Magnetic Nanoparticles for Application in Nanomedicine

This contribution will summarize the information about the ways of synthesizing biocompatible magnetic nanoparticles and complexes containing them and the possibility of their application in nanomedicine at magnetic drug targeting and thermal treatment of diseases by hyperthermia effect. Some procedures of the preparation of biocompatible magnetizable complexes as magnetic nanoparticles, magnetic fluids, some proteins and enzymes covalently bound to the freshly prepared magnetic nanoparticles in the presence of carbodiimide (bovine serum albumin, streptokinase, chymotrypsin, dispase, glucose oxidase), entrapment of magnetic particles into magnetoliposomes and encapsulation of clinically important drug as indomethacin and taxol together with magnetite nanoparticles in biodegradable polymer. We will summarize the results from the study of structural, magnetic and hyperthermic properties of bacterial magnetite nanoparticles i.e. magnetosomes prepared by biomineralization process of magnetotactic bacteria as a promising material for application in nanomedicine

Nonadditive changes in conductivity of micro PDLC under the influence of carbon nanotubes and magnetic nanoparticles

Investigated in this work has been the effect of impurities – magnetic nanoparticles (MN) and multiwall carbon nanotubes (MWNT) – separately and together on morphology and dielectric properties of nematic liquid crystal 6CHBT dispersed in polyvinyl alcohol (PDLC). It has been shown that the nanoparticles and nanotubes together change the morphology of PDLC practically in the same manner as every type of impurity singly. The impurities influence also additively on the permittivity at low frequencies and electron component of the conductivity in the polymer matrix. We have found that when MN and MWNT act jointly their ion component of the conductivity exceeds the total changes in conductivity by six times greater than when each type of impurity acts singly. The most probable reason for this nonadditive change in conductivity can be aggregation of these nanoparticles

Effect of magnetic nanoparticles with various geometrical shapes on morphology and dielectric properties of nanodispersions of nematic liquid crystal in polymer matrix

Prepared in this work are dispersions of nematic liquid crystal in polyvinyl alcohol with sizes of liquid phase inclusions less than one micrometer (nano-polymer dispersed liquid crystal (PDLC)) by changing technology of mixing the components. It was shown that, like to the case of earlier examined dispersions with the droplet sizes 6 to 10 μm (micro-PDLC), the conductivity of nano-PDLC has two components: the ion one, which value does not depend on frequency, and the electron one, the value of which depends on frequency according to a power law. It was found that the ion conductivity of nano-PDLC is three orders of magnitude higher than that for micro-PDLC, and the exponent for the electron components of nano-PDLC conductivity is less than that for micro-PDLC. It was shown that the spherical and rod-like magnetic nanoparticles (MNs) influence in a different manner on the conductivity components of nano-PDLC. If for the maximum concentration of spherical MNs 2 * 10⁻³ wt.% the ion conductivity is 2-fold increased, then at the same concentration of rod-like MNs the ion conductivity value increases by more than one order of magnitud

Study of Magnetic Fredericksz Transition in Ferronematics. Liquid Crystals Doped with Fine Magnetic Particles

The magnetic Fredericksz transition in ferronematics (thermotropic nematic liquid crystals 7CB and MBBA combined with fine magnetic particles of size 10 nm) as a function of concentration of magnetic particles was studied by using simple dielectric tneasurements. 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 disscussed in framework of Brochard, de Gennes and Burylov, Raikher theories

Structural transitions in thermotropic ferronematics

271-275The structural instabilities in ferronematics based on different types of liquid crystals, exposed to electric or magnetic fields oriented perpendicular (Fredericksz transition) and parallel to the initial director, were studied within the Burylov and Raikher’s theory. Using the capacitance measurements the critical electric (magnetic) fields EFN (BFN), corresponding to the Fredericksz transition, and fields Emax, (Bmax,), at which the initial perpendicularity between director n→  and magnetic moment m→  breaks-down in field parallel to the initial director, were found. These values were then used for the estimation of the surface density of the anchoring energy W of liquid crystal molecules on the magnetic particle surface