Bio-3D printed organs as drug testing tools

Evaluations of side effects and therapeutic efficacy are key steps in drug development. This process is time-consuming and costly and is often discontinued owing to differences in the drug response between animal models and humans, necessitating alternative approaches to animal models. One promising alternative for evaluations of therapeutic efficacy and adverse reactions is human induced pluripotent stem cells (iPS cells). Human iPS cells can differentiate into various cell types. Furthermore, using iPS cells derived from patients, useful human disease models can be established for the development of drugs against a wide range of diseases. Although cells are cultured on a culture dish, spheroids and organoids, which are aggregates of cells with tissue-specific functions, develop to mimic the three-dimensional (3D) cell environment. Bio-3D printing has been developed to generate scaffold-free constructs by using spheroids according to a desired design. The combination of organoids and bio-3D printing is expected to enable the fabrication of constructs with tissue-specific functions for drug testing. In this chapter, we discuss the current status of drug development and tissue engineering techniques as well as the fabrication of spheroids or organoids and applications for drug evaluation. Finally, we discuss the existing challenges and future prospects.