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Impact of macro channels on mechanical stability of bone scaffolds during indirect 3D printing
Vojníková, Michaela ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Porous materials are currently subject to the great interest of tissue engineering. They provide unique properties such as bioactivity, biodegradability, osteoconductivity, and vascularization. Particularly, ceramic porous systems show appreciable potential in medical applications. However, there is a crucial problem with the porous scaffold on account of their bad mechanic properties and therefore they are presently used only at low-load locations. This thesis focuses on the preparation of the scaffolds made of hydroxyapatite by using the freeze-casting method where the indirect 3D printing was applied to get open channels with the size over 200 µm. It also compares the mechanical properties of the scaffolds with different internal structures and monitors how the implementation of different types of grids affects the resulting stability. The scaffolds were prepared with a different arrangement of macro-channel in the internal structure, but they had equal dimensions as common property. The 3D grid was implemented before freezing into the mold and afterward the grid was eliminated by sintering, leaving only a channel system with the size 540-600 µm in the final scaffold. The influence of the type of the 3D grid on the resulting mechanical stability of the scaffold was determined. Rotation of this grid does not have a significant effect on the result, while it only helps with cracking in the direction of the helix. The combination of these methods reports very good controllability with directed macro-channels in the resulting scaffold and therefore it is suitable for the preparation of the bone-implants with different structures.
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Tailoring of cooling procedure during freeze-casting for bone replacement applications.
Šantavý, Tomáš ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Bachelor thesis focuses on preparation of hydroxyapatite ceramics by freeze-casting. Hydroxyapatite is an important ceramic material, due to its biocompatibility, biodegradability and bioactivity it has a wide range of use in medicinal applications especially in replacement of bone material. The chosen method, freeze-casting, is flexible, eco-friendly and we are able to achieve a high level of porosity. The method includes freezing, freeze drying and sintering which creates a porous structure of the prepared material. Objective of this bachelor thesis was to find out the impact on the created porosity and mechanical properties of the final material. Freezing rates were applied 3, 4, 5, 6, 7 and 26 m/s. During the experimental part it was established that the freezing rate has a significant influence on the newly formed inner microstructure, it directly influences the interlamellar distances and mechanical property which is compressive strength. With liquid nitrogen with a speed of 26 m/s the achieved compressive strength was of 15 MPa as well as the shortest interlamellar distances of 14-22 µm. With slower freezing rate the average interlamellar distances were 40-150 µm and compressive strength of 2-4 MPa with comparable porosity.
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Shaping of bioceramic hydroxyapatite scaffolds on micro level
Pejchalová, Lucie ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Due to increasing average age of population around the world, there are more patients who need surgery of musculoskeletal system. In some cases, it is even necessary to implant new bone scaffold or replace joints. Hydroxyapatite is the most frequently used material for its biocompatibility and bioactivity. On the other hand, mechanical properties constraints its use in porous scaffolds. The method providing both good mechanical stability and high porosity is freeze – casting. This method utilises controlled freezing to form lamellar structure. During freezing of slurry, ice crystals grow in direction of temperature gradient. In next step, ice crystals are removed by lyophilisation and lamellar structure is revealed. This structure is relatively unstable and needs to be reinforced by sintering. There are many aspects affecting resulting structure – freezing schedule, slurry concentration etc. We used water/ceramic slurries in various concentrations of hydroxyapatite (7,5 % vol., 10 % vol., 15 % vol. and 20 % vol.). These slurries were used for preparation of porous bone scaffolds. We tried to add 3D mash to form net of channels and we observed favourable changes in porosity. 3D mash was removed during sintering. Resulting bioceramics structure was highly porous (up to 90 %). These scaffolds had an acceptable ration between porosity and mechanical stability, too. We considered, adding of 3D mash, as good way to form channels of desired properties.
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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (referee) ; Salamon, David (advisor)
Pre regeneráciu a rast poranených nervových vlákien bolo preskúmaných mnoho postupov, no výsledný rast axónov je často náhodný až dezorganizovaný a odráža sa na zložitejšom zotavovaní pacienta. V tejto práci boli vyrobené nové skafoldy s mikroštruktúrnymi a mechanickými vlastnosťami nervového skafoldu pomocou metódy freeze-casting. Konkrétne boli vyrobené biokeramické skafoldy na báze fosforečnanov vápenatých, oxidu titaničitého alebo oxidu zirkoničitého. Pomocou kontrolovaného rastu ľadu v jednom smere bola pripravená orientovaná mikroštruktúra. Pozorovanie pomocou skenovacej elektrónovej mikroskopie potvrdilo lineárne orientované póry (lamelárny systém), v ktorých priemerná veľkosť pórov klesala so zvyšujúcou sa rýchlosťou mrazenia. Skafoldy pripravené pomocou mrazenia v tekutom dusíku vykazovali vynikajúce mechanické vlastnosti, kde pevnosť v ohybe bola získaná v rozmedzí 10–17 MPa. Tie isté skafoldy mali vzdialenosť medzilamelamelárnych priestorov 10–30 µm, ktorých parametre sú vhodné pre nervové skafoldy. Biokompatibilita bola vyhodnotená pomocou Schwannových buniek in vitro, kde bola pozorovaná adhézia a rast v lamelárnom smere. Cytotoxické testy odhalili negatívny vplyv vyššej koncentrácie vápnika na prežitie Schwannových buniek. Pripravené skafoldy mali schopnosť tvorby apatitu na povrchu v podobe embryonálnych a nukleačných centier a apatitu samotného. Skafoldy na báze fosforečnanov vápenatých a oxidu titaničitého vykazovali sľubné regeneračné vlastnosti, konkrétne adhéziu a rast prostredníctvom pórovitej štruktúry a taktiež vynikajúce mechanické vlastnosti.
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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (referee) ; Salamon, David (advisor)
Pre regeneráciu a rast poranených nervových vlákien bolo preskúmaných mnoho postupov, no výsledný rast axónov je často náhodný až dezorganizovaný a odráža sa na zložitejšom zotavovaní pacienta. V tejto práci boli vyrobené nové skafoldy s mikroštruktúrnymi a mechanickými vlastnosťami nervového skafoldu pomocou metódy freeze-casting. Konkrétne boli vyrobené biokeramické skafoldy na báze fosforečnanov vápenatých, oxidu titaničitého alebo oxidu zirkoničitého. Pomocou kontrolovaného rastu ľadu v jednom smere bola pripravená orientovaná mikroštruktúra. Pozorovanie pomocou skenovacej elektrónovej mikroskopie potvrdilo lineárne orientované póry (lamelárny systém), v ktorých priemerná veľkosť pórov klesala so zvyšujúcou sa rýchlosťou mrazenia. Skafoldy pripravené pomocou mrazenia v tekutom dusíku vykazovali vynikajúce mechanické vlastnosti, kde pevnosť v ohybe bola získaná v rozmedzí 10–17 MPa. Tie isté skafoldy mali vzdialenosť medzilamelamelárnych priestorov 10–30 µm, ktorých parametre sú vhodné pre nervové skafoldy. Biokompatibilita bola vyhodnotená pomocou Schwannových buniek in vitro, kde bola pozorovaná adhézia a rast v lamelárnom smere. Cytotoxické testy odhalili negatívny vplyv vyššej koncentrácie vápnika na prežitie Schwannových buniek. Pripravené skafoldy mali schopnosť tvorby apatitu na povrchu v podobe embryonálnych a nukleačných centier a apatitu samotného. Skafoldy na báze fosforečnanov vápenatých a oxidu titaničitého vykazovali sľubné regeneračné vlastnosti, konkrétne adhéziu a rast prostredníctvom pórovitej štruktúry a taktiež vynikajúce mechanické vlastnosti.
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Impact of macro channels on mechanical stability of bone scaffolds during indirect 3D printing
Vojníková, Michaela ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Porous materials are currently subject to the great interest of tissue engineering. They provide unique properties such as bioactivity, biodegradability, osteoconductivity, and vascularization. Particularly, ceramic porous systems show appreciable potential in medical applications. However, there is a crucial problem with the porous scaffold on account of their bad mechanic properties and therefore they are presently used only at low-load locations. This thesis focuses on the preparation of the scaffolds made of hydroxyapatite by using the freeze-casting method where the indirect 3D printing was applied to get open channels with the size over 200 µm. It also compares the mechanical properties of the scaffolds with different internal structures and monitors how the implementation of different types of grids affects the resulting stability. The scaffolds were prepared with a different arrangement of macro-channel in the internal structure, but they had equal dimensions as common property. The 3D grid was implemented before freezing into the mold and afterward the grid was eliminated by sintering, leaving only a channel system with the size 540-600 µm in the final scaffold. The influence of the type of the 3D grid on the resulting mechanical stability of the scaffold was determined. Rotation of this grid does not have a significant effect on the result, while it only helps with cracking in the direction of the helix. The combination of these methods reports very good controllability with directed macro-channels in the resulting scaffold and therefore it is suitable for the preparation of the bone-implants with different structures.
|
|
|
Tailoring of cooling procedure during freeze-casting for bone replacement applications.
Šantavý, Tomáš ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Bachelor thesis focuses on preparation of hydroxyapatite ceramics by freeze-casting. Hydroxyapatite is an important ceramic material, due to its biocompatibility, biodegradability and bioactivity it has a wide range of use in medicinal applications especially in replacement of bone material. The chosen method, freeze-casting, is flexible, eco-friendly and we are able to achieve a high level of porosity. The method includes freezing, freeze drying and sintering which creates a porous structure of the prepared material. Objective of this bachelor thesis was to find out the impact on the created porosity and mechanical properties of the final material. Freezing rates were applied 3, 4, 5, 6, 7 and 26 m/s. During the experimental part it was established that the freezing rate has a significant influence on the newly formed inner microstructure, it directly influences the interlamellar distances and mechanical property which is compressive strength. With liquid nitrogen with a speed of 26 m/s the achieved compressive strength was of 15 MPa as well as the shortest interlamellar distances of 14-22 µm. With slower freezing rate the average interlamellar distances were 40-150 µm and compressive strength of 2-4 MPa with comparable porosity.
|
|
|
Shaping of bioceramic hydroxyapatite scaffolds on micro level
Pejchalová, Lucie ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Due to increasing average age of population around the world, there are more patients who need surgery of musculoskeletal system. In some cases, it is even necessary to implant new bone scaffold or replace joints. Hydroxyapatite is the most frequently used material for its biocompatibility and bioactivity. On the other hand, mechanical properties constraints its use in porous scaffolds. The method providing both good mechanical stability and high porosity is freeze – casting. This method utilises controlled freezing to form lamellar structure. During freezing of slurry, ice crystals grow in direction of temperature gradient. In next step, ice crystals are removed by lyophilisation and lamellar structure is revealed. This structure is relatively unstable and needs to be reinforced by sintering. There are many aspects affecting resulting structure – freezing schedule, slurry concentration etc. We used water/ceramic slurries in various concentrations of hydroxyapatite (7,5 % vol., 10 % vol., 15 % vol. and 20 % vol.). These slurries were used for preparation of porous bone scaffolds. We tried to add 3D mash to form net of channels and we observed favourable changes in porosity. 3D mash was removed during sintering. Resulting bioceramics structure was highly porous (up to 90 %). These scaffolds had an acceptable ration between porosity and mechanical stability, too. We considered, adding of 3D mash, as good way to form channels of desired properties.
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