Self-Assembling Peptides as a Bioink

Researchers at Rice University have developed a bioprinting method that uses self-assembling peptides as a bioink. The technique involves using “multidomain peptides” that are hydrophobic at one end and hydrophilic at the other. When the peptides encounter water, they flip over each other to create hydrophobic sandwich structures that stack together to form fibers, creating the base structure of the printed hydrogel. This self-assembly helps the printed material to rapidly form a structure, and it will also reform after deformation. What makes the peptides highly suited for use in implanted constructs is their track record of safe use in the body and therapeutic record, including nerve regeneration and wound healing applications.

Bioprinting is evolving as a means to create new tissues and organs using a 3D printer. With shortages of donor organs and tissues, such technologies could be a lifeline for patients who are stuck on long waiting lists to get a transplant. While we still have a way to go before someone can get a new organ whipped up to order, the evolution of the technology is interesting, with various biomaterials being tested in their ability to be printed, form complex shapes, support cells, and integrate with the body’s own tissues.

This latest development involves using self-assembling peptides as a bioink. “There are 20 naturally occurring amino acids that make up proteins in the human body,” said Adam Farsheed, a researcher involved in the study. “Amino acids can be linked together into larger chains, like Lego blocks. When amino acid chains are longer than 50 amino acids, they are called proteins, but when these chains are shorter than 50 amino acids they are called peptides. In this work, we used peptides as our base material in our 3D-printing inks.”

The peptides contain a hydrophobic and hydrophilic end, which means that they flip over each other, and form stacks that make up the long fibers within the printed hydrogel construct. However, aside from this useful gelation behavior, which makes them highly suited for bioprinting, the peptides also have therapeutic potential in their own right, including in cancer treatment, nerve regeneration, and wound healing, making them highly suited as a base material for implantable structures.

“We know that the multidomain peptides can safely be implanted in the body,” said Farsheed said. “But what I was looking to do in this project was to go in a different direction and show that these peptides are a great 3D-printing ink. It might be counterintuitive since our material is so soft, but I recognized that our multidomain peptides are an ideal ink candidate because of the way they self-assemble. Our material can reassemble after being deformed, similar to how toothpaste forms a nice fiber when pushed out of a tube.”

See a video of the printing process: