Page 108 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani

within the scaffold [15]. With the further development of 3D-printing technologies, it is now possible to print cells simultaneously with the scaffold material referred to as “3D-bioprinting”. 3D- bioprinting has several advantages such as homogeneous distribution of cells in the scaffold and the ability to print several cell types at pre-defined locations in a single scaffold [16]. In order to prevent damage to the cells in the process of printing, cells need to be encapsulated in a hydrogel. Hydrogels are 3D networks that have a high water content. Several hydrogels such as fibrin [17], agarose [18], alginate [19], and gelatin methacrylate (GelMA) [20] have been used for cell printing. Alginate is a biocompatible natural polysaccharide composed of guluronic and mannuronic acids [21]. Due to its biodegradability, low cost, and gelation under mild conditions, alginate has been frequently used for encapsulation of cells in the bioprinting of bone tissue engineering scaffolds [22-25]. When cells are encapsulated in a hydrogel, some cell functions might be affected by the hydrogel properties [26]. Moreover, during the bioprinting process, cells might experience unintended shear stress that may affect their function [27]. Whether bioprinting in alginate or cell seeding post-printing is more effective to enhance pre-osteoblast proliferation and differentiation is currently unknown. In the present study, we incorporated MC3T3-E1 pre-osteoblasts in PLGA/β-TCP scaffolds by either seeding strategy, using alginate as the hydrogel carrier, and investigated whether differences exist in the response of pre-osteoblasts to these two scaffold types.
MATERIALS AND METHODS
Preparation of PLGA/β-TCP pellets
Medical grade PLGA granules (Purasorb, Purac Biomaterials, Netherlands) were melted on a hot plate at 100°C. β-TCP (particle size: 0.5-1 μm, Nik Ceram Razi, Isfahan, Iran) was added to the molten PLGA in a 25 wt% ratio, and was homogenized for 1 h to homogeneously disperse the β- TCP particles in the PLGA. Upon removal from the hot plate, PLGA/β-TCP pellets were obtained.
3D-printing of PLGA/β-TCP scaffolds
Scaffolds were designed using BioCADTM software (RegenHU, Villaz-St-Pierre, Switzerland). PLGA/β-TCP pellets were melted at 110°C in the heating tank of the 3D Discovery bioprinter (RegenHU) and extruded through a pre-heated needle at 0.4 MPa (4 Bar). The struts of PLGA/β- TCP were plotted layer-by-layer on the platform until the desired height was achieved. Cubical scaffolds with dimensions of 10×10×5 mm were fabricated.
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