Fakulta chemická

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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.
Translational Studies on the Potential of a VEGF Nanoparticle-Loaded Hyaluronic Acid Hydrogel
(MDPI, 2021-05-22) O’Dwyer, Joanne; Murphy, Robert; González-Vázquez, Arlyng; Kovářová, Lenka; Pravda, Martin; Velebný, Vladimír; Heise, Andreas; Duffy, Garry P.; Cryan, Sally Ann
Heart failure has a five-year mortality rate approaching 50%. Inducing angiogenesis following a myocardial infarction is hypothesized to reduce cardiomyocyte death and tissue damage, thereby preventing heart failure. Herein, a novel nano-in-gel delivery system for vascular endothelial growth factor (VEGF), composed of star-shaped polyglutamic acid-VEGF nanoparticles in a tyramine-modified hyaluronic acid hydrogel (nano-VEGF-HA-TA), is investigated. The ability of the nano-VEGF-HA-TA system to induce angiogenesis is assessed in vivo using a chick chorioallantoic membrane model (CAM). The formulation is then integrated with a custom-made, clinically relevant catheter suitable for minimally invasive endocardial delivery and the effect of injection on hydrogel properties is examined. Nano-VEGF-HA-TA is biocompatible on a CAM assay and significantly improves blood vessel branching (p < 0.05) and number (p < 0.05) compared to a HA-TA hydrogel without VEGF. Nano-VEGF-HA-TA is successfully injected through a 1.2 m catheter, without blocking or breaking the catheter and releases VEGF for 42 days following injection in vitro. The released VEGF retains its bioactivity, significantly improving total tubule length on a Matrigel(R) assay and human umbilical vein endothelial cell migration on a Transwell(R) migration assay. This VEGF-nano in a HA-TA hydrogel delivery system is successfully integrated with an appropriate device for clinical use, demonstrates promising angiogenic properties in vivo and is suitable for further clinical translation.
Effect of alkali salts on the hydration process of belite clinker
(MDPI, 2022-05-10) Iliushchenko, 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.
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.
Microstructural Characterization of Laser Weld of Hot-Stamped Al-Si Coated 22MnB5 and Modification of Weld Properties by Hybrid Welding
(MDPI, 2021-07-14) Šebestová, Hana; Horník, Petr; Mikmeková, Šárka; Mrňa, Libor; Doležal, Pavel; Novotný, Jan
The presence of Al-Si coating on 22MnB5 leads to the formation of large ferritic bands in the dominantly martensitic microstructure of butt laser welds. Rapid cooling of laser weld metal is responsible for insufficient diffusion of coating elements into the steel and incomplete homogenization of weld fusion zone. The Al-rich regions promote the formation of ferritic solid solution. Soft ferritic bands cause weld joint weakening. Laser welds reached only 64% of base metal's ultimate tensile strength, and they always fractured in the fusion zone during the tensile tests. We implemented hybrid laser-TIG welding technology to reduce weld cooling rate by the addition of heat of the arc. The effect of arc current on weld microstructure and mechanical properties was investigated. Thanks to the slower cooling, the large ferritic bands were eliminated. The hybrid welds reached greater ultimate tensile strength compared to laser welds. The location of the fracture moved from the fusion zone to a tempered heat-affected zone characterized by a drop in microhardness. The minimum of microhardness was independent of heat input in this region.

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