A biomimetic method was used to promote bioactivity of ZrTiO4. Zirconium titanate was obtained by using a combination of techniques such as mechanical milling and heat treatment of zirconia and titania powders. The effect of milling time on the evolution of the ZrTiO4 phase formation was studied. Powders were uniaxially pressed followed by heat treatment for 6 h at different temperatures within the range between 700 and 1500 ºC. Single phase ZrTiO4 was obtained after ball-milling for 30 h followed heat treating in air at 1500 ºC for 6 h. For the biomimetic coatings were obtained by immersion of the samples in a simulated body fluid (SBF) for 7, 14 and 21 days on a bed of wollastonite powder, and were characterized by SEM, EDS, XRD, FT-IR and TEM. For comparison purposes, experiments were also performed without using the bioactive powder bed. A bone-like apatite layer was formed on zirconium titanate after 21 days of immersion in SBF using a bed of wollastonite powder.

ABSTRACT Nowadays, iron oxide based magnetic nanoparticles are used in several science and technology applications due to their magnetic properties. Likewise, these materials are used in biomedical applications such as contrast agents for magnetic resonance imaging, magnetic hyperthermia, targeted drug delivery, etc. In this work, the synthesis and characterization of Mg, Zn-containing ferrites with the chemical formula of Mg1-xZnxFe2O4 (0-0,9) were performed. Synthesis was carried out by thermal decomposition method (DT) using metal acetylacetonates (Mg, Zn and Fe) as reactants and oleic acid/phenyl-ether as reaction medium. The obtaining materials were characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The X-ray diffraction patterns of the materials obtained exhibited the formation a single crystalline phase with an inverse spinel structure that corresponds to a magnesium ferrite (JCPDS 88-1935). Magnetic properties of obtained ferrites, such as saturation magnetization (Ms), remanent magnetization (Mr) and coercive field (Hc) were also evaluated by VSM. Ms increased as Zn2+ content was increased, reaching values within 20,22 to 40,03 emu/g, this increase was attributed to the variation of the cations distribution in the spinel structure. FT-IR and TEM results demonstrated that the synthesized nanoparticles have an oleic acid coating, an average size below 10 nm and morphology close to the spherical. According to these results it is possible to incorporate Zn2+ into a crystalline structure of MgFe2O4, by this particular DT method, obtaining ferrites potentially viable for biomedical applications.

RESUMEN Actualmente las nanopartículas magnéticas a base de óxido de hierro son utilizadas en diversas aplicaciones en las áreas de ciencia y tecnología, principalmente por sus propiedades magnéticas. Asimismo, estos materiales son utilizados en aplicaciones biomédicas tales como en la obtención de imágenes por resonancia magnética, hipertermia magnética, liberación de fármacos, etc. En este trabajo se reporta la síntesis y caracterización de ferritas de Mg y Zn con composición química Mg1-xZnxFe2O4 (x=0-0,9) mediante el método de descomposición térmica (DT). Se utilizaron acetilacetonatos metálicos (Mg, Zn y Fe) como reactivos y ácido oleico/feniléter como medio de reacción. Los materiales obtenidos se caracterizaron utilizando las técnicas de difracción de rayos X (DRX), magnetometría de muestra vibrante (MMV), espectroscopia de infrarrojo por transformada de Fourier (FT-IR) y microscopía electrónica de transmisión (MET). Los patrones de difracción de rayos X de los materiales obtenidos muestran la formación de una única fase cristalina con estructura de espinela inversa correspondiente a una ferrita de magnesio (JCPDS 88-1935). Las propiedades magnéticas, tales como magnetización de saturación (Ms), magnetización remanente (Mr) y campo coercitivo (Hc) de las ferritas Mg-Zn fueron evaluadas mediante MMV. Se encontró que la Ms aumenta a medida que se incrementa el contenido de Zn2+ alcanzando valores de 20,22 a 40,30 emu/g, dicho cambio se atribuye a la variación de la distribución de los cationes presentes en la estructura de espinela. Mediante FT-IR y MET se determinó que las partículas sintetizadas poseen un recubrimiento superficial de ácido oleico, una morfología cercana a la esférica y un tamaño de partícula inferior a los 10 nm. De estos resultados se confirma la viabilidad de la incorporación de iones Zn dentro de la estructura cristalina de MgFe2O4 utilizando el método de DT, obteniéndose ferritas potencialmente utilizables en aéreas biomédicas.

ABSTRACT In this work, the synthesis of MgxGa1-xFe2O4 magnetic nanoparticles (MNPs) by sol-gel method is presented. All synthesized samples were identified as a crystalline single phase and the saturation magnetization (Ms) values are within the range of 21,2 to 46,4 emu/g, while coercive field values are less than 100 Oe. The selected samples (x= 0,4 and 0,6) have an average particle size of 14 ± 4 nm, a near spherical shape and by solid state magnetic induction it was possible to demonstrate that a quantity of 6,0 mg of nanoparticles per mL of solution is enough to increase the temperature of the medium (H2O) up to 43,5 °C in less than 10 min. According to the presented results these synthesized nanoparticles are potential materials for their use in cancer treatment by magnetic hyperthermia therapy.

RESUMEN En este trabajo se documenta la síntesis de nanopartículas magnéticas (NPMs) de MnxGa1-xFe2O4, x=0,1 por el método de sol-gel identificando, para cada una de las muestras sintetizadas, la obtención de una única fase cristalina, valores de magnetización de saturación en el rango de 21,2 a 46,4 emu/g y valores de Hc menores a los 100 Oe. Las muestras seleccionadas (x= 0,4 y 0,6) poseen un tamaño promedio de 14 ± 4 nm y una forma cercana a la esférica y mediante la técnica de inducción magnética en estado sólido se encontró que una cantidad de 6,0 mg de nanopartículas por mL de solución es suficiente para incrementar la temperatura del medio (H2O) por encima de los 43,5 °C en un tiempo menor a los 10 min, haciendo a estos materiales potencialmente viables para su uso en el tratamiento del cáncer mediante la terapia de hipertermia magnética.

El cáncer es la segunda causa de muerte en el mundo. El tratamiento alternativo de hipertermia magnética consiste en elevar la temperatura de las células cancerígenas por medio de nanopartículas magnéticas. En este trabajo se presenta la síntesis y la caracterización de dos ferritas de zinc-calcio (Zn0.50Ca0.50Fe2O4 y Zn0.25Ca0.75Fe2O4). La síntesis de estas ferritas se llevó a cabo por el método de sol-gel, con posterior calcinación a 400 °C. La ferrita Zn0.50Ca0.50Fe2O4 (ZCF050) presentó una magnetización de 31.31 emu/g, y la ferrita Zn0.25Ca0.75Fe2O4 (ZCF075), de 38.30 emu/g. El tamaño de partícula promedio fue de 14 nm para la ZCF050 y de 12 nm para la ZCF075. Adicionalmente, se realizaron pruebas de bioactividad in vitro mediante la inmersión de muestras en un fluido fisiológico simulado por 21 días bajo condiciones fisiológicas de pH y temperatura. Se encontró que solo la ZCF075 fue bioactiva. La habilidad de calentamiento de las ferritas se evaluó utilizando un equipo de inducción magnética en estado sólido. Las condiciones de trabajo fueron las siguientes: un campo magnético de 10.2 kA/m y una frecuencia de 362 kHz. La ferrita ZCF050 alcanzó una temperatura de 41.2 °C, utilizando una concentración de ferrita/agua de 20 mg/2ml. La ferrita ZCF075 no logró alcanzar los 40 °C. Los resultados obtenidos del análisis de la ferrita ZCF050 indicaron que es un material potencial para su uso en tratamientos de cáncer por hipertermia magnética.

Cancer is the second cause of death in the world. Magnetic hyperthermia is an alternative treatment which consists of raising the temperature of cancer cells using magnetic nanoparticles. In this work, the synthesis and characterization of two calcium-zinc ferrites (Zn0.50Ca0.50Fe2O4 y Zn0.25Fe2O4) are presented. These ferrites were synthesized by sol-gel method, afterwards they were calcined at 400 °C. The saturation magnetization values were 31.31 and 38.30 emu/g for Zn0.50Ca0.50Fe2O4 (ZCF050) and Zn0.25Ca0.75Fe2O4(ZCF075, respectively. The average particle size was 14 nm for ZCF050 and 12 nm for ZCF075. Additionally, in vitro bioactivity assessment was performed by immersing samples in simulated body fluid (SBF) for 21 days under physiological conditions of pH and temperature. Only the ZCF075 ferrite showed to be bioactive. The heating capacity of ferrites was evaluated under an appropriate magnetic field using solid state magnetic induction. The working conditions were the following: A magnetic field of 10.4 KA/m and a frequency of 362 KHz. The ZCF050 ferrite reached a temperature of 41.2 °C using a concentration of ferrite/water 20 mg/2ml. The ZCF075 ferrite failed to reach 40 °C. The results obtained in the ferrite ZCF050 indicated that these nanoparticles are potential materials for cancer treatment by magnetic hyperthermia therapy.

O câncer é a segunda causa de morte no mundo. O tratamento alternativo de hipertermia magnética consiste em elevar a temperatura das células cancerígenas por meio de nanopartículas magnéticas. Neste trabalho se apresenta a síntese e a caracterização de duas ferritas de zinco-cálcio (Zn0.50Ca0.50Fe2O4 e Zn0.25Ca0.75Fe2O4). A síntese destas ferritas realizou-se pelo método de sol-gel, com posterior calcinação a 400 °C. A ferrita Zn0.50Ca0.50Fe2O4 (ZCF050) apresentou uma magnetização de 31.31 emu/g, e a ferrita Zn0.25Ca0.75Fe2O4 (ZCF075), de 38.30 emu/g. O tamanho médio de partícula foi de 14 nm para a ZCF050 e de 12 nm para a ZCF075. Adicionalmente, se realizaram provas de bioatividade in vitro mediante a imersão de amostras em um fluido fisiológico simulado por 21 dias sob condições fisiológicas de pH e temperatura. Encontrou-se que só a ZCF075 foi bioativa. A habilidade de aquecimento das ferritas avaliou-se utilizando um equipamento de indução magnética de estado sólido. As condições de trabalho foram as seguintes: um campo magnético de 10.2 kA/m e uma frequência de 362 kHz. A ferrita ZCF050 alcançou uma temperatura de 41.2 °C, utilizando uma concentração de ferrita/água de 20 mg/2ml. A ferrita ZCF075 não logrou alcançar os 40 °C. Os resultados obtidos da análise da ferrita ZCF050 indicaram que é um material potencial para uso em tratamentos de câncer por hipertermia magnética.

Calcium sulphoaluminate cement (CSAC) is an attractive candidate for biomedical applications due to its appropriate mechanical properties and high calcium content. In vitro bioactivity and hemocompatibility of calcium sulphoaluminate cement were assessed. The cement was prepared from a mixture of calcium sulphoaluminate (CSA) clinker, gypsum and water. Cement samples were immersed in a simulated body fluid (SBF) at 37 °C for different periods of time (7, 14 and 21 days). The analyses of these samples after their immersion in SBF revealed the formation of a bonelike apatite layer on their surface. The hemolytic activity was assessed by measuring hemoglobin released from erythrocytes when they were exposed to the cement. The results showed that the cement is hemocompatible.