Page 23 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani
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internal architecture made from the same material may result in different interaction between the cells and the scaffold surface and therefore, may result in different cell responses.
Cell-scaffold surface interactions
Scaffold surface properties play a significant role in cell-biomaterial interactions, ultimately controlling cellular responses. Surface hydrophilicity, topography, charge, stiffness, chemical functionalities, and presence of biologically active molecules on the surface are among the most important characteristics of the scaffold. All mentioned properties may affect cell behavior in terms of morphology, adhesion, proliferation, migration, differentiation, and metabolism [27]. It is hard to isolate each surface property as an independent variable to obtain conclusions about the precise influence of each one. For instance, surface hydrophilicity is affected by the functional groups on the surface as well as by the surface roughness [28]. Super hydrophilic and super hydrophobic surfaces both inhibit cell attachment and moderately hydrophilic surfaces (water contact angel between 45°- 80°) result in optimal adsorption of proteins, giving rise to optimal conditions for cell adhesion and proliferation [29-31].
Adsorption of proteins to any surface is also dependent on the size of topographical features on the surface [32]. Surface cues might cause cells to adopt shapes which correspond to certain cytoskeleton organizations that might enhance some signaling pathways that other shapes would not. Surfaces with relatively high roughness (high Ra values) and smooth surfaces with no roughness (low Ra values) are both not suitable for cell activities [33, 34]. Numerous surface modification methods including physical (e.g. ɣ-radiation and plasma treatment), chemical (e.g. hydrolysis and aminolysis) or biological methods (e.g. coating and immobilization of biologically active molecules such as proteins and/or ligands on the surface) have been used to improve scaffold surface properties. Hydrolysis of scaffolds made from poly(α-hydroxy esters) such as PCL by sodium hydroxide (NaOH) has been extensively used to increase surface hydrophilicity by creation of carboxyl and hydroxyl groups on the surface [35-37]. Immobilization of RGD peptide (R: arginine; G: glycine; D: aspartic acid) on the surface of polymeric scaffolds has also been used to facilitate cell attachment and proliferation [38-40]. A better understanding of the interaction of osteogenic cells with 3D-printed scaffolds can contribute in successful application of 3D-printed scaffolds for bone regeneration.
Scope of the thesis
The aim of the studies presented in this thesis was to evaluate and optimize the performance of 3D-(bio)printed scaffolds for bone tissue engineering purposes. We studied the interaction of pre-
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