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Scientists are working on a new way to repair organs. As this ScienCentral News video reports, they're trying to build replacement parts using a three-dimensional printer.
Printing Organs
At the bottom of the basement stairs in the physics building at the University of Missouri-Columbia, and just to the left, there is a brown steel door marked "Research." Behind it fluorescent lights hum, a miniature guillotine clicks, and a printer paces back and forth.
But this is no mad scientist's den, nor is it a traditional physics laboratory. Here researchers, led by biological physicist Gabor Forgacs are developing a three-dimensional printing technique that may one day be used to engineer replacement parts for worn-out or diseased organs. It is a method they hope will ultimately reduce the number of whole organ transplants needed by providing patients with just the spare parts they need.
"The primary manifestation of this technology," says Forgacs, "perhaps in practice, will be grafts, skin grafts, vascular grafts, and the like, but not necessarily complicated organs as in livers or hearts."
As reported in the journal Physical Review Letters, Forgacs team has managed to build sheets of cells, or tissues, as well as tubular structures, like blood vessels.
The researchers print their structures using what they call "bio-ink." The bio-ink is made much the way sausages are made. First the researchers create a thick paste that is densely packed with cells, then they feed it into a tiny tube no wider than half a millimeter. The paste is then pushed out the other end of the tube, while a twelve-inch tall guillotine cuts it into tiny cell clusters, each containing up to 40,000 cells.
Once the bio-ink cell clusters are made, the researchers put them into what looks very much like a syringe. This syringe is actually a dual-headed printing cartridge. In a separate compartment, adjacent to the bio-ink, is the "bio-paper."
"The paper is a biocompatible matrix, scaffold, or gel that the cells like," explains Forgacs.
Using a "layer-by-layer" construction process, the syringe first releases a stream of bio-paper scaffolding gel, carefully spreading it into a perfect square. Then, one at a time, it injects individual droplets of bio-ink into the bio-paper.
"And then another layer of bio-paper is printed. So the peculiarity of this technology is that the paper itself is also printed," says Forgacs, "Then the process continues in three dimensions as long as we want it to."
Depositing droplets of bio-ink on bio-paper image: Gabor Forgacs
Once they get the basic cellular architecture they want, the researchers cross their fingers and rely on the cells themselves to settle in and bind together. The fusing of the cells is called "self-assembly" and how the phenomenon works is not well understood.
Self-assembly is only one of the many hurdles the scientists face as they try and transform their technology into skin grafts for burn victims, or perhaps new arteries and patches of cardiac muscle for heart patients. They also have to think about compatibility between the bio-paper and the cells being printed, as well as making structures large enough to really be useful in the human body, not just what can fit in a Petri dish.
But Forgacs says his team already has partial solutions to both problems. While he admits it takes a lot of research to find a compatible match between the cell clusters and their gel, he also says cells are "happy under rather broad conditions."
To build larger tissue structures, the researchers will have to figure out how to integrate blood vessels — the carriers of oxygen, nutrients and waste products throughout our bodies — into their tissue blocks. But Forgacs points out that "If we know how to build tubular [blood vessel-like] structures, if we know how to build big blocks of tissue, if we can combine these two, then we will have a structure which is going to survive because it will get the nutrients from the blood vessel-like organ modules that we're going to print."
Massachusetts Institute of Technology tissue engineer Linda Griffith doubts the printing technique will ever really work. Because the printing process can only produce relatively large structures — structures that are "two orders of magnetitude" greater than what they need to be to make the microscopic blood vessels that support human tissues — she says she "can't imagine a tissue that it would work on."
Gibran is a little more positive. She says, "It's very sexy, very exciting, but we're not there yet." She adds that Forgacs will need to go through years of testing not only to make sure the printed tissues are safe for people, but also to realize the printing technique's full potential. She warns that sometimes experimental techniques that have great promise are used clinically too quickly and never become completely refined as a result.
Forgacs and his colleagues admit their work is still at the proof-of-concept stage. But they think that within the next ten years printed blood vessels may be moving out of their basement laboratory and into the operating room.
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