monitoring of the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET

Microemulsions are promising drug delivery systems for the oral administration of poorly water-soluble drugs. However, the evolution of microemulsions in the gastrointestinal tract is still poorly characterized, especially the structural change of microemulsions under the effect of lipase and mucus. To better understand the fate of microemulsions in the gastrointestinal tract, we applied small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET) to monitor the structural change of microemulsions under the effect of lipolysis and mucus. First, the effect of lipolysis on microemulsions was studied by SAXS, which found the generation of liquid crystalline phases. Meanwhile, FRET spectra indicated micelles with smaller particle sizes were generated during lipolysis, which could be affected by CaCl, bile salts and lecithin. Then, the effect of mucus on the structural change of lipolysed microemulsions was studied. The results of SAXS and FRET indicated that the liquid crystalline phases disappeared, and more micelles were generated. In summary, we studied the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET, and successfully monitored the appearance and disappearance of the liquid crystalline phases and micelles.

Crystal Modification on Lithium Disilicate Glass Ceramics Sintered Using Microwaves / Modificación de Cristales de Cerémicas de Vidrio de Disilicato de Litio Sinterizadas con Microondas

ABSTRACT: Microwaves are an interesting alternative to process dental ceramics. It is well documented that Microwave Hybrid Sintering (MHS) allows important savings in time and energy consumption. However, little is known about its effect on lithium disilicate glass ceramics, a popular material in dentistry today. We analyzed the microstructure of lithium disilicate glass ceramics sintered with MHS compared with conventional sintering. We sintered lithium disilicate glass ceramics using MHS and conventional furnaces, and we analyzed the samples using X-Ray diffraction and SEM. Samples sintered with MHS showed an increased crystalline phase, with an increased number of crystals. These crystals have larger perimeters compared with samples sintered in conventional furnaces. MHS produced a different crystallization pattern and crystal/ matrix ration in lithium disilicate glass ceramics when compared to conventional sintering. This can be associated with the improved mechanical properties of these materials reported previously.

RESUMEN: Las microondas son una interesante alternativa para procesar cerámicas dentales. Está bien documentado que el Sinterizado Híbrido por Microondas (MHS) permite ahorros importantes de tiempo y energía. Sin embargo, poco se ha publicado respecto a sus efectos en cerámicas de disilicato de litio, un material bastante popular en odontología en estos días. En este artículo analizamos la micro estructura de cerámicas de disilicato de litio sinterizada con MHS comparada con el sinterizado convencional. Sinterizamos muestras de cerámicas de disilicato de litio usando MHS y hornos convencionales, y analizamos las muestras usando difracción de rayos X y SEM. Las muestras sintetizadas usando MHS tienen una mayor fase cristalina, con mayor número de cristales. Estos cristales tienen además perímetros mayores, comparados con las muestras sinterizadas en hornos convencionales. MHS produce patrones de cristalización y proporción de cristal/matrix diferentes a las producidos por sinterizado convencional. Esto puede asociarse a las mejoras en propiedades mecánicas reportadas previamente.

Cubosomes as drug delivery system: Recent advance / 第二军医大学学报

Cubosomes are self-assembled nanostructured particles formed by aqueous lipid and surfactant systems. Cubosomes are thermodynamically stable; they have a structure like "honeycombed" with bicontinuous domains of water and lipid in which surfactant assembles into bilayers and twisted into a three dimension, periodic, and minimal surface, forming a tightly packed structure. The properties of cubosomes, such as its unique bicontinuous cubic phase liquid crystals, its ability to solubilize hydrophobic, hydrophilic, and amphiphilic molecules at the same time, its biodegradability by simple enzyme action, its strong bioadhesion ability, and its simple preparation, make them a promising vehicle for drug delivery. Based on recent reports, this review introduces the structure, preparation, exosyndrome and drug delivery potential of cubosomes.

Polimorfismo farmacéutico / Pharmaceutical polymorphism

Se explica lo que es un sólido cristalino y el polimorfismo en general. Se muestra la relación estructura cristalina/propiedades físicas y químicas a partir del átomo de carbono. Se entrega la definición de polimorfismo de la FDA. Se muestra el polimorfismo del paracetamol y se dan algunas cifras relativas a la existencia del polimorfismo en principios activos de medicamentos. Se explica que la consecuencia más importante para los polimorfos farmacéuticos es la diferencia de solubilidad y cómo eso afecta propiedades como la biodisponibilidad y la bioequivalencia, entre otras. Se muestra la dificultad de elaboración de formas farmacéuticas a partir de polimorfos específicos a través del caso emblemático del medicamento Ritonavir. Se muestran las consecuencias económicas y de salud pública en América Latina a partir de una experiencia en países vecinos como Brasil y Argentina y se informa de una Resolución del ISP en Chile que reconoce la existencia de los polimorfos y su importancia en la estabilidad y Bio-Disponibilidad de los productos farmacéuticos.

An explanation is given of crystalline solids and polymorphism in general. The crystal structure/chemical and physical properties relation is illustrated for the element carbon. The FDA's definition of polymorphism is given. The polymorphism of phenacetin (para-acetylaminophenol) is shown and some figures are given for the existence of polymorphism in medicinal active principles. The fact that solubility difference is the most important consequence of pharmaceutical polymorphs is stated, and how it affects properties like bioavailability and bioactivity, among others, is explained. The difficulty of making pharmaceutical preparations from specific polymorphs is illustrated by means of the emblematic case of the drug Ritonavir. The economic and public health consequences in Latin America are shown using the experience of neighboring countries like Brazil and Argentina, and a Resolution of the Public Health Institute (ISP) of Chile in relation to the polymorphism is reported.