The purpose of this work was to prepare stable citrus (CF) and apple (AF) pectin aerogels for potential pharmaceutical applications. Different shapes of low ester pectin aerogels were prepared by two fundamental methods of ionic cross-linking. Pectins% spherical and multi-membrane gels were first formed by the diffusion method using 0.2 M CaCl2 solution as an ionic cross-linker. The highest specific surface area (593 m2/g) that had so far been reported for pectin aerogels was achieved using this method. Monolithic pectin gels were formed by the internal setting method. Pectin gels were further converted into aerogels by supercritical drying using CO2. As surface area/volume is one of the key parameters in controlling drug release, multi-membrane pectin aerogels were further used as drug delivery carriers. Theophylline and nicotinic acid were used as model drugs for the dissolution study. CF aerogels showed more controlled release behaviour than AF pectin aerogels. Moreover a higher release rate (100%) was observed with CF aerogels.
Density of CO2 saturated solutions of polyethylene glycols (PEGs) of different molecular weight was measured in pressure range from 8.0 MPa up to 47.7 MPa at a temperature of 343 K by a volumetric method. To validate the method density of pure CO2 was measured at different pressures and a temperature of 293 K. Viscosity of CO2 saturated solutions of polyethylene glycols (PEGs) of different molecular weight at different pressures and at a temperature of 343 K was measured using a high pressure view cell. Also a temperature impact on the viscosity of pure PEGs was observed at ambient pressure.
The presented review covers the latest research on supercritical impregnation into organic and inorganic aerogels by investigating those factors that influence the impregnation. Supercritical impregnation is a promising method for incorporating drugs within porous carriers including for water insoluble drugs. An additional step (reduction from metallic precursor to metal) is required for the supercritical impregnation of metallic precursors. Hence, this expanded method is preferably termed as supercritical fluid deposition or adsorption. Supercritical impregnation of drugs, as well as metals, are mostly influenced by interactions between the compound and aerogel matrix, supercritical impregnation conditions, and the characteristics of a compound within a supercritical fluid.