Researchers have used a 3D printing method to bioprint models of hearts, arteries, bones and brains out of biological materials. They say their work could one day lead to a world in which transplants are no longer necessary to repair damaged organs.

Coronary artery structure being 3D bioprinted. Credit: Carnegie MellonCoronary artery structure being 3D bioprinted. Credit: Carnegie Mellon"We've been able to take MRI images of coronary arteries and 3D images of embryonic hearts and 3D bioprint them with unprecedented resolution and quality out of very soft materials like collagens, alginates and fibrins," says Adam Feinberg, an associate professor of Materials Science and Engineering and Biomedical Engineering at Carnegie Mellon University. Feinberg leads the Regenerative Biomaterials and Therapeutics Group, whose study was published in the journal Science Advances.

Typical 3-D printers build hard objects made of plastic or metal, and they work by depositing material onto a surface layer-by-layer to create the 3-D object. Printing each layer requires sturdy support from the layers below, so printing with soft materials like gels has been limited, the researchers say.

The challenge with soft materials—something with the consistency of Jello—is that they collapse under their own weight when 3D printed in air. The Carnegie Mellon researchers developed a method of printing these soft materials inside a support bath material and they print one gel inside of another gel, which allows them to position the soft material as it is being printed, layer-by-layer.

One attribute of this technique, termed FRESH, or "Freeform Reversible Embedding of Suspended Hydrogels," is that the support gel can be melted away and removed by heating to body temperature. This process does not damage the biological molecules or living cells that were bioprinted, the researchers say. As a next step, the group is working to incorporate real heart cells into these 3D-printed tissue structures, providing a scaffold to help form contractile muscle.

To date, most 3D bioprinters have cost more than $100,000 and/or require specialized expertise to operate, limiting wider-spread adoption, Feinberg's group says. The researchers say they have been able to implement their technique on a range of consumer-level 3D printers by using open-source hardware and software.

"Not only is the cost low, but by using open-source software, we have access to fine-tune the print parameters, optimize what we're doing and maximize the quality of what we're printing," Feinberg says.

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