An overview of extrusion-based bioprinting with a focus on induced shear stress and its effect on cell viability

Three dimensional bioprinting is an emerging fabrication technique in the field of tissue engineering. Extrusion-based bioprinting is one of the widely employed biofabrication techniques; researchers tend to use it because of its simplicity, affordability and scalability. During the extrusion-based bioprinting process, cells are subjected to mechanical forces of different kinds. Among these mechanical forces, shear stress is of a special significance and concern as it is considered the main cause of cell damage/death. This review covers the principle of extrusion-based bioprinting, and highlights extrusion-based bioprinting induced shear stress, how cells sense it and respond to it. Moreover, it discusses the bioinks that are commonly used in extrusion-based bioprinting along with their properties that have proven to have an effect on process induced shear stress and cell viability. In addition, it discusses, in detail, the relationship between shear stress, cell viability and different material properties and printing parameters. Furthermore, it provides examples of successfully extrusion-based bioprinted 3D tissues. Finally, it sheds light upon approaches to overcome shear stress effect and therefore preserve cell viability.