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1
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Study of Magnetic Fredericksz Transition in Ferronematics

100%
Kopčanský P., Koneracká M., Jadżyn J., Czechowski G., Żywucki B.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
437-440
EN
The magnetic Fredericksz transition in ferronematics (thermotropic nematic liquid crystals 7CB and MBBA combined with fine magnetic particles of a size 10 nm) as a function of concentration of magnetic particles was studied by using simple dielectric measurements. The increase of the threshold magnetic field is observed in 7CB based ferronematic while the decrease of threshold field in MBBA based ferronematic is observed when the concentration of magnetic particles is increased. Experimental results are discussed in the framework of Brochard, de Gennes and Burylov, Raikher theories.
2
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Study of Composites Consisting of High-T_{c} Superconductor and Fine Magnetic Particles

100%
Timko M., Kopčanský P., Kováč J., Koneracká M., Plecháček V.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
389-392
EN
The composite systems as a mixture of fine magnetic particles of Fe_{3}O_{4} and superconducting powder such as Bi_{1.8}Pb_{0.2}Sr_{2}Ca_{2}Cu_{3}O_{10+x} were prepared. The influence of internal magnetic field (generated by magnetic particles) on the superconducting properties of prepared composites were studied as a function of concentration of magnetic particles and their magnetic state. The observed data both of the shielding and the Meissner effect were compared with corresponding linear combination of pure signals of magnetite and superconductor, respectively. The large differences were observed for demagnetized samples. It means that result must be discussed in the frame of the distribution of internal magnetic field created by the magnetic particles.
3
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The Structural Phase Transitions in 6CB-Based Ferronematics

86%
Tomašovičová N., Koneracká M., Kopčanský P., Timko M., Závišová V., Tomčo L., Jadżyn J.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
336-338
EN
The structural transitions in ferronematics based on the thermotropic nematic liquid crystal 4-cyano-4'-hexylbiphenyl were studied. The ferronematic samples were prepared by doping with magnetic suspension consisting of Fe_3O_4 particles (10 nm in diameter) coated with oleic acid as a surfactant with different volume concentrations of magnetic particles (from 10^{-5} to 10^{-3}). Freedericksz transitions were studied in combined electric and magnetic fields. The experimental results indicated soft anchoring with perpendicular initial orientation between the magnetic moment of the magnetic particles and director.
4
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Thermal Analysis of Magnetic Nanoparticles Modified with Dextran

86%
Juríková A., Csach K., Miškuf J., Koneracká M., Závišová V., Kubovčíková M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1296-1298
EN
In the work the thermal behaviour of the magnetic nanoparticles modified with polysaccharide dextran of different weight ratios to the magnetite Fe_3O_4 was investigated using thermoanalytical methods - differential scanning calorimetry and thermogravimetric analysis. The adsorption of dextran on the magnetic nanoparticles was confirmed and the influence of the dextran amount in the modified magnetic fluid on the thermal decomposition of the complex system was studied. The results showed that magnetite catalyzed the thermal decomposition of dextran, the adsorbed dextran showed lower initial decomposition temperatures in comparison with the free one.
5
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Thermogravimetric Study of the Decomposition of BSA-Coated Magnetic Nanoparticles

86%
Csach K., Juríková A., Miškuf J., Koneracká M., Závišová V., Kubovčíková M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1293-1295
EN
Magnetic nanoparticles used in biomedicine have to be biocompatible, which can be achieved by the modification of the magnetic particle surface with an appropriate biocompatible substance. In the work protein bovine serum albumin (BSA) was chosen to modify the surface of magnetic nanoparticles. The BSA-coated magnetic nanoparticles with different input weight ratios of BSA to the magnetite Fe_3O_4 were prepared and thermally characterized using thermogravimetric and differential scanning calorimetric analysis. The adsorption of BSA on the magnetic nanoparticles in wide range of concentration was confirmed. The activation energies of the thermal decomposition of the complex system were estimated.
6
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Magnetic Properties of Encapsulated Magnetite in PLGA Nanospheres

86%
Koneracká M., Závišová V., Timko M., Kopčanský P., Tomašovičová N., Csach K.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
595-598
EN
In this study, the biocompatible magnetic fluid was encapsulated in biodegradable polymer PLGA (poly D, L/lactide-co-glycolide acid) by the nanoprecipitation method. We characterized these spheres in terms of morphology, magnetite content and magnetic properties. The results showed good encapsulation with magnetite content 22wt% and magnetization 3.4 mT. The transmission electron microscopy and scanning electron microscopy images showed that magnetic particles have almost a spherical shape with approximate size 250 nm. Infrared spectroscopy and thermogravimetric analysis measurements were used to confirm incorporation of magnetic particles into the PLGA polymer.
7
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Dielectric Properties of Magnetic Liquids in High Electric Fields

86%
Herchl F., Kopčanský P., Timko M., Koneracká M., Marton K., Kolcunová I., Tomčo L.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
569-572
EN
In this work, dielectric properties of magnetic fluids composed of magnetite particles dispersed in transformer oil and subjected to a uniform magnetic field were investigated at the high alternating electric field intensities in the range of 0.5-2.5 MV/m. Dielectric stability of the magnetic fluid with the particle volume concentrationΦ= 0.0019 was observed. The magnetic fluid with the concentrationΦ= 0.019 showed the significant changes of permittivity and dielectric losses, too.
8
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Thermal Analysis of Magnetic Polymer Nanospheres for Drug Targeting

86%
Juríková A., Csach K., Miškuf J., Koneracká M., Závišová V., Kopčanský P.
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issue 5
990-992
EN
Poly(D,L-lactic-co-glycolic) acid (PLGA) polymer nanospheres loaded with different input amounts of anticancer drug taxol were prepared by the modified nanoprecipitation method. Magnetite was incorporated into the polymer nanospheres to impart them superparamagnetic properties. Thermal properties of the drug loaded magnetic polymer nanospheres were characterized using differential scanning calorimetry and thermogravimetric analysis. The solid state solubility of taxol in PLGA nanospheres and the influence of external magnetic field on their thermal stability were estimated. The investigations have revealed that the samples of dried taxol loaded magnetic PLGA nanospheres undergo mass loss at three stages during heating.
9
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SANS Study of Poly(ethylene glycol) Solutions in D_2O

86%
Lancz G., Avdeev M., Petrenko V., Garamus V., Koneracká M., Kopčanský P.
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issue 5
980-982
EN
Poly(ethylene glycol) is used for coating of colloidal particles and other surfaces for gaining biocompatibility. Particularly, it can be introduced into magnetic fluids. The aim of the current study was to reveal the structural characteristics of poly(ethylene glycol) in neat D_2O using small-angle neutron scattering technique. Solutions of poly(ethylene glycol) (at temperature of 37°C) with different molecular weights in an interval of 400-20000 were investigated. It is concluded that at low concentrations (less than 2% of mass fraction) poly(ethylene glycol) molecules behave as Gaussian coils.
10
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Preparation and Complex Characterization of Magnetic Nanoparticles in Magnetic Fluid

86%
Kubovčíková M., Antal I., Kováč J., Závišová V., Koneracká M., Kopčanský P.
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vol. 126
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issue 1
268-269
EN
This paper deals with the preparation and complex characterization of magnetite nanoparticles (MNPs), stabilized with sodium oleate (SO), by the routine methods such as infrared spectroscopy (FTIR), magnetic measurements, scanning electron microscopy (SEM) and dynamic light scattering (DLS). The FTIR spectra showed that SO molecules were linked to MNPs through chemical bonding. Magnetic measurements proved that the MNPs are superparamagnetic in nature. Four different methods were used to determine the size and size distribution of the MNPs: SEM, DLS, differential centrifugal sedimentation (DCS) and magnetic measurements. SEM analysis showed a relatively narrow size distribution of roughly spherical MNPs with a mean diameter of 61 nm. DLS analysis confirmed monodispersed MNPs production with hydrodynamic diameter of 75 nm. The size distribution determined by DCS was found to be 69 nm. Finally, the calculated magnetic core diameter obtained from magnetization curve was 10 nm. The obtained results demonstrate that SO coated MNPs fulfil the requirements for a useful drug delivery system.
11
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Magnetic Field Induced Structural Transitions in 6CHBT-Based Ferronematics

73%
Tomašovičová N., Timko M., Koneracká M., Závišová V., Jadżyn J., Beaugnon E., Chaud X., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1276-1278
EN
Ferronematics are stable colloidal suspensions of magnetic particles in nematic liquid crystals. The presence of the magnetic particles enhances the magnetic susceptibility of ferronematics, in comparison with pure liquid crystals. In this work the thermotropic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT) and 6CHBT dissolved in phenyl isothiocyanate were doped with spherical magnetic nanoparticles with aim to increase the sensitivity of the liquid crystal on an external magnetic field. The volume concentration of the magnetic particles was 5 × 10^{-4}. The phase transition temperature from isotropic to nematic phase in the external magnetic field up to 12 T was monitored by precise capacitance measurements in the capacitance cells filled with nematic sample as well as with the prepared ferronematic sample. There was no observable shift in the transition temperature in the case of pure 6CHBT, 6CHBT doped with spherical particles and 6CHBT dissolved in phenyl isothiocyanate while in the case of 6CHBT dissolved in phenyl isothiocyanate doped with spherical magnetic particles the shift in the temperature about 9C of the phase transition from isotropic to droplet state at the external magnetic field 12 T was observed.
12
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Magnetic Properties of Magnetite Formed by Biomineralization and Chemical Synthesis

73%
Timko M., Džarová A., Kopčanský P., Závišová V., Koneracká M., Kováč J., Šprincová A., Vaclavíková M., Ivaničová L., Vávra I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
573-576
EN
In this work, the magnetic properties of biologically produced magnetite (magnetosomes) by biomineralization process were compared to those of chemically synthesized Fe_3O_4. The coercivity of 185 Oe in magnetosomes is connected with the fact that the mean diameter is larger than critical size for transition from superparamagnetic to ferromagnetic behavior. A sharp magnetic transition at 105 K (Verwey transition) is clearly present in magnetosomes while in opposite, this transition is missing in Fe_3O_4.
13
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Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles

73%
Mitróová Z., Tomašovičová N., Timko M., Koneracká M., Tomčo L., Jadżyn J., Palewski, T., Kopčanský P., Kovalchuk O.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1299-1301
EN
The paper presents a study of the polymer dispersed liquid crystals that consist of liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT) microdroplets dispersed in polyvinyl alcohol and doped with various kinds of magnetic particles. As magnetic nanoparticles there were used single walled carbon nanotubes and magnetite labeled single walled carbon nanotubes. The volume concentration of the particles was 2 × 10^{-3}. Magnetic properties were investigated by a SQUID magnetometer. The higher saturation magnetization has been achieved in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes. The phase transition temperature from isotropic to nematic phase at the external magnetic field 0 T and 12 T was monitored by precise capacitance measurements in the capacitance cell filled with prepared sample. The significant shift of the phase transition temperature (0.2°C) at the external magnetic field 12 T has been observed in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes.
14
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The Anchoring Energy of Liquid Crystal Molecules to Magnetic Particles in HAB-Based Ferronematics

73%
Tomašovičová N., Koneracká M., Kopčanský P., Timko M., Závišová V., Vajda A., Fodor-Csorba K., Éber N., Tóth-Katona T., Jadzyn J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
591-594
EN
In this work we describe the magnetic Freedericksz transition in HAB-based (4, 4'-di-n-heptylazoxybenzene) ferronematics. The ferronematic samples were prepared with two different volume concentrations of magnetic particles φ_1 = 2×10^{-5} and φ_2 = 2×10^{-4}. The liquid crystal HAB is nematic at the temperatures from ≈53°C to 70°C and smectic A at the temperatures under 53°C. The anisotropy of dielectric permitivity of HAB liquid crystal is positive in nematic phase and negative in smectic A phase. The magnetic Fredericksz transition was studied in nematic phase at temperature 60°C.
15
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The Dynamics of the Soret Effect in Thin Film of Magnetic Fluid

73%
Kopčanský P., Tomčo L., Timko M., Ocelík V., Koneracká M., Turek I., Štelina J., Musil C.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
875-878
EN
The Soret effect in interference field of two intensive laser beams in the thin film of magnetic fluid was used to create a periodical structure of density of magnetic particles. The structures obtained were indicated using the self-diffraction of the optical beam creating the structures. The relaxation phenomena after switching off the laser interference field were discussed in terms of the spectrum of relaxation times. This spectrum is proportional to hydrodynamic particle size distribution. The relaxation of optical grating consists of two well-defined channels, i.e. decay through single particles and small aggregates, respectively.
16
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Sensitivity of 6CHBT Liquid Crystal Doped with Ferroelectric or Magnetic Particles to Electric and Magnetic Fields

73%
Majorošová J., Tomašovičová N., Timko M., Koneracká M., Studenyak I., Kovalchuk O., Kovalchuk S., Jadżyn J., Kopčanský P.
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vol. 126
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issue 1
260-261
EN
Introduction of ferroelectric or magnetic nanoparticles into nematic liquid crystal is a promising method for the improvement of the electro-optic or magneto-optic properties of different nematic liquid crystals by non-chemical way. This work is devoted to the study of composite systems of liquid crystal with spherical ferroelectric or magnetic particles with the aim to study their sensitivity to electric and magnetic fields. The nematic 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) liquid crystal was doped with SbSI ferroelectric particles or with Fe_{3}O_{4} magnetic particles. The structural transitions in ferronematic samples were indicated by capacitance measurements in a capacitor made of ITO-coated glass electrodes in combined electric and magnetic fields. The obtained results showed the increase of the shift in critical voltage with increasing magnetic field in both kinds of samples.
17
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Thermal Stability of Bent-Core Liquid Crystals Doped with Magnetic Nanoparticles

59%
Juríková A., Csach K., Miškuf J., Tomašovičová N., Mitróová Z., Závišová V., Koneracká M., Kopčanský P., Timko M., Éber N., Fodor-Csorba K., Vajda A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
638-640
EN
In the work phase transitions in bent-core liquid crystals were studied using differential scanning calorimetry. For the binary mixture of bent-core molecules with 50 wt% of rod-shaped compound, the nematic to smectic transition occured below 40°C and the crystallization temperature shifted to sub-ambient temperatures. The influence of doping of the bent-core liquid crystals with magnetic nanoparticles on the kinetics of observed phase transitions was studied. The phase transition temperatures were shifted depending on the nanoparticle type and changed with varying cooling rate for all studied liquid crystal samples.
18
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Magnetic Properties of Biocompatible Magnetic Fluid after Electron Irradiation

59%
Tomašovičová N., Haysak I., Koneracká M., Kováč J., Timko M., Závišová V., Okunev A., Parlag A., Fradkin A., Sakhno V., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1302-1304
EN
The magnetic particles in the water-based magnetic fluids were sterically stabilized by natrium oleate to prevent their agglomeration and consequently the adsorption of poly-ethylene-glycol (PEG) was carried out to improve the biocompatibility of the magnetic particles. Two sets of samples were prepared. The first set of the samples was with different molar weight of PEG (Mw = 400, 1000, 10000 and 20000) at the constant weight ratio of PEG/Fe_3O_4 = 0.25 and the second one was with different weight ratio of PEG/Fe_3O_4 and constant molar weight of PEG (Mw = 1000). The samples were irradiated with 20 Gy. The same reduction of saturated magnetization (about 10%) after electron irradiation with 20 Gy was observed for all prepared samples.
19
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Structural Phase Transition in Liquid Crystal Doped with Gold Nanoparticles

59%
Kopčanský P., Tomašovičová N., Koneracká M., Timko M., Mitróová Z., Závišová V., Éber N., Fodor-Csorba K., Tóth-Katona T., Vajda A., Jadzyn J., Beaugnon E., Chaud X.
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issue 5
988-989
EN
The influence of the inclusion of the dodecanethiol functionalized gold particles (with diameter 3-5 nm) on the structural transitions was investigated. The studied samples were based on the nematic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). The volume concentration of the gold particles was ϕ_1 = 2 × 10^{-4} and ϕ_2 = 10^{-3}. The obtained results showed that the inclusion of the gold particles in the 6CHBT liquid crystal increases the sensitivity of such system on the external magnetic field.
20
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Characterization of Fe_3O_4 Magnetic Nanoparticles Modified with Dextran and Investigation of Their Interaction with Protein Amyloid Aggregates

59%
Koneracká M., Antošová A., Závišová V., Lancz G., Gažová Z., Šipošová K., Juríková A., Csach K., Kováč J., Tomašovičová N., Fabián M., Kopčanský P.
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issue 5
983-985
EN
Functionalised magnetic nanoparticles composed of Fe_3O_4 particles stabilised by sodium oleate and subsequently modified with dextran (MFDEX) were prepared by the co-precipitation method. Their morphology and particle size distribution were observed by scanning electron microscopy and photon cross correlation spectroscopy. In order to confirm the modification of magnetite surface with dextran physical techniques, including infrared spectroscopy, thermal analysis, and magnetic measurement, were used. Finally, the effect of MFDEX on amyloid fibrillar aggregates of human insulin and hen egg white lysozyme, typical amyloidogenic proteins, was investigated. In vitro interaction of MFDEX with protein amyloid fibrils resulted into destruction of amyloid aggregates. The anti-amyloid activity makes MFDEX of potential interest as therapeutic agent against amyloid-related diseases.
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