Presentación

En las últimas décadas, la investigación en la Universidad de Santiago de Chile ha recibido un fuerte impulso, liderando diversas áreas de investigación en el país. Un aporte a la difusión de nuestras actividades en investigación lo constituye la revista CONTRIBUCIONES, pues a través de ella difundimos a la comunidad de la Universidad de Santiago de Chile y a comunidades académicas externas, algunos de nuestros estudios, en un formato ameno que permite su lectura también a no especialistas

Superparamagnetic Poly (3-hydroxybutyrate-co-3 hydroxyvalerate) (PHBV) nanoparticles for biomedical applications

Indexación: ScieloBackground: The progress in material science and the recent advances in biodegradable/biocompatible polymers and magnetic iron oxide nanoparticles have led to develop innovative diagnostic and therapeutic strategies for diseases based on multifunctional nanoparticles, which include contrast medium for magnetic resonance imaging, agent for hyperthermia and nanocarriers for targeted drug delivery. The aim of this work is to synthesize and characterize superparamagnetic iron oxide (magnetite), and to encapsulate them into poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles for biomedical applications. Results: The magnetite nanoparticles were confirmed by X-ray diffraction and exhibited a size of 22.3 ± 8.8 nm measured by transmission electron microscopy (TEM). Polymeric PHBV nanoparticles loaded with magnetite (MgNPs) were analyzed using dynamic light scattering and showed a size of 258.6 ± 35.7 nm and a negative zeta potential (-10.8 ± 3.5 mV). The TEM examination of MgNPs exhibited a spherical core-shell structure and the magnetic measurements showed in both, non-encapsulated magnetite and MgNPs, a superparamagnetic performance. Finally, the in vitro studies about the magnetic retention of MgNPs in a segment of small intestine of rats showed an active accumulation in the region of the magnetic field. Conclusions: The results obtained make the MgNPs suitable as potential magnetic resonance imaging contrast agents, also promoting hyperthermia and even as potential nanocarriers for site-specific transport and delivery of drugs. Keywords: hyperthermia, magnetic resonance image (MRI), magnetite, PHBV, polymeric nanoparticles.http://ref.scielo.org/cxt57

Superparamagnetic Poly (3-hydroxybutyrate-co-3 hydroxyvalerate) (PHBV) nanoparticles for biomedical applications

Background: The progress in material science and the recent advances in biodegradable/biocompatible polymers and magnetic iron oxide nanoparticles have led to develop innovative diagnostic and therapeutic strategies for diseases based on multifunctional nanoparticles, which include contrast medium for magnetic resonance imaging, agent for hyperthermia and nanocarriers for targeted drug delivery. The aim of this work is to synthesize and characterize superparamagnetic iron oxide (magnetite), and to encapsulate them into poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles for biomedical applications. Results: The magnetite nanoparticles were confirmed by X-ray diffraction and exhibited a size of 22.3 \ub1 8.8 nm measured by transmission electron microscopy (TEM). Polymeric PHBV nanoparticles loaded with magnetite (MgNPs) were analyzed using dynamic light scattering and showed a size of 258.6 \ub1 35.7 nm and a negative zeta potential (-10.8 \ub1 3.5 mV). The TEM examination of MgNPs exhibited a spherical core-shell structure and the magnetic measurements showed in both, non-encapsulated magnetite and MgNPs, a superparamagnetic performance. Finally, the in vitro studies about the magnetic retention of MgNPs in a segment of small intestine of rats showed an active accumulation in the region of the magnetic field. Conclusions: The results obtained make the MgNPs suitable as potential magnetic resonance imaging contrast agents, also promoting hyperthermia and even as potential nanocarriers for site-specific transport and delivery of drugs

Tuning domain wall dynamics by shaping nanowires cross-sections.

The understanding of the domain wall (DW) dynamics along magnetic nanowires is crucial for spintronic applications. In this work, we perform a detailed analysis of the transverse DW motion along nanowires with polygonal cross-sections. If the DW displaces under a magnetic field above the Walker limit, the oscillatory motion of the DW is observed. The amplitude, the frequency of oscillations, and the DW velocity depend on the number of sides of the nanowire cross-section, being the DW velocity in a wire with a triangular cross-section one order of magnitude larger than that in a circular nanowire. The decrease in the nanowire cross-section area yields a DW behavior similar to the one presented in a cylindrical nanowire, which is explained using an analytical model based on the general kinetic momentum theorem. Micromagnetic simulations reveal that the oscillatory behavior of the DW comes from energy changes due to deformations of the DW shape during the rotation around the nanowire

Meio de armazenamento magnético de alta densidade

DepositadaMeio de armazenamento magnético de alta densidade constituído por partículas ferromagnéticas de baixa simetria, nos quais as partículas são formadas por segmentos ou barras, ou por sistemas de barras e combinações destas, que foram estruturas com diferentes geometrias

Measurement of the vortex core in sub-100 nm Fe dots using polarized neutron scattering

We use polarized neutron scattering to obtain quantitative information about the magnetic state of sub-100 nm circular magnetic dots. Evidence for the transition from a single domain to a vortex state, as a function of the dot diameter and magnetic field, is found from magnetization curves and confirmed by micromagnetic and Monte-Carlo simulations. For 20 nm-thick Fe dots with diameters close to 60 nm, the vortex is the ground state. The magnetization of the vortex core (140 ± 50 emu/cm3) and its diameter (19 ± 4 nm) obtained from polarized neutron scattering are in agreement with simulations

Box model for hysteresis loops of arrays of Ni nanowires

In the present work, by means of a phenomenological model, we simulate the hysteresis loop of an hexagonal array of Ni nanowires. Our model is based on the assumption that the hysteresis loop of a single wire is a rectangular box with a particular value of the coercive field, and the effect of the array is to generate a distribution of the coercive fields. Our results are in good agreement with experimental data.This work was supported by CONICYT Program Fellowship, FONDECYT-CHILE grant number 1040354, Millennium project P02-054-F.Peer reviewe