An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer

The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer solutions were studied. The rheological behaviour of lecithin-chitosan vesicles was determined by shear stress against shear rate measurements, as well as by the variation on the hysteresis loop area. The results were compared with the rheopectic behaviour of soy lecithin dispersions without chitosan. An important change on the rheological properties of the complex dispersion was observed, depicting in a thixotropic behaviour with a plastic character in the presence of chitosan. This observation indicates that chitosan promotes the transition of planar sheets into closed structures, such as vesicles. The influence on the rheological and the electrokinetic behaviours of several electrolytes, such as NaCl, CaCl2 and AlCl3 with concentrations ranging between 10-5 and 10-2 mol/L were also studied. In all of the cases, an estimation of the diameters of the closed structures was obtained. © 2007 Elsevier B.V. All rights reserved.Se estudiaron las propiedades reológicas y electrocinéticas de vesículas de lecitina de soya preparadas a partir de dispersiones concentradas de lecitina de soya (250 g/L) obtenidas por hinchamiento lento en condiciones de cizallamiento y mezcladas con soluciones de biopolímeros de quitosano. El comportamiento reológico de las vesículas de lecitina-quitosano fue determinado por el esfuerzo de cizallamiento frente a las mediciones de velocidad de cizallamiento, así como por la variación en el área del bucle de histéresis. Los resultados se compararon con el comportamiento reopéctico de dispersiones de lecitina de soja sin quitosano. Se observó un cambio importante en las propiedades reológicas de la dispersión del complejo, presentándose un comportamiento tixotrópico con carácter plástico en presencia de quitosano. Esta observación indica que el quitosano promueve la transición de láminas planas a estructuras cerradas, como vesículas. También se estudió la influencia en el comportamiento reológico y electrocinético de varios electrolitos, como NaCl, CaCl2 y AlCl3 con concentraciones que oscilan entre 10-5 y 10-2 mol/L. En todos los casos se obtuvo una estimación de los diámetros de las estructuras cerradas. © 2007 Elsevier B.V. Todos los derechos reservados.Universidad Nacional, Costa RicaEscuela de Químic

Composite soy lecithin–decylpolyglucoside vesicles: A theoretical and experimental study

In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a decylpolyglucoside surfactant, (OrNS10), were formulated and their physicochemical properties were studied with the aim to design a drug delivery system suitable for different applications. To this purpose, morphology, size distribution, ζ-potential and apparent viscosity of the prepared vesicles were studied. Vesicles were also characterized by using optical and light polarized microscopy, transmission electron microscopy and photon correlation spectroscopy. A stability study was also performed by checking mean size and ζ-potential value variation of the several formulations during 4 weeks. Moreover, theoretical advances on geometric and thermodynamic aspects related to lipid vesicle formation were applied to this study. © 2007 Elsevier B.V. All rights reserved.En el presente trabajo se prepararon y caracterizaron vesículas elaboradas con lecitina de soya y una mezcla comercial de alquil poliglucósidos. Se formularon vesículas con una cantidad constante de lecitina de soja y una cantidad creciente de un tensioactivo decilpoliglucósido (OrNS10) y se estudiaron sus propiedades fisicoquímicas con el objetivo de diseñar un sistema de administración de fármacos adecuado para diferentes aplicaciones. Para ello se estudió la morfología, distribución de tamaños, potencial ζ y viscosidad aparente de las vesículas preparadas. Las vesículas también se caracterizaron mediante el uso de microscopía óptica y polarizada de luz, microscopía electrónica de transmisión y espectroscopía de correlación de fotones. También se realizó un estudio de estabilidad comprobando el tamaño medio y la variación del valor del potencial ζ de las diversas formulaciones durante 4 semanas. Además, se aplicaron a este estudio los avances teóricos sobre aspectos geométricos y termodinámicos relacionados con la formación de vesículas lipídicas. © 2007 Elsevier B.V. Todos los derechos reservados.Universidad Nacional, Costa Rica.Escuela de Químic

Composite soy lecithin-decylpolyglucoside vesicles: A theoretical and experimental study

In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a decylpolyglucoside surfactant, (OrNS10), were formulated and their physicochemical properties were studied with the airn to design a drug delivery system suitable for different applications. To this put-pose, morphology, size distribution, zeta-potential and apparent viscosity of the prepared vesicles were studied. Vesicles were also characterized by using optical and light polarized microscopy, transmission electron microscopy and photon correlation spectroscopy. A stability study was also performed by checking mean size and C-potential value variation of the several formulations during 4 weeks. Moreover, theoretical advances on geometric and thermodynamic aspects related to lipid vesicle formation were applied to this study. (c) 2007 Elsevier B.V. All rights reserved