| Summary: | 博士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 104 === This study investigated the effect physo-chemical properties of materials on cell behavior and developed the water-based multi-component three-dimensional (3D) printing inks for use in tissue engineering. In the fist section, a series of biodegradable anionic polyurethane (PU) was synthesized with different extents of surface functional group rearrangement in response to aqueous environment. The recruitment of carboxyl and amino groups from the bulk material to the surface can interact with calcium ion. The surface-bound calcium was observed to enter mesenchymal stem cells (MSCs), which prompted MSC migration and assembly. The MSC aggregate formation was associated with the NF-kB pathway while the aggregate size was connected to the Hippo pathway. The MSC aggregates had greater expressions of Oct4, Nanog, and Sox2 as well as multi-differentiation capacities than attached MSCs. This part of study suggested that the critical importance of surface functional group and its calcium binding capacity on the self-assembly of MSCs, which may help define and design the appropriate MSC-substrate interaction for tissue engineering applications. In the second section, scaffolds were fabricated from the biodegradable PU dispersion by water-based 3D printing using polyethylene oxide as a viscosity enhancer. Not any toxic organic solvent, crosslinker, or initiator was used. The green process generated a highly elastic scaffold with good affinity to cells. In the 3D-printed PU scaffolds, cells tended to aggregate in clusters. Chondrocytes in 3D-printed PU scaffolds have excellent proliferation and matrix production. In this part of study, we developed a green water-based 3D printing platform to fabricate biodegradable/elastic scaffolds for cartilage tissue engineering applications. In the third section, we developed a 3D-printed scaffold to promote the spontaneous chondrogenesis of MSCs. The scaffolds were printed from the water-based ink containing PU, hyaluronan (HA), and Y27632 (or TGFB3). MSCs seeded in the scaffolds were self-assembled into MSC aggregates and underwent chondrogenesis effectively. The use of Y27632 could prevent the expression of hypertrophic marker. Transplantation of the MSC-seeded PU/HA/Y scaffold in rabbit chondral defects significantly improved the cartilage regeneration. This part of study suggested that the water-based 3D printed PU/HA/Y scaffolds may have potential applications in customized cartilage tissue engineering. In the fourth section, we evaluated the effect of fractal dimension (Df) of hydrogels on cell proliferation and stem cell differentiation. Fibroblasts and mesenchymal stem cells grow faster in hydrogels with a higher Df. Hydrogels with the Df matched to that of a specific tissue favor the tissue-specific differentiation. Chondrogenesis, osteogenesis, and neurogenesis are each preferred in hydrogels with Df ≥ 1.8, ≥ 1.6, and ≤ 1.4, respectively. This part of study suggested that the fractal structure of gel can modulate cell proliferation and fate, which supply a new design rationale to design the appropriate fractal and molecular structure of hydrogels for applications of 3D printing.
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