Micro y nano encapsulación para la liberación controlada de compuestos en la producción pecuaria: Caso selenio

La nanociencia y la nanotecnología son áreas del conocimiento que estudian de manera interdisciplinaria la preparación y manipulación de materiales con dimensiones de entre 1 y 100 nm, así como la búsqueda de nuevas aplicaciones tecnológicas a dichos materiales. Éstas ofrecen un panorama muy prometedor por las potenciales aplicaciones que puede llegar a tener en distintos campos; entre ellos, la industria agropecuaria. En este artículo se mencionan diferentes metodologías de preparación de microcápsulas y su posible aplicación en el campo pecuario, mediante la encapsulación del selenio y su utilización de forma específica en el sitio de acción, reduciendo con ello la cantidad a utilizarse y evitar su toxicidad

Magnetic nanoparticles for magnetically guided therapies against neural diseases

Neurological pathologies and nerve damage are two problems of significant medical and economic impact because of the hurdles of losing nerve functionality in addition to significant mortality and morbidity, and demanding rehabilitation. There are currently a number of examples of how nanotechnology can provide new solutions for biomedical problems. Current strategies for nerve repair rely on the use of functionalized scaffolds working as nerve guidance channels to improve axonal regeneration and to direct axonal re-growth across the nerve lesion site. Since low invasiveness and high selectivity of the growth stimulation are usually conflicting requirements, new approaches are being pursued in order to overcome such limitations. Engineered magnetic nanoparticles (MNPs) have emerged from this need for noninvasive therapies for both positioning and guiding neural cells in response to an external magnetic field. Here, we review the current state of the use of MNPs for neuroprotective and magnetically guided therapies. We discuss some conceivable outcomes of current magnetically driven strategies seeking integrated platforms for regenerative action on damaged tissues

Cell damage produced by magnetic fluid hyperthermia on microglial BV2 cells

We present evidence on the effects of exogenous heating by water bath (WB) and magnetic hyperthermia (MHT) on a glial micro-tumor phantom. To this, magnetic nanoparticles (MNPs) of 30-40 nm were designed to obtain particle sizes for maximum heating efficiency. The specific power absorption (SPA) values (f = 560 kHz, H = 23.9 kA/m) for as prepared colloids (533-605 W/g) dropped to 98-279 W/g in culture medium. The analysis of the intracellular MNPs distribution showed vesicle-trapped MNPs agglomerates spread along the cytoplasm, as well as large (~0.5-0.9 µm) clusters attached to the cell membrane. Immediately after WB and MHT (T = 46 °C for 30 min) the cell viability was ˜70% and, after 4.5 h, decreased to 20-25%, demonstrating that metabolic processes are involved in cell killing. The analysis of the cell structures after MHT revealed a significant damage of the cell membrane that is correlated to the location of MNPs clusters, while local cell damage were less noticeable after WB without MNPs. In spite of the similar thermal effects of WB and MHT on the cell viability, our results suggest that there is an additional mechanism of cell damage related to the presence of MNPs at the intracellular space

Gold-decorated magnetic nanoparticles design for hyperthermia applications and as a potential platform for their surface-functionalization

The integration of noble metal and magnetic nanoparticles with controlled structures that can couple various specific effects to the different nanocomposite in multifunctional nanosystems have been found interesting in the field of medicine. In this work, we show synthesis route to prepare small Au nanoparticles of sizes <d> = 3.9 ± 0.2 nm attached to Fe 3 O 4 nanoparticle cores (<d> = 49.2 ± 3.5 nm) in aqueous medium for potential application as a nano-heater. Remarkably, the resulted Au decorated PEI-Fe 3 O 4 (Au@PEI-Fe 3 O 4 ) nanoparticles are able to retain bulk magnetic moment M S = 82–84 Am 2 /kg Fe3O4 , with the Verwey transition observed at T V = 98 K. In addition, the in vitro cytotoxicity analysis of the nanosystem microglial BV2 cells showed high viability (>97.5%) to concentrate up to 100 µg/mL in comparison to the control samples. In vitro heating experiments on microglial BV2 cells under an ac magnetic field (H 0 = 23.87 kA/m; f = 571 kHz) yielded specific power absorption (SPA) values of SPA = 43 ± 3 and 49 ± 1 µW/cell for PEI-Fe 3 O 4 and Au@PEI-Fe 3 O 4 NPs, respectively. These similar intracellular SPA values imply that functionalization of the magnetic particles with Au did not change the heating efficiency, providing at the same time a more flexible platform for multifunctional functionalization

Enhanced Cellular Transduction of Nanoparticles Resistant to Rapidly Forming Plasma Protein Coronas

Nanoparticles (NPs) are increasingly being developed as biomedical platforms for drug/nucleic acid delivery and imaging. However, in biological fluids, NPs interact with a wide range of proteins that form a coating known as protein corona. Coronae can critically influence self-interaction and binding of other molecules, which can affect toxicity, promote cell activation, and inhibit general or specific cellular uptake. Glycosaminoglycan (GAG)-binding enhanced transduction (GET) is developed to efficiently deliver a variety of cargoes intracellularly; employing GAG-binding peptides, which promote cell targeting, and cell penetrating peptides (CPPs) which enhance endocytotic cell internalization. Herein, it is demonstrated that GET peptide coatings can mediate sustained intracellular transduction of magnetic NPs (MNPs), even in the presence of serum or plasma. NP colloidal stability, physicochemical properties, toxicity and cellular uptake are investigated. Using label-free snapshot proteomics, time-resolved profiles of human plasma coronas formed on functionalized GET-MNPs demonstrate that coronae quickly form (<1 min), with their composition relatively stable but evolving. Importantly GET-MNPs present a subtly different corona composition to MNPs alone, consistent with GAG-binding activities. Understanding how NPs interact with biological systems and can retain enhanced intracellular transduction will facilitate novel drug delivery approaches for cell-type specific targeting of new nanomaterials

Low-Dimensional Assemblies of Magnetic MnFe2O4 Nanoparticles and Direct In Vitro Measurements of Enhanced Heating Driven by Dipolar Interactions: Implications for Magnetic Hyperthermia

Magnetic fluid hyperthermia (MFH), the procedure of raising the temperature of tumor cells using magnetic nanoparticles (MNPs) as heating agents, has proven successful in treating some types of cancer. However, the low heating power generated under physiological conditions makes it necessary a high local concentration of MNPs at tumor sites. Here, we report how the in vitro heating power of magnetically soft MnFe2O4 nanoparticles can be enhanced by intracellular low-dimensional clusters through a strategy that includes: (a) the design of the MNPs to retain Neel magnetic relaxation in high-viscosity media, and (b) culturing MNP-loaded cells under magnetic fields to produce elongated intracellular agglomerates. Our direct in vitro measurements demonstrated that the specific loss power (SLP) of elongated agglomerates (SLP = 576 +/- 33 W/g) induced by culturing BV2 cells in situ under a dc magnetic field was increased by a factor of 2 compared to the SLP = 305 +/- 25 W/g measured in aggregates freely formed within cells. A numerical mean-field model that included dipolar interactions quantitatively reproduced the SLPs of these clusters both in phantoms and in vitro, suggesting that it captures the relevant mechanisms behind power losses under high-viscosity conditions. These results indicate that in situ assembling of MNPs into low-dimensional structures is a sound possible way to improve the heating performance in MFH

The relevance of Brownian relaxation as power absorption mechanism in Magnetic Hyperthermia

The Linear Response Theory (LRT) is a widely accepted framework to analyze the power absorption of magnetic nanoparticles for magnetic fluid hyperthermia. Its validity is restricted to low applied fields and/or to highly anisotropic magnetic nanoparticles. Here, we present a systematic experimental analysis and numerical calculations of the specific power absorption for highly anisotropic cobalt ferrite (CoFe 2 O 4 ) magnetic nanoparticles with different average sizes and in different viscous media. The predominance of Brownian relaxation as the origin of the magnetic losses in these particles is established, and the changes of the Specific Power Absorption (SPA) with the viscosity of the carrier liquid are consistent with the LRT approximation. The impact of viscosity on SPA is relevant for the design of MNPs to heat the intracellular medium during in vitro and in vivo experiments. The combined numerical and experimental analyses presented here shed light on the underlying mechanisms that make highly anisotropic MNPs unsuitable for magnetic hyperthermia

Controlling the dominant magnetic relaxation mechanisms for magnetic hyperthermia in bimagnetic core-shell nanoparticles

We report a simple and effective way to control the heat generation of a magnetic colloid under alternate magnetic fields by changing the shell composition of bimagnetic core-shell Fe 3 O 4 /Zn x Co 1-x Fe 2 O 4 nanoparticles. The core-shell structure constitutes a magnetically-coupled biphase system, with an effective anisotropy that can be tuned by the substitution of Co 2+ by Zn 2+ ions in the shell. Magnetic hyperthermia experiments of nanoparticles dispersed in hexane and butter oil showed that the magnetic relaxation is dominated by Brown relaxation mechanism in samples with higher anisotropy (i.e., larger concentration of Co within the shell) yielding high specific power absorption values in low viscosity media as hexane. Increasing the Zn concentration of the shell, diminishes the magnetic anisotropy, which results in a change to a Néel relaxation that dominates the process when the nanoparticles are dispersed in a high-viscosity medium. We demonstrate that tuning the Zn contents at the shell of these exchange-coupled core/shell nanoparticles provides a way to control the magnetic anisotropy without loss of saturation magnetization. This ability is an essential prerequisite for most biomedical applications, where high viscosities and capturing mechanisms are present. This journal i

Magnetic Nanoparticles for Power Absorption: optimizing size, shape and magnetic properties

We present a study on the magnetic properties of naked and silica-coated Fe3O4 nanoparticles with sizes between 5 and 110 nm. Their efficiency as heating agents was assessed through specific power absorption (SPA) measurements as a function of particle size and shape. The results show a strong dependence of the SPA with the particle size, with a maximum around 30 nm, as expected for a Neel relaxation mechanism in single-domain particles. The SiO2 shell thickness was found to play an important role in the SPA mechanism by hindering the heat outflow, thus decreasing the heating efficiency. It is concluded that a compromise between good heating efficiency and surface functionality for biomedical purposes can be attained by making the SiO2 functional coating as thin as possible.Comment: 15 pages, 7 figures, 2 table

Magnetic hyperthermia experiments with magnetic nanoparticles in clarified butter oil and paraffin: A thermodynamic analysis

In specific power absorption models for magnetic fluid hyperthermia (MFH) experiments, the magnetic relaxation time of nanoparticles (NPs) is known to be a fundamental descriptor of the heating mechanisms. The relaxation time is mainly determined by the interplay between the magnetic properties of NPs and the rheological properties of NPs’ environment. Although the role of magnetism in MFH has been extensively studied, the thermal properties of the NP medium and their changes during MFH experiments have been underrated so far. Herein, we show that ZnxFe3-xO4 NPs dispersed through different media with phase transition in the temperature range of experiment as clarified butter oil (CBO) and paraffin. These systems show nonlinear behavior of the heating rate within the temperature range of MFH experiments. For CBO, a fast increase at ~306 K is associated with changes in the viscosity (¿(T)) and specific heat (cp(T)) of the medium at its melting temperature. This increment in the heating rate takes place around 318 K for paraffin. The magnetic and morphological characterization of NPs together with the observed agglomeration of NPs above 306 and 318 K for CBO and paraffin, respectively, indicate that the fast increase in MFH curves could not be associated with the change in the magnetic relaxation mechanism, with Neél relaxation being dominant. In fact, successive experimental runs performed up to temperatures below and above the CBO and paraffin melting points resulted in different MFH curves due to agglomeration of NPs driven by magnetic field inhomogeneity during the experiments. Our results highlight the relevance of the thermodynamic properties of the system NP-medium for an accurate measurement of the heating efficiency for in vitro and in vivo environments, where the thermal properties are largely variable within the temperature window of MFH experiments