5. 3D Bioprinting of Thermal-Sensitive Bioink

In this chapter, we aim to explore the property of a common thermal-sensitive bioink and its effects on structure printability and embryonic stem cells (ESCs) viability. Despite progress in bioinks development, the effect of bioink properties on the formation of 3D construct and cell damage during the extrusion process are poorly characterized. Moreover, the parameter optimization based on specific cell type might not be applicable to other types of cells, especially those with high sensibilities, such as ESCs. In this study, we systematically study the construct printability and cell viability in a temperature-controlled bioprinting process by using gelatin-alginate hybrid materials. A novel method is established to determine suitable conditions that could achieve both good printability and high cell viability. The rheological properties of the bioinks are evaluated to determine the gelation properties under different gelatin concentrations, testing temperatures and time. The printability of a lattice construct is characterized by using a semi-quantified method. The LIVE/DEAD^TM assay show that ESCs viability increased with the increase of printing temperature increased and decrease of gelatin concentration. Furthermore, a fitting exponential relationship was obtained between cell viability and induced shear stress. By defining the proper printability and acceptable viability range, a conjunction parameters region is obtained to guide the parameter choosing. This study will provide insight into the fine-tuning of 3D bioprinting process regarding the integrity of printed construct and incorporated cells, especially for easily damaged cells like ESCs.