The field of tissue engineering has seen a lot of progress, with complex 3D systems being developed that offer strength, contain multiple cell types, and that can even perform a biological function. 
All this is child’s play if there is no viable vascular network to supply the nutrients to all the cells and to route waste products out, among other things that vascular network perform. Many organs have uniquely intricate ways that vessels twist and turn, which are important in giving these organs their functionality. It has been impossible to create highly complex, pre-programmed vascular networks suitable for tissue engineering that can perform similar to those found in our own bodies. Now researchers at Rice University, University of Washington, Duke, and others came together to develop a way of building arbitrarily complex vascular structures out of hydrogels, and they used this technique to mimic a simple lung-like structure that pumps and perfuses.
The new 3D printing method is called stereolithography apparatus for tissue engineering, or SLATE, and it combines nifty materials, a 3D printer, special inks, and a projector, to selectively harden some parts of a structure while letting other parts, namely the vessels, remain empty. A special liquid, which hardens and becomes a hydrogel when exposed to blue light, is illuminated, layer by layer using a projector. Special dyes are used to assist this process, as well as a mechanism that makes sure only the right spots on the hydrogel are illuminated with the projector light.
The resolution of the system is about 10 microns, which allows for very small vessels to be built using this framework. It was even tried by introducing living liver cells taken from mice, into a structure containing this vascular network. The whole complex was then implanted back into the mice, where it was shown that the cells continued living within the complex, supplied by a human-engineered blood network.
A Texas company called Volumetric has been setup that is commercializing some parts of this research, including the bioink and bioprinter technology.
Here’s a Rice University video showing off this impressive technology:
Link: Volumetric homepage…
Study in Science: Multivascular networks and functional intravascular topologies within biocompatible hydrogels…
Via: Rice University…