Fakulta chemická

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Nanometals incorporation into active and biodegradable chitosan films
(CELL PRESS, 2024-04-15) Dordević, Simona; Dordevič, Dani; Těšíková, Karolína; Sedláček, Petr; Kalina, Michal; Vápenka, Lukáš; Nejezchlebová, Marcela; Treml, Jakub; Tremlová, Bohuslava; Mikulášková, Hana
This study investigates the effects of incorporating ZnO, TiO2, and colloidal Ag nanoparticles on the antioxidant, antimicrobial, and physical properties of biodegradable chitosan films. The research focuses on addressing the growing demand for sustainable packaging solutions that offer efficient food preservation while mitigating environmental concerns. In this investigation, the physical properties including thickness, water content, solubility, swelling degree, tensile strength, and elasticity of the chitosan films were examined. Additionally, the samples were analyzed for total polyphenol content, antimicrobial activity, and antioxidant capacity. Notably, the incorporation of ZnO nanoparticles led to the lowest water content and highest strength values among the tested films. Conversely, the addition of colloidal Ag nanoparticles resulted in films with the highest antioxidant capacities (DPPH: 32.202 +/- 1.631 %). Remarkably, antimicrobial tests revealed enhanced activity with the inclusion of colloidal silver nanoparticles, yet the most potent antimicrobial properties were observed in films containing ZnO (E.coli: 2.0 +/- 0.0 mm; MRSA: 2.0 +/- 0.5 mm). The findings of this study hold significant implications for the advancement of edible biodegradable films, offering potential for more efficient food packaging solutions that address environmental sustainability concerns. By elucidating the effects of nanoparticle incorporation on film properties, this research contributes to the ongoing discourse surrounding sustainable packaging solutions in the food industry.
Influence of alkali metal formates and calcium formate on workability, hydration and basic properties of reactive powder concrete
(Springer Nature, 2024-10-29) Kratochvílová, Nikola; Šoukal, František; Novotný, Radoslav; Sedlačík, Martin; Švec, Jiří; Másilko, Jiří; Ptáček, Petr; Bocian, Luboš; Hajzler, Jan; Marko, Michal
This work aims to study whether it would be possible to use alkali metal formates and calcium formate in order to increase the workability of reactive powder concrete (RPC) and how these additives affect hydration, mechanical properties and mineralogical composition of RPC. These substances were added together with superplasticizer. Therefore, paper deals with possibility of increase in workability which would be higher when compared to the sole addition of only the superplasticizer themself. The effect of alkali metal formates and their replacement with calcium formate on slump flow, mechanical properties and pH of RPC was studied. Furthermore, the influence of potassium formate and its replacement with calcium formate and with calcium oxide on the hydration of RPC was observed with the help of isothermal calorimetry and thermal analysis. The results showed that the addition of studied compounds allows to achieve an increase in RPC slump flow. However, it is necessary to add these substances in an optimal ratio of alkali metal formate/calcium formate because a higher content of calcium formate leads to a decrease in slump flow. For ideal ratios, the compressive strength after 90 days is still above 218 MPa and the flexural strength is still above 23 MPa. In calorimetric measurements, it was observed that the addition of potassium formate leads to a decrease in the total amount of heat developed in the induction period. According to thermal analysis, additions of the studied additives to RPC caused changes in the content of portlandite and calcite.
Hydrothermal synthesis and characterization of calcium phosphate-based coatings on AZ31 magnesium alloy
(Sciendo, 2023-05-01) Horáková, Lenka; Doskočil, Leoš; Wasserbauer, Jaromír; Buchtík, Martin
This study aims to analyze the influence of process parameters used for hydrothermal synthesis of CaP coatings on their properties and to improve their corrosion resistance and biocompatibility compared to the substrat AZ31. The parameters monitored were deposition time, pH of the reaction mixture, and concentration of precursors in the reaction mixture. For the deposited CaP coatings on AZ31 magnesium alloy, the surface morphology and the number of structural defects were evaluated using scanning electron microscopy. Electrochemical corrosion properties were evaluated using polarization techniques in Hank’s solution. The results showed that the best properties were obtained for the sample prepared in a reaction mixture at 120 °C, pH 5 for a deposition time of 120 min, when the concentration of precursors in the reaction mixture was 0.30 mol/l Ca(NO3)2·4H2O and 0.28 mol/l NH4H2PO4. Under these conditions, the best electrochemical corrosion properties were achieved.
Degradation of P(3HB-co-4HB) Films in Simulated Body Fluids
(MDPI, 2022-05-13) Vodička, Juraj; Wikarská, Monika; Trudičová, Monika; Juglová, Zuzana; Pospíšilová, Aneta; Kalina, Michal; Slaninová, Eva; Obruča, Stanislav; Sedláček, Petr
A novel model of biodegradable PHA copolymer films preparation was applied to evaluate the biodegradability of various PHA copolymers and to discuss its biomedical applicability. In this study, we illustrate the potential biomaterial degradation rate affectability by manipulation of monomer composition via controlling the biosynthetic strategies. Within the experimental investigation, we have prepared two different copolymers of 3-hydroxybutyrate and 4-hydroxybutyrate-P(3HB-co-36 mol.% 4HB) and P(3HB-co-66 mol.% 4HB), by cultivating the thermophilic bacterial strain Aneurinibacillus sp. H1 and further investigated its degradability in simulated body fluids (SBFs). Both copolymers revealed faster weight reduction in synthetic gastric juice (SGJ) and artificial colonic fluid (ACF) than simple homopolymer P3HB. In addition, degradation mechanisms differed across tested polymers, according to SEM micrographs. While incubated in SGJ, samples were fragmented due to fast hydrolysis sourcing from substantially low pH, which suggest abiotic degradation as the major degradation mechanism. On the contrary, ACF incubation indicated obvious enzymatic hydrolysis. Further, no cytotoxicity of the waste fluids was observed on CaCO-2 cell line. Based on these results in combination with high production flexibility, we suggest P(3HB-co-4HB) copolymers produced by Aneurinibacillus sp. H1 as being very auspicious polymers for intestinal in vivo treatments.
Effect of alkali salts on the hydration process of belite clinker
(MDPI, 2022-05-10) Hrubá, Valeriia; Kalina, Lukáš; Sedlačík, Martin; Cába, Vladislav; Másilko, Jiří; Novotný, Radoslav
Belite-rich cement represents one of the low carbon footprint binders. Nevertheless, its use is ac-companied by a low initial rate of hydration. This can be partially eliminated by the grinding to high specific surfaces or by the addition of admixtures (mineralizators or activators). The influence of alkaline activators: CaSO4, Na2SO4 and Na2CO3 (in the amount of 5wt.% related to the clinker weight) on hydration course as well as the quantity of hydration products of belite-rich cements were investigated within this paper. Belite-rich clinker was laboratory synthetized and grinded together with activators to prepare various belite-rich cements. Next, the hydration kinetics and the hydrated phase assemblage were investigated using the isothermal calorimetry, X-ray powder diffraction and thermogravimetric and differential thermal analyses. The use of selected admixtures allows to obtain belite-rich cements with the higher hydraulic activity in initial times.

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