Page 24 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani

osteoblasts with 3D-printed scaffolds fabricated from different biomaterials for bone tissue engineering. In order to achieve our aim, we addressed the following scientific questions:
1. Which surface modification of PCL, i.e. chemical modification by NaOH or immobilization of RGD on the surface, is more effective to enhance pre-osteoblast proliferation and differentiation (Chapter 2)?
2. Can finite element modeling of the force distribution in a bone defect site allow customization of the 3D-printed scaffolds to match the in situ bone mechanical properties (Chapter 3)?
3. What is the difference in the osteogenic response of pre-osteoblasts seeded on scaffolds fabricated from the same material, but either produced by solvent casting-porogen leaching thus with random porous internal structure versus 3D-printed scaffold with ordered internal structure (Chapter 4)?
4. Does bioprinting of pre-osteoblasts in the scaffold enhance cell retention, proliferation, and differentiation compared with cell-seeding post-printing (Chapter 5)?
PCL is frequently used for fabrication of bone tissue engineering scaffolds due to its biodegradability, biocompatibility, and high mechanical properties. However, since its hydrophobicity may hamper cell attachment and subsequent cellular responses, we assessed in Chapter 2 whether and how chemically or RGD immobilized surface modifications of 3D-printed PCL scaffolds affect the osteogenic activity of MC3T3-E1 pre-osteoblasts.
Mechanical properties of bone tissue engineering scaffolds are considered to play a major role in their in vivo performance. Therefore, prediction of forces within native bone during normal functioning, which will vary depending on the location, is important in the design, fabrication, and integration of a scaffold with the host. In Chapter 3 we predicted the forces and torques induced on the mandibular symphysis during jaw opening and closing by finite element modeling and customized the mechanical properties of 3D-printed PCL scaffolds accordingly.
Scaffold internal architecture can affect cellular responses. Composites consisting of MC3T3-E1 pre-osteoblasts seeded on either porous spongy scaffolds prepared by solvent casting-porogen leaching, or ordered 3D-printed PLGA/β-TCP scaffolds were prepared. Proliferative and osteogenic potential of these composites were determined in vitro (Chapter 4).
Effective incorporation of cells in 3D scaffolds remains a challenge. Conventional cell seeding may result in inhomogeneous distribution of cells in the scaffold and low seeding efficiency. Bioprinting of cells in the scaffold may adversely affect cell viability due to harsh printing conditions, and/or may hamper subsequent cell growth and differentiation. In Chapter 5 we
22