A team at MIT and Harvard Medical School has worked out how to cast bricks of artificial tissue into different shapes, and then get them to assemble automatically. The "living Lego bricks" are cast of polyethylene glycol—a biocompatible polymer—and solidified with light exposure. The self-assembling part happens when the bricks absorb water and are then agitated in a bath of mineral oil: The oil/water mix means the bricks move around and can be fixed when they're in the right place with more light (as shown in the picture here, rod-shaped bricks in red stuck to a central green-stained piece).

By repeating the process, and varying the agitation rates and the shape and size of the tissue bricks, structures like branches and cubes can be built up. The team has also built very complex structures that resemble blood vessels running through tissue, and know that yet more complex and "realistic" structures are possible.

While this is a technology in its infancy, it has advantages over current tissue-engineering techniques (which rely on a sort of "top-down" system, tying cells to a polymer mould) in that it has the potential to emulate natural repeating units in organs like the liver, pancreas, heart-muscle and so on. There are plenty of challenges before we can, for example, grow artificial pancreatic tissue, but this is a pretty amazing start. The results are published today in the Proceedings of the National Academy of Sciences. [Technology Review]