Optimizing extrusion-based 3D bioprinting of plant cells with enhanced resolution and cell viability

3D bioprinting of plant cells has emerged as a promising technology for plant cell immobilization and related applications. Despite the numerous progress in mammalian cell printing, the bioprinting of plant cells is still in its infancy and needs further investigation. Here, we present a systematic study on optimizing the 3D bioprinting of plant cells, using carrots as an example, towards enhanced resolution and cell viability. We mainly investigated the effects of cell cluster forms and nozzle size on the rheological, extrusion, and printability properties of plant cell bioinks, as well as on the resultant cell viability and growth. We found that when the printing nozzle is larger than 85% of the cell clusters embedded in the bioink, smooth extrusion and good printability can be achieved together with considerable cell viability and long-term growth. Specifically, we optimized a bioink composited with suspension-cultured carrot cells, which exhibited better uniformity, smoother extrusion, and higher cell viability over 1 month culture compared to those with the regular callus or fragmented callus. This work provides a practical guideline for optimizing plant cell bioprinting from the bioink development to the printing outcome assessment. It highlights the importance of selecting a matched nozzle and cell cluster and might provide insights for a better understanding and exploitation of plant cell bioprinting.