Uso potencial de arcillas modificadas con metales para la obtención de formulaciones de liberación lenta de herbicidas.

9 páginas., 5 gráficos, 2 tablas y 9 referencias. Versión extendida de la comunicación presentada en la "XIX Reunión Científica de la Sociedad Española de Arcillas - SEA05", celebrada en Salamanca del 26 al 28 de Septiembre de 2005. Enlace a la web de la Sociedad Española de Arcillas http://www.sea-arcillas.es/publicacionesSEA.htm[EN]Abstract A slow release system of the herbicide imazapyr was designed by adsorption on pillared clays. Pillared clays based on aluminum and mixed aluminum-copper solutions were synthesized. The aim was to check whether the introduction into the pillars of a metal complexing the herbicide molecules enhanced the sorption and release properties of the clay for the herbicide. A commercial aluminum pillared clay was also examined as a potential sorbent. The chemical analysis data as well as those of X-ray diffraction show that copper from pillaring solutions was partially introduced, and the basal spacing were increased about 9 Å in good agreement with the size of the Keggin ion. The textural properties indicate a reduction in the micro- and mesoporosity of the pillared clays after pillaring with copper solutions. The largest the copper content in the mixed Al-Cu pillared clays the largest the decrease in the surface area. However, imazapyr adsorption increased up to three-fold compared to the commercial pillared clay, and desorption percentages from the Cu-Al pillared clays were three-fold lower than the commercial one, whose desorption was completely reversible. These preliminary results show the potential use of Cu-Al pillared clays for the development of slow release formulations of the herbicide imzapyr, unlike those whose pillars are only made of aluminum.[ES]Resumen En el presente trabajo se ha intentado desarrollar un sistema de liberación lenta del herbicida imazayr mediante su adsorción en arcillas pilareadas. Se han sintetizado arcillas pilareadas con aluminio y con soluciones mixtas Cu-Al, a fin de comprobar si la formación de pilares mixtos de aluminio con un metal complejante del herbicida mejoraba las propiedades de adsorción y liberación del mismo. También se ha estudiado el empleo potencial de una arcilla pilareada comercial formada con pilares exclusivos de aluminio. Los resultados de análisis químico así como de difracción de rayos X muestran que parte del cobre de las soluciones pilareantes se ha introducido en las arcillas finales, cuyos espaciados basales presentan un incremento de aproximadamente 9 Å, que se corresponde con el tamaño del ión Keggin. Las propiedades texturales indican una disminución tanto de la microporosidad como de la mesoporosidad en las arcillas tras su pilarización con soluciones de Cu-Al, que es tanto mayor cuanto mayor es el contenido de Cu. A pesar de la reducción en la superficie de estas arcillas sintetizadas con Cu, la adsorción de imazapyr incrementaba hasta 3 veces con respecto a la arcilla pilareada comercial. A su vez los porcentajes de desorción en la arcillas pilareadas con Cu-Al eran hasta tres veces inferiores a los correspondientes a la arcilla pilareada comercial, cuya desorción era prácticamente reversible. Estos resultados preliminares avalan el uso potencial de arcillas pilareadas con Cu-Al para el desarrollo de formulaciones de liberación lenta del herbicida imazapyr, a diferencia de aquellas en las que los pilares se encuentran formados únicamente por aluminio.Peer Reviewe

Structure and Mobility of Lactose in Lactose/Sodium Montmorillonite Nanocomposites

This study aims at investigating the molecular level organization and molecular mobility in montmorillonite nanocomposites with the uncharged organic low-molecular-weight compound lactose commonly used in pharmaceutical drug delivery, food technology, and flavoring. Nanocomposites were prepared under slow and fast drying conditions, attained by drying at ambient conditions and by spray-drying, respectively. A detailed structural investigation was performed with modulated differential scanning calorimetry, powder X-ray diffraction, solid-state nuclear magnetic resonance, scanning electron microscopy, microcalorimetry, and molecular dynamic simulations. The lactose was intercalated in the sodium montmorillonite interlayer space regardless of the clay content, drying rate, or humidity exposure. Although, the spray-drying resulted in higher proportion of intercalated lactose compared with the drying under ambient conditions, non-intercalated lactose was present at 20 wt% lactose content. This indicates limitations in maximum load capacity of nonionic organic substances into the montmorillonite interlayer space. Furthermore, a fraction of the intercalated lactose in the co-spray-dried nanocomposites diffused out from the clay interlayer space upon humidity exposure. Also, the lactose in the nanocomposites demonstrated higher molecular mobility than that of neat amorphous lactose. This study provides a foundation for understanding functional properties of nanocomposites, such as loading capacity and physical stability

Intestine-Specific, Oral Delivery of Captopril/Montmorillonite: Formulation and Release Kinetics

The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an intestine-selective drug delivery system that has a captopril-loading capacity of up to ca. 14 %w/w and which exhibits near-zero-order release kinetics