Effect of La0.8Sr0.2MnO3 powder addition in the precursor solution on the properties of cathode films deposited by spray pyrolysis

Films of lanthanum strontium manganite, LSM (La0.8Sr0.2MnO3) were deposited on yttria stabilized zirconia(YSZ) substrates by different methods aiming to establish the most suitable route to prepare cathodes forsolid oxide fuel cells (SOFC). Samples were obtained by using a solution of lanthanum, strontium andmanganese nitrates or a dispersion of the LSM powder in this solution. Both commercial and synthetizedLSM powders were used, the last one obtained by amorphous citrate method. The films were deposited byspray pyrolysis on YSZ substrates prepared by uniaxial and isostatic pressing. Samples were characterized byscanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction and two-probeconductivity measurements. The area specific resistance and relaxation to cathodic activation were measuredby electrochemical impedance spectroscopy. The substrate obtained by uniaxial pressing and the commercialLSM produced films with the highest amount of surface cracks. The film obtained from the suspensionshowed area specific resistance and activation energy lower than the other produced from the solution. Forboth samples, the cathodic activation process resulted in an initial reduction of the total resistance of around20%, the sample produced from the suspension being more resistant to relaxation. Therefore, the LSMsuspension is more suitable than the salts solution for preparing films by spray pyrolysis on YSZ substrates toobtain efficient cathodes for SOFC

Heating Capacity and Biocompatibility of Hybrid Nanoparticles for Magnetic Hyperthermia Treatment

Cancer is one of the deadliest diseases worldwide and has been responsible for millions of deaths. However, developing a satisfactory smart multifunctional material combining different strategies to kill cancer cells poses a challenge. This work aims at filling this gap by developing a composite material for cancer treatment through hyperthermia and drug release. With this purpose, magnetic nanoparticles were coated with a polymer matrix consisting of poly (L-co-D,L lactic acid-co-trimethylene carbonate) and a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer. High-resolution transmission electron microscopy and selected area electron diffraction confirmed magnetite to be the only iron oxide in the sample. Cytotoxicity and heat release assays on the hybrid nanoparticles were performed here for the first time. The heat induction results indicate that these new magnetic hybrid nanoparticles are capable of increasing the temperature by more than 5 °C, the minimal temperature rise required for being effectively used in hyperthermia treatments. The biocompatibility assays conducted under different concentrations, in the presence and in the absence of an external alternating current magnetic field, did not reveal any cytotoxicity. Therefore, the overall results indicate that the investigated hybrid nanoparticles have a great potential to be used as carrier systems for cancer treatment by hyperthermia

Cerâmicas bioativas: estado da arte Bioactive ceramics: state of the arts

<abstract language="eng">Bioactive glasses undergo corrosion with leaching of alkaline ions when exposed to body fluids. This results in the spontaneous formation of a layer of hydroxyapatite (HA), the mineral component of natural bone, which in turn can induce bone growth in vivo. This paper describes the different types of bioactive glasses, the characterization methods currently used, and the main factors that influence their bioactivity. Nucleation and crystallization, the main mechanisms involved in the formation of hydroxyapatite, Ca10(PO4)6(OH)2, are discussed as a function of the chemical composition and the reactivity of the surface of the material. Finally, promising applications are considered

Zeta potential measurement in bioactive collagen

The focus of this work is to show the influence of surface charge on the bioactivity of modified collagen fiber surface. Because silica plays an important role on bone mineralization process, silica obtained by a sol-gel process was used as a surface modification agent. Zeta potential (xi) of silica-coated and non-coated samples was measured as a function of pH. It was observed a shift in xi vs. pH. The isoelectric point for silica-coated collagen was 6.8, while that of non-treated sample it was near 10. Pure silica has isoelectric point near 2, and the shift observed indicates that at least part of the silica was incorporated onto the surface during the treatment. The ability of samples exposed to biological simulated fluids (SBF) to form a hydroxyapatite layer has been used to recognize bioactive materials. The pH of these biological solutions is about 7.3. It means that treated samples acquire negative charge when in contact with the biological solution and attract ions like Ca2+, HPO4(2-), and OH- to form HA coatings. Micrographs of chemically treated samples corroborate this assumption. For treated samples, the formation of a coating layer is clear after 5-day immersion in SBF, while pure collagen remains practically unaltered. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P-O vibration bands near 1060 cm-1 and 600 cm-1 characteristic of hydroxyapatite (HA)

Preparation of composite with silica-coated nanoparticles of iron oxide spinels for applications based on magnetically induced hyperthermia.

It is reported a novel method to prepare magnetic core (iron oxide spinels)–shell (silica) composites containing well-dispersed magnetic nanoparticles in aqueous solution. The synthetic process consists of two steps. In a first step, iron oxide nanoparticles obtained through co-precipitation are dispersed in an aqueous solution containing tetramethylammonium hydroxide; in a second step, particles of this sample are coated with silica, through hydrolyzation of tetraethyl orthosilicate. The intrinsic atomic structure and essential properties of the core–shell system were assessed with powder X-ray diffraction, Fourier transform infrared spectrometry, Mössbauer spectroscopy and transmission electron microscopy. The heat released by this ferrofluid under an AC-generated magnetic field was evaluated by following the temperature evolution under increasingmagnetic field strengths.Results strongly indicate that this ferrofluid based on silica-coated iron oxide spinels is technologically a very promising material to be used in medical practices, in oncology

José Luis Rivas, Premio Nacional de Ciencias y Artes 2009

This work aimed at putting in evidence the influence of the pH on the chemical nature and properties of the synthesized magnetic nanocomposites. Saturation magnetization measurements evidenced a marked difference of the magnetic behavior of samples, depending on the final pH of the solution after reaction. Magnetite and maghemite in different proportions were the main magnetic iron oxides actually identified. Synthesis with final pH between 9.7-10.6 produced nearly pure magnetite with little or no other associated iron oxide. Under other synthetic conditions, goethite also appears in proportions that depended upon the pH of the synthesis medium