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Alternative crosslinking methods for sodium alginate resulting in hydrogels with suitable application properties
Kouřilová, Ludmila ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
This diploma thesis is focused on the preparation of alginate gels with the potential to influence their final application properties (transparency, syneresis, viscoelastic properties, etc.). Based on literature review, a total of three gelation strategies leading to the gelation of sodium alginate were selected, namely ionotropic gelation by external gelation method, ionotropic gelation by internal gelation method, and alginate crosslinking with phytic acid, which is capable of forming both ionic bonds and intramolecular hydrogen bonds. Subsequently, the preparation of alginate gels was optimized, their mechanical properties were characterized, and finally, the influence of several factors (polymer concentration, amount of crosslinking agent, gelation time, addition of sucrose, etc.) on the resulting properties of the prepared gels was monitored. Within the scope of the thesis, it was demonstrated that the resulting properties of sodium alginate-based gels are influenced not only by the polymer concentration, the amount of crosslinking agent used, gelation rate, or syneresis, but in the case of ionotropic gelation by external gelation, for example, also by the type of anion used. An interesting part of the thesis is also the optimization of determining the mechanical properties of alginate gels through compression tests. During these tests, the sample is compressed between two rheometer sensors, and the mechanical response of sample to the applied force is measured. It is one of the most easily conceivable rheometric tests.
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Derivatization of Sodium Hyaluronate as a Possible Tool for Increasing of the Stability of Model Artificial Synovial Fluid
Hrochová, Eliška ; Mravec, Filip (referee) ; Kalina, Michal (advisor)
This master thesis deals with the optimization of the procedure of modification of hyaluronic acid structure for the use in the artificial synovial liquids. Based on the literature research, the amino acid alanine was used for the modification of carboxylic group in the glucuronic acid. The main subject of study is the improvement of the stability and mechanical properties of synovial liquid. DLS microrheology, macrorheology, thermogravimetric analysis (TGA), multi-angle light scattering with flow-field flow fractionation (AF4-MALS) and infrared spectroscopy (FTIR) were used for characterization. The theoretical part of this theses submits review of the musculoskeletal system, role of hyaluronic acid in metabolism and summary of synovial liquid. The experimental part focuses on the measurement of the stability and mechanical properties of three artificial samples (first with no modification, second with modified hyaluronic acid and third with modified hyaluronic acid and chondroitin sulphate). These samples were compared with real horse synovial fluid and artificial viscosupplement Orthovisc®.
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Viscoelastic properties of hydrogels depending on relative humidity
Kouřilová, Ludmila ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This bachelor thesis is mainly aimed on the determination of the dependence of the viscoelastic properties of physically crosslinked hydrogels on the relative humidity controlled by humidity cell (as an accessory to a rotary rheometer), or the desiccator with the drying medium. The main objective was to optimise the methodology of the humidity cell for the rheological determination of the viscoelastic properties of hydrogel materials as a function of relative humidity and to verify experimental setup on the agarose hydrogel. The results showed that the agarose hydrogel gradually loses its dispersion medium after exposure to chosen relative humidity, resulting in a loss of contact between the upper rheometer sensor and the sample when measured with the standard measurement gap control setting, which is constant during the measurement. The setting of the control of normal force proved to be an appropriate solution, which has led to a gradual reduction in the height of the upper rheometer sensor in an attempt to keep the normal force at the desired level during the drying of the hydrogel. A humidity cell proves to be an appropriate method for determining the dependence of the viscoelastic properties of hydrogels on relative humidity. Unlike the use of a desiccator with drying medium, the drying of the hydrogel sample does not result in such rapid drying that it breaks the texture on its surface. Another advantage of a humidity cell is the ability to maintain the desired relative humidity value even if the gel begins to release dispersion medium into its surroundings, which was not possible with a desiccator with drying medium.
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Rheology of Alkali-Activated Slag during Its Early Hydration Stages
Pazour, Miroslav ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis focuses on the measurement of viscoelastic parameters of mixtures based on alkali-activated blast furnace slag during hydration. Hydration was monitored using isothermal calorimeter and initial and final setting time was determined for another comparsion by Vicat’s needle. These parameters were measured depending on activator dosage (water glass) and organic admixture dosage (hexylene glycol) and compared with each other. It was observed that storage modulus prevailed over loss modulus in fresh mixtures with lower dosage of activator, whereas in mixtures with higher dosage of activator viscous component began to prevail and complex modulus was rather descreasing. Conversely, in mixtures with higher hexylene glycol dosage complex modulus was significantly increasing. Evolution of modules in time correlated with calorimetric curves and setting times. During setting time, which is assigned to formation of primary C-A-S-H, values of viscoelastic parameters was remarkably increasing.
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Optimization of preparation and characterization of hybrid hydrogels with respect to viscoelastic and flow properties
Zhurauliova, Darya ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on the study of hybrid hydrogels that combine the properties of the hydrogel system together with oleogels, which is a gel on the base of oil. The aim of the thesis is to carry out a study of the current state of the solved issue on the topic of preparation of hybrid hydrogels, on this basis to design and optimize the appropriate procedure of preparation and in the form of viscoelastic measurements to perform the basic reological characterization of the prepared systems. A system based on sodium alginate dissolved in deionized water and meshed with calcium chloride solution was chosen as a suitable hydrogel system, and a system based on beeswax dissolved in sunflower oil was chosen as oleogel. Sodium alginate has been chosen because it is used as a thickener, emulsifier, stabilizer or gelling agent in the creams and preparation of pharmaceutical forms. By mixing hydrogels and oleogels of different proportions, a hydrogel/oleogel system, also called bigel, was created, the properties of which were tested in terms of flow and viscoelastic properties. In the practical part, amplitude, frequency and flow tests of both the hydrogel itself and the hybrid hydrogel with a ratio of 50:50 (hydrogel vs. oleogel) were measured. These tests provided information on gel preparations, i.e. what is their character, what are the mechanical properties and how it depends on the amplitude of deformation. By comparing the measurement results, it was possible to determine how oleogel acts on the properties and structure of the hydrogel.
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Preparation and characterization of hydrogels with diffusion gradient
Tvrdoňová, Anna ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The presented bachelor thesis deals with the preparation and further characterization of hydrogels with a diffusion gradient. The aim of the thesis is a literature research on the issue of hydrogels with a diffusion gradient, and a selection of a suitable method for its preparation. Moreover, conducted pilot experiments lead to the characterization of the properties of the prepared systems, especially with regard to proving the gradient structure of hydrogels. The performed evaluation was based on visual observation, determination of transport, and viscoelastic properties. In addition, a simple method consisting of weighing the prepared hydrogels was used. Hydrogels were compared depending on the choice of crosslinking agent, its concentration, and crosslinking time. Gradient hydrogels based on polysaccharide sodium alginate were prepared. The results suggest that by selecting the concentration of the crosslinking agent, as well as the crosslinking time, the final properties (viscoelastic and transport) of the hydrogels can be adjusted to the desired values. In the discussion of the results, we propose steps for a more comprehensive view of the issue and providing options for the following research.
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Corelation of transport and viscoelastic properties of hydrogels with diffusion gradient
Ščotková, Romana ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
The aim of the presented bachelor thesis was to prepare hydrogels with diffusion gradient and to demonstrate the gradient structure of hydrogels in terms of viscoelastic and transport properties. With regard to potential biomedical applications, the cationic polysaccharide chitosan was selected for the preparation, especially for its antimicrobial and biocompatible properties. The resulting gradient hydrogels were subsequently characterized by oscillation tests to observe the differences using different concentrations and molecular weights of chitosan, crosslinking agent concentrations, dispersion environments for chitosan dissolution, and different gel crosslinking times. The samples were also subjected to drying experiments to confirm the gradient structure formed. The ability of the hydrogels to transport the active species was confirmed by visually evaluating the permeation of the anionic dye (bromothymol blue) during the gelation process. From the results obtained during the experimental part of the bachelor thesis it can be concluded that the viscoelastic properties of hydrogels can be modified by changing selected parameters during the preparation itself. It was also confirmed the assumption that with better mechanical properties of hydrogels there is a deterioration of transport properties. By controlled diffusion method, it was possible to prepare a hydrogel with a gradual gradient of crosslinking density, thus modifying the viscoelastic and transport properties.
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Preparation and characterization of polysaccharide hydrogel systems with gradient structure
Škutová, Patricie ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with the preparation of polysaccharide hydrogels with a diffusion gradient and their subsequent characterization in terms of viscoelastic properties, which are used to demonstrate the gradient structure. The main goal was to select a suitable method for the preparation of chitosan hydrogels with different molecular weights (168 kDa - 437 kDa). The biopolymer chitosan is a cationic polysaccharide that is suitable for use in biomedical applications due to its excellent biocompatible properties. First, concentration-uniform hydrogels without gradient structure were prepared, in which the influence of various parameters (chitosan molecular weight, chitosan concentration, sodium hydroxide concentration) was investigated. To prove the created gradient structure, the samples were subjected to the drying method (determination of the dispersion fraction) and determination of mechanical properties by oscillatory rheometry. Increased attention was paid to the search for a suitable preparation method for gradient chitosan hydrogels with higher molecular weight, which showed some problems with the already established method of preparation of hydrogels with gradient structure controlled by diffusion. From the results of the measurements obtained, it can be concluded that the viscoelastic properties of the hydrogels can be modified by changing the selected parameters and the method of preparation. By the controlled diffusion method, it was possible to prepare hydrogels with a gradual gradient of cross-linking density, which confirmed the assumption that the more cross-linked the layer, the higher the values of viscoelastic moduls and therefore the higher resistance to stress was confirmed.
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Formulation and characterization of hydrogels for local treatment of musculoskeletal infections
Drdová, Pavlína ; Šnejdrová, Eva (advisor) ; Vraníková, Barbora (referee)
Charles University Faculty of Pharmacy in Hradec Kralove Department of Pharmaceutical Technology Author: Pavlína Drdová Title of thesis: Formulation and characterization of hydrogels for local treatement of musculoskeletal infection Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Local anti-infective therapy for musculoskeletal infections eliminates systemic drug toxicity. By selecting a suitable drug delivery system, higher drug concentrations at the site of infection and sustained release can be achieved. Such a system may be gels, formulated and tested in the submitted diploma thesis. The theoretical part of the work was devoted to the description of musculoskeletal infections and their treatment, characterization of gels and their use in parenteral administration. Hydrophilic gels based on hypromellose, carrageenan, gelatin and fish gelatin containing vamcomycin hydrochloride and gentamicin sulfate were formulated. Flow and viscoelastic properties were tested on a rotational rheometer. The analysis of flow curves by the Power law model proved a non-Newtonian type of flow. The most sensitive to applied stress is a 3 % hypromellose gel, the least a dispersion of iota-carrageenan with povidone 25. Viscoelastic properties were evaluated based on elastic, viscous and complex modulus, phase angle and yield...
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Formulation and characterization of hydrogels for local treatment of musculoskeletal infections
Drdová, Pavlína ; Šnejdrová, Eva (advisor) ; Vraníková, Barbora (referee)
Charles University Faculty of Pharmacy in Hradec Kralove Department of Pharmaceutical Technology Author: Pavlína Drdová Title of thesis: Formulation and characterization of hydrogels for local treatement of musculoskeletal infection Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Local anti-infective therapy for musculoskeletal infections eliminates systemic drug toxicity. By selecting a suitable drug delivery system, higher drug concentrations at the site of infection and sustained release can be achieved. Such a system may be gels, formulated and tested in the submitted diploma thesis. The theoretical part of the work was devoted to the description of musculoskeletal infections and their treatment, characterization of gels and their use in parenteral administration. Hydrophilic gels based on hypromellose, carrageenan, gelatin and fish gelatin containing vamcomycin hydrochloride and gentamicin sulfate were formulated. Flow and viscoelastic properties were tested on a rotational rheometer. The analysis of flow curves by the Power law model proved a non-Newtonian type of flow. The most sensitive to applied stress is a 3 % hypromellose gel, the least a dispersion of iota-carrageenan with povidone 25. Viscoelastic properties were evaluated based on elastic, viscous and complex modulus, phase angle and yield...
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