Researchers at University of Illinois Chicago are advancing 3D bio-printing by utilizing a gel to eliminate scaffold structures that model the shape of the organ or tissue being printed. The previous standard for 3D bio-printing involved creating a scaffold, typically from a biological polymer, and seeding it with stem cells that eventually differentiate and populate the structure to create the desired tissue. The challenge this technique poses is that the scaffold structure needs to be perfectly matched to the stem cells so that the scaffold degrades as the stem cells grow and differentiate into the desired structure. This new technique of 3D bio-printing by depositing the cells directly into a gel solves the problem of mismatched timing and should expedite and facilitate the printing of larger and more complex organs.
Researchers are working to improve 3D printing by overcoming hurdles that decrease printing efficiency, particularly with larger structures. A joint effort of several universities yielded a technique that improves the vascularization (formation of blood vessels) in printed tissues by utilizing food dye. The technique allows researchers to label and track where the blood vessels and other functional structures would be located in the organs, improving the survival of the printed structures thereby overcoming a major hurdle [survival] of 3D tissue printing. This is particularly important in organs like lungs, where different, overlapping vessels are required for the transport of blood and oxygen, with the dye helping to distinguish between them.
The American Chemical Society (ACS) has published a study that uses 3D printing to create organ frames that can be populated with cells to resemble fully fledged organs. The researchers used a structural sugar called cellulose that plants, archaea and some bacteria use for structural support in their cells. This structural component is also used in making paper, and it is therefore easy to store for prolonged periods of time and inexpensive to produce. Additionally, since cellulose structures are easy to manipulate, the researchers were able to create channels resembling blood vessels, which they then populated with human epithelial cells that typically line blood vessels.
Researchers at UC Berkeley have been working on improving and scaling up and the printing of biomaterials with stem cells. They have developed a unique approach to ‘3D’ bioprinting by incorporating flash freezing into their process. They have improved on current techniques by printing layers of flat tissues [2D] and freezing them until they can be combined into a 3D structure. This technique was developed to overcome one of the major hurdles in scaling up 3D printing: the survival of the printed cells during the lengthy process of printing complex structures. By using 2D layers and flash freezing them before bringing them together to form a 3D organ or tissue structure, the new technique assures the survival of the cells throughout bigger, and more complex organs.
Researchers at North Carolina State University, led by Assoc. Prof. Rohan Shirwaiker, have created a method to “herd” stem cells into desired structures using a biological 3D printer to create specialized structures more easily, overcoming one of the major hurdles in biological 3D printing. While researchers rely on biological scaffolds to help the stem cells differentiate into a particular organ or tissue, this new technique gives the researchers more control in guiding the cells into the desired structure.