Figure 17.

Bioprinting stand-alone vascular structures. (A) Bioprinted alginate hollow microfibers perfused with a purple dye. (B) (Left) microscopic images showing the hollow channel and L929 mouse fibroblast-laden wall of the bioprinted hollow alginate microfiber and (right) live (green)/dead (red) staining of the cells. Reproduced with permission from ref.^[214]. (C) Schematic diagram showing two independent crosslinking processes of a composite bioink, where alginate and GelMA/PEGTA were ionically and covalently crosslinked, respectively, upon exposure to CaCl₂ solution and UV light, as well as representations of bioprinting processes including (ci) differently designed nozzles and (cii) different layers. (D) Fluorescence micrograph and photographs showing injection of red fluorescent microbeads into the lumen of a single, continuous bioprinted tube. (E) Representative confocal micrograph showing f-actin staining of encapsulated vascular cells after 21 days of culture post-bioprinting in the 3D tubular construct. Reproduced with permission from ref.^[216]. (F) Multi-cellular spheroids assembled into a tubular structure, which underwent fusion to form an integral blood vessel. Reproduced with permission from ref.^[217]. (G) Schematic of the “Kenzan” method in which cell aggregates were sewed onto an array of needles based on a computer program. (H) Cell aggregates eventually fused to form a uniform layer in the wall of a blood vessel. Reproduced with permission from ref.^[219].