Page 100 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani
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was also shown for the currently used pre-osteoblastic cell line MC3T3-E1 by Wei et al. [29]. The findings of Wei et al appear to be confirmed by our results. Also, from the differentiation data (discussed in more detail below), we can deduce that the Ra value of the porous scaffolds was too high to optimally promote osteogenesis, while the slightly rough surface of the 3D-printed PLGA/β-TCP scaffolds facilitated osteoblastic maturation potential of the MC3T3-E1 pre- osteoblasts upon application of osteogenic media. We conclude that the 3D-printed PLGA/β-TCP scaffolds having a hydrophilic surface with slight roughness resulted from β-TCP particles might be favorable for pre-osteoblasts osteogenic differentiation.
Another pivotal aspect is the pore structure in the two types of scaffolds; pore size has a direct impact on cellular responses [30]. There are conflicting reports in the literature on the optimal scaffold pore size for successful bone tissue engineering [31-34]. In our study, the sugar leaching process in the porous scaffolds gave pores with dimensions of 408 ± 90 μm while the 3D-printed scaffolds had square shaped pores with dimensions of 315 ± 17 μm. We found that a dense cellular network was formed on and between the struts of the 3D-printed scaffolds while such network of cells was not formed in the porous scaffolds. Cells were less spread on the surface of the porous scaffolds compared with the 3D-printed scaffolds. Our results agree with data by others who observed better cell growth within 3D-printed scaffolds compared with freeze- dried porous scaffolds [35].
Last but not least, it has been shown that mechanical properties of bone tissue engineering scaffolds can modulate cellular responses (i.e. cell morphology, proliferation, migration, and differentiation) [36,37]. The compressive strength of the 3D-printed PLGA/β-TCP scaffolds was significantly higher compared with the porous scaffolds. This was expected based on the lower porosity of the 3D-printed scaffolds (39 ± 7%) compared with the porous scaffolds (85 ± 5%). It has been previously shown that the compressive strength of scaffolds reduces significantly as the porosity of the scaffolds increases [38]. Higher compressive strength of the 3D-printed PLGA/β-TCP scaffolds indicates another advantage of these scaffold for bone tissue engineering compared with the porous PLGA/β-TCP scaffolds.
MC3T3-E1 pre-osteoblasts seeding efficiency of porous and 3D-printed PLGA/β-TCP scaffolds was similar after 16 h of culture. Moreover, cells had a similar proliferation rate on the two scaffold types. In addition, collagenous matrix deposition was not significantly different between the two scaffolds. This indicates that although the difference in surface structure and internal architecture between the two scaffold types resulted in different cell attachment and spreading pattern, it did not have a significant effect on proliferation and matrix deposition ability of the cells. However, it did have a significant effect on the osteogenic differentiation of the pre-
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