Abstract
Bioprinting utilizes the advantages of 3D printing technologies to fabricate cell-laden structures with various biomaterials that mimic the structure and function of natural tissues and greatly promote the development in the fields of tissue engineering and regenerative medicine. The capacity of wood-derived polymers has been well demonstrated in the field of 3D printing. Even though they present great biocompatibility, their application in bioprinting has not been extensively developed yet. The main reason is that wood-derived polymers can not be well integrated into the bioink system and that they lack biofunctionality.
This thesis focused on the incorporation of functionalized wood-derived biomaterials, mainly nanocellulose and hemicellulose, in the bioink systems for bioprinting. The thesis aims to leverage the unique properties of these wood-derived materials for 3D printing, and further address the challenges to achieve bioprinting. This research journey involves mainly two light-based 3D printing techniques: extrusion-based and digital light processing (DLP) printing. According to the unique properties of wood-derived polymers, a series of chemical modifications were conducted to meet the demand for different types of light-based 3D printing technologies. A methacryloyl gelatin (GelMA) and dextran-based aqueous two-phase emulsion (ATPE) system was used to formulate macropore-forming bioinks in this thesis. The functionalized wood-derived polymers could overcome the drawbacks of the ATPE bioink systems and leverage their own strength, thus effectively bringing out the best features of wood-based polymers.
During the progress of this thesis, rheological analysis of the bioinks provided crucial information, such as flow behavior and crosslinking kinetics, to guide the printing process. The rheological results also offered insights into the interaction between different polymers within the bioinks. Biocompatibility assays were conducted on the cell-laden hydrogels, highlighting the role of wood-derived materials in supporting and promoting cellular activity. Moreover, the designed wood-derived polymers demonstrated their potential to stimulate cell differentiation, which is critical for the increasing demand for customized bioinks.
Firstly, inks composed of cellulose nanofibrils with neutral or negative surface charge groups and photo-crosslinkable polymers, either protein or polysaccharide-based, were formulated for light-assisted extrusion-based 3D printing. Rheological analysis was used to characterize the intermolecular interactions between two types of cellulose nanofibrils and two types of photo-crosslinkable polymers under phosphate-buffered saline (PBS) or water environments.
An all-wood-derived photoresin composed of thiolated nanocellulose and methacrylated hemicellulose was designed for DLP printing. The printed hydrogels could be degraded through enzymatic hydrolysis in PBS at 37 °C and showed potential for controlled release of therapeutic ions. The as-synthesized thiolated nanocellulose showed the potential to function as a nanorod crosslinker in photoresin design with other polymers with -ene groups.
By utilizing photo-crosslinkable hemicellulose as a bio-glue, we proposed a novel bioresin formulation based on the ATPE system for one-step bioprinting of high poros microgel-based hydrogels. A high porosity facilitates cell spreading and mass transfer. This method simplifies the bioprinting process, reducing the complexity and time required to fabricate microgel-based cell-laden hydrogels.
Lastly, we introduced phosphorylated cellulose nanofibrils (pCNF) as a multifunctional additive to enhance the ATPE-based bioinks. The incorporation of pCNF in the ATPE system improved the physiochemical properties of the bioinks, but also enhanced the biological performance, transforming the bioprinted hydrogels into a suitable platform for engineering in vitro bone models.
In summary, in this work, we developed sustainable, and potentially cost-effective wood-derived biomaterials for bioink development. The design of the bioinks shows the potential of wood-derived biomaterials in bioprinting and contributes to the development of the field of biofabrication.
This thesis focused on the incorporation of functionalized wood-derived biomaterials, mainly nanocellulose and hemicellulose, in the bioink systems for bioprinting. The thesis aims to leverage the unique properties of these wood-derived materials for 3D printing, and further address the challenges to achieve bioprinting. This research journey involves mainly two light-based 3D printing techniques: extrusion-based and digital light processing (DLP) printing. According to the unique properties of wood-derived polymers, a series of chemical modifications were conducted to meet the demand for different types of light-based 3D printing technologies. A methacryloyl gelatin (GelMA) and dextran-based aqueous two-phase emulsion (ATPE) system was used to formulate macropore-forming bioinks in this thesis. The functionalized wood-derived polymers could overcome the drawbacks of the ATPE bioink systems and leverage their own strength, thus effectively bringing out the best features of wood-based polymers.
During the progress of this thesis, rheological analysis of the bioinks provided crucial information, such as flow behavior and crosslinking kinetics, to guide the printing process. The rheological results also offered insights into the interaction between different polymers within the bioinks. Biocompatibility assays were conducted on the cell-laden hydrogels, highlighting the role of wood-derived materials in supporting and promoting cellular activity. Moreover, the designed wood-derived polymers demonstrated their potential to stimulate cell differentiation, which is critical for the increasing demand for customized bioinks.
Firstly, inks composed of cellulose nanofibrils with neutral or negative surface charge groups and photo-crosslinkable polymers, either protein or polysaccharide-based, were formulated for light-assisted extrusion-based 3D printing. Rheological analysis was used to characterize the intermolecular interactions between two types of cellulose nanofibrils and two types of photo-crosslinkable polymers under phosphate-buffered saline (PBS) or water environments.
An all-wood-derived photoresin composed of thiolated nanocellulose and methacrylated hemicellulose was designed for DLP printing. The printed hydrogels could be degraded through enzymatic hydrolysis in PBS at 37 °C and showed potential for controlled release of therapeutic ions. The as-synthesized thiolated nanocellulose showed the potential to function as a nanorod crosslinker in photoresin design with other polymers with -ene groups.
By utilizing photo-crosslinkable hemicellulose as a bio-glue, we proposed a novel bioresin formulation based on the ATPE system for one-step bioprinting of high poros microgel-based hydrogels. A high porosity facilitates cell spreading and mass transfer. This method simplifies the bioprinting process, reducing the complexity and time required to fabricate microgel-based cell-laden hydrogels.
Lastly, we introduced phosphorylated cellulose nanofibrils (pCNF) as a multifunctional additive to enhance the ATPE-based bioinks. The incorporation of pCNF in the ATPE system improved the physiochemical properties of the bioinks, but also enhanced the biological performance, transforming the bioprinted hydrogels into a suitable platform for engineering in vitro bone models.
In summary, in this work, we developed sustainable, and potentially cost-effective wood-derived biomaterials for bioink development. The design of the bioinks shows the potential of wood-derived biomaterials in bioprinting and contributes to the development of the field of biofabrication.
| Original language | English |
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| Supervisors/Advisors |
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| Print ISBNs | ISBN 978-952-12-4402-5 |
| Electronic ISBNs | ISBN 978-952-12-4403-2 |
| Publication status | Published - 2024 |
| MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- Wood-Derived Functional Biomaterials
- Bioprinting
- 3D printing
- CNF
- GGM
- CNC
- aqueous two-phase emulsion