Bioprinting using aqueous two-phase system

A key for successful bioprinting is the design and formulation of a suitable "ink" that maintains cell viability while being patternable. Here, we describe the uses of aqueous two-phase systems (ATPS) to bioprint or micropattern cells as well as reagents. The unique advantage of the method compared to other bioprinting methods is that one can pattern while fully immersed in aqueous solutions without diffusion or dispersion of the aqueous ink. The fully aqueous environment is advantageous for cell printing where even brief drying can be lethal. Additionally, bioprinting with ATPS is typically performed in a noncontact manner allowing printing over delicate materials such as living cells, tissues, and hydrogels straightforward. While bioprinting generally implies additive fabrication, sculpting of existing biological structures can also serve to create cellular patterns. This chapter thus provides an overview of the use of ATPS bioinks to perform both additive and subtractive fabrication.