|
|
Poly(3-hydroxybutyrate) based materials for 3D printing in medical applications
Krobot, Štěpán ; Vojtová, Lucy (oponent) ; Přikryl, Radek (vedoucí práce)
This master's thesis deals with the preparation and testing of 3D printed scaffolds for bone tissue engineering. The aim of the thesis is laboratory preparation of polymer blends on the basis of poly(3-hydroxybutyrate), poly(lactic acid) and polycaprolactone and their processing into the form of 3D printing filaments. Three polymeric blends were prepared and processed into the form of 3D printing filaments. Differential scanning calorimetry was conducted to evaluate the thermal properties, followed by temperature tower test and warping test to determine the processing conditions for 3D printing. The lowest warping coefficient was 1.26 for a blend of poly(3-hydroxybutyrate) with polycaprolactone and plasticizer. Tensile test, three-point flexural test and compression test were used to study the mechanical properties of materials. Scaffolds with different surfaces for bone tissue engineering were 3D printed from prepared filaments to determine the most optimal surface for cell proliferation. To determine the surface properties and their influence on cell adhesion, optical contact angle measurement with the use of OWRK method to calculate surface energy was conducted. 3D printed surfaces were also subjected to roughness analysis by confocal microscopy to determine their roughness and its effect on contact angle with water and cell growth. Finally, in the last part, in vitro tests on scaffolds were conducted in collaboration with the Institute of Experimental Medicine (Czech Academy of Sciences) to find out whether the prepared materials are non-cytotoxic and how the surface of scaffold affects the cell growth and proliferation. In the end, two out of three materials were proven to be non-cytotoxic (both blends of poly(3-hydroxybutyrate) with polycaprolactone) and that their mechanical properties were comparable with human trabecular bone. The most optimal surface for cell growth is probably grid diameter 50 m with roughness along the perimeter 1.9 m, which corresponds with water contact angle 74.1°.
|
|
|
Mechanical Reinforcement of Bioglass®-Based Scaffolds
Bertolla, Luca ; Prof. Dr.-Ing. habil. Aldo R. Boccaccini (oponent) ; Kotoul, Michal (oponent) ; Pabst, Willi (oponent) ; Dlouhý, Ivo (vedoucí práce)
Bioactive glasses exhibit unique characteristics as a material for bone tissue engineering. Unfortunately, their extensive application for the repair of load-bearing bone defects is still limited by low mechanical strength and fracture toughness. The main aim of this work was two-fold: the reinforcement of brittle Bioglass®-based porous scaffolds and the production of bulk Bioglass® samples exhibiting enhanced mechanical properties. For the first task, scaffolds were coated by composite coating constituted by polyvinyl alcohol (PVA) and microfibrillated cellulose (MFC). The addition of PVA/MFC coating led to a 10 fold increase of compressive strength and a 20 fold increase of tensile strength in comparison with non-coated scaffolds. SEM observations of broken struts surfaces proved the reinforcing and toughening mechanism of the composite coating which was ascribed to crack bridging and fracture of cellulose fibrils. The mechanical properties of the coating material were investigated by tensile testing of PVA/MFC stand–alone specimens. The stirring time of the PVA/MFC solution came out as a crucial parameter in order to achieve a more homogeneous dispersion of the fibres and consequently enhanced strength and stiffness. Numerical simulation of a PVA coated Bioglass® strut revealed the infiltration depth of the coating until the crack tip as the most effective criterion for the struts strengthening. Contact angle and linear viscosity measurements of PVA/MFC solutions showed that MFC causes a reduction in contact angle and a drastic increase in viscosity, indicating that a balance between these opposing effects must be achieved. Concerning the production of bulk samples, conventional furnace and spark plasma sintering technique was used. Spark plasma sintering performed without the assistance of mechanical pressure and at heating rates ranging from 100 to 300°C /min led to a material having density close to theoretical one and fracture toughness nearly 4 times higher in comparison with conventional sintering. Fractographic analysis revealed the crack deflection as the main toughening mechanisms acting in the bulk Bioglass®. Time–dependent crack healing process was also observed. The further investigation on the non-equilibrium phases crystallized is required. All obtained results are discussed in detail and general recommendations for scaffolds with enhanced mechanical resistance are served.
|
|
|
Moderní metody přípravy porézní biokeramiky
Šťastný, Přemysl ; Částková, Klára (oponent) ; Trunec, Martin (vedoucí práce)
Práce se zabývá metodami přípravy porézních keramik se zaměřením na biokeramické podpůrné systémy kostních tkání, anglicky nazývané "bioscaffolds". Rešerše je členěna do tří částí. První část je věnována koloidním suspenzím, jejich přípravě a konsolidaci. Druhá část se zabývá metodami výroby porézních struktur a část třetí je věnována problematice využití porézních biokeramik v medicíně. Praktická část práce se věnuje testům gelace.
|
|
|
Vícefázové biokeramické porézní náhrady kostní tkáně na bázi fosforečnanů vápenatých
Smiešková, Jana ; Šťastná, Eva (oponent) ; Šťastný, Přemysl (vedoucí práce)
Bakalářská práce se zabývá shrnutím poznatků na téma: Vícefázové biokeramické porézní náhrady kostní tkáně na bázi fosforečnanů vápenatých. Práce je členěna do dvou částí. První část představuje literární rešerši, která se zabývá biokeramickými materiály na bázi fosforečnanů vápenatých a jejich interakcí s tělem příjemce. Druhá část je experimentální. Popisuje přípravu směsných keramik (jedná se o směsi hydroxyapatitu (HA) a fosforečnanu vápenatého (TCP)) a vyhodnocení jejich mikrostruktury a změn fázového složení.
|
|
|
Customized hybrid bioscaffolds for bone regeneration
Šťastný, Přemysl ; Šupová,, Monika (oponent) ; Pabst, Willi (oponent) ; Trunec, Martin (vedoucí práce)
The doctoral thesis titled “Customized hybrid bioscaffolds for bone regeneration” is divided into two parts. The first part tries to reveal the theoretical background of a bone-to-implant interaction and the current state of the art in the research of calcium phosphate materials and calcium phosphate-based implants for bone tissue engineering. The customization concept and a careful selection of phase composition represents two main points of the second, experimental, part of the doctoral thesis. The customization concept in this work is not only just a simple shape and dimension optimization process of an implant, but additionally attention is paid to the microstructural features, phase composition and phase distribution allowing the rational design and a production of tailor-made materials for dinstinct medical applications. Cellular and biological responses to the ceramic materials were evaluated both by in-vitro and in-vivo tests and were discussed against the material composition and the microstructural features. The doctoral thesis shows how a fundamental understanding of physical and chemical properties of the material under question can help to design implants material with an outstanding biological response. The in-vivo application of the customized implant and its comparison with the current gold standard bone graft material – bone autograft is a unique and valuable outcome of the doctoral thesis.
|
|
|
Poly(3-hydroxybutyrate) based materials for 3D printing in medical applications
Krobot, Štěpán ; Vojtová, Lucy (oponent) ; Přikryl, Radek (vedoucí práce)
This master's thesis deals with the preparation and testing of 3D printed scaffolds for bone tissue engineering. The aim of the thesis is laboratory preparation of polymer blends on the basis of poly(3-hydroxybutyrate), poly(lactic acid) and polycaprolactone and their processing into the form of 3D printing filaments. Three polymeric blends were prepared and processed into the form of 3D printing filaments. Differential scanning calorimetry was conducted to evaluate the thermal properties, followed by temperature tower test and warping test to determine the processing conditions for 3D printing. The lowest warping coefficient was 1.26 for a blend of poly(3-hydroxybutyrate) with polycaprolactone and plasticizer. Tensile test, three-point flexural test and compression test were used to study the mechanical properties of materials. Scaffolds with different surfaces for bone tissue engineering were 3D printed from prepared filaments to determine the most optimal surface for cell proliferation. To determine the surface properties and their influence on cell adhesion, optical contact angle measurement with the use of OWRK method to calculate surface energy was conducted. 3D printed surfaces were also subjected to roughness analysis by confocal microscopy to determine their roughness and its effect on contact angle with water and cell growth. Finally, in the last part, in vitro tests on scaffolds were conducted in collaboration with the Institute of Experimental Medicine (Czech Academy of Sciences) to find out whether the prepared materials are non-cytotoxic and how the surface of scaffold affects the cell growth and proliferation. In the end, two out of three materials were proven to be non-cytotoxic (both blends of poly(3-hydroxybutyrate) with polycaprolactone) and that their mechanical properties were comparable with human trabecular bone. The most optimal surface for cell growth is probably grid diameter 50 m with roughness along the perimeter 1.9 m, which corresponds with water contact angle 74.1°.
|
|
|
Vícefázové biokeramické porézní náhrady kostní tkáně na bázi fosforečnanů vápenatých
Smiešková, Jana ; Šťastná, Eva (oponent) ; Šťastný, Přemysl (vedoucí práce)
Bakalářská práce se zabývá shrnutím poznatků na téma: Vícefázové biokeramické porézní náhrady kostní tkáně na bázi fosforečnanů vápenatých. Práce je členěna do dvou částí. První část představuje literární rešerši, která se zabývá biokeramickými materiály na bázi fosforečnanů vápenatých a jejich interakcí s tělem příjemce. Druhá část je experimentální. Popisuje přípravu směsných keramik (jedná se o směsi hydroxyapatitu (HA) a fosforečnanu vápenatého (TCP)) a vyhodnocení jejich mikrostruktury a změn fázového složení.
|
|
|
Možnosti využití kmenových buněk pro léčbu poškození povrchu oka
Kössl, Jan ; Holáň, Vladimír (vedoucí práce) ; Drbal, Karel (oponent)
Poškození očního povrchu představuje jednu z nejčastějších příčin zhoršené kvality nebo ztráty zraku. Transplantace rohovky je dodnes první volbou v léčbě těchto defektů. Pokud je poškození rozsáhlé, zasahuje oblast limbu a narušuje tak niku limbálních kmenových buněk (LSCs), dochází k deficienci LSCs a reparace společně s regenerací rohovky je narušena. Jedinou zatím vhodnou léčbou je transplantace limbu nebo autologních LSCs z nepoškozeného oka. Pokud je LSC deficience oboustranná, nelze použít autologní LSCs. Léčba alogenními LSCs zahrnuje podávání systémových a lokálních imunosupresivních léků, které mají negativní vedlejší účinky u pacientů a nejsou často účinné. Alternativou pro léčbu poškození povrchu oka a LSC deficience je tak nalezení vhodné autologní náhrady, kterou jsou např. mezenchymální kmenové buňky (MSCs). Tyto kmenové buňky mohou být poměrně snadno získány z kostní dřeně nebo tukové tkáně daného pacienta. MSCs lze snadno kultivovat in vitro a mohou být přeneseny na poškozený oční povrch pomocí vhodného nosiče. Tam je využito jejich schopnosti diferenciace v buňky rohovkového epitelu, imunomodulačních vlastností a produkce různých trofických a růstových faktorů. Pokusy s MSCs na zvířecích modelech s mechanicky nebo chemicky poškozenou rohovkou mají dobré výsledky. Po transplantaci...
|
|
|
Mechanical Reinforcement of Bioglass®-Based Scaffolds
Bertolla, Luca ; Prof. Dr.-Ing. habil. Aldo R. Boccaccini (oponent) ; Kotoul, Michal (oponent) ; Pabst, Willi (oponent) ; Dlouhý, Ivo (vedoucí práce)
Bioactive glasses exhibit unique characteristics as a material for bone tissue engineering. Unfortunately, their extensive application for the repair of load-bearing bone defects is still limited by low mechanical strength and fracture toughness. The main aim of this work was two-fold: the reinforcement of brittle Bioglass®-based porous scaffolds and the production of bulk Bioglass® samples exhibiting enhanced mechanical properties. For the first task, scaffolds were coated by composite coating constituted by polyvinyl alcohol (PVA) and microfibrillated cellulose (MFC). The addition of PVA/MFC coating led to a 10 fold increase of compressive strength and a 20 fold increase of tensile strength in comparison with non-coated scaffolds. SEM observations of broken struts surfaces proved the reinforcing and toughening mechanism of the composite coating which was ascribed to crack bridging and fracture of cellulose fibrils. The mechanical properties of the coating material were investigated by tensile testing of PVA/MFC stand–alone specimens. The stirring time of the PVA/MFC solution came out as a crucial parameter in order to achieve a more homogeneous dispersion of the fibres and consequently enhanced strength and stiffness. Numerical simulation of a PVA coated Bioglass® strut revealed the infiltration depth of the coating until the crack tip as the most effective criterion for the struts strengthening. Contact angle and linear viscosity measurements of PVA/MFC solutions showed that MFC causes a reduction in contact angle and a drastic increase in viscosity, indicating that a balance between these opposing effects must be achieved. Concerning the production of bulk samples, conventional furnace and spark plasma sintering technique was used. Spark plasma sintering performed without the assistance of mechanical pressure and at heating rates ranging from 100 to 300°C /min led to a material having density close to theoretical one and fracture toughness nearly 4 times higher in comparison with conventional sintering. Fractographic analysis revealed the crack deflection as the main toughening mechanisms acting in the bulk Bioglass®. Time–dependent crack healing process was also observed. The further investigation on the non-equilibrium phases crystallized is required. All obtained results are discussed in detail and general recommendations for scaffolds with enhanced mechanical resistance are served.
|
|
|
Moderní metody přípravy porézní biokeramiky
Šťastný, Přemysl ; Částková, Klára (oponent) ; Trunec, Martin (vedoucí práce)
Práce se zabývá metodami přípravy porézních keramik se zaměřením na biokeramické podpůrné systémy kostních tkání, anglicky nazývané "bioscaffolds". Rešerše je členěna do tří částí. První část je věnována koloidním suspenzím, jejich přípravě a konsolidaci. Druhá část se zabývá metodami výroby porézních struktur a část třetí je věnována problematice využití porézních biokeramik v medicíně. Praktická část práce se věnuje testům gelace.
|
host ::
RSS.