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Thermal induced morphological changes of poly(ethylene oxide) nanofibrous webs
Polášková, M. ; Peer, Petra ; Ponížil, P. ; Čermák, R.
The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve the structure of electrospun fibres in order to increase physical and mechanical properties of nonwoven webs are obvious. Post-process thermal treatment is one of the possibilities of the crystallinity enhancement that can be easily included to the finishing operation of final products. For the experiment we used poly(ethylene oxide) representing electrospun-friendly material and two solvents - methanol and water, both ensuring good electrospinnability. It is demonstrated that a choice of polymer solvents plays a significant role in fibre diameter and their capabilities to resist applied heat. However, in all cases the enhancement of crystallinity is detected at the short time of thermal exposure.
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The role of solvents in the preparation of hydrophobic nanofibrous membrane containing fumed silica
Peer, Petra ; Polášková, M. ; Musilová, I. ; Filip, Petr
It is well-known that a type of used fumed silica nanoparticles plays a dominant role in wettability of the corresponding nanofibrous mats. As a result, the desired contact angle can be approximately achieved by a choice of adequate fumed silica nanoparticles. However, less attention has been hitherto paid to an active role of solvents in connection with the tailoring this contact angle. For analysis we used poly(vinyl butyral) representing electrospun-friendly material, various types of fumed silica nanoparticles and two solvents - methanol and ethanol. It is demonstrated that a choice of polymer solvents plays a significant role in contact angle changes. Hence, in combination of the type of fumed silica nanoparticles and the type of solvent it is possible to achieve a finer partition of the required contact angles.
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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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Electrospinning of ceramic fibers
Nemčovský, Jakub ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
This diploma thesis focuses on the fabrication of ceramic fibres by electrospinning. The theoretical part of the thesis summarizes the currently available information regarding ceramic fibres, their properties, applications and fabrication. The theoretical part also describes the process of electrospinning as one of the most frequently used methods of nanofibre fabrication, as well as the parametres influencing this process. The experimental part is aimed at the fabrication of ceramic fibres based on titania, pure non-doped zirconia and yttria-doped zirconia by electrospinning and at the characterization of thus fabricated fibres. Ceramic precursors based on propoxide and polyvinylpyrrolidone were subjected to electrospinning. The experimental part of this diploma thesis also describes the influence of precursor composition, process conditions and calcination temperature on the morphology and phase composition of the fibres. Precursors were characterized by viscosity measurements. Thermogravimetric analysis (TGA), Röntgen analysis (RTG) and scanning electron microscopy (SEM) were used to describe the fibres. By performing electrospinning of precursors based on titanium propoxide and subsequent calcination at 500-1300 °C, TiO2 fibres with thickness of 100-2500 nm were fabricated. The phase composition changed with calcination temperature from 500 °C from anatase phase through rutile blend to pure rutile at 900 °C. By performing electrospinning of precursors based on zirconium propoxide and subsequent calcination at 550-1100 °C, 0 – 8 mol% Y2O3 doped ZrO2 fibres with thickness of 50-1000 nm were fabricated. An analysis of fibres based on non-doped ZrO2, calcined at 550 °C showed a composition of predominantly monoclinic phase. An analysis of 3 or 8 mol% Y2O3 doped ZrO2 fibres calcined at 900 °C showed a composition of predominantly tetragonal phase or purely cubic phase, respectively. With the increasing calcination temperature, the morphology of the fibres changed from porous nanostructure to chain-like non-porous structure consisting of micrometer grains of TiO2 or ZrO2. The ZrO2 fibres calcined at 700 °C remained flexible as well as the spun ones, while their fragility increased with the increase in calcination temperature.
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The influence of PEO source on nanofiber layer preparation
Grufíková, Jana ; Knotek,, Petr (referee) ; Knotková, Kateřina (advisor)
The electrospinning process of polymer solutions is affected by many different parameters that can be divided into solution parameters, process parameters, and ambient parameters. This study is focused on characteristics of a polymer and its solution, which are ranging into the solution parameters. The aim of this study is to compare poly(ethylene oxide) characteristics in the relation to electrospinning of hyaluronic acid, to find the difference between them using available analytic, thermic and spectral methods, and to define the influence of properties on polymeric solutions behavior during electrospinning. It was find that poly(ethylene oxides) obtained from two different sources behave differently in an electrostatic field, although their molar mass is declared as the same. It was also confirmed that the electrospinning process of polymeric solutions is affected mainly by their viscosity and conductivity. This two properties are determined especially by the molar mass of polymer and also by the content of impurities or content of some another polymer during electrospinning of mixed solution.
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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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Nanofibrous scaffolds in controlled delivery of autologous growth factors
Buzgo, Matej ; Amler, Evžen (advisor) ; Gášková, Dana (referee)
Platelet preparations are a source of various autologous growth factors and have numerous applications in tissues engineering. The aim of this work was to development electrospun nanofiber scaffolds with platelet preparations. Scaffolds based on the adhesion of platelets on nanofiber meshes were developed. The scaffolds were able to enhance chondrocyte proliferation in vitro. The main disadvantage of this system is the burst release of growth factors immediately after adhesion. To overcome this, we developed coaxially electrospun scaffolds with incorporated alpha granules. Alpha granules are novel platelet preparations with high amounts of growth factors. This system was able to stimulate chondrocyte proliferation and maintain TGF- 1 concentrations for 7 days. Additionally, a novel drug delivery system with coaxially incorporated liposomes was developed. Liposomes incorporated into nanofibers remain intact and can be used for the delivery of various molecules. The ability to maintain HRP activity was compared to systems based on coaxial electrospinning with liposomes, coaxial electrospinning without liposomes and blend electrospinning. When compared to other systems, coaxial electrospinning with liposomes preserves enzyme activity twice as long. These results clearly indicate the potential of...
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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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