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Blue-light crosslinked hydrogels from modified natural gum for medical applications
Waclawiková, Petra ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
The main aims of the presented master’ thesis are focused on the modification of natural gum and its consequential crosslinking via blue or ultraviolet light, in order to develop a sprayable hydrogel applicable for controlled wound healing. The theoretical part of the work deals with the preparation of hydrogels, especially by photopolymerization, and the possibilities of using different light sources for crosslinking. Related to this, the work contains and overview of photoinitiators suitable for the preparation of water-based hydrogels. Thesis introduce examples of functionalization in order to implement a photosensitive functional group into the polymer structure, especially methacrylation. The experimental part of the presented work deals with the preparation and characterization of hydrogels composed of synthetic and natural polymers. The default material was the natural polysaccharide Gum Karaya (GK), which was chemically modified and consequently crosslinked via water-soluble photoinitiator. Chemical modification of Karaya gum saccharide was characterized by two spectroscopic techniques. The attenuated total reflection method of Fourier transform infrared spectroscopy (ATR-FTIR) was used to determine changes in chemical structure. Furthermore, Raman spectroscopy was used as a supplement to the ATR-FTIR method. UV-Vis spectrophotometry was used to evaluate the optical properties of the samples before and after photocrosslinking. The application properties of the synthesized polysaccharide and the prepared hydrogels were tested by the swelling method and the sprayability was verified by rheology. Based on the results, the chemical modification of gum Karaya was successful and it was possible prepare a photocrosslinked hydrogels after the photoinitiator addition.
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The effect of biopolymers on adhesive and rheological properties of calcium phosphate bone cements
Scholz, David ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
This thesis deals with bone cement composed of tricalcium phosphate and thermosensitive copolymer. The main aim was to improve especially the adhesive properties of the cement by adding polysaccharide. The theoretical part of the thesis deals with the characterization of bone cements and their application and also a description of polymeric additives used in bone cements mainly focused on polysaccharides. In the experimental part, the prepared cements were characterized using rheology, powder X-ray diffraction and static mechanical tests on the cured cement alone and glued bones. Rheology was used to measure the setting time of the cements as a function of time and temperature. Furthermore, rheology was also intended to measure the adhesive properties of copolymer solutions, but this was not possible due to the nonreproducible results caused by inhomogeneity of the copolymer solutions with polysaccharide. Powder X-ray diffraction was used to measure the effect of polysaccharide on the conversion of tricalcium phosphate to calcium deficient hydroxyapatite. It was found out that polysaccharide does not significantly affect the conversion of tricalcium phosphate. Static mechanical tests were used to measure maximal compressive strength for the cured cement samples and also to measure the adhesion strength of glued bone samples. Cured samples with low polysaccharide concentration showed higher compressive strength compared to control samples. Inconclusive results were obtained during testing of the bone samples due to the complexity of the measurement. In particular, it concerns the preparation of bone samples and their gluing with bone cement.
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Catecholamine modified polymer-composite bone cement: preparation, characterization and in-vitro evaluation
Raszková, Alena ; Vojtová, Lucy (oponent) ; Michlovská, Lenka (vedoucí práce)
This bachelor thesis is focused on preparation, characterization of catecholamine-modified calcium phosphate cement and evaluation of in-vitro tests. The theoretical part deals with the characterization of calcium phosphate cements and their material property. This part also includes overview of additives used to modify cements in order to improve both their chemo-physical and biological properties. The increasing use of catecholamine in tissue engineering is also discussed here. First part of experimental work focuses on optimization of preparation and characterization of catecholamine modified calcium phosphate cement. The phase composition kinetics was evaluated by X-ray diffraction analysis and chemical composition by Fourier-transformed infrared spectroscopy. The second part of the work is then focused on the optimization and evaluation of in-vitro cytotoxicity of modified cements. In conclusion, it was found that the conversion rate during curing was faster when catecholamine was used to prepare phosphate cement. Modified cements exhibit almost 93 % conversion after 3 days with respect to unmodified one where the conversion reach only 79 % at the same time. For in-vitro testing, the new method for preparation of samples was approached. It was found that further optimization of the preparation method and test conditions are necessary for the successful in-vitro tests. Due to attractive properties, catecholamine-modified calcium phosphate cement seems to be an interesting material for bone regeneration.
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Influence of antibacterial enzymes on preparation and properties of phosphate cements
Přečková, Barbora ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
The subject of the bachelor thesis is to prepare tricalcium phosphate bone cement (CPC) modified with antibacterial enzyme for effective and safe bone infection (osteomyelitis) treatment in comparison to antibiotics therapy. The theoretical part of this bachelor thesis provides informations about the structure of bone, osteomyelitis and treatment of osteomyelitis by different types of antibacterial bone cements, specifically by calcium phosphate bone cements. The experimental part deals with optimization in sample preparation, description of the used methods and characteristics of enzyme release kinetics from the cured CPC. To better understand the enzyme release mechanism from the cement, model both enzyme and protein-loaded CPC samples were also prepared and evaluated. Antibacterial properties of the prepared samples were tested by disk-diffusion, dilution and plate method resulting in the positive inhibition effect of antibacterial enzyme on Gram-positive bacteria (G+) of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) strains but negligible effect on Gram-negative bacteria (G-) Escherichia coli. In the following work, the in vitro biocompatibility of the enzyme-loaded cements will be evaluated.
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Effect of enzymes on the degradation of thermosensitive copolymers for controlled release of drugs
Dávidíková, Anna Mária ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Thermosensitive hydrogels used for drug delivery systems are of great interest these days. They serve as a drug vehicle that transport drugs to a target place and then they serve as a drug depot in the body. Hydrogels can be tuned to be able to encapsulate various drugs, to be sensitive to various external stimuli, or to degrade slower (maintain the drug longer in the body). To tune hydrogels, we need to know their degradation process and their behaviour in different degradation media; thus, we can predict how they will behave. In this proposed thesis, the degradations of various thermosensitive hydrogel solutions were studied in different degradation media. The theoretical part of this work provides a short review of thermosensitive hydrogels, their characterisation, properties, use for drug delivery systems, and degradation. Firstly, a triblock thermosensitive copolymer PLGA-PEG-PLGA that consists of poly(D,L-lactic acid-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(D,L-lactic acid-co-glycolic acid) was synthesized via living ring-opening polymerization under an inert atmosphere and characterized via proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. This copolymer was further used for hydrogel water solutions in 10, 15 and 20 wt. % concentrations. Hydrogel samples prepared at 37 were degraded in various media (UPW (ultrapure water), NaCl, PBS (phosphate-buffered saline), and PBS with enzyme) in the incubator for 30 days. The sample removal was set for 1, 2, 3, 7, 9, 14, 16, 21, 23 and 30 days except for the enzyme solution where we expected quick degradation. Degraded hydrogels were analysed via gel permeation chromatography and degradation media via liquid chromatography with mass spectroscopy. Gravimetric analysis and measurement of pH over time were also part of the hydrogel behaviour study. The last aim of this work was to evaluate the collected data and see whether the used enzyme affected the PLGA-PEG-PLGA hydrolytic degradation kinetics. The results proved a minor acceleration in the degradation by the enzyme. These results will serve as a foundation for further degradation studies.
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Crosslinking of thermosensitive functionalized copolymers by blue light
Křivánková, Nikola ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
The aim of this thesis was to prepare a hydrogel with a hybrid network of only one type of biodegradable copolymer. The new degradable hydrogel, containing both physical interactions (arising at physiological temperature of 37 °C) and chemical bonds initiated by blue light could be used as a resorbable wound dressing or as an injectable carrier with a gradual and well controlled drug release. Thermosensitive PLGA–PEG–PLGA copolymer synthesized by living ring-opening polymerization was subsequently functionalized with itaconic anhydride to form ITA/PLGA–PEG–PLGA/ITA light-sensitive and temperature-sensitive macromonomer. At 37 °C, the copolymer forms a micellar network due to hydrophobic interactions. Itaconic acid double bonds, which are attached to the ends of the copolymer chain, allow photochemical crosslinking of micelles with a view to increase the hydrolytic stability of novel hydrogel. The synthesized copolymers were characterized by GPC and 1H NMR methods. The formation of a physical network at physiological temperature was confirmed by rheological analysis. The physically crosslinked ITA/PLGA–PEG–PLGA/ITA hydrogel was then irradiated with blue light (430 – 490 nm) in the presence of a water soluble biocompatible photoinitiator LiTPO and chemically characterized by ATR-FTIR. The resulting hydrogel was transparent, flexible, absorbed up to 1176 % water, and was stable for 20 days in saline at 37 °C. The ITA/PLGA–PEG–PLGA/ITA hydrogel with hybrid network was also prepared in the presence of a crosslinker PEGDA, that significantly reduced the time required for crosslinking the hydrogel, but further analyses are needed to more fully understand the principles of the novel hydrogel types.
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Optimization of antibacterial properties of polymer-phosphate bone fillers
Grézlová, Veronika ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Proposed diploma thesis is focused on the preparation of polymer-phosphate bone cement. The aim is to optimize antibacterial properties of the cement by adding selenium nanoparticles (SeNPs). The theoretical part describes the characteristics of bone, properties od tricalcium phosphate (TCP) and its polymorphs, the use of bone cement and antibacterial nanoparticles in medicine. The experimental part deals with the preparation of samples, description of the used methods and evaluation of the effect of SeNPs on the bone cement setting reaction, morphology, crystallinity, mechanical, rheological and antibacterial properties. As a result, SeNPs improved bone cement injectability and increased setting reaction with the positive effect on cement mechanical properties. Antibacterial properties of samples were tested using both disk and dilution method resulting in the positive inhibition effect of SeNPs on gram-positive bacteria (G+), especially Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus. The quantitative SeNPs release from modified polymer-phosphate bone cement enable its use as antibacterial bone filler (e.g. for osteomyelitis treating).
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Effect of body fluids on setting, structure and mechanical properties of phosphate bone cements
Bednaříková, Vendula ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Presented diploma thesis describes the preparation and characterization of composite calcium-phosphate bone cements (CPCs). In the literature review properties and structure of tricalcium phosphates (TCPs) are described, including their interaction with body environment. In the experimental work, first of all, sample preparation technique was determined by experiments with setting reactions provided in ultrapure water environment. Optimal technique of setting CPC samples included memory foam setting mold, ending setting reactions by absolute cold ethanol and vacuum drying procedures. Consequently, the work describes the sample preparation and process of TCP bone cement setting in both natural (pig blood) and simulated body fluids (physiological, Hank´s and Ringer´s solutions). Morphology study by Scanning Electron Microscopy (SEM) was performed for samples set for 1 day, 1 week, 2 weeks and 1 month, due to the significant change in crystalline structure proving as well by X-ray diffraction (XRD) analysis by determining -TCP conversion to calcium-deficient hydroxyapatite (CDHA). Porosity investigated by X-ray computed microtomography (-CT) was slightly higher at sample set in natural blood. Mechanical properties of CPC samples measured by mechanical compression tests showed stable cement strength set in physiological solution already after 1 day while cements set in blood has shown still increasing strength even at 1 month. On contrary, strength of cement samples rapidly decreased after 2 weeks of setting in both Hank´s and Ringer´s solutions probably due to its slightly acidic pH accelerating CPC disintegration. As a result, setting environment has significant effect on resulting CPC properties and natural blood in comparison to simulated plasma had shown better CPC properties while more closely imitating the in vivo conditions.
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