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3-D Printing

Hydrogel adult heart printed to scale at unprecedented detail

3-D-printed replicas of people’s hearts could help surgeons plan complicated procedures

by Alla Katsnelson, special to C&EN
November 18, 2020 | A version of this story appeared in Volume 98, Issue 45


Photograph of a human heart replica 3-D-printed out of alginate and dyed purple.
Credit: ACS Biomater. Sci. Eng.
This replica of an individual's heart was 3-D printed out of hydrogel and dyed purple.

Researchers have 3-D printed a detailed replica of an individual’s full-sized adult human heart out of a seaweed-derived hydrogel (ACS Biomater. Sci. Eng. 2020, DOI: 10.1021/acsbiomaterials.0c01133). Such a precisely tailored model heart can serve as a crucial tool to train surgeons and help them plan complicated procedures, says Adam Feinberg, a biomedical engineer at Carnegie Mellon University whose team developed the technique. “The near-term applications can hopefully have tremendous benefit to patients in the clinic,” he says. “The next step is getting it into surgeons’ hands, getting their feedback, and improving it.”

While researchers would one day like to be able to 3-D print a replacement for a person’s heart by extruding cells, such a scenario is at least a decade away because of challenges with printing soft materials that hold their shape, as well as producing and assembling so many different cell types, says Feinberg. In the meantime, hydrogel can create organs with similar texture that can serve as models tailored to an individual. Currently, most surgical training and planning is done with rigid plastic or silicone, at best. But a model made from a hydrogel or collagen— a protein that acts as the structural foundation of most human tissues—would allow surgeons to cut, suture and cauterize a more lifelike material, he says.

The new study builds on the group’s previous work in which they demonstrated the process at smaller scale (Sci. Adv. 2015, DOI: 10.1126/sciadv.1500758; Science 2019, DOI: 10.1126/science.aav9051). Researchers first fill a container with a support material made from gelatin microparticles. Then, directed by an MRI or other imaging scan, a syringe filled with a seaweed-derived hydrogel called alginate moves through the support material to bioprint the organ. The material gels as it leaves the syringe. “Whatever you extrude out of the needle gets embedded in place,” says Feinberg. “That allows us to print an entire 3-D structure.” The researchers then incubate the whole setup at body temperature, melting away the gelatin and leaving the hydrogel organ.

In the new study, the researchers made a larger setup to print a full-size adult organ from a person’s MRI. Printing the heart took four days. The alginate heart can be handled and sutured, but it’s a little weaker than actual heart tissue, Feinberg says. His team is still working to make the hydrogel version more like the real thing and attempting to bioprint other soft-tissue body parts. “Before our technology, bioprinting something taller than a centimeter, even a 1 cm tube, was considered state of the art,” Feinberg says. “Now, any detail we can get out of an MRI image, we can print.”

“The work is very interesting, as there are few examples where organ-sized printed constructs have been obtained, particularly from soft materials,” Jason Burdick, a bioengineer at the University of Pennsylvania says. Burdick is an associate editor at ACS Biomaterials Science and Engineering, the journal that published the paper. The next challenge, he says, will be creating tissues in which multiple materials or cell types are combined into a single structure.


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