Page 87 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani

INTRODUCTION
Bone is a tissue with self-repairing capacity; however, certain large bone defects caused by congenital deformities, trauma, tumor resection and other causes cannot be regenerated by the natural bone healing capacity. Treatment of such bone defects by autografts (i.e. bone harvested from the same patient) and allografts (i.e. bone harvested from another person) possess several drawbacks such as limited availability, need for multiple surgeries, donor site morbidity, and rejection [1]. Bone tissue engineering is a developing field aiming to overcome the limitations of conventional treatments of bone diseases.
Bioresorbable scaffolds are a key component in current bone tissue engineering approaches by providing a temporary mechanical and structural osteoconductive support. Poly(α- hydroxy esters) such as poly(ɛ-caprolactone) (PCL), polylactic acid (PLA), and poly(lactic-co- glycolic) acid (PLGA) are FDA approved biodegradable materials widely used for fabrication of bone tissue engineering scaffolds [2]. These polymers have adjustable degradation rates with degradation products that can be removed by natural pathways in the body [2,3]. However, poly(α- hydroxy esters) lack osteoconductivity and cell recognition sites [2,4]. Therefore, these polymers are often used as composites with osteoconductive calcium phosphates such as hydroxyapatite and β-tricalcium phosphate (β-TCP) [5-8].
The 3D porous scaffolds fabricated by conventional techniques such as freeze drying, solvent casting-porogen leaching, and gas foaming, aim to mimic the structure of cancellous bone [9]. However, control over the internal structure with high accuracy is difficult [10]. Moreover, creating patient-specific scaffolds with shapes fitting the defect geometry is virtually impossible. To tackle these issues, three-dimensional (3D) printing technology is currently extensively being used [11]. In this technology, the shape of the defect site is first identified using medical imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI). Geometrical modelling is then conducted to generate a 3D computer-aided design (CAD) model. The 3D scaffold is then printed layer by layer according to the designed model [12].
The current study aimed to determine whether the much tighter control of shape and nano/microstructure of 3D-printed PLGA/β-TCP scaffolds is more effective in promoting osteogenesis than the 3D porous scaffolds produced by solvent casting-porogen leaching using the same components. This was evaluated by detailed characterizations of scaffold properties (i.e. surface morphology and hydrophilicity, β-TCP particle dispersion, pore size, porosity, and compressive strength), as well as multi-parameter assessment of functional osteogenic responses (i.e. proliferation, matrix deposition, and alkaline phosphatase activity) in MC3T3-E1
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