3D-printed heart muscle beating through fiber-infused ink. Credit: Harvard SEAS
Key Points:
- Researchers created a new hydrogel ink that enables 3D printing of a functional heart ventricle.
- The key is the addition of gelatin fibers within the printable ink.
- The team found by controlling the printing direction of cardiomyocytes, they could also control how the heart muscle cells align.
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new hydrogel ink infused with gelatin fibers that enables 3D printing of a functional heart ventricle that mimics beating like a human heart.
The innovation lies in the addition of the fibers within the printable ink, or fiber-infused gel (FIG) ink.
“FIG ink is capable of flowing through the printing nozzle but, once the structure is printed, it maintains its 3D shape,” said Suji Choi, research associate at SEAS and first author on the paper. “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.”
To create the FIG ink, Choi leveraged a rotary jet spinning technique that fabricates microfiber materials using an approach similar to the way cotton candy is spun. With the technique, Choi and her team produced a sheet of material with a similar appearance to cotton. Next, she used sonification to break that sheet into fibers 80 to 100 micrometers long and 5 to 10 micrometers in diameter. Then, she dispersed those fibers into a hydrogel ink.
As the researchers printed 2D and 3D structures using FIG ink, the cardiomyocytes lined up in tandem with the direction of the fibers inside the ink. By controlling the printing direction, Choi could also control how the heart muscle cells would align. When she applied electrical stimulation to 3D-printed structures made with FIG ink, she found it triggered a coordinated wave of contractions in alignment with the direction of those fibers.
As Choi and team experimented with more printing directions and ink formulas, they found they could generate even stronger contractions within ventricle-like shapes.
“Compared to the real heart, our ventricle model is simplified and miniaturized,” said Choi.
The team is now working toward building more life-like heart tissues with thicker muscle walls that can pump fluid more strongly. Despite not being as strong as real heart tissue, the 3D-printed ventricle could pump 5 to 20 times more fluid volume than previous 3D-printed heart chambers.
The researchers say the technique can also be used to build heart valves, dual-chambered miniature hearts, and more.