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1.
ACS Nano ; 13(7): 7716-7728, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31173684

RESUMO

The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe3O4 nanocubes with edge length in the 9-80 nm range, with excellent cubic morphology and high crystallinity by only minor adjustments in the synthesis parameters. The accurate size control provides evidence that even 1-2 nm size variations can be critical in determining the functional properties, for example, for improved nuclear magnetic resonance T2 contrast or enhanced magnetic hyperthermia. The rationale behind the changes introduced in the synthesis procedure (e.g., the use of three solvents or adding Na-oleate) is carefully discussed. The versatility of this synthesis route is demonstrated by expanding its capability to grow other spinel oxides such as Co-ferrites, Mn-ferrites, and Mn3O4 of different sizes. The simplicity and adaptability of this synthesis scheme may ease the development of complex oxide nanocubes for a wide variety of applications.

2.
Adv Drug Deliv Rev ; 138: 68-104, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30553951

RESUMO

Ferrimagnetic iron oxide nanoparticles (magnetite or maghemite) have been the subject of an intense research, not only for fundamental research but also for their potentiality in a widespread number of practical applications. Most of these studies were focused on nanoparticles with spherical morphology but recently there is an emerging interest on anisometric nanoparticles. This review is focused on the synthesis routes for the production of uniform anisometric magnetite/maghemite nanoparticles with different morphologies like cubes, rods, disks, flowers and many others, such as hollow spheres, worms, stars or tetrapods. We critically analyzed those procedures, detected the key parameters governing the production of these nanoparticles with particular emphasis in the role of the ligands in the final nanoparticle morphology. The main structural and magnetic features as well as the nanotoxicity as a function of the nanoparticle morphology are also described. Finally, the impact of each morphology on the different biomedical applications (hyperthermia, magnetic resonance imaging and drug delivery) are analysed in detail. We would like to dedicate this work to Professor Carlos J. Serna, Instituto de Ciencia de Materiales de Madrid, ICMM/CSIC, for his outstanding contribution in the field of monodispersed colloids and iron oxide nanoparticles. We would like to express our gratitude for all these years of support and inspiration on the occasion of his retirement.


Assuntos
Sistemas de Liberação de Medicamentos , Nanopartículas de Magnetita/química , Animais , Desenho de Fármacos , Humanos , Ligantes , Nanopartículas de Magnetita/administração & dosagem
3.
Nano Lett ; 18(9): 5854-5861, 2018 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-30165026

RESUMO

The atomic structure of nanoparticles can be easily determined by transmission electron microscopy. However, obtaining atomic-resolution chemical information about the individual atomic columns is a rather challenging endeavor. Here, crystalline monodispersed spinel Fe3O4/Mn3O4 core-shell nanoparticles have been thoroughly characterized in a high-resolution scanning transmission electron microscope. Electron energy-loss spectroscopy (EELS) measurements performed with atomic resolution allow the direct mapping of the Mn2+/Mn3+ ions in the shell and the Fe2+/Fe3+ in the core structure. This enables a precise understanding of the core-shell interface and of the cation distribution in the crystalline lattice of the nanoparticles. Considering how the different oxidation states of transition metals are reflected in EELS, two methods of performing a local evaluation of the cation inversion in spinel lattices are introduced. Both methods allow the determination of the inversion parameter in the iron oxide core and manganese oxide shell, as well as detecting spatial variations in this parameter, with atomic resolution. X-ray absorption measurements on the whole sample confirm the presence of cation inversion. These results present a significant advance toward a better correlation of the structural and functional properties of nanostructured spinel oxides.

4.
Small ; 14(30): e1800804, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29952138

RESUMO

Understanding the microstructure in heterostructured nanoparticles is crucial to harnessing their properties. Although microscopy is ideal for this purpose, it allows for the analysis of only a few nanoparticles. Thus, there is a need for structural methods that take the whole sample into account. Here, a novel bulk-approach based on the combined analysis of synchrotron X-ray powder diffraction with whole powder pattern modeling, Rietveld and pair distribution function is presented. The microstructural temporal evolution of FeO/Fe3 O4 core/shell nanocubes is studied at different time intervals. The results indicate that a two-phase approach (FeO and Fe3 O4 ) is not sufficient to successfully fit the data and two additional interface phases (FeO and Fe3 O4 ) are needed to obtain satisfactory fits, i.e., an onion-type structure. The analysis shows that the Fe3 O4 phases grow to some extent (≈1 nm) at the expense of the FeO core. Moreover, the FeO core progressively changes its stoichiometry to accommodate more oxygen. The temporal evolution of the parameters indicates that the structure of the FeO/Fe3 O4 nanocubes is rather stable, although the exact interface structure slightly evolves with time. This approach paves the way for average studies of interfaces in different kinds of heterostructured nanoparticles, particularly in cases where spectroscopic methods have some limitations.

5.
Small ; 14(15): e1703963, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29479814

RESUMO

Although cubic rock salt-CoO has been extensively studied, the magnetic properties of the main nanoscale CoO polymorphs (hexagonal wurtzite and cubic zinc blende structures) are rather poorly understood. Here, a detailed magnetic and neutron diffraction study on zinc blende and wurtzite CoO nanoparticles is presented. The zinc blende-CoO phase is antiferromagnetic with a 3rd type structure in a face-centered cubic lattice and a Néel temperature of TN (zinc-blende) ≈225 K. Wurtzite-CoO also presents an antiferromagnetic order, TN (wurtzite) ≈109 K, although much more complex, with a 2nd type order along the c-axis but an incommensurate order along the y-axis. Importantly, the overall magnetic properties are overwhelmed by the uncompensated spins, which confer the system a ferromagnetic-like behavior even at room temperature.

6.
Nanoscale ; 7(7): 3002-15, 2015 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-25600147

RESUMO

The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.

7.
Int J Mol Med ; 26(4): 533-9, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20818493

RESUMO

In this study we present a morphological approach in observing the interaction of cationic magnetic nanoparticles with A-549 cells (human lung adenocarcinoma). Under our experimental conditions, nanoparticles easily penetrated cells and were observed in vivo, using bright light microscopy. In fixed cells, nanoparticles remained inside cells, showing quantity and distribution patterns similar to those in unfixed cells. The presence of nanoparticles did not affect cell viability or the morphologic parameters assessed. We determined the potential internalization mechanism of nanoparticles into cells using endocytosis inhibitors. The results suggest that nanoparticles used in this study penetrate A-549 cells mainly through a macropinocytosis process.


Assuntos
Endocitose , Compostos Férricos/metabolismo , Nanopartículas/química , Cátions/química , Cátions/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular , Clatrina/metabolismo , Compostos Férricos/química , Humanos , Magnetismo , Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Nanopartículas/ultraestrutura , Tamanho da Partícula , Eletricidade Estática , Tubulina (Proteína)/análise
8.
Nanomedicine (Lond) ; 5(3): 397-408, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20394533

RESUMO

BACKGROUND & AIM: Uptake, cytotoxicity and interaction of improved superparamagnetic iron oxide nanoparticles were studied in cells, tissues and organs after single and multiple exposures. MATERIAL & METHOD: We prepared dimercaptosuccinic acid-coated iron oxide nanoparticles by thermal decomposition in organic medium, resulting in aqueous suspensions with a small hydrodynamic size (< 100 nm), high saturation magnetization and susceptibility, high nuclear magnetic resonance contrast and low cytotoxicity. RESULTS: In vitro and in vivo behavior showed that these nanoparticles are efficient carriers for drug delivery to the liver and brain that can be combined with MRI detection.


Assuntos
Encéfalo/anatomia & histologia , Compostos Férricos/química , Fígado/anatomia & histologia , Imagem por Ressonância Magnética/métodos , Nanopartículas/química , Succímero/química , Animais , Sobrevivência Celular , Células HeLa , Humanos , Nanopartículas/ultraestrutura , Ratos
9.
Nanotechnology ; 20(11): 115103, 2009 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-19420433

RESUMO

The internalization and biocompatibility of iron oxide nanoparticles surface functionalized with four differently charged carbohydrates have been tested in the human cervical carcinoma cell line (HeLa). Neutral, positive, and negative iron oxide nanoparticles were obtained by coating with dextran, aminodextran, heparin, and dimercaptosuccinic acid, resulting in colloidal suspensions stable at pH 7 with similar aggregate size. No intracellular uptake was detected in cells incubated with neutral charged nanoparticles, while negative particles showed different behaviour depending on the nature of the coating. Thus, dimercaptosuccinic-coated nanoparticles showed low cellular uptake with non-toxic effects, while heparin-coated particles showed cellular uptake only at high nanoparticle concentrations and induced abnormal mitotic spindle configurations. Finally, cationic magnetic nanoparticles show excellent properties for possible in vivo biomedical applications such as cell tracking by magnetic resonance imaging (MRI) and cancer treatment by hyperthermia: (i) they enter into cells with high effectiveness, and are localized in endosomes; (ii) they can be easily detected inside cells by optical microscopy, (iii) they are retained for relatively long periods of time, and (iv) they do not induce any cytotoxicity.


Assuntos
Endocitose , Compostos Férricos/metabolismo , Magnetismo , Nanopartículas/química , Neoplasias/patologia , Morte Celular , Células HeLa , Humanos , Concentração de Íons de Hidrogênio , Microtúbulos/metabolismo , Nanopartículas/ultraestrutura , Neoplasias/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Temperatura
10.
J Phys Chem B ; 113(19): 7033-9, 2009 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-19378984

RESUMO

Colloidal dispersions of monodispersed and high-crystalline magnetite nanoparticles have been used to establish a relationship between magnetic properties and magnetic resonance (MR) relaxometric parameters in vitro. Magnetite nanoparticles with diameters between 4 and 14 nm were synthesized by thermal decomposition of Fe(acac)3 in different organic solvents and transformed to hydrophilic by changing oleic acid for dimercaptosuccinic acid (DMSA). A final treatment in alkaline water was critical to make the suspension stable at pH 7 with xi-potential values of -45 mV and hydrodynamic sizes as low as 50 nm. Samples showed superparamagnetic behavior at room temperature, which is an important parameter for biomedical applications. Susceptibility increased with both particle and aggregate size, and for particles larger than 9 nm, the aggregate size was the key factor controlling the susceptibility. Relaxivity values followed the same trend as the suspension susceptibilities, indicating that the aggregate size is an important factor above a certain particle size governing the proton relaxation times. The highest relaxivity value, r2=317 s(-1) mM(-1), much higher than those for commercial contrast agents with similar hydrodynamic size, was obtained for a suspension consisting of 9 nm particles and 70 nm of hydrodynamic size, and it was assigned to the higher particle crystallinity in comparison to particles prepared by coprecipitation. Therefore, it can be concluded that in addition to the sample crystallinity, both particle size and aggregate size should be considered in order to explain the magnetic and relaxivity values of a suspension.

11.
Contrast Media Mol Imaging ; 3(6): 215-22, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-19072767

RESUMO

A new methodology for the synthesis of hydrophilic iron oxide nanoparticles has been developed. This new method is based on the direct chemical modification of the nanoparticles' surfactant molecules. Using this methodology both USPIO (ultrasmall super paramagnetic iron oxide) (hydrodynamic size smaller than 50 nm) and SPIO (super paramagnetic iron oxide) (hydrodynamic size bigger than 50 nm) were obtained. In addition, we also show that it is possible to further functionalize the hydrophilic nanoparticles via covalent chemistry in water. The magnetic properties of these nanoparticles were also studied, showing their potential as MRI contrast agents.


Assuntos
Compostos Férricos/síntese química , Nanopartículas/química , Meios de Contraste/síntese química , Imagem por Ressonância Magnética , Magnetismo , Métodos , Tamanho da Partícula , Água
13.
J Control Release ; 130(2): 168-74, 2008 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-18588929

RESUMO

Attachment of cytokines to magnetic nanoparticles has been developed as a system for controlled local drug release in cancer therapy. We studied the adsorption/release of murine interferon gamma (IFN-gamma) on negatively charged magnetic nanoparticles prepared by three different methods, including coprecipitation, decomposition in organic media, and laser pyrolysis. To facilitate IFN-gamma adsorption, magnetic nanoparticles were surface modified by distinct molecules to achieve high negative charge at pH 7, maintaining small aggregate size and stability in biological media. We analyzed carboxylate-based coatings and studied the colloidal properties of the resulting dispersions. Finally, we incubated the magnetic dispersions with IFN-gamma and determined optimal conditions for protein adsorption onto the particles, as well as the release capacity at different pH and as a function of time. Particles prepared by decomposition in organic media and further modified with dimercaptosuccinic acid showed the most efficient adsorption/release capacity. IFN-gamma adsorbed on these nanoparticles would allow concentration of this protein or other biomolecules at specific sites for treatment of cancer or other diseases.


Assuntos
Antineoplásicos , Sistemas de Liberação de Medicamentos/métodos , Interferon gama , Magnetismo , Nanopartículas/química , Adsorção , Animais , Antineoplásicos/química , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Portadores de Fármacos/química , Composição de Medicamentos , Estabilidade de Medicamentos , Concentração de Íons de Hidrogênio , Interferon gama/química , Interferon gama/farmacologia , Interferon gama/uso terapêutico , Macrófagos Peritoneais/efeitos dos fármacos , Macrófagos Peritoneais/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de Transmissão , Neoplasias/tratamento farmacológico , Neoplasias/imunologia , Propriedades de Superfície , Difração de Raios X
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