3D Bioprinting of Liquid High-Cell-Proportion Bioinks in Liquid Granular Bath

Embedded 3D bioprinting techniques have emerged as a powerful method to fabricate 3D engineered constructs using low strength bioinks; however, there are challenges in simultaneously satisfying the requirements of high-cell-activity, high-cell-proportion, and low-viscosity bioinks. In particular, the printing capacity of embedded 3D bioprinting is limited as two main challenges: spreading and diffusion, especially for liquid, high-cell-activity bioinks that can facilitate high-cell-proportion. Here, a liquid-in-liquid 3D bioprinting (LL3DBP) strategy is developed, which used a liquid granular bath to prevent the spreading of liquid bioinks during 3D printing, and electrostatic interaction between the liquid bioinks and liquid granular baths is found to effectively prevent the diffusion of liquid bioinks. As an example, the printing of positively charged 5% w/v gelatin methacryloyl (GelMA) in a liquid granular bath prepared with negatively charged κ-carrageenan is proved to be achievable. By LL3DBP, printing capacity is greatly advanced and bioinks with over 90% v/v cell can be printed, and printed structures with high-cell-proportion exhibit excellent bioactivity.