3 research outputs found
A Single Picture Explains Diversity of Hyperthermia Response of Magnetic Nanoparticles
Progress in the design of nanoscale
magnets for localized hyperthermia
cancer therapy has been largely driven by trial-and-error approaches,
for instance, by changing of the stoichiometry composition, size,
and shape of the magnetic entities. So far, widely different and often
conflicting heat dissipation results have been reported, particularly
as a function of the nanoparticle concentration. Thus, achieving hyperthermia-efficient
magnetic ferrofluids remains an outstanding challenge. Here we demonstrate
that diverging heat-dissipation patterns found in the literature can
be actually described by a single picture accounting for both the
intrinsic magnetic features of the particles (anisotropy, magnetization)
and experimental conditions (concentration, magnetic field). Importantly,
this general magnetic-hyperthermia scenario also predicts a novel
non-monotonic concentration dependence with optimum heating features,
which we experimentally confirmed in iron oxide nanoparticle ferrofluids
by fine-tuning the particle size. Overall, our approach implies a <i>magnetic hyperthermia trilemma</i> that may constitute a simple
strategy for development of magnetic nanomaterials for optimal hyperthermia
efficiency
Modulation of Magnetic Heating via Dipolar Magnetic Interactions in Monodisperse and Crystalline Iron Oxide Nanoparticles
In the pursuit of controlling the
heat exposure mediated by magnetic nanoparticles, we provide new guidelines
for tailoring magnetic relaxation processes via dipolar interactions.
For this purpose, highly crystalline and monodisperse magnetic iron
oxide nanocrystals whose sizes range from 7 to 22 nm were synthesized
by thermal decomposition of iron organic precursors in 1-octadecene.
The as-synthesized nanoparticles are soft nanomagnets, showing superparamagnetic-like
behavior and SAR values which progressively increase with particle
size, field frequency, and amplitude up to 3.6 kW/g<sub>Fe</sub>.
Our data show the influence of media viscosity, particle size, and
concentration on dipolar interactions and consequently on the magnetic
relaxation processes related to the heat release. Understanding the
role of dipolar interactions is of great importance toward the use
of iron oxide nanoparticles as efficient hyperthermia mediators
High-Performance Implantable Sensors based on Anisotropic Magnetoresistive La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> for Biomedical Applications
We present the design, fabrication, and characterization
of an
implantable neural interface based on anisotropic magnetoresistive
(AMR) magnetic-field sensors that combine reduced size and high performance
at body temperature. The sensors are based on La0.67Sr0.33MnO3 (LSMO) as a ferromagnetic material, whose
epitaxial growth has been suitably engineered to get uniaxial anisotropy
and large AMR output together with low noise even at low frequencies.
The performance of LSMO sensors of different film thickness and at
different temperatures close to 37 °C has to be explored to find
an optimum sensitivity of ∼400%/T (with typical detectivity
values of 2 nT·Hz–1/2 at a frequency of 1 Hz
and 0.3 nT·Hz–1/2 at 1 kHz), fitted for the
detection of low magnetic signals coming from neural activity. Biocompatibility
tests of devices consisting of submillimeter-size LSMO sensors coated
by a thin poly(dimethyl siloxane) polymeric layer, both in
vitro and in vivo, support their high suitability
as implantable detectors of low-frequency biological magnetic signals
emerging from heterogeneous electrically active tissues