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Impact of macro channels on mechanical stability of bone scaffolds during indirect 3D printing
Vojníková, Michaela ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
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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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (oponent) ; Salamon, David (vedoucí práce)
Several procedures have been investigated for the regeneration of injured nerves. However, the resulting axonal growth can be random or disorganized and has limitations reflected on patient recovery. Therefore, the novel freeze-casted scaffolds were manufactured with mechanical and microstructural properties suitable for the neural scaffold. Concretely, the bioceramic scaffolds were based on calcium phosphates, titania, and zirconia. The oriented microstructure was prepared by controlled ice growth in one direction. The observation with scanning electron microscopy confirmed linearly oriented pores (lamellar system) in which average pore size decreased with a higher freezing rate. According to the results, the scaffolds prepared by freezing in liquid nitrogen showed excellent mechanical properties, where flexural strength was in the range of 10–17 MPa. Interlamellar distances of these scaffolds were 10–30 µm, which are appropriate for neural scaffolds. Biocompatibility was evaluated with Schwann cells’ line in vitro, where the adhesion and growth in the lamellar direction were observed. Cytotoxic tests revealed a negative impact of a high calcium level on Schwann cell’ survival. The prepared scaffolds could form an apatite layer on its surface in the form of embryonic and nucleation centers and apatite itself. Calcium phosphate and titania scaffolds exhibited promising regenerative characteristics of adhesion and ingrowth through porous structures with outstanding mechanical properties.
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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (oponent) ; Salamon, David (vedoucí práce)
Several procedures have been investigated for the regeneration of injured nerves. However, the resulting axonal growth can be random or disorganized and has limitations reflected on patient recovery. Therefore, the novel freeze-casted scaffolds were manufactured with mechanical and microstructural properties suitable for the neural scaffold. Concretely, the bioceramic scaffolds were based on calcium phosphates, titania, and zirconia. The oriented microstructure was prepared by controlled ice growth in one direction. The observation with scanning electron microscopy confirmed linearly oriented pores (lamellar system) in which average pore size decreased with a higher freezing rate. According to the results, the scaffolds prepared by freezing in liquid nitrogen showed excellent mechanical properties, where flexural strength was in the range of 10–17 MPa. Interlamellar distances of these scaffolds were 10–30 µm, which are appropriate for neural scaffolds. Biocompatibility was evaluated with Schwann cells’ line in vitro, where the adhesion and growth in the lamellar direction were observed. Cytotoxic tests revealed a negative impact of a high calcium level on Schwann cell’ survival. The prepared scaffolds could form an apatite layer on its surface in the form of embryonic and nucleation centers and apatite itself. Calcium phosphate and titania scaffolds exhibited promising regenerative characteristics of adhesion and ingrowth through porous structures with outstanding mechanical properties.
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Impact of macro channels on mechanical stability of bone scaffolds during indirect 3D printing
Vojníková, Michaela ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
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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