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Item type:Publication, Access status: without files , Stiffening of biopolymer aerogel networks upon wetting: A model-based study(2020-03-01); ; ; The mechanism behind the stiffening effect observed in the stress-strain response of alginate-starch aerogels upon being exposed to wetting is investigated in this paper, via a physically motivated model approach. A network decomposition concept is introduced, whereby the highly nanoporous network is decomposed into a swollen aerogel network and a hydrogel-like network. The aerogel network is modeled by considering idealized square-shaped microcells of varying sizes. An attempt is made to explain the stiffening of the network, upon wetting, based on changes in the fibril characteristics of the aerogel network upon swelling and formation of a hydrogel-like phase in the microporous region. In this first approach, the aerogel network is described based on a micro-mechanical model, while the hydrogel-like network is described using a phenomenological one. The results of the proposed model idea are in very good agreement with the experimental data of alginate-starch aerogels under different degrees of wetting.Publicationtype: Journal Article120 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effect of surface functionalization of silica aerogel on their adsorptive and release propertiesDue to their high surface area, open pore structure and biocompatibility silica aerogels were shown to be a promising candidate for drug delivery systems. This work aims to show the possibility of functionalizing silica aerogel with functional groups to tailor their surface properties for specific applications. Amino groups were taken as a model functional group. Ketoprofen loading on aerogels was taken as a drug delivery application. Two different functionalization approaches were followed: pretreatment of the gel before the drying step, and a post treatment of the dried aerogels. The amino-functionalized aerogels obtained by both methods were characterized by CHN and BET analysis, as well as UV-spectroscopy. It has been shown that the functionalized silica aerogels obtained by these methods maintain similar structural properties as the original ones. For the first time transparent amino-modified aerogels with a surface area up to 1000 m2/g were obtained. These aerogels were loaded with the drug ketoprofen by adsorption from supercritical CO2. The loading was shown to be a function of the concentration of the amino groups on the aerogel surface, due to their strong adsorptive interactions with the acidic group of ketoprofen. The release rate of ketoprofen from the loaded amino-modified aerogels was close to that of original ones. Thus, aerogels functionalization opens the possibility to design a high capacity carrier for a specific active substance, as well as to control the release of that substance in the corresponding media.Publicationtype: Journal Article25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Polysaccharide-based aerogels as drug carriersThe application of aerogels as drug delivery system was successfully demonstrated for silica aerogels previously. However, being biocompatible silica matrices are not biodegradable, which is a certain disadvantage for a number of pharmaceutically oriented applications. For these purposes biodegradable materials are beneficial. Supercritical drying of polysaccharide gels results in highly porous biodegradable aerogel matrices with large surface areas. Structural properties of the polysaccharide aerogels depend on the preparation method and chemical nature of the gel phase. In this work different polysaccharide precursors (starch, alginate) were used to produce aerogels, which later on were loaded with the drugs ibuprofen and paracetamol. Furthermore release kinetics was studied in vitro. Thereby it has been shown that the release rate depends primary on the properties of the matrix. The presented results demonstrate for the first time the high potential of polysaccharide aerogels for pharmaceutical applications.Publicationtype: Journal Article22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Feasibility study of hydrophilic and hydrophobic silica aerogels as drug delivery systemsThe feasibility of silica aerogels as oral drug delivery systems was investigated. Silica aerogels were loaded with several drugs by adsorption from their solutions in supercritical CO2. It was demonstrated that for all three drugs investigated here, high loading of the aerogel could be achieved. The loaded aerogels were characterized by IR- and UV spectroscopy and X-ray diffraction in order to show that no degradation of the drugs occurred during the loading procedure. The release profiles of two drugs (ketoprofen and griseofulvin) from loaded aerogels were measured. It was found that the drugs adsorbed on hydrophilic silica aerogels dissolve faster than the corresponding crystalline drugs. This fact can be explained by both an increase in the specific surface area of the drug adsorbed on the aerogel and its non-crystallinity in this state. The influence of density and hydrophobicity of aerogels on both the adsorption and release of drugs were studied.Publicationtype: Journal Article28