Three-Dimensional Printing and Angiogenesis: Tailored Agarose-Type I Collagen Blends Comprise Three-Dimensional Printability and Angiogenesis Potential for Tissue-Engineered Substitutes.

Three-dimensional (3D) bioprinting is a promising technology for manufacturing cell-laden tissue-engineered constructs. Larger tissue substitutes, however, require a vascularized network to ensure nutrition supply. Therefore, tailored bioinks combining 3D printability and cell-induced vascularization are needed. We hypothesize that tailored hydrogel blends made of agarose-type I collagen and agarose-fibrinogen are 3D printable and will allow the formation of capillary-like structures by human umbilical vein endothelial cells and human dermal fibroblasts. Samples were casted, incubated for 14 days, and analyzed by immunohistology and two-photon laser scanning microscopy. The 3D printability of the hydrogel blends was examined using a drop-on-demand printing system. The rheological behavior was also investigated. Substantial capillary network formation was observed in agarose-type I collagen hydrogel blends with concentrations of 0.2% or 0.5% collagen and 0.5% agarose. Furthermore, storage moduli of agarose-collagen blends were significantly increased compared to those of the corresponding single components (448 Pa for 0.5% agarose, 148 Pa for 0.5% collagen, and 1551 Pa for 0.5% agarose-0.5% collagen). Neither the addition of collagen nor fibrinogen significantly impaired the printing resolution. In conclusion, we present a tailored hydrogel blend that can be printed in 3D and in parallel exhibits cell-induced vascularization capability.