Nataliya Nedelko

Local atomic structure and magnetic ordering of iron in Fe-chitosan complexes.

The iron crosslinked chitosan (Ch-Fe-CL) and N-carboxylmethyl chitosan (N-CM-Ch-Fe) complexes were studied by complementary techniques: structurally sensitive Mössbauer and X-ray absorption methods, as well as static magnetic measurements. A detailed and consistent description of these complexes including, besides the overall magnetic behavior, the spin ordering and local atomic structure around Fe ions is presented. Fe atoms in the investigated samples are mostly penta-coordinated and appear in a high spin Fe (3+) ionic state. In Ch-Fe-CL, two kinds of Fe near neighbors are equally probable and several Fe atoms are situated in the second coordination sphere. The magnetic interactions between these Fe ions lead to a sperimagnetic-like ordering. In N-CM-Ch-Fe, only one Fe neighborhood was found. Other Fe atoms were identified neither in the first nor in the second coordination sphere, but the third coordination sphere indicates the presence of Fe atoms. The magnetic coupling between these atoms is antiferromagnetic, but the dominant part of Fe in this sample remains in a paramagnetic state.

Adsorption of As(III) on chitosan-Fe-crosslinked complex (Ch-Fe)

It was reported the adsorption of As(III) on the surface of the chitosan-Fe-crosslinked complex. Theoretical correlation of the experimental equilibrium adsorption data for As(III)/Ch-Fe system is best explained by the non-linearized form Langmuir-Freundlich isotherm model. At optimum conditions, pH 9.0, the maximum adsorption capacity, calculated using the Langmuir-Freundlich isotherm model was 13.4 mg g⁻¹. The adsorption kinetics of As(III) onto Ch-Fe are described by the pseudo-first-order kinetic equation. The results of the Mössbauer spectroscopy showed that there is no redox process on the surface of the adsorbent.

Synthesis, characterization and in vitro drug release of magnetic N-benzyl-O-carboxymethylchitosan nanoparticles loaded with indomethacin

Magnetic N-benzyl-O-carboxymethylchitosan nanoparticles were synthesized through incorporation and in situ methods and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and magnetization measurements. Indomethacin was incorporated into the nanoparticles via the solvent evaporation method. The indomethacin-loaded magnetic nanoparticles were characterized by the same techniques, and also by transmission electron microscopy. The nanoparticles containing the polymer showed a drug loading efficiency of between 60.8% and 74.8%, and the magnetic properties were not significantly affected by incorporation of the drug. The in vitro drug release study was carried out in simulated body fluid, pH 7.4 at 37°C. The profiles showed an initial fast release, which became slower as time progressed. The percentage of drug released after 5 h was between 60% and 90%, and the best fitting mathematical model for drug release was the Korsmeyer-Peppas model, indicating a Fickian diffusion mechanism.

Structural and magnetic characterization of functional surface coated maghemite nanoparticles

Nanoparticles composed of magnetic γ-Fe2O3 core and organic shell were synthesized via template synthesis in the presence of functional oligoperoxide surfactants and further graft-polymerization initiated from their surface. X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements (PPMS) were used to characterize the obtained magnetic system of core-shell nanoparticles. XRD results confirm the existence of γ-Fe2O3 phase as well as show an average diameter of nanoparticles around 10 nm. The obtained particles are superparamagnetic at the room temperature. Magnetic measurements indicate also sufficiently strong dipolar interparticle interactions at low temperatures.