Technique could eventually allow scientists to 'print' living forms that resemble human tissue, which could be used for drug testing.

Using a special redesigned inkjet printer loaded with "biological ink," Swiss researchers have moved one step closer to being able to print out artificial — but living — human tissue, reports Physorg.com. The breakthrough could soon lead to advanced techniques for testing drugs and other medical procedures without the need for animal testing.

The challenge of the project was twofold. First, researchers had to design an appropriate printing sequence for the specialized printer. The second, and perhaps biggest, task was inventing an ink that was biological and structured like real living tissue, but that could still be "printed."

"Mixing the right ingredients isn't sufficient. The cells grow in a haphazard manner, randomly, and won't develop into viable tissue," explained professor Matthias Lutolf, head of the laboratory where the ink was developed.

For the cells to function like true living tissue, they need to be fostered within an environment that encourages them to act appropriately as a whole. In living tissue, environmental cues are supplied by what is called a complex extracellular matrix, or ECM. The ECM is generally made up of molecules that catalyze cellular behaviors like proliferation, migration, differentiation or death.

Researchers were able to reconstruct such a matrix by developing a unique gel made up of concentrated calcium. The gel served as a base so that when each droplet of ink landed on a surface, it would stick and retain its initial shape instead of spreading out.

"The various tissue elements don't blend together uncontrollably," explained Jürgen Brügger, lead researcher on the project. "Above all, the material polymerizes more quickly and becomes flexible and malleable, which allows us to assemble several layers and to envision building channels, which are indispensable for fluid perfusion, nutrient input and waste elimination."

In other words, with the help of an appropriate printing sequence, the gel served both as structure for the cells to organize into tissues, and as a base to deliver them as ink.

Brügger was quick to point out that the technology is still a long away from producing true living human tissue: "We have not yet created tissue, strictly speaking. At this stage, we have essentially studied a way in which to structure biological materials in three dimensions; this research will improve cell culture and then will eventually be used as a base for creating tissues."

The breakthrough should not be understated, however. At this point it's more a question of when the technology will be fully realized, rather than if. But some might be left with a more pervasive question: Why?

The benefit of being able to generate artificial living tissue from an inkjet printer is that it could lead to more effective and controlled ways of testing new drugs. Before long, animal lovers could finally be assured that scientists might no longer require animal testing before drugs can be streamlined for human trials.