Synthesis strategies of single-core and multi-core iron oxide magnetic nanoparticles for biomedical applications

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Física I, leída el 27-10-2017.En esta tesis, las nanoparticulas de óxidos de hierro han sido el caso del estudio (específicamente las fases magnetita y maghemita de los óxidos de hierro) ya que este nanomaterial presenta algunas características y ventajas interesantes, que surgen de su composición química y estructura atómica: pueden ser manipuladas por un gradiente de campo magnético externo y pueden responder a un campo magnético externo que cambia con el tiempo con resultados ventajosos relacionados con la transferencia energética de dicho campo de excitación a las nanopartículas.[1] Por último, las nanopartículas magnéticas afectan a la relaxividad de los protones circundantes. En base a estos atributos, las nanopartículas magnéticas son uno de los materiales funcionales emergentes tanto en la industria de la ciencia de materiales como en biomedicina...In this thesis, iron oxides nanoparticles has been the case of study (more specifically magnetite and maghemite iron oxide phases), since this nanomaterial presents some interesting features and advantages that arise from its chemical composition and atomic structure. First, the most important feature is that magnetic nanoparticles obey Coulomb’s law,[1] and this means that they can be manipulated by an external magnetic field gradient. Moreover, magnetic nanoparticles can be made to resonantly respond to a time-varying magnetic field, with advantageous results related to the transfer of energy from the exciting field to the nanoparticle.[2] Finally, magnetic nanoparticles affect the relaxivity of surrounding protons. Based on these features, magnetic nanoparticles are emerging functional materials in material science industry and biomedicine...Depto. de Química FísicaFac. de Ciencias QuímicasTRUEunpu

Why consumers purchase organic products? The role of environment, health and age

El mercado de productos ecológicos está aumentando en todo el mundo, especialmente en la categoría de los alimentos, en particular de productos orgánicos. El objetivo de este estudio es entender mejor porque los consumidores compran productos orgánicos, profundizando en su preocupación ambiental, conciencia de salud y edad. La evidencia empírica se basa en una encuesta online, utilizando una muestra de 279 compradores habituales de productos orgánicos en España y Portugal. Los resultados muestran que existe una relación positiva entre preocupación ambiental, conciencia de salud y comportamiento de compra verde. La preocupación ambiental es más fuerte que la salud para explicar esta relación. También la edad es un predictor de la compra y los consumidores mayores de 35 años compran más productos orgánicos que los más jóvenes. Para los profesionales de marketing, el estudio permite desarrollar mejores estrategias de marketing para atraer y retener a estos consumidores.The market of green products is increasing all over the world, especially in food category that shows a great demand for biologic and organics. The aim of this study is to better understand the why consumers buy organic products, more specifically environmental concern, health consciousness and age The empirical evidence is based on an online survey, using a sample of 279, regular shoppers of organic products in Portugal and Spain. The results show there is a positive relation between environmental concern, health consciousness and green purchase behavior. Environmental concern is stronger than health to explain this relation. Also age is a predictor of green purchase behavior and older consumers with more than 35 years purchase more organics than younger consumers. For managers and marketers, the study enables to develop better marketing strategies to address these consumers and to enhance environmental concern, health and age to foster organics consumption

Why consumers purchase organic products? The role of environment, health and age

The market of green products is increasing all over the world, especially in food category that shows a great demand for biologic and organics. The aim of this study is to better understand the why consumers buy organic products, more specifically environmental concern, health consciousness and age The empirical evidence is based on an online survey, using a sample of 279, regular shoppers of organic products in Portugal and Spain. The results show there is a positive relation between environmental concern, health consciousness and green purchase behavior. Environmental concern is stronger than health to explain this relation. Also age is a predictor of green purchase behavior and older consumers with more than 35 years purchase more organics than younger consumers. For managers and marketers, the study enables to develop better marketing strategies to address these consumers and to enhance environmental concern, health and age to foster organics consumption.El mercado de productos ecológicos está aumentando en todo el mundo, especialmente en la categoría de los alimentos, en particular de productos orgánicos. El objetivo de este estudio es entender mejor porque los consumidores compran productos orgánicos, profundizando en su preocupación ambiental, conciencia de salud y edad. La evidencia empírica se basa en una encuesta online, utilizando una muestra de 279 compradores habituales de productos orgánicos en España y Portugal. Los resultados muestran que existe una relación positiva entre preocupación ambiental, conciencia de salud y comportamiento de compra verde. La preocupación ambiental es más fuerte que la salud para explicar esta relación. También la edad es un predictor de la compra y los consumidores mayores de 35 años compran más productos orgánicos que los más jóvenes. Para los profesionales de marketing, el estudio permite desarrollar mejores estrategias de marketing para atraer y retener a estos consumidores.info:eu-repo/semantics/publishedVersio

Clickable polymer ligand-functionalized iron oxide nanocubes: A promising nanoplatform for 'local hot spots' magnetically triggered drug release

Exploiting the local heat on the surface of magnetic nanoparticles (MNPs) upon exposure to an alternating magnetic field (AMF) to cleave thermal labile bonds represents an interesting approach in the context of remotely triggered drug delivery. Here, taking advantages of a simple and scalable two-step ligand exchange reaction, we have prepared iron oxide nanocubes (IONCs) functionalized with a novel multifunctional polymer ligand having multiple catechol moieties, furfuryl pendants, and polyethylene glycol (PEG) side chains. Catechol groups ensure a strong binding of the polymer ligands to the IONCs surface, while the PEG chains provide good colloidal stability to the polymer-coated IONCs. More importantly, furfuryl pendants on the polymer enable to click the molecules of interest (either maleimide–fluorescein or maleimide–doxorubicin) via a thermal labile Diels–Alder adduct. The resulting IONCs functionalized with a fluorescein/doxorubicin-conjugated polymer ligand exhibit good colloidal stability in buffer saline and serum solution along with outstanding heating performance in aqueous solution or even in viscous media (81% glycerol/water) when exposed to the AMF of clinical use. The release of conjugated bioactive molecules such as fluorescein and doxorubicin could be boosted by applying AMF conditions of clinical use (16 kAm–1 and 110 kHz). It is remarkable that the magnetic hyperthermia-mediated release of the dye/drug falls in the concentration range 1.0–5.0 μM at an IONCs dose as low as 0.5 gFe/L and at no macroscopical temperature change. This local release effect makes this magnetic nanoplatform a potential tool for drug delivery with remote magnetic hyperthermia actuation and with a dose-independent action of MNPs.This work was partially supported by the Marie Sklodowska-Curie Innovative training network MSCA-ITN-ETN (HeatNMof project, GA 860942), partially by the AIRC Foundation (AIRC IG-14527 to T.P.), partially by the European Research Council (starting grant ICARO, Contract No. 678109), and partially by ERC proof of concept Hypercube, Contract No. 899661)

Anisotropic magnetic nanoparticles for biomedicine : Bridging frequency separated AC-field controlled domains of actuation

Magnetic nanoparticles (MNPs) constitute promising nanomedicine tools based on the possibility of obtaining different actuations (for example, heating or mechanical response) triggered by safe remote stimuli. Particularly, the possibility of performing different tasks using the same entity constitutes a main research target towards optimizing the treatment. But such a goal represents, in general, a very difficult step because the requisites for achieving efficient responses for separate actuations are often disparate-if not completely incompatible. An example of this is the response of MNPs to external AC fields, which could in principle be exploited for either magneto-mechanical actuation (MMA) at low frequencies (tens of Hz); or heat release at high frequency (0.1-1 MHz range) for magnetic fluid hyperthermia (MFH). The problem is that efficient MMA involves large torque, the required material parameters for which are detrimental to high heating, thus hindering the possibility of effective alternation between both responses. To overcome such apparent incompatibility, we propose a simple approach based on the use of anisotropic MNPs. The key idea is that the AC-frequency change must be concurrent with a field-amplitude variation able to promote-or impede-the reversal over the shape-determined anisotropy energy barrier. This way it is possible to switch the particle response between an efficient (magnetically dissipationless) rotation regime at low-f, for MMA, and a "frozen" (non-rotatable) high-energy-dissipation regime at high-f, for MFH. Furthermore, we show that such an alternation can also be achieved within the same high-f MFH regime. We use combined Brownian dynamics and micromagnetic simulations, based on real experimental samples, to show how such a field threshold can be tuned to working conditions with hexagonal-disk shape anisotropy

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

Here, we investigate the nature of the moment coupling between 10-nm DMSA-coated magnetic nanoparticles, in both colloidal dispersion and in powder form. The individual iron oxide cores were composed of > 95% maghemite and agglomerated to clusters. At room temperature the ensemble behaved as a superparamagnet according to M\"ossbauer and magnetization measurements, however, with clear signs of dipolar interactions at low temperatures. Analysis of temperature-dependent AC susceptibility data in the superparamagnetic regime indicates a tendency for dipolar coupled anticorrelations of the core moments within the clusters. To resolve the directional correlations between the particle moments we performed polarized small-angle neutron scattering and determined the magnetic spin-flip cross-section of the powder in low magnetic field at 300 K. We extract the underlying pair distance distribution function of the magnetization vector field by an indirect Fourier transform of the cross-section, and which suggests positive as well as negative correlations between nearest neighbor moments, with anticorrelations clearly dominating for next-nearest moments. These tendencies are confirmed by Monte Carlo simulations of such core-clusters.Comment: 11 pages, 6 figure

EXPERIÊNCIA DE INOVAÇÃO: “CLUBE DE ASTRONOMIA ORION: O CONHECIMENTO DO UNIVERSO AO ALCANCE DAS SUAS MÃOS”

The inclusion of the study of astronomy in school activities, showing students how this discipline links together different areas of knowledge, was the initial idea behind the creation of a club in 2003, in the El Rodeo School, which would gather a group of teachers, children, and young students with a common interest: to learn about the universe. This type of association was established because it allowed for the development of a collaborative learning environment among its members without separating it from the academic context, which made it attractive to students. It is an experience, which is oriented, by focusing on astronomy, to contribute to the improvement of learning and the development of thinking skills in students, such as observation, experimentation, analysis, and argumentation, without distinguishing between academic levels and areas of knowledge, thanks to its specific design that transcends classroom, curriculum, school grades, and school hours. This is accomplished, in terms of methodology, by taking inquiry-based teaching as a reference point and by developing projects by students with advice from teachers. Didactically, it materializes through multiple strategies such as workshops, conferences, video-forums, participation in institutional and international projects, science fairs, recreational activities, day and night observations, and the use of astronomical softwares, among others.El incluir en la escuela el estudio de la astronomía, mostrándoles a los estudiantes cómo en esta disciplina se vincula diferentes áreas de conocimiento, es la idea inicial con la que en el año 2003, en el colegio El Rodeo, nace un club que vincula a un grupo de maestros, niños y jóvenes con un interés común, conocer sobre el universo. Se establece este tipo de asociación porque permite el desarrollo de un ambiente de aprendizaje colaborativo entre sus integrantes sin desligarla del contexto académico, haciéndola atractiva a los estudiantes. Es una experiencia orientada, desde la astronomía, a contribuir en el mejoramiento del aprendizaje al desarrollar habilidades de pensamiento como observación, experimentación, análisis y argumentación en los estudiantes, sin distinguir niveles académicos ni áreas del conocimiento, por estar diseñada para trascender el aula, el currículo, los grados escolares y la jornada académica.Esto se logra, metodológicamente, al tomarse como referente la enseñanza basada en la indagación y al orientarse al desarrollo de proyectos por parte de los estudiantes con la asesoría de los maestros; didácticamente, se materializa, al utilizar múltiples estrategias tal como talleres, conferencias, video – foros, vinculación a proyectos institucionales e internacionales, ferias, actividades lúdicas, observaciones diurnas y nocturnas, uso de software astronómico, entre otras.Incluir na escola o estudo da astronomia, mostrando para os estudantes como essa disciplina está vinculada a várias áreas do conhecimento, foi o principal objetivo com o qual, no ano 2003, no colégio El Rodeo, foi criado um clube que une um grupo de professores, crianças e jovens com um interesse comum: conhecer sobre o universo. Estabeleceu-se esse tipo de associação porque permite o desenvolvimento de um ambiente de aprendizagem colaborativa para seus membros sem desvinculá-la do contexto acadêmico, fazendo-a, assim, atrativa para os estudantes. É uma experiência orientada, desde a astronomia, para contribuirpara o melhoramento da aprendizagem ao desenvolver habilidades de pensamento como observação, experimentação, análise e argumentação nos estudantes, sem diferenciar níveis acadêmicos nem áreas do conhecimento por estar concebida para transcender a aula, o currículo, os níveis escolares e o horário de estudos. Isso é possível, metodologicamente, por tomar como referência o ensino baseado na indagação e por estar orientada para o desenvolvimento de projetos por parte dos estudantes com a assessoria dos professores; didaticamente, é possível graças a múltiplas estratégias como oficinas, conferências, vídeofóruns, vinculação a projetos institucionais e internacionais, feiras, atividades lúdicas,observações diurnas e noturnas, uso de software astronômico, entre outras

Understanding the Influence of a Bifunctional Polyethylene Glycol Derivative in Protein Corona Formation around Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles are one of the most prominent agents used in theranostic applications, with MRI imaging the main application assessed. The biomolecular interface formed on the surface of a nanoparticle in a biological medium determines its behaviour in vitro and in vivo. In this study, we have compared the formation of the protein corona on highly monodisperse iron oxide nanoparticles with two different coatings, dimercaptosuccinic acid (DMSA), and after conjugation, with a bifunctional polyethylene glycol (PEG)-derived molecule (2000 Da) in the presence of Wistar rat plasma. The protein fingerprints around the nanoparticles were analysed in an extensive proteomic study. The results presented in this work indicate that the composition of the protein corona is very difficult to predict. Proteins from different functional categories—cell components, lipoproteins, complement, coagulation, immunoglobulins, enzymes and transport proteins—were identified in all samples with very small variability. Although both types of nanoparticles have similar amounts of bonded proteins, very slight differences in the composition of the corona might explain the variation observed in the uptake and biotransformation of these nanoparticles in Caco-2 and RAW 264.7 cells. Cytotoxicity was also studied using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Controlling nanoparticles’ reactivity to the biological environment by deciding on its surface functionalization may suggest new routes in the control of the biodistribution, biodegradation and clearance of multifunctional nanomedicines

Formation Mechanism of Maghemite Nanoflowers Synthesized by a Polyol-Mediated Process

Magnetic nanoparticles are being developed as structural and functional materials for use in diverse areas, including biomedical applications. Here, we report the synthesis of maghemite (γ-Fe₂O₃) nanoparticles with distinct morphologies: single-core and multicore, including hollow spheres and nanoflowers, prepared by the polyol process. We have used sodium acetate to control the nucleation and assembly process to obtain the different particle morphologies. Moreover, from samples obtained at different time steps during the synthesis, we have elucidated the formation mechanism of the nanoflowers: the initial phases of the reaction present a lepidocrocite (γ-FeOOH) structure, which suffers a fast dehydroxylation, transforming to an intermediate “undescribed” phase, possibly a partly dehydroxylated lepidocrocite, which after some incubation time evolves to maghemite nanoflowers. Once the nanoflowers have been formed, a crystallization process takes place, where the γ-Fe₂O₃ crystallites within the nanoflowers grow in size (from ∼11 to 23 nm), but the particle size of the flower remains essentially unchanged (∼60 nm). Samples with different morphologies were coated with citric acid and their heating capacity in an alternating magnetic field was evaluated. We observe that nanoflowers with large cores (23 nm, controlled by annealing) densely packed (tuned by low NaAc concentration) offer 5 times enhanced heating capacity compared to that of the nanoflowers with smaller core sizes (15 nm), 4 times enhanced heating effect compared to that of the hollow spheres, and 1.5 times enhanced heating effect compared to that of single-core nanoparticles (36 nm) used in this work