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Hydrogels modified by amphiphilic structures
Heger, Richard ; Sedlařík, Vladimír (referee) ; Kráčalík, Milan (referee) ; Pekař, Miloslav (advisor)
The submitted dissertation deals with the influence of amphiphilic structures on hydrogel properties. Additions of various amphiphilic substances associated with the formation of highly ordered structures affect the mechanical, transport and structural properties of hydrogels. The main inspiration for this type of work was living tissue, more precisely the extracellular matrix, which is often mimicked by hydrocolloids, and its high orderliness is responsible for its unique properties. The knowledge obtained from this tissue was applied to the hydrogel systems studied in this work. Various cross-linked hydrogel matrices (physically cross-linked agarose and gelatin, ionically cross-linked alginate and chemically cross-linked mixture of polyvinyl alcohol and chitosan) were suitable representatives for this work. These hydrogel systems were modified by the addition of various amphiphilic substances. The human body’s own phospholipid, lecithin, or variously charged more classic surfactants (CTAB, SDS and Triton X-100). Experimentally, this work is divided into three areas, the study of mechanical properties using rheology, the description of transport properties via release and flow experiments using various model drugs (rhodamine 6G, eosin B, amido black 10B, methylene blue and riboflavin), and morphological characterization using SEM. The characterization of hydrogel systems was supported by other techniques used in this work, such as drying and swelling experiments or gas sorption.
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Hydrogels with incorporated enzymes
Geistová, Karolína ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the study of incorporation of enzymes into phase separated hydrogels. The aim of this work is to determine the enzyme activity in phase separated gels. Gels were prepared by the dry-way based on the interaction of negatively charged polyelectrolyte (hyaluronan) with positively charged surfactant (Septonex). Two enzymes, bromelain and collagenase, were incorporated into the hydrogels. To determine enzyme activity, the modified albumin protein with bound sulfanilamide group (azoalbumin) was used as a substrate. The enzyme activity of the enzyme itself, the enzyme activity affected by one of the two components of the system as well as the activity of the enzyme directly in the hydrogel was determined on UV-VIS spectrophotometry. The enzyme was found to be incorporated in the hydrogel. Furthermore, a significant effect of the positively charged surfactant on the enzyme activity was detected in phase-separated hydrogels.
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Preparation, characterization of trimethylchitosan and verification of its interaction ability with regards to variable charged ionic compounds
Bayerová, Zuzana ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The aim of this thesis is to study the interactions of trimethylchitosan with oppositely charged substances with regard to its potential biomedical use. A substantial step before the study of interactions was a successful synthesis of trimethylchitosan, which was subsequently confirmed by characterization of the final synthesis product using physico-chemical methods (infrared spectroscopy, elemental analysis, nuclear magnetic resonance). The result product was subjected to negatively charged interactions such as sodium dodecyl sulphate as a representative of the ionic surfactant, alginate as a natural polysaccharide representative and Chicago Blue as a representative of the anionic dye. The ability to interact with sodium dodecyl sulfate and alginate was demonstrated by the formation of hydrogels, which were subsequently characterized by mechanical viscosity tests using rheometric properties. The positive affinity of trimethylchitosan for organic dyes has been investigated in agarose-based support hydrogel matrices for changes in transport and barrier properties.
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Characterization of hydrogels based on photocross-linked derivative of hyaluronan
Hekrlová, Veronika ; Smilek, Jiří (referee) ; Klučáková, Martina (advisor)
This bachelor thesis focuses on characterization of hydrogels based on photocross-linked Tyramine-modified hyaluronan (HA-Tyr). In the first part of the work, swelling of gels in saline and porcine plasma was examined, in which the hydrogels swell significantly less. The second part of the thesis is focused on rheology. First, dependence of the apparent viscosity of precursor solutions on shear rate was tested. The apparent viscosity increases with the concentration of derivative and Mw. This trend can also be observed when measuring viscoelastic properties (the elastic modulus) in oscillation mode (strain sweep test). The elastic modulus can also be affected by using a higher concentration of the photoinitiator riboflavin (RF), higher radiation intensity or by longer exposure times, although the material can be degraded. The work also includes an ATP bioluminescence method cytotoxicity test, which proved that the methods used are safe for in situ application.
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Preparation, characterization and evaluation of application potential of semiIPN hydrogels
Papežíková, Hana ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
Aim of this thesis os to optimize set up of hydrogel based on semi-interpenetrated polymer networks. Polyhydroxyethylmethyl acrylate was chosen as an model example of hydrogel due to its common use in biomedicine. At first, thermoiniciation was used for preparation and changed to photoiniciation afterwards. Following the optimisation of the hydrogel set up with proper qualities, the polyelectrolyte sodium polystyrene sulfonate was implanted. Object of research was its impact on structure, flowing and transport features of hydrogels. All qualities were tested by drying, rheology, and fluorescence correlation spectroscopy. Results clearly validate influence of hydrogel features by polyelectrolytes.
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Development of Material Based on Hyaluronic Acid s Hydrogels for Myocardial Regeneration
Kovářová, Lenka ; Kubala,, Lukáš (referee) ; Prokš,, Vladimír (referee) ; Pekař, Miloslav (advisor)
The thesis is focused on material development based on hyaluronic acid usable in regenerative medicine, especially for heart tissue regeneration after myocardial infarction. The object of the study is the oxidized form of hyaluronic acid (HA-Ox) and hydroxyphenyl derivative of HA (HA-TA). HA-Ox can be crosslinked with a bifunctional alkoxyamine POA and HA-TA undergoes an enzymatic reaction in the presence of hydrogen peroxide catalysed by horseradish peroxidase leading to gel formation. To describe the materials, chemical and physical properties, gelation kinetics and conditions of crosslinking reactions were studied. Hydrogels were characterized by mechanical and viscoelastic properties, degradability or stability in simulated body fluids. These hydrogels serve as scaffolds for the selected cell type. To promote cell adhesion and viability, an RGD sequence has been bonded to the structure of HA-TA. This resulting material is also compatible with selected applicators. Its viscosity and extrusion force are low enough to allow application with a catheter with a very small internal diameter. The applicability of the material through the supply tube to the hydrogel reservoir of the second SPREADS device showed good homogeneity, cell distribution and viability. Finally, the material was applied in vivo using these devices during a preclinical study.
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Study on reactivity of humic acids via method of diffusion cells
Hrubá, Pavla ; Weidlich,, Tomáš (referee) ; Sedláček, Petr (advisor)
The diploma thesis focuses on utilization of diffusion cells in reactivity mapping study on humic acids. In the experimental part, samples 6 humic acids of different origin or chemical modification were studied. All the samples were characterized by basic analytical and physico-chemical methods (elemental analysis, thermogravimetry, determination of acidity, spectrometry). Methylene blue was utilized as a model reactive probe and agarose gel as an inert support medium. An effect of interactions between humic acids and methylene blue on diffusivity of the dye in the hydrogel was determined and discussed.
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Hydrogels amino-dextran-surfactant: phase diagram
Daňková, Kristýna ; Hurčíková, Andrea (referee) ; Pekař, Miloslav (advisor)
This bachelor thesis deals with a study about hydrogel systems based on the physical interactions of the oppositely charged particles, specifically interactions between positive polyelectrolyte and negative detergent. The phase diagrams were created based on the visual evaluation of results of the laboratory experiment, which is a part of this thesis, for in advance chosen concentration of the polymer diethylaminoethyl-dextran hydrochloride and detergents sodium dodecyl sulphate and sodium tetradecyl sulphate. These phase diagrams characterize incurred dextran systems.
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Studying the quality of hydrophobic domains in the phase separated hydrogels
Burešová, Natálie ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
The thesis deals with the study of hydrophobic domains in phase separated hydrogels. Two types of polyelectrolytes (hyaluronan, dextran) and oppositely charged surfactants (carbethopendecinium bromide, sodium dodecylsulphate ) are used. Phase separated hydrogels are formed by electrostatic interactions. The target of the thesis is to study the polarity of environment in phase separated hydrogeles by fluorescence spectroscopy. Fluorescence measurements is performed by using pyrene, Nile red and laurdane as fluorescence probes. All probes are sensitive to the polarity of the environment. The results showed that probes can be expected in the polar environment of hydrogels.
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Hydrogels based on cationic polyelectrolytes
Jarábková, Sabína ; Lehocký,, Marián (referee) ; Pekař, Miloslav (advisor)
This diploma thesis deals with the study of physical hydrogels based on positively-charged polyelectrolyte. The study is to investigate the interaction of selected positively-charged polyelectrolytes with oppositely charged surfactants in water and in physiologicla saline solution (0.15 M NaCl). The influence of the process for preparing hydrogels. Hydrogels were prepared by dry or wet. Were tested solubilization abilities hydrogels prepared using the hydrophobic dye oil red O were also measured rheological properties of the hydrogels prepared using frequency oscillatory tests and flow tests, depending on the concentration of the polymer or surfactant. For the rheological experiments suggest that chitosan is capable of forming rigid hydrogels with better mechanical properties than the dextran in the presence of both surfactants. Selected samples were also carried out experiments using fluorescent sold prodan, nile red and -naphthol as fluorescent probes. And in selected experiments was determined by solids content in percentage depending on the concentration used polyelectrolytes or surfactants.
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