Bratislav Antić

Preparation and in vivo evaluation of multifunctional 90 Y-labeled magnetic nanoparticles designed for cancer therapy

Two different types of magnetic nanoparticles (MNPs) were synthesized in order to compare their efficiency as radioactive vectors, Fe₃O₄-Naked (80 ± 5 nm) and polyethylene glycol 600 diacid functionalized Fe₃O₄(Fe₃O₄-PEG600) MNPs (46 ± 0.6 nm). They were characterized based on the external morphology, size distribution, and colloidal and magnetic properties. The obtained specific power absorption value for Fe₃O₄-PEG600 MNPs was 200 W/g, indicated their potential in hyperthermia based cancer treatments. The labeling yield, in vitro stability and in vivo biodistribution profile of (90) Y-MNPs were compared. Both types of MNPs were (90)Y-labeled in reproducible high yield (>97%). The stability of the obtained radioactive nanoparticles was evaluated in saline and human serum media in order to optimize the formulations for in vivo use. The biodistribution in Wistar rats showed different pharmacokinetic behaviors of nanoparticles: a large fraction of both injected MNPs ended in the liver (14.58%ID/g for (90)Y-Fe₃O₄-Naked MNPs and 19.61%ID/g for (90)Y-Fe₃O₄-PEG600 MNPs) whereas minor fractions attained in other organs. The main difference between the two types of MNPs was the higher accumulation of (90)Y-Fe₃O₄-Naked MNPs in the lungs (12.14%ID/g vs. 2.00%ID/g for (90)Y-Fe₃O₄-PEG600 MNPs) due to their in vivo agglomeration. The studied radiolabeled magnetic complexes such as (90)Y-Fe₃O₄-PEG600 MNPs constitute a great promise for multiple diagnostic-therapeutic uses combining, for example, MRI-magnetic hyperthermia and regional radiotherapy.

Metal contamination of short-term snow cover near urban crossroads: Correlation analysis of metal content and fine particles distribution

Snow samples were collected near crossroads in Novi Sad, Serbia, during December 2009 to assess metal concentrations (Ca, K, Zn, Fe, Cu, Mn, Al, Pb and Na), fine particle distribution and pH value. The filtered samples of melted snow were analysed, with a focus on particles smaller than a few μm. The most common values of the frequency number distribution curve were either in the range of 0.05-0.07 μm or one order of magnitude higher (0.2-0.5 μm). At examined locations metal concentrations varied from 0.0004 mg L(-1) for Pb to 18.9 mg L(-1) for Na. Besides Na, which mostly originated from de-icing salt, Ca is found to be the most abundant element in snow indicating the dominant influence of natural factors on snow chemistry. No significant difference was found in concentration of the elements at locations near crossroads with either low or high traffic volume, except for Na and Zn. To investigate how metals were related a correlation analysis was done for the concentrations of metals and with respect to the particle size distribution parameters and pH values. The major influence on the fine particle volume (mass) was concluded to be due to the elements from anthropogenic sources. This conclusion was based on the significant positive correlation between Fe, Zn and Al and the fine particle volume based distribution parameters.

Temperature-induced structure and microstructure evolution of nanostructured Ni0.9Zn0.1O

The crystal structure and microstructure of as-prepared and annealed Ni0.9Zn0.1O were refined at room temperature in both the Fm{\overline 3}m and R{\overline 3}m space groups. It is shown that below the Neel point (458 K), where magnetic ordering triggers the presence of a trigonal strain, the common usage of a higher-symmetry non-admissible space group for crystal structure and microstructure analysis via the Rietveld method may result in both an incorrect structure description and incorrect microstructure parameters (size and strain). More realistic microstructure data can be obtained by whole powder pattern modelling of the powder diffraction data. Increasing the annealing temperature causes a reduction of the trigonal distortion as well as an increase in domain size. Simultaneously, the Raman spectra become less resolved, a clear indication of domain growth and structural evolution of the structure towards cubic symmetry (R{\overline 3}m → Fm{\overline 3}m).

X-ray powder diffraction line broadening analysis and magnetism of interacting ferrite nanoparticles obtained from acetylacetonato complexes

A study of the microstructures and magnetic properties of nanosize Zn ferrite (ZnFe2O4), Mn ferrite (MnFe2O4), and the cation deficit Zn–Mn ferrites Zn0.70Mn0.23Fe1.89O4 (S1), Zn0.41Mn0.50Fe1.84O4 (S2) and Zn0.18Mn0.67Fe1.85O4 (S3) was performed. The crystallite size for all samples was determined by x-ray powder diffraction (XRPD) analysis using four different methods, and was close to the particle size found from transmission electron microphotography. Among different methods of XRPD line broadening analysis it seems that the cubic harmonic function method is more precise and reliable than the Warren–Averbach and simplified integral breadth methods. M(T) and M(H) magnetization curves at different fields/temperatures indicate superparamagnetic behaviour of the samples. Asymmetric hysteresis loops and differences in coercive fields, HC−(FC) − HC−(ZFC), are discussed by both the core/shell model of nanoparticles and spin canting. The magnetic measurements with a maximum in the FC magnetization branches, the difference in M/MS versus H/T curves above Tmax (temperature of maximum in ZFC magnetization), the nonlinearity in HC versus T1/2, the remanence/saturation ratio value, MR/MS and observation of the Almeida–Thouless line for low-field magnetization data (Tmax versus H2/3) indicate that the samples consist of an interacting ferrite nanoparticle ensemble.

Spin glass formation in Li-substituted Co2TiO4 spinel

DC magnetization and AC susceptibility measurements point to the formation of as pin glassstate in the ternary spinel-type compounds Li1.33x Co2−2x Ti1+0.67x O4. The dynamics of spin freezing was analysed with both the critical slowing down and the thermally activated dynamics models. The parameter values obtained, as well as the behaviour of the zero-field-cooled and field-cooled magnetization as a function of temperature, indicate the existence of a cluster glass state in disordered spinel samples with x = 0.25 and 0.40, and probably also in the ordered spinel with x = 0.50. Ordered spinel samples with x = 0.75 and 0.875 were found to be paramagnetic down to th et emperature of 1.7 K with a random distribution of Co 2+ ions.

Development and evaluation of 90Y-labeled albumin microspheres loaded with magnetite nanoparticles for possible applications in cancer therapy

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

Magnetic Properties of Lithium Ferrite Nanoparticles with a Core/Shell Structure

We present a magnetic study of lithium ferrite nanoparticles of composition Li0.5Fe2.5O4, synthesized by a citrate gel decomposition method. The as prepared sample was composed of nearly spherical nanoparticles with an average particle size TEM~12 nm. Further annealing at 573 K and 673 K for 4 hours did not increase particle size noticeably, while annealing at 973 K led to morphology changes and significant increase in size ranging from 40 to above 200 nm. The magnetic properties of samples have been studied using Mössbauer specroscopy, and static magnetic measurements. The hyperfine parameters obtained from Mössbauer data at T = 10 K are in agreement to the bulk lithium ferrite phase. Annealed samples showed an evolution from monodomain structure to polycrystalline behaviour, what is evident from TEM imagines, as well as the evolution of the coercive filed, HC, and the saturation magnetization, MS, with particle size increase. The exchange interactions have been observed in the single domain nanoparticles, which probably originate from their core shell structure. At low temperatures and in high enough magnetic fields, the cubic magnetic anisotropy stays preserved and the magnetic moments in the particle core are aligned along 111 directions of the spinel structure.

Novel multifunctional 90Y-labelled albumin magnetic microspheres for cancer therapy

We present in vitro and in vivo studies of yttrium-90 (Y)-labelled human serum albumin magnetic microspheres (HSAMMS) as multifunctional agent for bimodal radionuclidehyperthermia cancer therapy. The HSAMMS were produced using a modified emulsificationheat stabilization technique and contained 10-nm magnetite nanoparticles coated with citric acid, distributed as inhomogeneous clusters within the albumin microspheres. The average particle size of the complete HSAMMS was 20 μm, and they exhibited superparamagnetic behavior at

Neutron diffraction study of the magnetic and structure properties of Co2.50Sb0.50O4 spinel

Neutron diffraction study of the magnetic and structure properties of Co2.50Sb0.50O4 spinel.

Gallium-68 Labeled Iron Oxide Nanoparticles Coated with 2,3-Dicarboxypropane-1,1-diphosphonic Acid as a Potential PET/MR Imaging Agent: A Proof-of-Concept Study

The aim of this study was to develop a dual-modality PET/MR imaging probe by radiolabeling iron oxide magnetic nanoparticles (IONPs), surface functionalized with water soluble stabilizer 2,3-dicarboxypropane-1,1-diphosphonic acid (DPD), with the positron emitter Gallium-68. Magnetite nanoparticles (Fe3O4 MNPs) were synthesized via coprecipitation method and were stabilized with DPD. The Fe3O4-DPD MNPs were characterized based on their structure, morphology, size, surface charge, and magnetic properties. In vitro cytotoxicity studies showed reduced toxicity in normal cells, compared to cancer cells. Fe3O4-DPD MNPs were successfully labeled with Gallium-68 at high radiochemical purity (>91%) and their stability in human serum and in PBS was demonstrated, along with their further characterization on size and magnetic properties. The ex vivo biodistribution studies in normal Swiss mice showed high uptake in the liver followed by spleen. The acquired PET images were in accordance with the ex vivo biodistribution results. Our findings indicate that 68Ga-Fe3O4-DPD MNPs could serve as an important diagnostic tool for biomedical imaging.