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- ItemDetermination of Critical Parameters of Drug Substance Influencing Dissolution: A Case Study(Hindawi Publishing Corporation, 2014-09-15) Bojňanská, Erika; Kalina, Michal; Pařízek, Ladislav; Bartoníčková, Eva; Opravil, Tomáš; Veselý, Michal; Pekař, Miloslav; Jampílek, JosefThe purpose of this study was to specify critical parameters (physicochemical characteristics) of drug substance that can affect dissolution profile/dissolution rate of the final drug product manufactured by validated procedure from various batches of the same drug substance received from different suppliers.The target was to design a sufficiently robust drug substance specification allowing to obtain a satisfactory drug product. For this reason, five batches of the drug substance and five samples of the final peroral drug products were analysed with the use of solid state analysis methods on the bulk level. Besides polymorphism, particle size distribution, surface area, zeta potential, and water content were identified as important parameters, and the zeta potential and the particle size distribution of the drug substance seem to be critical quality attributes affecting the dissolution rate of the drug substance released from the final peroral drug formulation.
- ItemEdible films from carrageenan/orange essential oil/trehalose—structure, optical properties, and antimicrobial activity(MDPI, 2021-02-01) Jančíková, Simona; Dordevič, Dani; Sedláček, Petr; Nejezchlebová, Marcela; Treml, Jakub; Tremlová, BohuslavaThe research aim was to use orange essential oil and trehalose in a carrageenan matrix to form edible packaging. The edible packaging experimentally produced by casting from an aqueous solution were evaluated by the following analysis: UV-Vis spectrum, transparency value, transmittance, attenuated total reflectance Fourier-Transform spectroscopy (FTIR), scanning electron microscopy (SEM) and antimicrobial activity. The obtained results showed that the combination of orange essential oil with trehalose decreases the transmittance value in the UV and Vis regions (up to 0.14% +/- 0.02% at 356 nm), meaning that produced films can act as a UV protector. Most produced films in the research were resistant to Gram-positive bacteria (Staphylococcus aureus subsp. aureus), though most films did not show antibacterial properties against Gram-negative bacteria and yeasts. FTIR and SEM confirmed that both the amount of carrageenan used and the combination with orange essential oil influenced the compatibility of trehalose with the film matrix. The research showed how different combinations of trehalose, orange essential oils and carrageenan can affect edible film properties. These changes represent important information for further research and the possible practical application of these edible matrices.
- ItemAccumulation of Poly(3-hydroxybutyrate) Helps Bacterial Cells to Survive Freezing(PLoS, 2016-06-17) Obruča, Stanislav; Sedláček, Petr; Mravec, Filip; Kučera, Dan; Benešová, Pavla; Márová, IvanaAccumulation of polyhydroxybutyrate (PHB) seems to be a common metabolic strategy adopted by many bacteria to cope with cold environments. This work aimed at evaluating and understanding the cryoprotective effect of PHB. At first a monomer of PHB, 3-hydroxybutyrate, was identified as a potent cryoprotectant capable of protecting model enzyme (lipase), yeast (Saccharomyces cerevisiae) and bacterial cells (Cupriavidus necator) against the adverse effects of freezing-thawing cycles. Further, the viability of the frozen-thawed PHB accumulating strain of C. necator was compared to that of the PHB non-accumulating mutant. The presence of PHB granules in cells was revealed to be a significant advantage during freezing. This might be attributed to the higher intracellular level of 3-hydroxybutyrate in PHB accumulating cells (due to the action of parallel PHB synthesis and degradation, the so-called PHB cycle), but the cryoprotective effect of PHB granules seems to be more complex. Since intracellular PHB granules retain highly flexible properties even at extremely low temperatures (observed by cryo-SEM), it can be expected that PHB granules protect cells against injury from extracellular ice. Finally, thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences.
- ItemThe Role of Concentration and Solvent Character in the Molecular Organization of Humic Acids(MDPI AG, 2016-10-21) Klučáková, Martina; Věžníková, KateřinaThe molecular organization of humic acids in different aqueous solutions was studied over a wide concentration range (0.01–10 g/dm3). Solutions of humic acids were prepared in three different media: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. Potentiometry, conductometry, densitometry, and high resolution ultrasound spectrometry were used in order to investigate conformational changes in the humic systems. The molecular organization of humic acids in the studied systems could be divided into three concentration ranges. The rearrangements were observed at concentrations of ~0.02 g/dm3 and ~1 g/dm3. The first “switch-over point” was connected with changes in the hydration shells of humic particles resulting in changes in their elasticity. The compressibility of water in the hydration shells is less than the compressibility of bulk water. The transfer of hydration water into bulk water increased the total compressibility of the solution, reducing the ultrasonic velocity. The aggregation of humic particles and the formation of rigid structures in systems with concentrations higher than 1 g/dm3 was detected.
- ItemSilver Nanoparticles Stabilised by Cationic Gemini Surfactants with Variable Spacer Length(MDPI, 2017-10-23) Pisárčik, Martin; Jampílek, Josef; Lukáč, Miloš; Horáková, Renáta; Devínsky, Ferdinand; Bukovský, Marián; Kalina, Michal; Tkacz, Jakub; Opravil, TomášThe present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.