UC Berkeley

The use of 3D bioprinted scaffolds has many advantages over the use of 2D cell culture for modeling the human body, as significant evidence shows that cells behave differently in 2D environments. Reliance on 2D cell culture during drug development contributes to high failure rate for new drugs. 3D bioprinted scaffolds are an alternative that can precisely mimic the 3D microenvironment of the body. However, the use of 3D bioprinting has been held back by the difficulty of cryopreserving 3D bioprinted scaffolds. Freezing a large, 3D scaffold creates an uneven temperature gradient and an unequal distribution of cryoprotectants, which compromises cell viability. This thesis presents “Temperature-Controlled-Cryoprinting” as a method of both fabricating and cryopreserving 3D bioprinted scaffolds. During Temperature-Controlled-Cryoprinting, a cell-laden ink is printed on a freezing plate. As each layer is printed, the print plate descends further into a cooling bath, which ensures that all cells in the scaffold are frozen at the same rate. In Chapter 2 of this thesis, we explore the fundamentals of Temperature-Controlled-Cryoprinting, including the impact that freezing has on the mechanical and material properties of the scaffolds. In Chapter 3, we discuss the optimization of the 3D printing process and how to enhance scaffold stability with crosslinking. In Chapter 4, we discuss the advantages of Temperature-Controlled-Cryoprinting for the cryopreservation of 3D bioprinted scaffolds. Finally, in Chapter 5, we conclude with a discussion about the ways in which Temperature-Controlled-Cryoprinting could accelerate drug development and offer future perspectives.