Authors: Dong Hua Wan, Fen Lin, Qu Xiang Liao
Abstract: It’s well known that curcumin is practically insoluble in water. Therefore, to improve the drug dissolution rate, fusion approach was employed to prepare curcumin solid dispersions (SDs) in the carrier Pluronic F68 with three different drug loads. The dissolution rate of curcumin from the SDs was measured at simulated gastric fluid. The concentration of the dissolved drug in the medium was determined by HPLC. The dissolution rates of the formulations were dependent on the drug loading in SDs. 92.2% CUR was dissolved in 10 min from the SDs with 8.97% drug load, whereas the amounts of drug released were 65.8% and 84.2% within 120 min from the SDs with 18.9% and 29.0% drug loads, respectively. The Fourier transform infrared spectra indicated hydrogen bond between the drug and carrier. Furthermore, their physicochemical properties were well investigated using differential scanning calorimetry and X-ray diffraction. In the dispersions containing 8.97% CUR, the drug was in the molecular state. At a composition of approximately 18.9%, CUR was dispersed as micro-fine crystals. These interesting results indicate that the physical states of the drug in the carrier, which are governed by the drug loading, can affect the dissolution rate improvement.
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Authors: Thomas Pavlitschek, Yu Jin, Johann Plank
Abstract: Environmental scanning electron microscopy (ESEM) and complementary methods were employed to study the time dependent film formation of a non-ionic latex dispersion in water @ pH 12.8 and cement pore solution. A commercial liquid ethylene-vinyl acetate latex dispersion stabilized with PVOH possessing a minimum film forming temperature (MFFT) of 3 °C and a Tg of 19 °C was employed in the study. Prior to ESEM imaging the latex dispersion was stored at room temperature and then transferred into the ESEM instrument for imaging. Subsequently, micrographs monitoring its film forming behaviour are obtained. The analysis revealed that upon removal of water, film formation occurs as a result of particle packing, particle deformation and finally particle coalescence. In synthetic cement pore solution film formation occurs faster than in water and is complete within one day. This acceleration can be ascribed to the presence of PVOH on the surface of the latex particles. In water at neutral pH, PVOH forms a shell around the latex particle and hinders the interdiffusion of the macromolecules while in cement pore solution, PVOH precipitates due to high pH and high concentration of cations. This way the latex particles can coalesce faster into a polymer film.
316
Authors: Sahar Kafashi, Ramin Taghdimi, Gholamreza Karimi
Abstract: This study was aimed to investigate the rheological properties and the possibility of nano(Na, Ca )- bentonites nanoproducts to meet the required drilling mud properties. Sepiolite (Sp) and the mixture of 2% nanoNaB with 1% Sp were collected and prepared from Irans oil Company (NIOC). The nanoclay performance evaluation involved the experimental tests of the rheological properties, filtration and gel strength. According to the results obtained from flow properties tests for the mixture, it was indicated that the mixture was not adequate to be a suitable drilling fluid. The main objective was to make stable dispersions with nanobentonite and sepiolite by using a water soluble polymer as stabilizer. The changes in the rheological properties of bentonite were investigated at various concentrations of polyvinyl alcohol (PVA) to discover the stability of the dispersions. The standard API tests were applied for drilling fluid to determine the properties of dispersions.
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