vitro, in phosphate-buffered saline, in McDougall's buffer and in a rumen fluid. Thereafter we also performed in-vivo measurements. Using buffers we determined pH response in the liquids both at the fundamental frequency of the functionalised foils, and at the 1st overtone. We argue that observed frequency changes vs pH are mainly due to changes of trapped liquid when the bead layers shrink or expand as a response to changed pH. The data obtained from the pH response of magnetoelastic foils at different bead coverages was modelled by a simple two-parameter model that corroborates this assumption.

  • 28.
    Sepehri, Sobhan
    et al.
    Chalmers University of Technology, Sweden.
    Eriksson, Emil
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kalaboukhov, Alexei
    Chalmers University of Technology, Sweden.
    Zardán Gómez de la Torre, Teresa
    Uppsala University, Sweden.
    Kustanovich, Kiryl
    Chalmers University of Technology, Sweden.
    Jesorka, Aldo
    Chalmers University of Technology, Sweden.
    Schneiderman, Justin F.
    Chalmers University of Technology, Sweden ; University of Gothenburg, Sweden.
    Blomgren, Jakob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Strømme, Maria
    Uppsala University, Sweden.
    Winkler, Dag
    Chalmers University of Technology, Sweden.
    Volume-amplified magnetic bioassay integrated with microfluidic sample handling and high-Tc SQUID magnetic readout2017In: APL Bioengineering, Vol. 2, no 1, article id 016102Article in journal (Refereed)
    Abstract [en]

    A bioassay based on a high-Tc superconducting quantum interference device (SQUID) reading out functionalized magnetic nanoparticles (fMNPs) in a prototype microfluidic platform is presented. The target molecule recognition is based on volume amplification using padlock-probe-ligation followed by rolling circle amplification (RCA). The MNPs are functionalized with single-stranded oligonucleotides, which give a specific binding of the MNPs to the large RCA coil product, resulting in a large change in the amplitude of the imaginary part of the ac magnetic susceptibility. The RCA products from amplification of synthetic Vibrio cholera target DNA were investigated using our SQUID ac susceptibility system in microfluidic channel with an equivalent sample volume of 3 μl. From extrapolation of the linear dependence of the SQUID signal versus concentration of the RCA coils, it is found that the projected limit of detection for our system is about 1.0 × 105 RCA coils (0.2 × 10−18 mol), which is equivalent to 66 fM in the 3 μl sample volume. This ultra-high magnetic sensitivity and integration with microfluidic sample handling are critical steps towards magnetic bioassays for rapid detection of DNA and RNA targets at the point of care.

  • 29.
    Sette, Erik
    et al.
    Chalmers University of Technology, Sweden.
    Pallars, David
    Chalmers University of Technology, Sweden.
    Johnsson, Filip
    Chalmers University of Technology, Sweden.
    Ahrentorp, Fredrik
    RISE, Swedish ICT, Acreo.
    Ericsson, Anders
    RISE, Swedish ICT, Acreo.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Magnetic tracer-particle tracking in a fluid dynamically down-scaled bubbling fluidized bed2015In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 138, p. 368-377Article in journal (Refereed)
    Abstract [en]

    A method for 3-dimensional (3D) magnetic tracer particle tracking in a fluid dynamically downscaled fluidized bed is presented. The method applies anisotropic magnetoresistive (AMR) sensors to track a magnetic tracer particle in the form of an NdFeB-based permanent magnet. The fluid dynamically downscaled bed has a cross-section of 0.17 × 0.17 m2and is operated at ambient conditions with bronze powder as bulk solids and the tracer particle corresponding to a fuel particle. After up-scaling the bed corresponds to a 0.85 × 0.85 m2 bed of fuel ash or silica sand operated with air at 900 °C using anthracite coal as a fuel. Thus, the method provides continuous tracking of the tracer particle trajectorywhich, combined with the fluid dynamic scaling yields quantitativeinformation applicable to the study of fuel mixing in large-scale fluidized-bed processes operating under hot conditions. Application of the method represents a significant step forward compared to other experimental studies which are limited to qualitative interpretations; performed in 2D units and in cold 3D units which are not fluid dynamically scaled.

    It is shown that the AMR sensor system is able to work with the (non-magnetic) bronze powder resulting from the fluid dynamical downscaling, i.e. overcoming the limitation in signal penetration which prevents tracking of radioactive objects in such dense media. Thus, successful application of the AMR method for continuous 3D object tracking in a fluid dynamically downscaled unit is demonstrated for the first time. The measurement system provides both translational and rotational data, unleashing possibilities also as a validation tool of CFD models. The preliminary results show a spatial resolution on the order of 1 mm, while temporal resolution is on the order of milliseconds.

  • 30.
    Sommertune, Jens
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Sugunan, Abhilash
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Ahniyaz, Anwar
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Stjernberg Bejhed, Rebecca
    Uppsala University, Sweden.
    Sarwe, Anna
    RISE, Swedish ICT, Acreo.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Balceris, Cristoph
    Technische Universität Braunschweig, Germany.
    Ludwig, Frank
    Technische Universität Braunschweig, Germany.
    Posth, Oliver
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Fornara, Andrea
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Polymer/iron oxide nanoparticle composites—A straight forward and scalable synthesis approach2015In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 16, no 8, p. 19752-19768Article in journal (Refereed)
    Abstract [en]

    Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

  • 31.
    Sriviriyakul, Thana
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Bogren, Sara
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Schaller, Vincent
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Blomgren, Jakob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ahrentorp, Fredrik
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Lopez-Sanchez, Patricia
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Berta, Marco
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Grüttner, Cordula
    micromod Partikeltechnologie GmbH, Germany.
    Zeng, Lunjie
    Chalmers University of Technology, Sweden.
    Stading, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Nanorheological studies of xanthan/water solutions using magnetic nanoparticles2019In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 473, p. 268-271Article in journal (Refereed)
    Abstract [en]

    We show results of nanorheological studies of different concentrations of xanthan (non-Newtonian fluid) in water using magnetic nanoparticles (MNPs) together with the AC susceptibility (ACS) vs frequency method. For comparison we also show the ACS response for different concentrations of glycerol in water (Newtonian fluid). The ACS response is measured, and the data is modelled using dynamic magnetic models and different viscoelastic models. We study the ACS response (in-phase and out-of-phase ACS components) at different concentrations of xanthan in water (up to 1 wt% xanthan) and with a constant concentration of MNPs. We use MNP systems that show Brownian relaxation (sensitive to changes in the environmental properties around the MNPs). ACS measurements are performed using the DynoMag system. The Brownian relaxation of the MNP system peak is shifting down in frequency and the ACS response is broadening and decreases due to changes in the viscoelastic properties around the MNPs in the xanthan solution. The viscosity and the storage moduli are determined at each excitation frequency and compared with traditional macroscopic small amplitude oscillatory shear rheological measurements. The results from the traditional rheological and nanorheological measurements correlate well at higher xanthan concentration.

  • 32.
    Tian, Bo
    et al.
    Uppsala University, Sweden.
    Qiu, Zhen
    Uppsala University, Sweden.
    Ma, Jing
    Uppsala University, Sweden.
    Zardán Gómez de la Torre, Teresa
    Uppsala University, Sweden.
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Svedlindh, Peter
    Uppsala University, Sweden.
    Strömberg, Mattias
    Uppsala University, Sweden.
    Attomolar Zika virus oligonucleotide detection based on loop-mediated isothermal amplification and AC susceptometry2016In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 86, p. 420-425Article in journal (Refereed)
    Abstract [en]

    Because of the serological cross-reactivity among the flaviviruses, molecular detection methods, such as reverse-transcription polymerase chain reaction (RT-PCR), play an important role in the recent Zika outbreak. However, due to the limited sensitivity, the detection window of RT-PCR for Zika viremia is only about one week after symptom onset. By combining loop-mediated isothermal amplification (LAMP) and AC susceptometry, we demonstrate a rapid and homogeneous detection system for the Zika virus oligonucleotide. Streptavidin-magnetic nanoparticles (streptavidin-MNPs) are premixed with LAMP reagents including the analyte and biotinylated primers, and their hydrodynamic volumes are dramatically increased after a successful LAMP reaction. Analyzed by a portable AC susceptometer, the changes of the hydrodynamic volume are probed as Brownian relaxation frequency shifts, which can be used to quantify the Zika virus oligonucleotide. The proposed detection system can recognize 1 aM synthetic Zika virus oligonucleotide in 20% serum with a total assay time of 27 min, which can hopefully widen the detection window for Zika viremia and is therefore promising in worldwide Zika fever control.

  • 33.
    Wells, James
    et al.
    National Physical Laboratory, UK; Physikalisch-Technische Bundesanstalt, Germany.
    Kazakova, Olga
    National Physical Laboratory, UK.
    Posth, Oliver
    Physikalisch-Technische Bundesanstalt, Germany.
    Steinhoff, Uwe
    Physikalisch-Technische Bundesanstalt, Germany.
    Petronis, Sarunas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Bogart, Lara
    Healthcare Biomagnetics Laboratory, UK.
    Southern, Paul
    Healthcare Biomagnetics Laboratory, UK.
    Pankhurst, Quentin
    Healthcare Biomagnetics Laboratory, UK.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Standardisation of magnetic nanoparticles in liquid suspension2017In: Journal of Physics D: Applied Physics, Vol. 50, no 383003, p. 1-25Article in journal (Refereed)
    Abstract [en]

    Suspensions of magnetic nanoparticles offer diverse opportunities for technology innovation,spanning a large number of industry sectors from imaging and actuation based applicationsin biomedicine and biotechnology, through large-scale environmental remediation uses suchas water purification, to engineering-based applications such as position-controlled lubricantsand soaps. Continuous advances in their manufacture have produced an ever-growing rangeof products, each with their own unique properties. At the same time, the characterisation ofmagnetic nanoparticles is often complex, and expert knowledge is needed to correctly interpretthe measurement data. In many cases, the stringent requirements of the end-user technologiesdictate that magnetic nanoparticle products should be clearly defined, well characterised,consistent and safe; or to put it another way—standardised. The aims of this document areto outline the concepts and terminology necessary for discussion of magnetic nanoparticles,to examine the current state-of-the-art in characterisation methods necessary for the mostprominent applications of magnetic nanoparticle suspensions, to suggest a possible structurefor the future development of standardisation within the field, and to identify areas and topicswhich deserve to be the focus of future work items. We discuss potential roadmaps for thefuture standardisation of this developing industry, and the likely challenges to be encounteredalong the way.

  • 34.
    Wetterskog, Erik
    et al.
    Uppsala University, Sweden.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Smilgies, Detlef-M
    Cornell University, USA.
    Schaller, Vincent
    Chalmers industriteknik, Sweden.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Svedlindh, Peter
    Uppsala University, Sweden.
    Colossal Anisotropy of the Dynamic Magnetic Susceptibility in Low-Dimensional Nanocube Assemblies2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 2, p. 1403-1412Article in journal (Refereed)
    Abstract [en]

    nanocubes display a significant augmentation of the magnetic susceptibility and dissipation as compared to 0D and 2D systems. The performance of the nanocube needles is highlighted by a colossal anisotropy factor defined as the ratio of the parallel to the perpendicular magnetization components. We show that the origin of this effect cannot be ascribed to shape anisotropy in its classical sense; as such, it has no analogy in bulk magnetic materials. The temperature-dependent anisotropy factors of the in- and out-of-phase components of the magnetization have an extremely strong particle size dependence and reach values of 80 and 2500, respectively, for the largest nanocubes in this study. Aided by simulations, we ascribe the anisotropy of the magnetic susceptibility, and its strong particle-size dependence to a synergistic coupling between the dipolar interaction field and a net anisotropy field resulting from a partial texture in the 1D nanocube needles.

  • 35.
    Witte, Kerstin
    et al.
    University of Rostock, Germany; Micromod Partikeltechnologie GmbH, Germany.
    Müller, Knut
    Micromod Partikeltechnologie GmbH, Germany.
    Grüttner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Westphal, Fritz
    Micromod Partikeltechnologie GmbH, Germany.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Particle size- and concentration-dependent separation of magnetic nanoparticles2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 427, p. 320-324Article in journal (Refereed)
    Abstract [en]

    Small magnetic nanoparticles with a narrow size distribution are of great interest for several biomedical applications. When the size of the particles decreases, the magnetic moment of the particles decreases. This leads to a significant increase in the separation time by several orders of magnitude. Therefore, in the present study the separation processes of bionized nanoferrites (BNF) with different sizes and concentrations were investigated with the commercial Sepmag Q system. It was found that an increasing initial particle concentration leads to a reduction of the separation time for large nanoparticles due to the higher probability of building chains. Small nanoparticles showed exactly the opposite behavior with rising particle concentration up to 0.1 mg(Fe)/ml. For higher iron concentrations the separation time remains constant and the measured Z-average decreases in the supernatant at same time intervals. At half separation time a high yield with decreasing hydrodynamic diameter of particles can be obtained using higher initial particle concentrations.

1 - 35 of 35
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