Researchers have developed a first-of-its-kind technique that brings the field of tissue engineering one step closer to being able to 3D print a full-sized, adult human heart.
The method, described in the journal Science, can allow anyone to 3D bioprint tissue scaffolds out of collagen, the major structural protein in the human body, the researchers said.
The technique, known as Freeform Reversible Embedding of Suspended Hydrogels (FRESH), has allowed the researchers to overcome many challenges associated with existing 3D bioprinting methods, and to achieve unprecedented resolution and fidelity using soft and living materials.
Each of the organs in the human body, such as the heart, is built from specialised cells that are held together by a biological scaffold called the extracellular matrix (ECM).
This network of ECM proteins provides the structure and biochemical signals that cells need to carry out their normal function.
However, until now it has not been possible to rebuild this complex ECM architecture using traditional biofabrication methods.
"What we've shown is that we can print pieces of the heart out of cells and collagen into parts that truly function, like a heart valve or a small beating ventricle," said Adam Feinberg, a professor at Carnegie Mellon University in the US.
"By using MRI data of a human heart, we were able to accurately reproduce patient-specific anatomical structure and 3D bioprint collagen and human heart cells," Feinberg said.
The need for replacement organs is immense, and new approaches are needed to engineer artificial organs that are capable of repairing, supplementing, or replacing long-term organ function.
Feinberg is working to solve these challenges with a new generation of bioengineered organs that more closely replicate natural organ structures.
"Collagen is an extremely desirable biomaterial to 3D print with because it makes up literally every single tissue in your body," said Andrew Hudson, a PhD student in Feinberg's lab.
"What makes it so hard to 3D print, however, is that it starts out as a fluid -- so if you try to print this in air it just forms a puddle on your build platform. So we've developed a technique that prevents it from deforming," said Hudson.
The FRESH 3D bioprinting method allows collagen to be deposited layer-by-layer within a support bath of gel, giving the collagen a chance to solidify in place before it is removed from the support bath.
With FRESH, the support gel can be easily melted away by heating the gel from room temperature to body temperature after the print is complete.
The researchers can remove the support gel without damaging the printed structure made of collagen or cells.
This method is truly exciting for the field of 3D bioprinting because it allows collagen scaffolds to be printed at the large scale of human organs, researchers said.
It is not limited to collagen, as a wide range of other soft gels including fibrin, alginate, and hyaluronic acid can be 3D bioprinted using the FRESH technique, providing a robust and adaptable tissue engineering platform, they said.
The researchers also developed open-source designs so that nearly anyone, from medical labs to high school science classes, can build and have access to low-cost, high-performance 3D bioprinters.
The noted that FRESH has applications in many aspects of regenerative medicine, from wound repair to organ bioengineering, but it is just one piece of a growing biofabrication field.