Defect-Engineering by Solvent Mediated Mild Oxidation as a Tool to Induce Exchange Bias in Metal Doped Ferrites.

The crystal site occupancy of different divalent ions and the induction of lattice defects represent an additional tool for modifying the intrinsic magnetic properties of spinel ferrites nanoparticles. Here, the relevance of the lattice defects is demonstrated in the appearance of exchange-bias and in the improvement of the magnetic properties of doped ferrites of 20 nm, obtained from the mild oxidation of core@shell (wüstite@ferrite) nanoparticles. Three types of nanoparticles (Fe0.95 O@Fe3 O4 , Co0.3 Fe0.7 O@Co0.8 Fe2.2 O4 and Ni0.17 Co0.21 Fe0.62 O@Ni0.4 Co0.3 Fe2.3 O4 ) are oxidized. As a result, the core@shell morphology is removed and transformed in a spinel-like nanoparticle, through a topotactic transformation. This study shows that most of the induced defects in these nanoparticles and their magnetic properties are driven by the inability of the Co(II) ions at the octahedral sites to migrate to tetrahedral sites, at the chosen mild oxidation temperature. In addition, the appearance of crystal defects and antiphase boundaries improves the magnetic properties of the starting compounds and leads to the appearance of exchange bias at room temperature. These results highlight the validity of the proposed method to impose novel magnetic characteristics in the technologically relevant class of nanomaterials such as spinel ferrites, expanding their potential exploitation in several application fields.

Spin-to-Charge Conversion in All-Oxide La2/3Sr1/3MnO3/SrIrO3 Heterostructures.

Spin injection and spin-charge conversion processes in all-oxide La2/3Sr1/3MnO3/SrIrO3 (LSMO/SIO) heterostructures with different SIO layer thickness and interfacial features have been studied. Ferromagnetic resonance (FMR) technique has been used to generate pure spin currents by spin pumping (SP) in ferromagnetic (FM) half-metallic LSMO. The change of the resonance linewidth in bare LSMO layers and LSMO/SIO heterostructures suggests a successful spin injection into the SIO layers. However, low values of the spin mixing conductance, compared to more traditional permalloy (Py)/Pt or yttrium iron garnet (YIG)/Pt systems, are found. A thorough analysis of the interfaces by high-resolution scanning transmission electron microscopy (HR-STEM) imaging suggests that they are structurally clean and atomic sharp, but a compositional analysis by energy-dispersive X-ray spectroscopy (EDS) reveals the interdiffusion of La, Ir, and Mn atomic species in the first atomic layers close to the interface. Inverse spin Hall effect (ISHE) measurements evidence that interfacial features play a very relevant role in controlling the effectiveness of the spin injection process and low transversal ISHE voltage signals are detected. In addition, it is found that larger voltage signals are detected for the lowest SIO layer thickness highlighting the role of the spin diffusion length (λsd)/SIO layer thickness ratio. The values of ISHE voltage are rather low but allow us to determine the spin Hall angle of SIO (θSH ≈ 1.12% at T = 250 K), which is remarkably similar to that obtained for the well-known Py/Pt system, therefore suggesting that SIO could be a promising spin-Hall material.

Usefulness of Ultrasound in Assessing the Impact of Bariatric Surgery on Body Composition: a Pilot Study.

BACKGROUND: Bariatric surgery (BS) has a significant impact on body composition. The purpose of the study is to evaluate the usefulness of musculoskeletal ultrasound (MUS) to bioelectrical impedance (BIA) in the follow-up of patients undergoing BS in terms of body composition and quality of life (QoL). METHODS: This is a prospective pilot study including 32 subjects (75% female, mean age: 49.15 ± 1.9 years) who underwent BS. Fat mass (FM), lean mass (LM), and skeletal muscle index (SMI) were calculated by BIA. MUS measured subcutaneous fat (SF) and thigh muscle thickness (TMT) of the quadriceps. QoL was assessed by the Moorehead-Ardelt questionnaire. All these measurements were performed 1 month prior to BS and at 12-month follow-up. RESULTS: The mean BMI decreased by 6.63 ± 1.25 kg/m2 (p=0.001). We observed significant reductions in FM (p=0.001) and SF (p=0.007) and in LM (p=0.001) but not in SMI and TMT. We found a correlation between the FM and SF (pre-surgical, r=0.42, p=0.01; post-surgical, r=0.52, p=0.003) and between SMI and TMT (pre-surgical, r=0.35, p=0.04; post-surgical, r=0.38, p=0.03). QoL test showed significant improvement (p=0.001). In addition, a correlation between the QoL questionnaire and TMT post-surgery (r=0.91, p=0.019) was observed. However, we did not find any statistically significant correlation between QoL assessment and SMI or LM. CONCLUSIONS: Our results suggest that MUS can be complementary to BIA for the evaluation and the follow-up of body composition after BS. TMT of quadriceps can provide relevant information about regional sarcopenia and has a significant correlation with QoL.

Impact of gingivitis on oral health-related quality of life in 12-year-old schoolchildren of Quito, Ecuador.

PURPOSE: Evaluate the impact of gingivitis on oral health-related quality of life (OHRQoL) amongst 12-year-old schoolchildren from Quito, Ecuador. METHODS: We evaluated 998 school children using the Community Periodontal Index for gingival bleeding and calculus. OHRQoL was assessed with the Child Perceptions Questionnaire 11-14 (CPQ11-14) questionnaire. RESULTS: Of the 998 schoolchildren, 93% had gingival bleeding and 73% had dental calculus. Schoolchildren with more than one sextant with gingival bleeding had 1.18 times higher mean CPQ11-14 (RR 1.18, 95% CI 1.11-1.27) than those with none or just one affected sextant. Male schoolchildren presented a 15% lower mean Child Perceptions Questionnaire (CPQ) (RT 0.85; 95% CI 0.76-0.96). Children whose parents had incomplete secondary education had a 15% lower mean CPQ (RT 0.85; 95% CI 0.77-0.94). Bleeding in more than one sextant was significantly associated with worse quality of life in the emotional well-being (RT 1.40, 95% CI 1.03-1.90) and social well-being domains (RT 1.76, 95% CI 1.32-2.34). CONCLUSION: Gingival bleeding negatively impacted the OHRQoL of 12-year-old Ecuadorian schoolchildren living in Quito.

Spin Glass State in Strained La2/3Ca1/3MnO3 Thin Films.

Epitaxial strain modifies the physical properties of thin films deposited on single-crystal substrates. In a previous work, we demonstrated that in the case of La2/3Ca1/3MnO3 thin films the strain induced by the substrate can produce the segregation of a non-ferromagnetic layer (NFL) at the top surface of ferromagnetic epitaxial La2/3Ca1/3MnO3 for a critical value of the tetragonality τ, defined as τ = |c - a|a, of τC ≈ 0.024. Although preliminary analysis suggested its antiferromagnetic nature, to date a complete characterization of the magnetic state of such an NFL has not been performed. Here, we present a comprehensive magnetic characterization of the strain-induced segregated NFL. The field-cooled magnetic hysteresis loops exhibit an exchange bias mechanism below T ≈ 80 K, which is well below the Curie temperature of the ferromagnetic La2/3Ca1/3MnO3 layer. The exchange bias and coercive fields decay exponentially with temperature, which is commonly accepted to describe spin-glass (SG) behavior. The signatures of slow dynamics were confirmed by slow spin relaxation over a wide temperature regime. Low-energy muon spectroscopy experiments directly evidence the slowing down of the magnetic moments below ~100 K in the NFL. The experimental results indicate the SG nature of the NFL. This SG state can be understood within the context of the competing ferromagnetic and antiferromagnetic interactions of similar energies.

Can we correct first metatarsal rotation and sesamoid position with the 3D Lapidus procedure?

OBJECTIVE: We examine the technique and radiographic outcomes obtained with triplanar first tarsometatarsal arthrodesis (3D Lapidus) for the surgical correction of hallux valgus (HV). This procedure, apart from correcting angular deformity 1st-2nd intermetatarsal angle, HV angle, etc., is specifically intended to act on first ray pronation and place the sesamoids in their normal position, to alleviate the metatarsalgia often occurring in HV before and after surgery, possibly caused by their abnormal position. This study aims to examine the radiographic outcomes of the 3D Lapidus procedure. MATERIALS AND METHODS: Retrospective study of 37 feet operated on from April 2019 to December 2019, with a minimum 1-year follow-up (mean 420 days), using the 3D Lapidus procedure. Radiographic outcomes were evaluated. RESULTS: The intermetatarsal angle decreased from a mean value of 16.42° to 5.62° (p < 0.0001). The HV angle decreased from a mean value of 32.12° to 8.05° (p < 0.0001). The preoperative first metatarsocuneiform angle, with a mean value of 21.86°, was null after arthrodesis (p < 0.0001). The tibial sesamoid position, according to the Hardy and Clapham classification, decreased from a mean value of 4.84 to 1.27 after surgery, within normality (p < 0.0001). DISCUSSION: Correction of the deformity in a single plane is generally insufficient. It is necessary to act on the three planes of space to correct the deformity, obtain good outcomes, and avoid recurrence. CONCLUSIONS: Radiographic outcomes of triplanar correction with the 3D Lapidus procedure are excellent, achieving statistically significant differences in all parameters studied.

Strong Crystallographic Influence on Spin Hall Mechanism in PLD-Grown IrO2 Thin Films.

Spin-to-charge conversion is a central process in the emerging field of spintronics. One of its main applications is the electrical detection of spin currents, and for this, the inverse spin Hall effect (ISHE) has become one of the preferred methods. We studied the thickness dependence of the ISHE in iridium oxide (IrO2) thin films, producing spin currents by means of the spin Seebeck effect in γ-Fe2O3/IrO2 bilayers prepared by pulsed laser deposition (PLD). The observed ISHE charge current density, which features a maximum as a consequence of the spin diffusion length scale, follows the typical behaviour of spin-Hall-related phenomena. By fitting to the theory developed by Castel et al., we find that the spin Hall angle θSH scales proportionally to the thin film resistivity, θSH∝ρc, and obtains a value for the spin diffusion length λIrO2 of λIrO2=3.3(7) nm. In addition, we observe a negative θSH for every studied thickness and temperature, unlike previously reported works, which brings the possibility of tuning the desired functionality of high-resistance spin-Hall-based devices. We attribute this behaviour to the textured growth of the sample in the context of a highly anisotropic value of the spin Hall conductivity in this material.

Producción de sueros y vacunas en Chile, la importancia del abastecimiento local / Production of vaccines in Chile, the importance of local supply

Resumen En Chile, se produjeron vacunas desde fines del siglo XIX hasta inicios del siglo XXI de manera ininterrumpida. La producción se realizó en institutos del Estado, desde donde se abastecía al Servicio de Salud para los programas de vacunación. Además de fabricar, envasar y distribuir vacunas, los institutos del Estado, en particular el Instituto Bacteriológico (IB), exportaron vacunas a Latinoamérica y realizaron investigación y desarrollo, destacándose en este ámbito con la vacuna Fuenzalida-Palacios para el control de la rabia humana y canina. El presente estudio provee un listado de vacunas producidas en Chile en los institutos del Estado entre fines del siglo XIX y el año 2005, y una discusión sobre las visiones del rol de Estado que justificaron las acciones respecto de la producción de vacunas en Chile. El Estado desarrollista de mediados del siglo XX, dio paso al Estado neoliberal que se institucionalizó con la constitución de 1980 definiendo el rol subsidiario que ha guiado la discusión en materia de producción de vacunas locales en las últimas décadas.

Abstract In Chile, vaccines were produced from the late 19th century to the early 21st century without interruption. The production was carried out in State institutes, from where the health service was supplied for the vaccination programs. In addition to manufacturing, packaging and distributing vaccines, the State institutes, in particular the Instituto Bacteriológico (IB), exported vaccines to Latin America and carried out research and development, standing out in this area with the Fuenzalida-Palacios vaccine for the control of human and canine rabies. The present study provides a list of vaccines produced in Chile at State institutes between the end of the 19th century and 2005, and a discussion on the visions of the State role that justified the actions regarding the production of vaccines in Chile. The developmental State of the mid-twentieth century gave way to the neoliberal State that was institutionalized with the 1980 constitution, which defines the subsidiary role of the State that has guided the discussion on local vaccine production in the last decades.

Propuesta de un modelo difuso para determinar sobrepeso y obesidad en niños y adolescentes / A proposed diffuse model to determine overweight and obesity in children and adolescents

RESUMEN México se encuentra entre los países con mayor prevalencia de sobrepeso y obesidad entre los niños y adolescentes. Por tanto, surge la necesidad de una técnica económica, rápida, reproducible y de fácil implementación que permita detectar tempranamente en el ámbito escolar el sobrepeso y la obesidad en niños y adolescentes. En este trabajo se presenta una técnica que cumple con esas expectativas basada en un modelo de inferencia difuso con un conjunto de 81 reglas para la clasificación de la composición corporal de 92 niñas y 88 niños entre las edades de 10 y 14 años. Como atributos se tomaron, el peso, el índice de masa corporal, el porciento de masa grasa y el porciento de peso habitual. Para cada atributo se definieron tres conjuntos difusos, normal, sobrepeso y obeso y para clasificar el valor del atributo se usaron las referencias que más se utilizan en la literatura y por los nutriólogos y pediatras de la zona de estudio. Como resultado de la aplicación del modelo difuso, se obtuvo una precisión promedio de 97,6% con un 4,2% de error para la clasificación corporal de las niñas y de 93,4% con un 4,6% de error para niños.

ABSTRACT Mexico is among the countries with the highest prevalence of overweight and obesity among children and adolescents. Therefore, an economical, rapid, reproducible and easy to implement technique that allows early detection in the school environment of overweight and obesity in children and adolescents is need. This paper presents a technique that meets these expectations based on a diffuse inference model with a set of 81 rules for the classification of body composition among 92 girls and 88 boys between the ages of 10 and 14 years. Weight, body mass index, fat mass percentage and the percentage of habitual weight were taken as attributes. For each attribute three diffuse sets were defined: normal, overweight and obese. To classify the value of the attribute, the most used references in the literature and those used by consulted nutritionists and pediatricians were used. As a result of the application of the diffuse model, an average accuracy of 97.6% was obtained with a 4.2% error for the corporal classification of girls and 93.4% with a 4.6% error for boys.

Unraveling the mechanism of the one-pot synthesis of exchange coupled Co-based nano-heterostructures with a high energy product.

The development of reproducible protocols to synthesize hard/soft nano-heterostructures (NHSs) with tailored magnetic properties is a crucial step to define their potential application in a variety of technological areas. Thermal decomposition has proved to be an effective tool to prepare such systems, but it has been scarcely used so far for the synthesis of Co-based metal/ferrite NHSs, despite their intriguing physical properties. We found a new approach to prepare this kind of nanomaterial based on a simple one-pot thermal decomposition reaction of metal-oleate precursors in the high boiling solvent docosane. The obtained NHSs are characterized by the coexistence of Co metal and Co doped magnetite and are highly stable in an air atmosphere, thanks to the passivation of the metal with a very thin oxide layer. The investigation of the influence of the metal precursor composition (a mixed iron-cobalt oleate), of the ligands (oleic acid and sodium oleate) and of the reaction time on the chemical and structural characteristics of the final product, allowed us to rationalize the reaction pathway and to determine the role of each parameter. In particular, the use of sodium oleate is crucial to obtain a metal phase in the NHSs. In such a way, the one-pot approach proposed here allows the fine control of the synthesis, leading to the formation of stable, high performant, metal/ferrite NHSs with tailored magnetic properties. For instance, the room temperature maximum energy product was increased up to 19 kJ m-3 by tuning the Co content in the metal precursor.

[Production of vaccines in Chile, the importance of local supply]. / Producción de sueros y vacunas en Chile, la importancia del abastecimiento local.

In Chile, vaccines were produced from the late 19th century to the early 21st century without interruption. The production was carried out in State institutes, from where the health service was supplied for the vaccination programs. In addition to manufacturing, packaging and distributing vaccines, the State institutes, in particular the Instituto Bacteriológico (IB), exported vaccines to Latin America and carried out research and development, standing out in this area with the Fuenzalida-Palacios vaccine for the control of human and canine rabies. The present study provides a list of vaccines produced in Chile at State institutes between the end of the 19th century and 2005, and a discussion on the visions of the State role that justified the actions regarding the production of vaccines in Chile. The developmental State of the mid-twentieth century gave way to the neoliberal State that was institutionalized with the 1980 constitution, which defines the subsidiary role of the State that has guided the discussion on local vaccine production in the last decades.

Real space manifestations of coherent screening in atomic scale Kondo lattices.

The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation. Scanning tunneling spectroscopy is used to obtain maps of the Kondo resonance intensity with sub-atomic resolution. For sufficiently small interatomic separation, the spatial distribution of Kondo screening does not coincide with the position of the adatoms. It also develops enhancements at both edges of the chains. Since we can rule out any other interaction between Kondo impurities, this is explained in terms of the indirect hybridization of the Kondo orbitals mediated by a coherent electron gas, the mechanism that causes the emergence of heavy quasiparticles in the thermodynamic limit.

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 (CoFe2O4) 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.

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 = 3.9 ± 0.2 nm attached to Fe3O4 nanoparticle cores ( = 49.2 ± 3.5 nm) in aqueous medium for potential application as a nano-heater. Remarkably, the resulted Au decorated PEI-Fe3O4 (Au@PEI-Fe3O4) nanoparticles are able to retain bulk magnetic moment MS = 82-84 Am2/kgFe3O4, with the Verwey transition observed at TV = 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 (H0 = 23.87 kA/m; f = 571 kHz) yielded specific power absorption (SPA) values of SPA = 43 ± 3 and 49 ± 1 µW/cell for PEI-Fe3O4 and Au@PEI-Fe3O4 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.

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 Fe3O4/ZnxCo1-xFe2O4 nanoparticles. The core-shell structure constitutes a magnetically-coupled biphase system, with an effective anisotropy that can be tuned by the substitution of Co2+ by Zn2+ 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.

Subcutaneous adipose tissue therapy reduces fat by dual X-ray absorptiometry scan and improves tissue structure by ultrasound in women with lipoedema and Dercum disease.

Lipoedema is painful nodular subcutaneous adipose tissue (SAT) on legs and arms of women sparing the trunk. People with Dercum disease (DD) have painful SAT masses. Lipoedema and DD fat resists loss by diet and exercise. Treatments other than surgery are needed. Six women with lipoedema and one with DD underwent twelve 90-min sessions over 4 weeks. Body composition by dual X-ray absorptiometry scan, leg volume, weight, pain, bioimpedance, tissue size by caliper and ultrasound were analysed before and after SAT therapy by paired t-tests. There was a significant decrease from baseline to end of treatment in weight, 87.6 ± 21 to 86.1 ± 20.5 kg (P = 0.03), leg fat mass 17.8 ± 7.7 to 17.4 ± 7.6 kg (P = 0.008), total leg volume 12.9 ± 4 to 12 ± 3.5 L (P = 0.007), six of 20 calliper sites and tissue oedema. Pain scores did not change significantly. By ultrasound, six women had 22 hyperechoic masses in leg fat that resolved after treatment; five women developed seven new masses. Fascia improved by ultrasound after treatment. SAT therapy reduced amount and structure of fat in women with lipoedema and Dercum disease; studies are needed to compare SAT therapy to other therapies.

Recuperación de tradiciones reformistas en Argentina: Risieri Frondizi, "valores" y "contexto situacional" / Recovery of reformist traditions in Argentina: Risieri Frondizi, \"values\" and \"situational context"

La figura del Profesor de Filosofía Risieri Frondizi, egresado del Instituto del Profesorado Secundario en 1935 representa el contrapunto entre la tradición de una filosofía que rozaba lo psicológico y de una psicología que abrevaba en conceptos filosóficos. El presente artículo indaga sobre la recuperación de las tradiciones discursivas del reformismo en Argentina a través de la figura de Risieri Frondizi a partir del planteo que realiza el autor de los conceptos de "valor" y "contexto situacional". La indagación muestra que los referentes teóricos utilizados por el autor le permitieron releer el relativismo del valor afectivo acuñado por Alejandro Korn por "contexto situacional" y de este modo resolver el viejo problema de los valores: ya no serán entes trascendentales, inmanentes o innatos que excluían al sujeto. El valor se construye ahora a partir de una relación dialéctica de aspectos subjetivos y objetivos en un contexto situacional determinado.

The figure of Professor of Philosophy Risieri Frondizi, graduated from the Institute of Secondary Teachers in 1935 represents the counterpoint between the tradition of a philosophy that touched the psychological and a psychology that emptied into philosophical concepts. This article explores the recovery of the discursive traditions of reformism in Argentina through the figure of Risieri Frondizi based on the author\'s approach to the concepts of \"value\" and \"situational context\". The investigation shows that the theoretical referents used by the author allowed him to reread the relativism of the affective value coined by Alejandro Korn for \"situational context\" and in this way to solve the old problem of values: they will no longer be transcendental, immanent or innate entities that they excluded the subject. The value is now constructed from a dialectical relationship of subjective and objective aspects in a given situational context.

Microencapsulation of Eugenia uniflora L. juice by spray drying using fructans with different degrees of polymerisation.

The objective of this work was to microencapsulate pitanga (Eugenia uniflora L.) juice by spray drying, using High Performance Agave Fructans (HPAF) and High Degree of Polymerisation Agave Fructans (HDPAF) and maltodextrin (MD), respectively, as the wall materials. The physicochemical and antioxidant properties of the capsules during storage at various temperatures were evaluated. The microparticles developed using fructans HPAF and HDPAF, exhibited similar physicochemical and flow properties to those presented by the microparticles prepared with MD. The highest yield and concentration of anthocyanins after drying and during storage were found for a 1:6 core:wall material ratio. The total color change was a good indicator of the microcapsule stability. This study showed that both fructans fraction possess similar encapsulating properties to MD and that the HDPAF were more efficacious than MD at protecting the antioxidants during drying and storage.

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.