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Nanoparticle‐based magnetic hyperthermia is a well‐known thermal therapy platform studied to treat solid tumors, but its use for monotherapy is limited due to incomplete tumor eradication at hyperthermia temperature (45 °C). It is often combined with chemotherapy for obtaining a more effective therapeutic outcome. Cubic‐shaped cobalt ferrite nanoparticles (Co–Fe NCs) serve as magnetic hyperthermia agents and as a cytotoxic agent due to the known cobalt ion toxicity, allowing the achievement of both heat and cytotoxic effects from a single platform. In addition to this advantage, Co–Fe NCs have the unique ability to form growing chains under an alternating magnetic field (AMF). This unique chain formation, along with the mild hyperthermia and intrinsic cobalt toxicity, leads to complete tumor regression and improved overall survival in an in vivo murine xenograft model, all under clinically approved AMF conditions. Numerical calculations identify magnetic anisotropy as the main Co–Fe NCs’ feature to generate such chain formations. This novel combination therapy can improve the effects of magnetic hyperthermia, inaugurating investigation of mechanical behaviors of nanoparticles under AMF, as a new avenue for cancer therapy more...

Oriented attachment has created a great debate about the description of crystal growth throughout the last decade. This aggregationbased model has successfully described biomineralization processes as well as forms of inorganic crystal growth, which could not be explained by classical crystal growth theory. Understanding the nanoparticle growth is essential since physical properties, such as the magnetic behavior, are highly dependent on the microstructure, morphology and composition of the inorganic crystals. In this work, the underlying nanoparticle growth of cobalt ferrite nanoparticles in a bioinspired synthesis was studied. Bioinspired syntheses have sparked great interest in recent years due to their ability to influence and alter inorganic crystal growth and therefore tailor properties of nanoparticles. In this synthesis, a short synthetic version of the protein MMS6, involved in nanoparticle formation within magnetotactic bacteria, was used to alter the growth of cobalt ferrite. We demonstrate that the bioinspired nanoparticle growth can be described by the oriented attachment model. The intermediate stages proposed in the theoretical model, including primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron diffraction measurements. The change of particle diameter with time agrees with the recently proposed kinetic model for oriented attachment more...

© 2018 Elservier Science Fundacion Neurociencias y Envejecimiento has supported this work through project 359/2014 as well as MINECO through the project MAT2016-80182-R. The authors thank the ICTS National Center for Electron Microscopy of the UCM for access., Fe3O4@SiO2 and CoFe2O4@SiO2 and their corresponding amino-functionalized nanocomposites were successfully synthesized by a process of two steps including the preparation by coprecipitation or hydrothermal synthesis of the corresponding magnetic cores, the coating of its surface with a silica coating followed by its subsequent functionalization with 3-aminopropyltriethoxysilane (APTES). All magnetic samples were characterized by XRD using FULPROFF program, FTIR analysis, TEM and M-H hysteresis loops. The results showed diffraction maxima indexed in a cubic symmetry of S. G. Fd-3m with Z = 8 compatible with an inverse spinel-type structure. FTIR spectra of all samples show the characteristic bands of the magnetic cores and others bands corresponding to the asymmetric vibration of O-Si-O and Si-O-Si bonds of silica. The TEM images confirm that all the nanoparticles are coated, finding the largest thickness of the coating in the Fe3O4 sample prepared hydrothermally, which are the smaller ones. An expected reduction of the saturation magnetization of the magnetic cores is achieved with the coating and functionalization, although the behaviour of the Fe3O4 -samples remains practically superparamagnetic while the corresponding ones of cobalt are still ferrimagnetic. Fe3O4 nanocomposites respond to more quickly in the presence of an external magnetic field, something important against the removal of contaminating species in aqueous media. UV-Vis spectroscopy studies confirm the adsorption capacity of Cu2+ in aqueous solutions of the prepared nanocomposites, having found that a small thickness of the coating leads a greater adsorption, so that the best adsorption is found for CPFe3O4@SiO2-APTES nanocomposite. (C) 2018 Elsevier B.V. All rights reserved., Ministerio de Economía y Competitividad (MINECO), Fundacion Neurociencias y Envejecimiento, Depto. de Física de la Tierra y Astrofísica, Depto. de Química Inorgánica, Fac. de Ciencias Físicas, Fac. de Ciencias Químicas, TRUE, pub more...

© 2018 Elservier Science Fundacion Neurociencias y Envejecimiento has supported this work through project 359/2014 as well as MINECO through the project MAT2016-80182-R. The authors thank the ICTS National Center for Electron Microscopy of the UCM for access., Fe3O4@SiO2 and CoFe2O4@SiO2 and their corresponding amino-functionalized nanocomposites were successfully synthesized by a process of two steps including the preparation by coprecipitation or hydrothermal synthesis of the corresponding magnetic cores, the coating of its surface with a silica coating followed by its subsequent functionalization with 3-aminopropyltriethoxysilane (APTES). All magnetic samples were characterized by XRD using FULPROFF program, FTIR analysis, TEM and M-H hysteresis loops. The results showed diffraction maxima indexed in a cubic symmetry of S. G. Fd-3m with Z = 8 compatible with an inverse spinel-type structure. FTIR spectra of all samples show the characteristic bands of the magnetic cores and others bands corresponding to the asymmetric vibration of O-Si-O and Si-O-Si bonds of silica. The TEM images confirm that all the nanoparticles are coated, finding the largest thickness of the coating in the Fe3O4 sample prepared hydrothermally, which are the smaller ones. An expected reduction of the saturation magnetization of the magnetic cores is achieved with the coating and functionalization, although the behaviour of the Fe3O4 -samples remains practically superparamagnetic while the corresponding ones of cobalt are still ferrimagnetic. Fe3O4 nanocomposites respond to more quickly in the presence of an external magnetic field, something important against the removal of contaminating species in aqueous media. UV-Vis spectroscopy studies confirm the adsorption capacity of Cu2+ in aqueous solutions of the prepared nanocomposites, having found that a small thickness of the coating leads a greater adsorption, so that the best adsorption is found for CPFe3O4@SiO2-APTES nanocomposite. (C) 2018 Elsevier B.V. All rights reserved., Ministerio de Economía y Competitividad (MINECO), Fundacion Neurociencias y Envejecimiento, Depto. de Física de la Tierra y Astrofísica, Depto. de Química Inorgánica, Fac. de Ciencias Físicas, Fac. de Ciencias Químicas, TRUE, pub more...

High quality CoFe2O4 nanoparticles were synthesized using a one-pot, microwave assisted method, that allows forming stable colloidal solutions in alcoholic solvents, as required for the preparation by Chemical Solution Deposition of hybrid nanocomposite ferromagnetic-high Tc YBa2Cu3O7 superconducting films or devices. We have investigated how the thermal process necessary for the preparation of such epitaxial nanocomposites, involving high temperatures (800 °C) and oxygen partial pressures (1 atm), affects the structure and magnetic properties of the isolated nanoparticles. The NPs were fully characterised by XRD, SQUID, STEM-EELS and XMCD at four different stages of the thermal process. Results show that, despite intermediate changes in the cation distribution occur during the process, the final NP magnetization is stable against the thermal treatment. This result opens up perspectives for the preparation of hybrid YBCO films with embedded magnetic NPs using low-cost chemical-solution methods more...

Cobalt ferrite nanoparticles (20 nm) were synthesized and electrophoretically deposited onto aluminum foil, graphite paper, and carbon felt in order to study its potential as a cost-effective electrocatalyst for the oxidation of ammonium sulfite to ammonium sulfate in a proposed sulfur ammonia thermochemical cycle. Scanning electron microscopy and linear sweep voltammetry were used to characterize the deposited films and investigate their electrochemical activity. Furthermore, the effects of electrophoretic deposition conditions on deposit morphology and subsequently the effects of deposit morphology on electrochemical activity in 2 M ammonium sulfite were studied to better understand how to improve electrocatalysts. It was found that there is a critical deposit thickness for each substrate, where additional deposited particles reduce overall electrocatalytic activity of the deposits. For graphite paper, this thickness was estimated to be 3 particle layers for the EPD conditions studied. The 3 particle layer film on graphite paper resulted in a 5.5 fold increase in current density from a blank graphite paper substrate. For carbon felt, the deposit thickness threshold was calculated to be 0.13 of a particle layer for the EPD conditions studied. Moreover, this film was found to have a 4.3 fold increase in current density from a blank carbon felt substrate. more...

Cobalt ferrite nanoparticles (20 nm) were synthesized and electrophoretically deposited onto aluminum foil, graphite paper, and carbon felt in order to study its potential as a cost-effective electrocatalyst for the oxidation of ammonium sulfite to ammonium sulfate in a proposed sulfur ammonia thermochemical cycle. Scanning electron microscopy and linear sweep voltammetry were used to characterize the deposited films and investigate their electrochemical activity. Furthermore, the effects of electrophoretic deposition conditions on deposit morphology and subsequently the effects of deposit morphology on electrochemical activity in 2 M ammonium sulfite were studied to better understand how to improve electrocatalysts. It was found that there is a critical deposit thickness for each substrate, where additional deposited particles reduce overall electrocatalytic activity of the deposits. For graphite paper, this thickness was estimated to be 3 particle layers for the EPD conditions studied. The 3 particle layer film on graphite paper resulted in a 5.5 fold increase in current density from a blank graphite paper substrate. For carbon felt, the deposit thickness threshold was calculated to be 0.13 of a particle layer for the EPD conditions studied. Moreover, this film was found to have a 4.3 fold increase in current density from a blank carbon felt substrate. more...

Oriented attachment has created a great debate about the description of crystal growth throughout the last decade. This aggregationbased model has successfully described biomineralization processes as well as forms of inorganic crystal growth, which could not be explained by classical crystal growth theory. Understanding the nanoparticle growth is essential since physical properties, such as the magnetic behavior, are highly dependent on the microstructure, morphology and composition of the inorganic crystals. In this work, the underlying nanoparticle growth of cobalt ferrite nanoparticles in a bioinspired synthesis was studied. Bioinspired syntheses have sparked great interest in recent years due to their ability to influence and alter inorganic crystal growth and therefore tailor properties of nanoparticles. In this synthesis, a short synthetic version of the protein MMS6, involved in nanoparticle formation within magnetotactic bacteria, was used to alter the growth of cobalt ferrite. We demonstrate that the bioinspired nanoparticle growth can be described by the oriented attachment model. The intermediate stages proposed in the theoretical model, including primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron diffraction measurements. The change of particle diameter with time agrees with the recently proposed kinetic model for oriented attachment. © 2014 Wolff et al. more...

Nanoparticle syntheses utilizing biomimetic approaches have advanced in recent years. Polypeptides, with their ability to influence inorganic crystal growth, are a topic of great interest. Their effect on the particle formation has not been completely understood yet. Here we report a bioinspired synthesis of cobalt ferrite nanoparticles carried out in vitro under mild conditions using a short, synthetic polypeptide c25-mms6. The influence of c25-mms6 on the nanoparticle formation was investigated by comparing the particles synthesized with the polypeptide to particles synthesized under equivalent conditions without c25-mms6. A separation into D small,av = 10 nm small, superparamagnetic spheres and D big,av = 48 nm disc-like single-domain particles was observed. Non-stoichiometric cobalt ferrite particles with a shape-dependent stoichiometry were produced in the polypeptide-free synthesis. Stoichiometric D small,av = 10 nm CoFe 2O 4 spheres and D big,av = 60-70 nm Co 2FeO 4 ferromagnetic discs were obtained in the polypeptide-enhanced synthesis. The results indicate that the polypeptide acts as a catalyst during the multistep biomineralization process and allows the formation of stoichiometric phases which cannot be synthesized at room temperature using conventional bottom-up syntheses. © Springer Science+Business Media B.V. 2012. more...

The relationship between the structure and composition with the magnetic properties of near stoichiometric cobalt ferrite nanoparticles CoxFe3-xO4+delta (0.85 < x < 1.1) prepared in large batches with average sizes in the range 60-210 nm has been investigated. Chemical analysis and Rietveld refinement of the X-ray diffraction data in conjunction with Mossbauer spectroscopy allowed us to identify an interplay between particle size, microstructure (concentration of interstitial ions, microstrain, cation arrangement in octahedral and tetrahedral sites), and composition, which sensitively controls the magnetic properties such as coercivity and saturation magnetization. In all cases, cobalt-rich compositions resulted in a higher coercivity, whereas lower degrees of inversion and higher iron contents led to slightly higher saturation magnetization values., QC 20100811 more...