Figure 3.

(a) Thermal inkjet bioprinting of microvasculature. (i) A schematic representation illustrating the deposition of human microvascular endothelial cells (HMVECs) in thrombin bioink using a modified thermal inkjet printer. The bioink containing cells was bioprinted into a fibrinogen substrate, allowing for the formation of fibrin channels while simultaneously depositing the cells into the scaffold. Bioprinted cells aligned within the fibrin channels and were poised for proliferation. (ii) A fibrin scaffold fabricated using a modified thermal inkjet printer which maintained its shape and structure post bioprinting. (iii) Channel structure of the bioprinted microvasculature cultured for 21 d. (A) Fluorescent staining (LIVE/DEAD) revealed bioprinted cells aligned within the fibrin scaffold. (B) Differential interference contrast (DIC) image showing the fibrin scaffold. (C) Bioprinted ring-shaped microvasculature after 21 d of culture. (D) When Texas Red-conjugated Dextran molecules were applied to the bioprinted structure, its integrated channel structure was able to expel dextran molecules via proliferated endothelial cells, which formed a robust and functional barrier. SEM images of bioprinted fibrin fiber: (E) cross-sectional view of a critically-dried fibrin fiber, revealing the channel structure at the cut section. The hole indicates the hollow nature of fibers for cell seeding and proliferation. (F) Close-up view highlighting the presence of nano-sized fibers on the surface of the bioprinted fibrin scaffold, facilitating cell attachment and proliferation. Reprinted from [156], Copyright (2009), with permission from Elsevier. (b) 3D coaxial bioprinting of vascular constructs. (i) 3D model representation of the coaxial nozzle and cross-sectional view of the coaxial nozzle assembly model illustrating the fluid flow paths for alginate and crosslinker solutions. Reproduced from [157], with permission from Springer Nature. (ii) (A) SEM image demonstrating cells encapsulated within bioprinted constructs. (B) A light microscopic image illustrating cell encapsulation and clear identification of the lumen in the center. (C) An SEM and (D) optical microscope image showing dehydrated 5% alginate constructs. Reproduced from [158] with permission from the Royal Society of Chemistry.