Imagine no longer needing arthritis medicine for aching joints.
Thanks to new developments in 3D bio-printing, it may be possible to patch up weak, worn-out joints.
Using Hydrogel to Repair Cartilage
Researches have previously attempted to create cartilage using hydrogels—materials composed of 90 percent water and polymer chains—as scaffolding for tissue growth. Surgeons would locate the damaged cartilage, drill small holes into the area and fill it with hydrogel. Blood vessels would then fill the gel, which creates an environment that encourages new tissue growth. However, there are insurmountable challenges to this approach.
“Hydrogels don’t allow cells to grow as normal,” said Dr. Ibrahim Ozbolat, a member of the Penn State Huck Institutes of the Life Sciences. “The hydrogel confines the cells and doesn’t allow them to communicate as they do in native tissues.”
In other words, hydrogels pose a problem for tissue mechanical integrity, since they degrade and also produce toxic compounds against cell growth.
3D Bioprinting Cartilage
From lab tests, engineers used strands of cow cartilage as ink in 3D bio-printing. Made up of one cell type and free of blood vessels, cartilage can be practically up-scaled in bio-printing. Experiments with cow cartilage show that it is possible to 3D print cartilage patches for worn-out joints. These may improve mechanical stability compared to hydrogels.
For a more natural approach, Ozbolat and his team eliminated the need for a scaffold. They created a tube made of alginate from 0.03 to 0.05 inches in diameter and injected cartilage cells into the tube. The cartilage grew for a week, bound to one another and remained separate from the alginate.
After the one-week period, they removed the tube and were left with a strand of cartilage. These strands form the “ink” in a 3D printer. With a specially designed nozzle, the printer can lay down rows of cartilage strands in any desired shape.
After about a half hour, the cartilage patch self-adheres enough to be moved into a petri dish. The nutrient media in which the cartilage is placed promotes further integration of the tissue until it fuses completely.
“We can manufacture the strands in any length we want,” said Ozbolat. “Because there is no scaffolding, the process of printing the cartilage is scalable, so the patches can be made bigger as well. We can mimic real articular cartilage by printing strands vertically and then horizontally to mimic the natural architecture.”
3D Printing a Cure for Arthritis
Although these results bring us one step closer to a more sustainable solution for cartilage replacement, the artificial cartilage’s mechanical properties present a new challenge.
Natural cartilage forms with pressure from the joints, so Ozbolat believes adding mechanical pressure to artificial cartilage will take it to the next level in performance.
Although the artificial cow cartilage is similar to natural cow cartilage, human applications would require a sample from the individual, cultivated either from existing cartilage or stem cells to prevent tissue rejection.
To read more about advancements in 3D bio-printing, check out this story on the first vascular structures to be 3D printed in zero gravity.