219 research outputs found
Size and polydispersity effect on the magnetization of densely packed magnetic nanoparticles
The magnetic properties of densely packed magnetic nanoparticles (MNP)
assemblies are investigated from Monte Carlo simulations. The case of iron
oxide nanoparticles is considered as a typical example of MNP. The main focus
is put on particle size and size polydispersity influences on the magnetization
curve. The particles are modeled as uniformly magnetized spheres isolated one
from each other by a non magnetic layer representing the organic coating. A
comparison with recent experimental results on FeO powder
samples differing by their size is given.Comment: To be published in the Journal of Applied Physics, to be found at
http://jap.aip.org
Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(Acrylic Acid) : Towards Stable Dispersions
We exploit a precipitation-redispersion mechanism for complexation of short
chain polyelectrolytes with cerium oxide nanoparticles to extend their
stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of
monodisperse cationic nanocrystalline particles having a hydrodynamic diameter
of 10 nm and a molecular weight 400000 gmol-1. We show that short chain
uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads
to macroscopic precipitation. As the pH is increased, the solution
spontaneously redisperses into a clear solution of single particles with an
anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide
nanosols and their hybrid polymer-inorganic complexes in solution are
investigated by static and dynamic light scattering, X-ray scattering, and by
chemical analysis. Quantitative analysis of the redispersed sol gives rise to
an estimate of 40 - 50 polymer chains per particle for stable suspension. This
amount represents 20 % of the mass of the polymer-nanoparticle complexes. This
complexation adds utility to the otherwise unstable cerium oxide dispersions by
extending the range of stability of the sols in terms of pH, ionic strength and
concentration.Comment: 6 Figures, 23 pages, submitte
Synthesis and activation of an iron oxide immobilized drug-mimicking reporter under conventional and pulsed X-ray irradiation conditions
Magnetization of densely packed interacting magnetic nanoparticles with cubic and uniaxial anisotropies: A Monte Carlo study
International audienceThe magnetization curves of densely packed single domain magnetic nanoparticles (MNP) are investigated by Monte Carlo simulations in the framework of an effective one spin model. The particles whose size polydispersity is taken into account are arranged in spherical clusters and both dipole dipole interactions (DDI) and magnetic anisotropy energy (MAE) are included in the total energy. Having in mind the special case of spinel ferrites of intrinsic cubic symmetry, combined cubic and uniaxial magnetocrystalline anisotropies are considered with different configurations for the orientations of the cubic and uniaxial axes. It is found that the DDI, together with a marked reduction of the linear susceptibility are responsible for a damping of the peculiarities due to the MAE cubic component on the magnetization. As an application, we show that the simulated magnetization curves compare well to experimental results for --FeO MNP for small to moderate values of the field
Superparamagnetic Bifunctional Bisphosphonates Nanoparticles: A Potential MRI Contrast Agent for Osteoporosis Therapy and Diagnostic
A bone targeting nanosystem is reported here which combined magnetic contrast agent for Magnetic Resonance Imaging (MRI) and a therapeutic agent (bisphosphonates) into one drug delivery system. This new targeting nanoplatform consists of superparamagnetic γFe2O3 nanoparticles conjugated to 1,5-dihydroxy-1,5,5-tris-phosphono-pentyl-phosphonic acid (di-HMBPs) molecules with a bisphosphonate function at the outer of the nanoparticle surface for bone targeting. The as-synthesized nanoparticles were evaluated as a specific MRI contrast agent by adsorption study onto hydroxyapatite and MRI measurment. The strong adsorption of the bisphosphonates nanoparticles to hydroxyapatite and their use as MRI T2∗ contrast agent were demonstrated. Cellular tests performed on human osteosarcoma cells (MG63) show that γFe2O3@di-HMBP hybrid nanomaterial has no citoxity effect in cell viability and may act as a diagnostic and therapeutic system
Self-organization on surfaces: foreword
After decades of work, the growth of continuous thin films, i.e.,
two-dimensional structures, is progressively becoming a technological issue
more than a field of fundamental research. Incidentally self-organization of
nanostructures on surfaces is now an important field of research, i.e.,
structures of dimensionality one or zero, with a steep rise of attention in the
past five years. Whereas self-organization was initially motivated by potential
applications, it has up to now essentially contributed to the advancement of
fundamental science in low dimensions, as model systems could be produced that
could not have been fabricated by lithography. This Special Issue aims at
giving a cross-community timely overview of the field. The Issue gathers a
broad panel of articles covering various self-organization mechanisms, specific
structural characterization, physical properties, and current trends in
extending the versatility of growth. The materials mostly covered here are
semiconductors and magnetic materials.Comment: Foreword of the Editor to Special Issue on Self-organization on
surface
Design and evaluation of multi-core raspberry-like platinum nanoparticles for enhanced photothermal treatment
New dextrin nanomagnetogels: production, characterization and in vivo performance as dual modality imaging bioprobe
Dual modality contrast agents, such as radiolabelle
d magnetic nanoparticles, are promising
candidates for a number of diagnostic applications,
since they combine two complementing
imaging modalities, namely photon emission computed
tomography (SPECT) and magnetic
resonance imaging (MRI). The benefit of such combin
ation lies on the ability to interpret more
accurately abnormalities
in vivo
, by integrating the high sensitivity of SPECT with
the superb
spatial resolution and anatomical information provi
ded by MRI [1]. Superparamagnetic iron
oxide nanoparticles (SPION) have been extensively s
tudied as MRI contrast agents [2]. SPIONs
need to be coated in order to allow formulation in
aqueous solutions and to increase
in vivo
stability [3].
Dextrin nanomagnetogels consists on superparamagnet
ic iron oxide nanoparticles (
γ
-Fe
2
O
3
)
stabilized within hydrophobized-dextrin nanogel (sc
heme 1). The nanomagnetogel formulation,
with about 4 mM of iron and a diameter of 100 nm, p
resents relevant features such as
superparamagnetic behaviour, high stability, narrow
size distribution and potential for magnetic
guidance to target areas by means of an external ma
gnetic field [4]. The functionalization of the
dextrin nanomagnetogel with a DOTA-monoamide
ω
-thiol metal chelator and radiolabelling with
111
In were used to ascertain its
in vivo
stability and behavior (blood clearance rate and o
rgan
distribution) after intravenous administration in m
ice model. The surface modification of the
nanomagnetogel with PEG 5,000 was accomplished in a
n attempt to escape the phagocytic
system. The unloaded radiolabeled dextrin nanogel (
around 30 nm) showed lower uptake in the
liver, spleen and kidneys than the nanomagnetogel l
oaded with SPIONs (around 110 nm). This
difference in biodistribution profile can be ascrib
ed to the differences in the particle size.
Nanomagnetogel pegylation resulted in lower liver a
nd spleen accumulation. The blood half-life
obtained was approximately 4 hours for all formulat
ions. A good correlation between the amount
of polymer (quantified through radioactivity) and t
he amount of iron (ICP measurement) in the
spleen was observed, indicating that leakage of iro
n from the nanomagnetogels after
intravenous administration was negligible. The pilo
t imaging study demonstrated good
performance of dextrin nanomagnetogels as dual moda
lity imaging (MRI and SPECT)
bioprobes as expected by the high transverse relaxi
vity (215-248 mM
-1
s
-1
) obtained
in vitro
,
higher than those of commercial available formulati
ons (160-177 mM
-1
s
-1
). The production of the
nanomagnetogel is simple and easy to scale up, thus
offering great technological potential
Dextrin-based nanomagnetogel: in vivo biodistribution and stability
The biodistribution profile of a new dextrin nanomagnetogel, which consists on -Fe2O3 superparamagnetic nanoparticles loaded within a polymeric matrix of modified dextrin, was studied in mice. The nanomagnetogel bear a monomodal size distribution profile (average diameter 110 nm) close to neutral surface charge and higher relaxivity (r2 = 215-248 mM-1s-1 and r2/r1 = 13-11) than those of commercial formulations (r2 = 160-177 mM-1s-1 and r2/r1 = 4-7). Also the observed blood half-life - approximately 4 hours - is superior to that of similar commercially available formulations, which remain few minutes in circulation. Pegylation resulted in 1.7 and 1.2-fold lower accumulation in the liver and spleen, respectively, within the first 24 h. Noteworthy, a good correlation was obtained between the amount of polymer (quantified by scintigraphy) in the spleen, 48 h after administration, and the amount of iron physically loaded through hydrophobic interactions (quantified by ICP) indicating the absence of iron leakage from the polymeric matrix. This study provides evidence on the in vivo stability of a self-assembled nanomagnetogel, a much relevant feature which is seldom reported in the literature.The authors thank the Project “strong>BioHealth - Biotechnology and Bioengineering approaches to improve health quality”, Ref. NORTE-07-0124-FEDER-000027, co-funded by the Programa Operacional Regional do Norte (ON.2 O Novo Norte), QREN, FEDER. The authors thank the Magnisense Corporation for providing a MIAplex Reader and CFGCG the EU COST TD1004 Action “Theragnostics Imaging and Therapy”. The authors thank Professor Cidália Botelho for the iron analysis by Atomic Absorbance Spectroscopy at the Oporto University, Chemical Engineering Department. C. Gonçalves, J. P. Silva, J. A. Martins, and M. F. M. Ferreira acknowledge FCT Portugal, for postdoc grants SFRH/BPD/70524/2010 and SFRH/BPD/64958/2009, sabbatical grant SFRH/BSAB/ 1328/2013 and PhD grant SFRH/BD/63994/2009, respectively
Synthesis of 64CuII–Bis(dithiocarbamatebisphosphonate) and Its Conjugation with Superparamagnetic Iron Oxide Nanoparticles: In Vivo Evaluation as Dual-Modality PET–MRI Agent**
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