Harvard scientists make a 3D

Harvard

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3D printing technology is already changing the way we produce things. Opening up a world of limitless possibilities, we now have the largest 3D-printed building in Florida and even a 3D-printed replica of the Lamborghini Aventador SV.

In the medical field, scientists in the last couple of years have created 3D-printed parts of heart structures and even full-size 3D bioprinted human heart models, which are a big push in the effort to find new treatments for heart diseases, a leading cause of death in the U.S.

And now, as per a new paper published, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new hydrogel ink containing gelatin fibers and used it to 3D print a functional heart chamber that mimics how a human heart beats.

The fiber-infused gel (FIG) ink allows the 3D-printed heart muscle cells to align and beat in coordination like a human heart chamber. The immediate goal of the researchers is to discover new therapeutics for heart disease, while the long-term plan is to fabricate implantable tissues.

Explaining how the 3D printing technology as of yet hasn’t been able to achieve alignment of cardiomyocytes cells responsible for the contraction of a heart, the first author of the paper, Suji Choi, said, “People have been trying to replicate organ structures and functions to test drug safety and efficacy as a way of predicting what might happen in the clinical setting.”

“FIG ink is capable of flowing through the printing nozzle but, once the structure is printed, it maintains its 3D shape. Because of those properties, I found it’s possible to print a ventricle-like structure and other complex 3D shapes without using extra support materials or scaffolds,” Choi added.

Choi explains that the most challenging part of the process was maintaining the desired ratio between fibers and hydrogel in the ink. Once that was achieved, she applied electrical stimulation to 3D-printed structures made with FIG ink, which triggered a coordinated wave of contractions.

“It was very exciting to see the chamber actually pumping in a similar way to how real heart ventricles pump,” said Choi.

The team hopes that the FIG ink will be used to build dual-chambered miniature heart valves.

The study was published in Nature Materials.

Study abstract:

Hydrogels are attractive materials for tissue engineering, but efforts to date have shown limited ability to produce the microstructural features necessary to promote cellular self-organization into hierarchical three-dimensional (3D) organ models. Here we develop a hydrogel ink containing prefabricated gelatin fibres to print 3D organ-level scaffolds that recapitulate the intra- and intercellular organization of the heart. The addition of prefabricated gelatin fibres to hydrogels enables the tailoring of the ink rheology, allowing for a controlled sol–gel transition to achieve precise printing of free-standing 3D structures without additional supporting materials. Shear-induced alignment of fibres during ink extrusion provides microscale geometric cues that promote the self-organization of cultured human cardiomyocytes into anisotropic muscular tissues in vitro. The resulting 3D-printed ventricle in vitro model exhibited biomimetic anisotropic electrophysiological and contractile properties.