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Study on relaxation properties of hydrogels using rheological techniques
Lorenc, Pavel ; Klučáková, Martina (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis deals with the study of relaxation and time stress of viscoelastic substances (hydrogels) using selected rheological techniques, especially with regard to oscillation tests. Hydrogels with different types of crosslinking were prepared and their properties were compared during the measurement. Agarose hydrogels (physically), alginate hydrogels (physicochemically), polyvinyl alcohol hydrogels (chemically) and hyaluronic acid hydrogels (ionically). In this bachelor's thesis, methods for measuring the relaxation properties of these hydrogels using a rheometer were designed and subsequently applied. We examined the relaxation properties of hydrogels using time-dependent tests that examined changes in amplitude over time. We performed a test that had 3 intervals, in which we monitored the response of hydrogels to the changes by changing the amplitudes of deformation with time. The relaxation properties of these hydrogels were studied, which showed significant differences in the behavior of hydrogels in measurements.By these methods, it was found that the structure of hydrogels and concentrations have an influence on relaxation. From the measured results, it was shown that the best relaxing properties have chemically crosslinked polyvinyl alcohol hydrogel, the lowest ability to relax was shown by physico-chemically crosslinked alginate hydrogel.The results from the measured data were finally compared, assessed and commented on the differences between the individual hydrogels.
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Development of a new type of energy drinks containing natural active components
Vysoká, Marie ; Němcová, Andrea (referee) ; Skoumalová, Petra (advisor)
The aim of this thesis is the development and preparation of a new energy drink. The theoretical part of the thesis focuses on the comparison of the drinks available in market, the presentation of the main active ingredients and the proposal of enriching the new energy drink. It also describes the possibility of using an encapsulation and the method used to determine specific compound in energy drink or encapsulated particles. In the experimental part of the work, at the beginning, the main content of energy drinks were characterized, for instance caffeine, sugar, polyphenol and vitamin C. Subsequently the energy drink based on selected types of loose teas that were enriched with the encapsulated extract of acai, acerola, maca, goji and ginseng was designed. All extracts contained large amounts of polyphenols and antioxidants. In addition, acerola extracts contained very high amounts of vitamin C. Two types of particles, alginate particles and liposomes were prepared for encapsulation. For all particles, encapsulation efficiency, size, stability, and antioxidant activity were determined. Long-term stability was then monitored within three months. The particles were also exposed to artificial gastric, pancreatic and bile juice. All tested particles showed very good encapsulation efficiency. In terms of long-term storage stability in an aqueous environment. Particularly liposome particles, which also showed high stability by zeta potential measurement, were suitable. On the contrary, in case of alginate particles, when stored in an aqueous medium, the release of active substances occurred. Finally, an energy drink was created and subjected to sensory analysis. The best energy drink was based on black or green tea with alginate particles acai, goji and ginseng.
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Encapsulation of probiotics and prebiotics for use in nutritional products for children
Šnajdarová, Karolína ; Němcová, Andrea (referee) ; Skoumalová, Petra (advisor)
The Diploma thesis deals with designing of probiotic dietary supplement for children with strains Lactobacillus acidophilus and Bifidobacterium breve and with prebiotics. Used prebiotics were Inulin, Chia fiber, Bamboo fiber, Chlorella + Spirulina and Yakon syrup. The theoretical part is focused on probiotics, prebiotics and their biological influence. In experimental part the possibilities of encapsulation into alginate particle and lyophilisation of probiotic cells were observed to find their good form to final nutritional product for children. Several types of probiotic with addition of prebiotics were tested in model conditions of gastrointestinal tract. It was found that addition of prebiotic highly increases viability of probiotic cells and their resistance to model conditions of gastrointestinal tract. In this case, the best prebiotic was found in Yakon syrup. The prebiotics were also characterised in terms of nutritional composition, amount of total and reducing sugars, oligosaccharides, proteins, lipids, polyphenols and chlorophyll were obtained. Finally, Chia fiber, Chlorella + Spirulina and Yakon syrup were chosen as prebiotics with best characterisation/properties. In conclusion, a dietary supplement with lyophilized alginate particles containing probiotic cells and with the most appropriate prebiotics were designed. Forms of the product were powder and gummy-bear.
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Isolation and characterization of natural active components and their application in food supplements
Šmídová, Veronika ; Němcová, Andrea (referee) ; Skoumalová, Petra (advisor)
The diploma thesis is focused on the characterisation and isolation of naturally occurred active compounds, especially on lipophilic compounds. The next part of the thesis deals with enzymes and their encapsulation into alginate particles to suggest new enzymatic dietary supplement for children with optimal nutrient composition. The theoretical part is focused on the issue of child nutrition, accordingly the necessary nutrients that children need to grow without any health difficulties. It is also focused on the availability of enzymatic food supplements for children. Finally, the theoretical part deals with the lack of chosen natural substances and their effects in connection with cancer. In the experimental part, four types of oils obtained from seeds were characterized. The oils were obtained by two methods: cold pressing with a Yoda kitchen press and extraction in an organic solvent with Soxtherm. Seeds were linseed, sesame, pumpkin, and cumin. With these oils were characterized natural active substances, polyphenols, flavonoids, antioxidants, carotenoids, chlorophylls, and fatty acids. Liposomes were also prepared from selected extracts, in which an effect on intestinal tumour cells were observed. Furthermore, some enzymes were selected, and they were encapsulated into alginate particles with average size 450 µm. In these particles was specified encapsulation efficiency as well as the proteolytic activity after testing in digest juices. The last part of this thesis was focused on the optimization of a complete enzymatic food supplement with addition of alginate particles as enzyme carriers. Samples of these supplements were finally subjected to a sensory analysis.
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Use of microcalorimetry in the study of hydration of biopolymers
Bola, Tomáš ; Smilek, Jiří (referee) ; Krouská, Jitka (advisor)
This master thesis deals with the using of microcalorimetry in the study of hydration of biopolymers. Lactose has been selected together with the other biopolymers although it is not among biopolymers but disaccharides. Selected biopolymers are alginate, dextrane, chitosan and hyaluronan of two molecular weights. Lactose has been selected for these purposes mainly because it is a model example to determine whether or not the reaction to moisture between the other samples and the saturated salt solution occurs. The biopolymer hydration study, as opposed to the commonly used perfusion calorimetry method using the possibility of measuring with adjustable moisture has been used an isothermal microcalorimetry method where at two constant temperatures the reaction of the sample to the different moisture released by the saturated salt solution was monitored.
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Preparation and characterization of hybrid hydrogels matrix
Magera, Lukáš ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis aims for preparation and subsequent optimisation of hybrid hydrogels, which represent material with high application potential because of their unique properties. Hybrid hydrogels have extraordinary mechanical resistance and other beneficial properties (e.g. transportation) due to their unique hybrid network structure, strong interpenetrating network entanglement and efficient energy dissipation system. This work engages in chemically-physically crosslinked hybrid gel, namely the combination of alginate-polyacrylamide. The hybrid hydrogel was formed and then underwent the tests of drying and swelling. The main purpose of the experimental part was to determine viscoelastic properties of hybrid hydrogels using standard oscillation tests. Swelling tests showed that the hybrid network containing limitedly swelling alginate gel reaches lower degree of swelling than the single unlimitedly swelling polyacrylamide gel. Viscoelastic tests unveiled an influence on the mechanical properties by value augmentation of the hybrid gel´s storage modulus in comparison with the reference alginate hydrogel. Hybrid hydrogel reported an increase in the linear viscoelastic area compared to the reference polyacrylamide gel, whose hybrid structure prevents from creating microcracks, that caused earlier rupture of the reference polyacrylamide gel.
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Study of barrier and transport properties of polyelectrolytes using diffusion techniques in hydrogels
Valentová, Kristýna ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
This diploma thesis was focused on study of barrier and transport properties of selected polyelectrolytes in hydrogel matrices by using diffusion techniques. The study of these properties was performed in horizontal diffusion cells where is observed the change in diffusion probe concentration over time. Diffusion experiments were performed on an agarose hydrogel with the addition of alginate, hyaluronic acid, polystyrene sulfonate, humic acids and as a model probe rhodamine 6G was used. Important parts of this thesis are also the methods which characterize the substances and hydrogel matrices such as rheology and potentiometric titration. The main aim of this diploma thesis was to investigate the effect of interactions between passing model dye (rhodamine 6G) and the appropriate gel (agarose + polyelectrolyte) on the fundamental diffusion parameters (effective diffusion coefficient, lag time, etc.).
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Preparation and characterization of enzyme-containing wound dressings
Jurová, Bronislava ; Szotkowski, Martin (referee) ; Skoumalová, Petra (advisor)
This diploma thesis is focused on the study and characterization of nanofiber wound dressings from natural biopolymers. Proteolytic enzymes, specifically collagenase and bromelain, were incorporated into these nanofiber covers. The theoretical part deals with a brief description of skin wounds, their healing and skin covers. There are also methods for preparing these covers and the methods used to characterize them. The practical part deals with the optimization of the preparation of nanofiber coatings based on polyhydroxybutyrate, gelatin, alginate and chitosan. These nanofibers were then enriched with active substances and their gradual release into the model environment was monitored. Finally, their proteolytic activity was determined for these substances.
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Phospholipids as the basis of biodegradable delivery systems
Burdíková, Jana ; Čeppan, Michal (referee) ; Mravec, Filip (advisor)
This thesis is focused on investigation of phospholipid-hyaluronan system. First, appropriate method for preparation of bulk solution of phospholipid/lipid and suitable fluorescence probe were chosen. Sonification was selected as a method for preparation of bulk solution and pyrene was chosen as a fluorescence probe. From the group of phospholipids lecithin was selected. Next to phospholipid, lipid with no phosphate group (DPTAP) was utilized for comparison, alternatively a mixture of lipid (DPTAP) and phospholipid (DPPC). Instead of hyaluronan another polyelectrolytes (sodium polystyrene sulfonate, sodium alginate) were used too. Measurements were performed in water environment and in phosphate buffer saline (PBS). All investigation was accomplished by fluorescence spectroscopy and dynamic light scattering.
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The Utilization of Light Scattering Techniques for the Study on Hydrogel Gelation
Candráková, Simona ; Smilek, Jiří (referee) ; Kalina, Michal (advisor)
This bachelor thesis focuses on the study of hydrogel gelation using light scattering methods. For these purposes two different biopolymers (agarose and sodium alginate), with different sol to gelation phase transition, were selected. In the case of agarose, the gelation is caused by temperature change. On the other side, the gelation of sodium alginate is initiated by addition of polyvalent cations. In the experimental part of the work, agarose gelation was studied by DLS, temperature gradients of agarose solutions (40 – 30 °C) were measured. During the measurement the particle size distributions in the solutions having different concentrations were monitored as well as the temperature influence on the diffusion coefficient. The DLS method provided the values of the gelling temperatures of the solutions at a concentration of 0,5 wt.% and 1,0 wt.%. Furthermore, the DLS microrheology method was used, where temperature dependences of viscoelastic characteristics of agarose solutions (40 – 30 °C) were also measured, from which the gelling temperatures of agarose solutions of 0,1 wt.% and 0,5 wt.% were evaluated. The classical rheology was also used in the work to compare the viscoelastic behaviour of the samples and to determine the gelation point of the agarose solutions. By this method were determined gelling temperatures for all studied concentration of agarose (0,1 wt.%, 0,5 wt.% and 1,0 wt.%). The DLS method was also used to monitor the interactions of sodium alginate with the addition of Ca2+ ions, these interactions were then also evaluated and discussed in the experimental part.
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