Cell-Laden 3D Printed Scaffolds for Bone Tissue Engineering

Abstract

Tissue engineering, relying on a combination of biomaterial scaffolds, cells, and bioactive molecules, has emerged as a promising strategy for the treatment of bone defects. The presence of viable cells inside the engineered tissue has been shown to be crucial for bone formation in vivo. However, cells require mechanical support and a physical template, or scaffold, to facilitate their attachment and to stimulate neotissue formation. The advent of additive manufacturing technologies, and most critically three-dimensional (3D) printing, has allowed the development of a new generation of scaffolds. Cells used alongside 3D bioprinting in bone tissue engineering are typically utilized in two different strategies. The first strategy, 3D bioprinting, involves the layer-by-layer deposition of a bioink, made of a scaffold material and cells. The second strategy focuses on the fabrication of a scaffold by printing an acellular material, followed by seeding living cells. Here we review these two approaches, discussing printing techniques, their inconveniences and advantages, hydrogels for 3D printing, and how to overcome obstacles. Finally, we consider the resulting engineered tissues from these two approaches, specifically their mechanical properties, matrix production, and tissue mineralization.