The researchers first used a 3D bioprinter to make an agarose (naturally derived sugar-based molecule) fiber template to serve as the mold for the blood vessels. They then covered the mold with a gelatin-like substance called hydrogel, forming a cast over the mold which was then reinforced via photocrosslinks.
"Our approach involves the printing of agarose fibers that become the blood vessel channels. But what is unique about our approach is that the fiber templates we printed are strong enough that we can physically remove them to make the channels," said senior study author, Ali Khademhosseini, PhD, biomedical engineer, and director of the BWH Biomaterials Innovation Research Center. "This prevents having to dissolve these template layers, which may not be so good for the cells that are entrapped in the surrounding gel."
Khademhosseini and his team were able to construct microchannel networks exhibiting various architectural features. They were also able to successfully embed these functional and perfusable microchannels inside a wide range of commonly used hydrogels, such as methacrylated gelatin or poly(ethylene glycol)-based hydrogels at different concentrations.
Methacrylated gelatin laden with cells, in particular, was used to show how their fabricated vascular networks functioned to improve mass transport, cellular viability and cellular differentiation. Moreover, successful formation of endothelial monolayers within the fabricated channels was achieved.
"In the future, 3D printing technology may be used to develop transplantable tissues customized to each patient's needs or be used outside the body to develop drugs that are safe and effective," said Khademhosseini.