An Overview of 3D Bioprinting Impact on Cell Viability: From Damage Assessment to Protection Solutions.

Three-dimensional (3D) bioprinting has become a widely exploited tissue engineering technique for producing functional constructs that can mimic and replace native tissues. To this end, different printing strategies can be adopted, including inkjet-based, light-assisted, and extrusion-based bioprinting. Despite the great improvements that these innovative techniques introduce, cell viability maintenance during and after the bioprinting process remains a challenging open question. Indeed, the reduction in cell viability is generally related to several crucial conditions during printing, such as high shear stresses and a nutrient-deficient environment of printed constructs. In this work, the current literature on 3D bioprinting technologies is reviewed, focusing on the level of cell damage that can be imparted during biomaterial printing. In particular, extrusion bioprinting, extrusion-associated shear stress and its impact on cell viability are described in detail. The simulation of the bioprinting process through computational fluid dynamics is proposed as an appropriate method to analyze the parameters involved during bioprinting. Moreover, the viability of cells encapsulated into bioink is discussed, as well as literature techniques aimed at enhancing it by both biomaterial modifications and cell micro-encapsulation.