Figure 14-.

Extrusion-based multi-material bioprinting for tissue-fabrication. (A) Schematic illustration of multi-material extrusion printhead design for hepatic lobule printing. (B) Left: Immunostaining of CD31 (green) and f-actin (red) for the bioprinted epithelial cells. Nuclei were counterstained in blue; right: Live (green) and dead (red) staining showing morphological changes and viability. (C) Immunostaining of CD31 (red), albumin (green), and MRP2 (green) for the bioprinted hepatic lobule with hepatocelluar cells. Nuclei were counterstained in blue. Reproduced with permission.^[82] Copyright 2020, Wiley-VCH. (D) Schematic showing the multi-material bioprinting setup for dual-cell MTU constructs fabrication. (E) Tensile behavior of the bioprinted MTU with both soft and rigid regions. (F) Fluorescence image showing bioprinted MTU after 7-day culture (green: DiO-labeled C2C12 cells; red: DiI-labeled NIH/3T3 cells). (G) Differential expression between the two cell types at the interface region (depicted by the dotted line) is observed. Reproduced with permission.^[225] Copyright 2015, Institute of Physics. (H) Schematic of dual-material FRESH printing using a collagen ink and a high-concentration cell ink. (I) Micrograph of FRESH-printed multi-component ventricle. (J) Side view of FRESH-printed ventricle stained with calcium-sensitive dye showing uniform cell distribution. (K) Calcium mapping of the subregion [yellow box in (J)] showing spontaneous, directional calcium wave propagation. Reproduced with permission.^[158] Copyright 2015, American Association for the Advancement of Science.