5 g Metakaolin in a glass mortar until a uniform paste was formed. The paste was molded in cylindrically shaped Teflon® molds resulting in pellets of the size 1.5 mm×1.5 mm (diameter×height) and in rubber molds resulting in rods for compression strength tests with a corresponding size of 6 mm×12 mm. The geopolymer

precursor was cured at 37 °C for 48 h in 100% relative humidity (RH) and stored in an 11% RH dessicator before analysis. The pellets prepared from pastes containing polymers in dissolved form and powder form were named after the polymer used with the extension D or P, respectively. In addition to the selleck compound samples named Control, Ko D, Ko P, PEG D, Alg-G P and Alg-M P, samples made from geopolymer pastes containing only half the amount of powder form Kollicoat and PEG (i.e. 0.5 g of excipient per 6.5 g of Metakaolin); viz. Ko-h P and PEG-h D, were prepared. Compositions with pre-dissolved Alginate (Alg-G D and Alg-M D) were prepared, but discarded as alginate degraded in the caustic synthesis environment

[14]. PEG P samples were also prepared, but the PEG powder did not homogenously mix into geopolymer paste, which therefore was discarded. The SEM micrographs of fracture surfaces of the pellets were taken with a Leo 1550 FEG microscope selleckchem (Zeiss, UK) equipped with an in-lens detector. A thin gold/palladium layer was sputtered onto the fracture surfaces of the non-conducting samples prior to analysis to minimize charging of the samples. The analysis was performed with 5 kV acceleration voltage. The compression strength of each composition (n=7) was measured as the maximum pressure that could be applied on the 6 mm×12 mm rods before breakage using an Autograph AGS-H universal testing equipment (Shimadzu Corp., Japan). Zolpidem release from the pellets was evaluated in a USP-2 dissolution bath (Sotax AT7 Smart, Sotax AG, Switzerland) equipped with 1000 ml vessels (37 °C, 50 rpm). 400 mg of pellets were placed in each vessel containing Carnitine palmitoyltransferase II 400 ml of either phosphate buffer set to pH 6.8 or 0.1 M HCl,

pH 1. In all experiments the quantities of pellets corresponded to a drug amount below 10% of the drug solubility in order to ensure that sink conditions always prevailed. Aliquots (1 ml) were manually withdrawn at different time points during the release, and the concentration of drug in these samples was analyzed with a UV/VIS photo-spectrometer (Shimadzu 1800, Japan). Any possible interference of dissolved polymer excipients in the drug absorbance/concentration measurements was evaluated by separately dissolving the polymers in the relevant buffer solutions. The absorbance of the polymers was found to be considerably lower than for the Zolpidem drug at its absorption peaks (241 and 300 nm). A photograph (Cybershot DSC-HX100V, Sony Corp., Japan) of the bottom of each dissolution vessel was taken after 6 h of drug release in pH 1. The drug release was studied for 6 h in pH 1 and for 24 h in pH 6.8.