Si-tricalcium phosphate cement: preparation, characterization and bioactivity in SBF

There are evidences considering the effectiveness of Si on enhancing biological properties of calcium phosphates; however, there are not many works relating to the Si-alpha-TCP bone cement. The influence of silicon doping on the properties of Α-TCP cement was analyzed. Si-TCP was obtained by a solid state reaction employing CaCO3, CaHPO4 and CaSiO3 and powder was analyzed by XRD, FTIR, XRF and BET specific area. Cement samples were analyzed for their surface of fracture morphology, mechanical resistance and SBF bioactivity. Cement mechanical resistance was not satisfactory for biomedical application; nonetheless, sample's surface was coated by an apatite layer after immersion in SBF. Notwithstanding, to ensure that silicon is the element responsible for increasing the material's bioactivity it is necessary to evaluate the in vivo performance of the bone cement obtained in this work.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo (UNIFESP) Instituto de Ciência e TecnologiaUniversidade Estadual de Campinas Instituto Nacional de Ciência e Tecnologia em BiofabricaçãoConsejo Superior de Investigaciones Científicas Instituto de Cerámica y VidrioUniversidade Estadual de Campinas Faculdade de Engenharia Mecânica Faculdade de Engenharia MecânicaUNIFESP, Instituto de Ciência e TecnologiaSciEL

Preparación y caracterización de composites de hidroxiapatita deficiente en calcio y quitosana

Se obtuvieron composites de quitosana/hidroxiapatita deficiente en calcio (CHI/CDHA) por un método biomimético (nucleación de la fase inorgánica dentro de la matriz polimérica), con el objetivo de obtener un nuevo material que combine la biodegradabilidad y flexibilidad de la quitosana y la bioactividad y osteoconductividad de la hidroxiapatita con vistas a su posible empleo como sustituto óseo. Con este fin se prepararon sistemas con composiciones de CHI/CDHA: 20/80, 50/50 y 80/20. Las muestras fueron preparadas en forma de partículas y su morfología fue analizada a través de una lupa. Se observó que las partículas de menor contenido de quitosana son menos esféricas, más pequeñas e irregulares. Las fases orgánica e inorgánica de los composites obtenidos fueron identificadas mediante espectroscopia FTIR, difracción de Rayos X y análisis térmico. Los espectros FTIR de los composites mostraron las bandas de absorción características de ambos componentes, la quitosana y la hidroxiapatita. El análisis térmico evidenció la existencia de interacción entre la matriz de quitosana y el componente inorgánico. Se observó además, una correspondencia entre la relación quitosana/componente inorgánico de la mezcla de alimentación y la del composite resultante. Por su parte, el ensanchamiento observado en los picos de los difractogramas fueron indicativos del pequeño tamaño de los cristales de la hidroxiapatita formada in situ. El análisis por rayos X de los residuos de los composites calcinados a 1 000 ºC por 15 h indica que la fase inorgánica de los composites es hidroxiapatita deficiente en calcio

Papel de la autofagia en los procesos iniciales de agregación de alfa-sinucleína

La enfermedad de Parkinson (EP) es una enfermedad neurodegenerativa que afecta al 1 % de la población de más de 65 años, lo que la convierte en la segunda enfermedad neurodegenerativa con mayor prevalencia del mundo. Se caracteriza por la pérdida de las neuronas dopaminérgicas en el sistema estriado de la substancia nigra y los cuerpos de Lewy, agregados proteicos citoplasmáticos que se componen mayoritariamente de α sinucleína (aSyn), una pequeña proteína altamente cargada que se expresa principalmente en neuronas. Todavía no se conocen con exactitud las funciones de la aSyn, pero los datos sugieren que participa en las conexiones sinápticas y la regulación de la síntesis de dopamina. Numerosos estudios relacionan, además, las alteraciones en el tráfico de vesículas con la EP, especialmente las que afectan a la autofagia, un mecanismo celular de degradación de componentes citosólicos infecciosos, disfuncionales o innecesarios. En el presente trabajo se utilizan modelos celulares para estudiar el papel de la autofagia en los procesos de agregación de aSyn. Para ello se emplearon dos variantes de la línea celular HAP 1: la variante silvestre y una deficiente en una proteína, ATG5, necesaria para la formación de la membrana de los autofagosomas. Mediante transfecciones transitorias se sobreexpresaron las proteínas aSyn, tau y p62, estando estas dos últimas implicadas en el transporte axonal y la autofagia selectiva, respectivamente. Se estudió la localización subcelular de las proteínas sobreexpresadas, así como su interacción mediante microscopía de fluorescencia, cross-linking y Western Blot. Se demostró la interacción de p62 con aSyn, pero no se evidenció la interacción entre tau y aSyn ni entre tau y p62. También se demostró la relación de la autofagia con la supervivencia de las células que sobreexpresan aSyn, aunque no se pudo detallar el proceso.<br /

Perioperative antibiotic prophylaxis

La principal utilidad de la profilaxis antibiótica perioperatoria es disminuir el grado de colonización bacteriana de la herida quirúrgica. Sin embargo ésta no es sino una medida de prevención más entre otras muchas que contribuyen a evitar la infección postquirúrgica. La no existencia de un protocolo reconocido en el ámbito de la cirugía podológica ha motivado a los autores ha realizar una revisión bibliográfica de la profilaxis antibiótica con el objetivo de fomentar su buena praxis y así evitar los efectos adversos derivados de una mala utilzación. Consideramos que la práctica quirúrgica debe condicionar un mínimo conocimiento de sus indicaciones y contraindicaciones en beneficio del paciente.The main goal of antibiotic prophylaxis is to decrease the grade of bacterial colonization in the surgical wound. However this only represents one of many preventive measures that contribute to avoid a postsurgical infection. Because at present there is no recognized protocol for the use of antimicrobials within Podiatric Surgery the authors have reviewed the current literature in order to encourage an adequate praxis and so to avoid adverse effects derived from an inappropriate use. The authors believe that the performance of surgery must determine a minimum knowledge of antibiotic prophylaxis, its indications and contraindications for patient’s benefit

Synthesis, characterization, bioactivity and biocompatibility of nanostructured materials based on the wollastonite-poly(ethylmethacrylate-co-vinylpyrrolidone) system

Composite materials are very promising biomaterials for hard tissue augmentation. The approach assayed in this work involves the manufacturing of a composite made of a bioactive ceramic, natural wollastonite (W) and a nanostructured copolymer of ethylmethacrylate (EMA) and vinylpyrrolidone (VP) to yield a bioresorbable and biocompatible VP–EMA copolymer. A bulk polymerization was induced thermally at 508C, using 1 wt % azobis(isobutyronitrile) (AIBN) as free-radical initiator. Structural characterization, compressive strength, flexural strength (FS), degradation, bioactivity, and biocompatibility were evaluated in specimens with a 60/40 VP/EMA ratio and ceramic content in the range 0–60%. A good integration between phases was achieved. Greater compression and FS, in comparison with the pure copolymer specimens was obtained only when the ceramic load got up to 60% of the total weight. The soaking in NaCl solution resulted in the initial swelling of the specimens tested. The maximum swelling was reached after 2–3 h of immersion and it was significantly greater for lower ceramic loads. This result makes the polymer component the main responsible for the interactions with the media. After soaking in SBF, microdomains segregation can be observed in the polymer component that can be related with a dramatic difference in the reactivity of both monomers in free radical polymerization, whereas the formation of an apatite-like layer on the W surfaces can be observed. Biocompatibility in vitro studies showed the absence of cytotoxicity of all formulations. The cells were able to adhere on the polystyrene negative control and on specimens containing 60 wt % wollastonite forming a monolayer and showing a normal morphology. However, a low cellular growth was observed. 2008 Wiley Periodicals, Inc. J Biomed Mater Res 88A: 53–64, 2009Peer reviewe

In situ synchrotron X-ray powder diffraction study of the early hydration of α-tricalcium phosphate/tricalcium silicate composite bone cement

Bioactivity, osteogenicity and mechanical properties of α-tricalcium phosphate (α-TCP) based phosphates cements can be improved by adding tricalcium silicate (C3S); however, the addition of C3S delays the precipitation and growth of calcium deficient hydroxyapatite (CDHA). Thus, the aim of this work was the study of in situ setting reaction of α-TCP/C3S composite bone cement under high energy X-ray generated by a synchrotron source within the first 72h. The results showed that the addition of C3S induces the precipitation of nanosized CDHA at early times depending on the added content. Calculated crystallite sizes showed that the higher the content of C3S, the smaller the crystal size at the beginning of the precipitation. These results are different from those obtained by conventional XRD method, suggesting that the proposed technique is a powerful tool in determining the composition and extent of reaction of CPCs surfaces in real time

Si-TCP synthesized from Mg-free reagents employed as calcium phosphate cement

The influence of silicon doping on calcium phosphate cement were explored in this work. &#945;-TCP and Si-&#945;-TCP were prepared by solid state reaction employing Mg-free CaHPO4, CaCO3 and CaSiO3 as precursors. It was possible to obtain TCP powders with low contents of &#946; phase as contaminant. Cement liquid phase was an aqueous solution containing 2.5 wt. (%) of Na2HPO4 and 1.5 wt. (%) of citric acid. The liquid-to-powder ratio was 0.6 mL.g-1. Chemical, physical and mechanical properties of the cement samples were determined by means of XRD, FTIR, XRF, compressive strength and SEM. The calcium phosphate cements obtained achieved satisfactory properties; however, Si-&#945;-TCP presented a decrease on the rate of setting reaction.568572Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Si-tricalcium phosphate cement: preparation, characterization and bioactivity in SBF

There are evidences considering the effectiveness of Si on enhancing biological properties of calcium phosphates; however, there are not many works relating to the Si-alpha-TCP bone cement. The influence of silicon doping on the properties of &#913;-TCP cement was analyzed. Si-TCP was obtained by a solid state reaction employing CaCO3, CaHPO4 and CaSiO3 and powder was analyzed by XRD, FTIR, XRF and BET specific area. Cement samples were analyzed for their surface of fracture morphology, mechanical resistance and SBF bioactivity. Cement mechanical resistance was not satisfactory for biomedical application; nonetheless, sample's surface was coated by an apatite layer after immersion in SBF. Notwithstanding, to ensure that silicon is the element responsible for increasing the material's bioactivity it is necessary to evaluate the in vivo performance of the bone cement obtained in this work.493498Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP