3D printing has been used for years to create prosthetics, but the technology has faced challenges in printing soft tissues. Researchers at Carnegie Mellon University have developed a solution that now makes soft tissue printing a possibility for medical use.

A Supportive Goo

Led by biomedical engineer Adam Feinberg, the team developed a supporting bath of goo with a similar consistency to mayonnaise, which allows them to 3D print soft biological structures without risking them collapsing under their own weight.

After they are printed, the researchers melt away the goo once the structures become stiff enough to support themselves.

The team printed sample structures such as model brains and hearts. According to Anthony Atala, a tissue engineer and director of the Wake Forest Institute for Regenerative Medicine, these models are the most complex of any body parts created so far. “I think it's a very nice strategy that will open up even more avenues for future development and research,” he said.

Feinberg and his team solved the problem with the goo made of blended collagen. The approach is called freeform reversible embedding of suspended hydrogels (FRESH). The goo’s melting point is much lower than that of the objects being constructed, making it easy to melt it away without damaging the structures.

A New Direction in Biomedical 3D Printing

The majority of research on biomedical applications for 3D printing were geared towards prosthetics, such as titanium plates for missing skull pieces or tracheal splints for collapsed airways. Researchers at several institutions have been experimenting with creating softer tissues, using watery gels of sugars or proteins. These matrices would be the support structure for live cells that are either printed or added after.

The matrix is formed by pushing molecules through a printer nozzle and cross-linking them to gels using chemicals or other stimuli. Usually, the resultant mixture looses form or collapses before it has the chance to harden into the required shape of the desired organ.

The team’s sample structures were modeled from resonance imaging and microscopy images. They printed a human brain and the heart of a baby chicken, both scaled to about the size of a quarter. They also produced a series of branching arteries.

Jonathan Butcher, a fellow biomedical engineer at Cornell University, thought the artery tree was quite impressive. “I don't know if we can make that geometry with our approach,” Butcher said. “The material complexity that they've been able to fabricate is really stunning.”

In future experiments, the team will need to add live cells to the gel matrix created by the FRESH method. They are already working on creating a functioning heart muscle with live cells. Next, they hope to create heart muscle patches to repair heart defects.

The artificial tissues will be valuable for researchers to test new drugs and monitor disease processes. In the future, the artificial heart muscle might be able to actually pump the blood of a living person.

Image Credits:
Carnegie Mellon