Characterization of porous polymer scaffolds for tissue engineering
Niemelä, Petteri (2023)
2023
Materiaalitekniikan DI-ohjelma - Master's Programme in Materials Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-06-12
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202306016393
https://urn.fi/URN:NBN:fi:tuni-202306016393
Tiivistelmä
In the everlasting search for the new golden standard for bone tissue replacement, new materials, and scaffold manufacturing methods have been invented. Recently due to advancements in many technological fields, tissue engineering has got its new generation of scaffold manufacturing methods. Different kinds of 3D printing methods have emerged with a promise to create more repeatable structures. The aim of this thesis is to compare the mechanical properties of tissue engineering scaffolds manufactured with traditional and modern methods.
This thesis first goes over the most important requirements of tissue engineering scaffolds, and where these come from. After that biomaterials and tissue engineering scaffold manufacturing methods are discussed in general. In the theory section manufacturing methods have been divided into traditional and modern methods by the ability to control porosity. After the theory extrusion-based 3D printed and supercritical carbon dioxide (scCO2) gas foamed scaffolds for tissue engineering have been tested mechanically. Gel permeation chromatography (GPC), Differential scanning calorimetry (DSC), and liquid penetration tests have also been conducted to determine molecular weight after processing, crystallinity after processing, and pore accessibility and interconnectivity.
This thesis shows that 3D printed scaffolds have a superior structure design from the point of view of open porosity. Pore accessibility and interconnectivity are shown to be excellent with the 3D printed scaffolds while the gas foamed materials did not have full liquid penetration of pores. Creating tissue engineering scaffolds using extrusion-based 3D printing can lead to the scaffolds having somewhat worse mechanical properties than what could be achieved with scCO2 gas foaming, but due to high variance in data, this could not be confirmed statistically. 3D printing seemed to cause the scaffolds to act more like an elastic solid rather than viscoelastic. This could have happened because the structure design with 3D printed scaffolds includes solid points of contact from top to bottom which are not found frequently from the gas foamed scaffolds. In this thesis, it could be found that because tissue engineering applications set a limit to the volume of scaffolds, tan δ, which is considered the measurement of materials damping capability, might not be the best measurement as volumetrically measured some materials can dissipate more energy even when the material has lower tan δ. During this thesis, the effect of changing the testing frequency was assessed and it was found to affect the loss modulus and tan δ exponentially. Increasing the frequency makes the material behave more like an elastic solid.
Overall, this thesis shows that the manufacturing method does affect the mechanical properties of the scaffolds, but other deciding factors, such as scaffold structure and porosity, should be considered when choosing the manufacturing method.
This thesis first goes over the most important requirements of tissue engineering scaffolds, and where these come from. After that biomaterials and tissue engineering scaffold manufacturing methods are discussed in general. In the theory section manufacturing methods have been divided into traditional and modern methods by the ability to control porosity. After the theory extrusion-based 3D printed and supercritical carbon dioxide (scCO2) gas foamed scaffolds for tissue engineering have been tested mechanically. Gel permeation chromatography (GPC), Differential scanning calorimetry (DSC), and liquid penetration tests have also been conducted to determine molecular weight after processing, crystallinity after processing, and pore accessibility and interconnectivity.
This thesis shows that 3D printed scaffolds have a superior structure design from the point of view of open porosity. Pore accessibility and interconnectivity are shown to be excellent with the 3D printed scaffolds while the gas foamed materials did not have full liquid penetration of pores. Creating tissue engineering scaffolds using extrusion-based 3D printing can lead to the scaffolds having somewhat worse mechanical properties than what could be achieved with scCO2 gas foaming, but due to high variance in data, this could not be confirmed statistically. 3D printing seemed to cause the scaffolds to act more like an elastic solid rather than viscoelastic. This could have happened because the structure design with 3D printed scaffolds includes solid points of contact from top to bottom which are not found frequently from the gas foamed scaffolds. In this thesis, it could be found that because tissue engineering applications set a limit to the volume of scaffolds, tan δ, which is considered the measurement of materials damping capability, might not be the best measurement as volumetrically measured some materials can dissipate more energy even when the material has lower tan δ. During this thesis, the effect of changing the testing frequency was assessed and it was found to affect the loss modulus and tan δ exponentially. Increasing the frequency makes the material behave more like an elastic solid.
Overall, this thesis shows that the manufacturing method does affect the mechanical properties of the scaffolds, but other deciding factors, such as scaffold structure and porosity, should be considered when choosing the manufacturing method.