Process-induced cell damage: pneumatic versus screw-driven bioprinting

During the bioprinting processes that employ either pneumatic or screw-driven mechanisms, living cells are subject to process-induced forces, which may cause cell injury or damage. However, the similarities and differences between these two mechanisms have not been discovered and documented in terms of process-induced forces and cell damage. In this paper, we examined the process-induced forces, including hydrostatic pressure, shear stress, extensional stress, and tensile/compressive forces that the cells experienced during the bioprinting processes by means of these two mechanisms; we also experimentally investigated the process-induced cell damage (featured by the rupture of the cell membrane) under various printing conditions or factors, including the volumetric flow rates, cell types, bioink solutions, needle types and sizes, and printing head-movement speeds. On this basis, we correlated the percent of cell damage to the process-induced forces, which were considered mainly responsible for the rupture of the cell membrane. Our results illustrate that compared to the pneumatic bioprinting process, the screw-driven bioprinting process generally induces more cell damage, varying with the printing conditions. This study, for the first time, discovers the similarities and differences between the pneumatic and screw-driven bioprinting processes and further demonstrates their merits and demerits for bioprinting in terms of printing-process control, process-induced forces, and cell damage.