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Studies towards the Preparation of Organic-Inorganic Hybrid Silica Fibers via Electrospinning
Koukolová, Anna ; Dzik, Petr (referee) ; Hüsing, Nicola (advisor)
Polyorganosilany spadají do skupiny hybridních materiálů třídy II, které nabízejí nové možnosti materiálových funkcí a jejich vlastností. Ačkoliv byly v této kategorii již některé materiály zkoumány a stejně tak i jejich aplikace, nebyly doposud vlákna na základě polyorganosilanu v mikro a nano rozměru popsány což bylo motivací pro tuto práci. Předkládaná diplomová práce se zabývá podrobným zkoumáním poly(vinylmethyldimethoxysilanu) jako možného prekurzoru pro elektrostatické zvlákňování. Za účelem přípravy polymeru na bázi vinylmethylsilanu byla provedena radikálová polymerace a podmínky reakce byly modifikovány se záměrem změny molekulové hmotnosti získaného polymeru. Stupeň polymerace byl upravován na základě změny koncentrace iniciátoru a byl stanovován dynamickým rozptylem světla v roztoku polymeru a spektroskopickou metodou nukleární magnetické rezonance. Elektrostatické zvlákňování je velkou měrou spojeno s vlastnostmi roztoku a důraz byl proto kladen právě na zjištění těchto vlastností. Na základě experimentů bylo zjištěno, že syntetizovaný polymer je na přípravu vláken vhodný. Nicméně byly získány i fragmenty vláken a to s využitím polymeru v roztoku methanolu. Předpokladem zvlákňování je dostatek propojení mezi polymerními řetězci. Tento přístup byl studován se zapojením sol-gel postupu a bylo zjištěno, že fáze sol-gel procesu je velmi významná s ohledem na tvorbu vláken. Dalším využitým postupem pro získání vláken bylo začlenění dalšího polymeru do směsi jako nosiče a tímto postupem byla získána vlákna s různým průměrem.
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Electrospinning of bioglass and glass-ceramic fibers
Kozáková, Zdenka ; Šťastná, Eva (referee) ; Částková, Klára (advisor)
Bachelor thesis is focused on the preparation of fibers based on bioglass and glass ceramics. The theoretical part of the work summarizes the division and description of biomaterials and their use in biomedical applications. The main part of the work deals with the preparation of bioglass with a focus on the preparation by electrospinning. Experimental part is focused on the preparation of fibers based on bioglass by electrospinning. Different types of bioglass precursors were studied and their spinnability, morphology and bioactivity of the prepared fibers were assessed. The fibers were analyzed by scanning electron microscopy and interactions in simulated body fluid. Fibers prepared from bioglass 45S5 and polyvinylalcohol precursor were evaluated as promising for biomedical applications.
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Electrical characterization of flexible nanofiber piezoelectric materials
Pokorná, Romana ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This bacherol thesis is focused on piezoelectric nanofibrous materials. The first part describes the formation, use and possible aplications of nanofibers. It further analyze the principle of piezoelectric effect. It is a conversion of mechanical energy into electric energy and conversely. The second part is focused on design of experimental workplace for measurement of functional material properties. The last section of the thesis is dedicated to the electrical characterization of PVDF nanofibers and to the measurement of the piezoelectric charge constant.
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Electrospinning of composite fiberous structures for piezoapplications
Schifferová, Zuzana ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
Polymer and composite polymer-ceramic nanofibers were prepared by electrospinning process. Solution of 20 wt.% polyvinylidene fluoride (PVDF) in a mixture of dimethyl sulfoxide (DMSO) and acetone in the ratio of 7:3 was chosen as the most suitable precursor. When preparing composite nanofibers, 20 wt.% of barium calcium zirconate titanate (BCZT) or barium titanate (BT) nanoparticles was added to this PVDF solution. Given parameters were defined as the most suitable for the process of electrospinning: voltage of 50 kV, feeding rate of 30 l/min, distance between emitter and collector of 20 cm and needle diameter of 17 G. The effect of polymer molecular weight and the rotation speed of collector was also studied. Various properties of prepared samples were studied: morphology and fiber diameter, phase composition with the use of x-ray diffraction and Fourier transform infrared spectroscopy and also chosen electrical properties. Lower fiber diameters appeared with lower polymer molecular weight and higher rotation speed of the collector. These parameters resulted in higher percentage of the piezoelectric phase as well. The smallest achieved fiber diameter was around 300 nm, the highest percentage of phase was 92 % and the highest piezoelectric constant had a value of 16 pC/N. Composite fibers filled with BT particles showed better properties that the ones filled with BCZT particles.
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Intelligent nanofibres functionalized with growth factors and blood derivatives for dermatology applications
Vocetková, Karolína ; Amler, Evžen (advisor) ; Rosina, Jozef (referee) ; Arenberger, Petr (referee)
Platelet derivatives are an attractive source of natural growth factors and they are widely used in various tissue engineering and regenerative medicine applications. The aim of this study was to optimize cell culture conditions using platelet lysate and to develop platelet-functionalized fibrous scaffolds as a controlled drug delivery system for native growth factors. Fibrous scaffolds were prepared by electrostatic and centrifugal spinning of PCL and they were functionalized by the platelets by surface adhesion or their encapsulation using emulsion spinning techniques. The cell culture study determined the 7% platelet lysate to be the optimum concentration as a medium supplement in keratinocyte and fibroblast culture. Additionally, following surface adhesion of the platelets to PCL electrospun nanofibres, the platelets were activated due to their contact with the nanofibre nanotopography, resulting in formation of fibrin network. Fibrin served as a reservoir of the growth factors, prolonging the half-time of EGF release to 1.7 days. Such platelet-functionalized samples fostered proliferation of keratinocytes, fibroblasts and melanocytes. Furthermore, adhesion of platelets to centrifugally spun nanofibrous scaffolds resulted in almost two-fold increase in the amount of immobilized platelet-derived...
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Nanofibrous Separators for Lithium-Ion Batteries
Pléha, David ; Míka, Martin (referee) ; Janderka,, Pavel (referee) ; Novák, Vítězslav (advisor)
Nanofibrous separators use in lithium-ion batteries brings many advantages. In contrast to contemporary used commercial separators, nanofibrous ones exhibit higher temperature resistance,ionic conductivity and higher electrolyte uptake. Better ionic conductivity is ensured by porous structure and large specific surface. Fibers creates channels for the ionic species motion. Amorphous texture of nanofibers allows quick lithium ionic species motion within the polymeric matrix of separator. Furthermore, these separators exhibit higher volume of uptaken electrolyte. Further advantage of electrospinned nanofibrous separators are both high porosity and chemical stability.
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Plasma modification of functionalized PVA nanofibers for the enhancement of mesenchymal stem cell adhesion, viability and proliferation.
Bezděková, Dagmar ; Amler, Evžen (advisor) ; Gášková, Dana (referee)
Electrospinning is widely used technique to produce nanoscale constructs for tissue engineering. This technique can be used to spin wide range of polymers. One of them is polyvinyl alcohol (PVA), which has very good properties for use in this field. PVA is nontoxic, has good mechanical strength and it's degradable and biocompatible. Electrospun PVA nanofibers have limitations because of their -OH side groups. These groups cause solubility of PVA in water. The solubility can be adjusted with crosslinking techniques, but PVA still remains very hydrophilic, which is causing low adhesion of cells. In recent research we decided to reduce the hydrophilicity of PVA using plasma modification. Polymer modification with cold plasma is an economic and quite simple process to change the surface chemistry without side effects that come with conventional chemical treatment. With radical, formed by discharge, we have deposited hydrocarbons on the PVA surface and we rapidly increased hydrophobicity of the polymer surface. The change of surface chemistry has only a little effect on the fiber morphology. The increase of hydrophobicity allowed better adhesion of mesenchymal stem cells on plasma modified PVA as compared to non-modified PVA and a huge change in cell morphology was observed. These changes suggest that we...
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Characterization of functionalized fibres for mesenchymal stem cells cultivation and differentiation
Greplová, Jarmila ; Amler, Evžen (advisor) ; Rosina, Jozef (referee)
Modification of nanofibers is an actual trend in tissue engineering. Polyvinylacohol (PVA) is nontoxic and biodegradable polymer suitable for preparation of submicron fibers by electrospinning. Main disadvantage of PVA fibers is rapid degradation in aqueous environment. On the other hand surface of fibers contains free hydroxyl group that could be chemically modified. In recent work, chemical modification of PVA nanofibers prepared by needleless electrospinning was investigated. Polyethylenglykol (PEG) linker was introduced to the fiber surface by acylation (PVA-PEG) and further modified by biotin (PVA-PEG-b) as a function agent. Process of chemical modification does not affected fibrous morphology of samples. Interestingly, linkage of PEG-b linker promoted stability of PVA in aqueous environment. PVA-PEG-b sample was stable for 41 days. Stability of samples was strongly dependent on amount of introduced PEG-b linker, thus proposed method of modification allows to prepare nanofibers of different solubility. Additionally, biocompatibility of chemically modified nanofibers with both mesenchymal stem cells (MSC) and chondrocytes was determined. Proliferation of both cell types was not sufficient and number of cells decreased in time, probably because of high hydrophility of modified PVA scaffold. To...
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Application of nanofiber scaffolds for vesel regeneration
Bezděková, Dagmar ; Amler, Evžen (advisor) ; Holzerová, Kristýna (referee)
Although plenty of systems for vessel regeneration have been developed, no system is successful in small diameter (under 6 mm) vessel replacement yet. Synthetic materials, such as Dacron and ePTFE, have good results in large vessels replacement, but they cause thrombosis in small vessels. In addition, they are not degradable and do not allow a natural remodeling of the vessel system. Furthemore, endothelial cells, which are essential for creating natural antithrombogenic endothelium, do not adhere on these materials, as well as smooth muscle cells. Decellularized xenogenic material is the non-synthetic alternative for vessel regeneration. Appropriate detergent removes donor's cells and only extracellular matrix remains, which is able to host acceptor's cells. The main disadvantages of this system are difficulties with animal's nurture and structure violations after detergent is used. It appears that electrospun materials are the best alternative. The relatively simple process can be modified in many ways and provides then a scaffold, which mimics extracellular matrix. A big advantage of this process is the possibility to incorporate bioactive substances into a fiber. The substances serve there as an attractant for blood cells or as an anticoagulation factor. In combination with the progenitor cells seems...
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The Rheological Behavior of Polymer Solutions Suitable for Electrospinning
Divínová, Nikol ; Voráč,, Zbyněk (referee) ; Chamradová, Ivana (advisor)
This diploma thesis deals with preparation and characterization of aqueous solutions of polyvinyl alcohol suitable for electrospinning. In the theoretical part method of electrospinning is described, including parameters which influence this process. Literary research also includes a chapter about rheology, which deals with the rheological properties of polymers, specifically PVA. The experimental part describes the preparation and rheological study of of aqueous solutions of polyvinyl alcohol, which were then spun. The morphology of prepared nanofibers was studied by using scanning electron microscopy (SEM). The effect of molecular weight, the solvent, concentration of solution, rheological properties, electrical conductivity and surface tension on the spinability, diameter and morphology of nanofibers is discussed.
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