Estudio sobre las propiedades mecánicas de cementos óseos preparados con metacrilatos funcionalizados

Los cementos óseos son materiales poliméricos que se utilizan con el objeto de fijar prótesis metálicas. Han estado en el mercado por casi 40 años desde que Sir John Charnley propuso su uso en ortopedia. Los cementos óseos convencionales exhiben altos calores de reacción, alta contracción y un elevado contenido de monómero residual; estas propiedades se traducen en un comportamiento mecánico inadecuado y finalmente en el aflojamiento de la prótesis. Nuevas formulaciones hacen uso de activadores de baja toxicidad, monómeros de bajo calor de reacción y cerámicos bioactivos para mejorar la biocompatibilidad. En este trabajo reportamos el uso de mezclas de metacrilato de metilo con ácido metacrílico (MAA) o dietil amino etil metacrilato (DEAEMA) en la síntesis de cementos óseos. Tiempos de curado y propiedades en tensión, compresión y flexión son reportadas en muestras sin y con acondicionamiento en fluido corporal simulado. Tiempos de curado cortos fueron observados en cementos preparados con MAA mientras que tiempos largos fueron obtenidos en muestras que contenían DEAEMA. Los ensayos mecánicos mostraron un aumento en la resistencia a la compresión y flexión en aquellos cementos que contenían ácido metacrílico comparada con la exhibida por los cementos preparados sin comonómero. Elevadas temperaturas de transición vítrea fueron asociadas a este comportamiento. Los cementos óseos preparados con DEAEMA en altas concentraciones presentaron una resistencia a la tensión, flexión y compresión menor a la obtenida con el cemento preparado sin comonómero. En general, las propiedades mecánicas exhibidas por estos cementos experimentales fueron comparables a las propiedades de cementos óseos comerciales disponibles en México. Sin embargo, las muestras acondicionadas en fluido corporal simulado presentaron una reducción en sus propiedades después de 3 meses de acondicionamiento. Pese a esto, el valor mínimo de resistencia a la compresión sugerido para su uso como cemento óseos (70 MPa) fue cumplido en todas las formulaciones excepto en aquellas preparadas con DEAEMA en altas concentraciones.Peer Reviewe

A Review Study on the Postharvest Decay Control of Fruit by <em>Trichoderma</em>

This chapter consists of an overview with the most relevant results about the efficacy of Trichoderma on postharvest disease control. The results of investigations demonstrate that this fungus can control several phytopathogens in different fruits. Postharvest losses represent a major problem in several countries. The constant application of fungicides not only at field but also at postharvest stage has led to microbial resistance cases, which make the control of these pathogens difficult. Biological control is a promising alternative to chemical fungicide applications. In this sense, an eco-friendly alternative and effective approach for controlling diseases is the use of microbial antagonists like Trichoderma, which have several mechanisms of action to stop disease development. A crucial treat in biological control is related to the maintenance of microbial viability and efficacy, that is why other technologies like their incorporation into edible films and coatings, nanotechnology, microbial mixtures, among others have been applied in combination with Trichoderma successfully. An enhancement in biocontrol activity is achieved when alternative systems are combined like GRAS substances, biopolymers, and other antagonists. Thus, Trichoderma is an eco-friendly alternative to threat postharvest diseases as an alternative to chemical treatments

Biomimetic potential of some methacrylate-based copolymers: A comparative study

Preparation of new biocompatible materials for bone recovery has consistently gained interest in the last few decades. Special attention was given to polymers that contain negatively charged groups, such as phosphate, carboxyl, and sulfonic groups toward calcification. This present paper work demonstrates that other functional groups present also potential application in bone pathology. New copolymers of 2-hydroxyethyl methacrylate with diallyldimethylammonium chloride (DADMAC), glycidyl methacrylate (GlyMA), methacrylic acid (MAA), 2-methacryloyloxymethyl acetoacetate (MOEAA), 2-methacryloyloxyethyltriethylammonium chloride (MOETAC), and tetrahydrofurfuryl methacrylate (THFMA) were obtained. The copolymers were characterized by FTIR, swelling potential, and they were submitted to in vitro tests for calcification and cytotoxicity evaluation. GlyMA and MOETAC-containing copolymers show promising results for further in vivo mineralization tests, as a potential alternative to the classical bone grafts, in bone tissue engineering

Agroindustrial

El tomate de cáscara es una de las hortalizas mas importantes distribuidas a nivel mundial, el fruto fresco se utiliza en la preparación de diversos productos alimenticios, y su importancia deriva del alto contenido de minerales (calcio, hierro y fósforo) y vitaminas (Tiamina, Niacina y Ácido ascórbico). Así mismo, presenta una gran demanda en México por ser insustituible para la preparación de salsa verde y en la preparación de un gran número de platillos regionales (Güemes et al., 2001), considerándose una de las principales hortalizas de la dieta de los mexicanos

Estudio sobre las propiedades mecánicas de cementos óseos preparados con metacrilatos funcionalizados

Los cementos óseos son materiales poliméricos que se utilizan con el objeto de fijar prótesis metálicas. Han estado en el mercado por casi 40 años desde que Sir John Charnley propuso su uso en ortopedia. Los cementos óseos convencionales exhiben altos calores de reacción, alta contracción y un elevado contenido de monómero residual; estas propiedades se traducen en un comportamiento mecánico inadecuado y finalmente en el aflojamiento de la prótesis. Nuevas formulaciones hacen uso de activadores de baja toxicidad, monómeros de bajo calor de reacción y cerámicos bioactivos para mejorar la biocompatibilidad. En este trabajo reportamos el uso de mezclas de metacrilato de metilo con ácido metacrílico (MAA) o dietil amino etil metacrilato (DEAEMA) en la síntesis de cementos óseos. Tiempos de curado y propiedades en tensión, compresión y flexión son reportadas en muestras sin y con acondicionamiento en fluido corporal simulado. Tiempos de curado cortos fueron observados en cementos preparados con MAA mientras que tiempos largos fueron obtenidos en muestras que contenían DEAEMA. Los ensayos mecánicos mostraron un aumento en la resistencia a la compresión y flexión en aquellos cementos que contenían ácido metacrílico comparada con la exhibida por los cementos preparados sin comonómero. Elevadas temperaturas de transición vítrea fueron asociadas a este comportamiento. Los cementos óseos preparados con DEAEMA en altas concentraciones presentaron una resistencia a la tensión, flexión y compresión menor a la obtenida con el cemento preparado sin comonómero. En general, las propiedades mecánicas exhibidas por estos cementos experimentales fueron comparables a las propiedades de cementos óseos comerciales disponibles en México. Sin embargo, las muestras acondicionadas en fluido corporal simulado presentaron una reducción en sus propiedades después de 3 meses de acondicionamiento. Pese a esto, el valor mínimo de resistencia a la compresión sugerido para su uso como cemento óseos (70 MPa) fue cumplido en todas las formulaciones excepto en aquellas preparadas con DEAEMA en altas concentraciones.Peer Reviewe

Carboxymethylation of ulvan and chitosan and their use as polymeric components of bone cements

Ulvan, extracted from the green algae Ulva lactuca, and chitosan, extracted from Loligo forbesis squid-pen, were carboxymethylated, yielding polysaccharides with an average degree of substitution of ∼98% (carboxymethyl ulvan, CMU) and ∼87% (carboxymethyl chitosan, N,O-CMC). The carboxymethylation was confirmed by Fourier transform infrared spectroscopy and quantified by conductimetric titration and 1H nuclear magnetic resonance. The average molecular weight increased with the carboxymethylation (chitosan, Mn 145→296 kDa and Mw 227→416 kDa; ulvan, Mn 139→261 kDa and Mw 368→640 kDa), indicating successful chemical modifications. Mixtures of the modified polysaccharides were tested in the formulation of polyacrylic acid-free glass-ionomer bone cements. Mechanical and in vitro bioactivity tests indicate that the inclusion of CMU in the cement formulation, i.e. 0.50:0.50 N,O-CMC:CMU, enhances its mechanical performance (compressive strength 52.4 ± 8.0 MPa and modulus 2.3 ± 0.3 GPa), generates non-cytotoxic cements and induces the diffusion of Ca and/or P-based moieties from the surface to the bulk of the cements.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. REGPOT-CT2012-31633-POLARIS. Thanks are also due to Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), European Union, QREN, FEDER and COMPETE for funding the QOPNA research unit (project PEst-C/QUI/UI0062/2011). R.A.P. and C.N. acknowledge their FCT post-doc Grants SFRH/BPD/39333/2007 and SFRH/BPD/46584/2008, respectively

Composites of poly(methyl methacrylate) with hybrid fillers (micro/nanohydroxyapatite): mechanical, setting properties, bioactivity and cytotoxicity in vitro

[EN] Novel composites of poly(methyl methacrylate) with silanized micro and nanohydroxyapatite (HA) particles were prepared. Coralina((R)) HA was the MicroHA filler and synthetic NanoHA was the reinforcement. The influence of the total inorganic content and the proportion of micro- to NanoHA on the setting properties (i.e., setting time and peak polymerization temperature), compressive strength, and in vitro bioactivity in simulated body fluid (SBF) was analyzed. The novel composites exhibited appropriate handling properties. Compressive strength ranged between 71.30 +/- 0.04 and 80.0 +/- 2.4 MPa. The peak polymerization temperatures varied from 44.5 +/- 0.5 to 50.8 +/- 1.8 degrees C, and thus complying with the ISO 5833 standard. The composites exhibited excellent calcium phosphate deposition in SBF and those with 30 wt% inorganic content showed no cytotoxicity on L929 fibroblastic cells. 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Setting properties of bone cement with added synthetic hydroxyapatite. Biomaterials, 6(1), 55-60. doi:10.1016/0142-9612(85)90039-0Murugan, R., & Ramakrishna, S. (2004). Bioresorbable composite bone paste using polysaccharide based nano hydroxyapatite. Biomaterials, 25(17), 3829-3835. doi:10.1016/j.biomaterials.2003.10.016Sanosh, K. P., Chu, M.-C., Balakrishnan, A., Kim, T. N., & Cho, S.-J. (2009). Preparation and characterization of nano-hydroxyapatite powder using sol-gel technique. Bulletin of Materials Science, 32(5), 465-470. doi:10.1007/s12034-009-0069-xIslas-Blancas, M. E., Cervantes-Uc, J. M., Vargas-Coronado, R., Cauich-Rodríguez, J. V., Vera-Graziano, R., & Martinez-Richa, A. (2001). Characterization of bone cements prepared with functionalized methacrylates and hydroxyapatite. Journal of Biomaterials Science, Polymer Edition, 12(8), 893-910. doi:10.1163/156856201753113088Lopez-Heredia, M. A., Sa, Y., Salmon, P., de Wijn, J. R., Wolke, J. G. C., & Jansen, J. A. (2012). 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Preparation of SBF with different HCO3- content and its influence on the composition of biomimetic apatites. Acta Biomaterialia, 2(2), 181-189. doi:10.1016/j.actbio.2005.11.001Dalby, M. J., Di Silvio, L., Harper, E. J., & Bonfield, W. (2002). Increasing hydroxyapatite incorporation into poly(methylmethacrylate) cement increases osteoblast adhesion and response. Biomaterials, 23(2), 569-576. doi:10.1016/s0142-9612(01)00139-9Qiu, H., Yang, J., Kodali, P., Koh, J., & Ameer, G. A. (2006). A citric acid-based hydroxyapatite composite for orthopedic implants. Biomaterials, 27(34), 5845-5854. doi:10.1016/j.biomaterials.2006.07.042Espigares, I., Elvira, C., Mano, J. F., Vázquez, B., San Román, J., & Reis, R. L. (2002). New partially degradable and bioactive acrylic bone cements based on starch blends and ceramic fillers. Biomaterials, 23(8), 1883-1895. doi:10.1016/s0142-9612(01)00315-5Arcos, D. (2001). Bioactivity in glass/PMMA composites used as drug delivery system. 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