As 3D bioprinting advances, it also diversifies, with researchers from all around the world developing new ways of 3D printing living cells. Each new bioprinting technique is developed to address certain challenges in the technology, and one frequent challenge is formulating an ink that can pass through a 3D printer’s nozzle, stick together well enough to form and hold a solid structure, and keep the cells intact and alive at the same time. This is a particular challenge in inkjet printing, but a group of researchers from Japan’s Osaka University have come up with a new method of inkjet bioprinting that does all of those things.
The researchers used an enzyme-driven approach to getting the inks to stick together and solidify, allowing for a variety of cells to be 3D printed. The research was published in a paper entitled “Drop-On-Drop Multimaterial 3D Bioprinting Realized by Peroxidase-Mediated Cross-Linking,” which you can access here.
“Printing any kind of tissue structure is a complex process,” said lead author Shinji Sakai. “The bio-ink must have low enough viscosity to flow through the inkjet printer, but also needs to rapidly form a highly viscose gel-like structure when printed. Our new approach meets these requirements while avoiding sodium alginate. In fact, the polymer we used offers excellent potential for tailoring the scaffold material for specific purposes.”
Schematic drawing of multi-ink inkjet modeling and photograph of three-dimensional structure modeled
Currently, sodium alginate is the most commonly used gelling agent for inkjet bioprinting, but it’s not compatible with all types of cells. The Osaka University researchers used a method based on hydrogelation mediated by horseradish peroxidase, an enzyme that can create cross-links between phenyl groups of an added polymer in the presence of the oxidant hydrogen peroxide.
Hydrogen peroxide can also damage cells, but the researchers very carefully tuned the delivery of cells and hydrogen peroxide to limit the contact between the two and to make sure the cells remained alive. In biological test gels prepared in this way, more than 90% of the cells were viable. Several complex test structures could also be grown from different types of cells.
“Advances in induced pluripotent stem cell technologies have made it possible for us to induce stem cells to differentiate in many different ways,” co-author Makoto Nakamura said. “Now we need new scaffolds so we can print and support these cells to move closer to achieving full 3D printing of functional tissues. Our new approach is highly versatile and should help all groups working to this goal.”
The 3D printing of complex, functional tissues is the goal of everyone working in the bioprinting sphere, and the work of the researchers at Osaka University brings everyone a step closer, making the dream of functional, transplantable 3D printed human organs a little bit closer to reality. Authors of the paper include S. Sakai, K. Ueda, E. Gantumur, M. Taya and M. Nakamura. The research was funded by the Japan Society for the Promotion of Science. If you’d like to learn more about this particular bioprinting research, you can do so here.
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[Images: Osaka University]
