Algae-based scaffold helps grow bioink for 3D-printed cartilage

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The team used strands of cartilage as ink, using a 3D printer with a specially designed nozzle to build up the material in layers to form the desired structure(Credit: Ozbolat Lab/Penn State)

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Degeneration of cartilage in joints can be seriously painful, and it can be extremely difficult to repair. A new research effort at the Pennsylvania State University (Penn State) could improve the situation, with scientists designing a new method for making artificial cartilage implants that leverages 3D-printing technology.

We've seen numerous efforts using pioneering technologies to help patch up damaged joints. Earlier this year we learned of a project using a man-made, self-healing bio-glass to encourage the regrowth of cartilage, and we've seen it grown in the lab before, taken from patients' noses and used to try and repair damage in their knees.

Previous attempts at creating artificial cartilage have tended to rely on growing it in a hydrogel scaffold, but according to the researchers, that technique doesn't allow for normal growth. The resulting implants have been found to either lack strength, or contain compounds that can inhibit normal cell growth.

The Penn State researchers' method is a little different, and the team believes that it could be used to create large-scale tissues, without the need for any kind of scaffold. It's a two-step process, with the team first creating tiny tubes of an algae extract called alginate, each of which measures just 3 to 5 one-hundredths of an inch in diameter.

These tubes are then injected with cartilage cells, which are allowed to grow for around a week. The cartilage cells begin to stick together, but don't stick to the alginate. After seven days, the cells are removed from the alginate tubes, leaving thin strands of cartilage.

Those strands of cartilage are then used as ink, with the team using a 3D printer with a specially designed nozzle to build up the material in layers to form the desired structure. That structure can be anything the researchers require, and it takes just half an hour until it's strong enough to move to a petri dish, where it's soaked in nutrients, helping the strands fuse together into a single piece of cartilage.

The cartilage that the researchers produced is very similar to natural cow cartilage, though not quite as strong. It is, however, still stronger than artificial cartilage made using hydrogel, and the team believes that it would be stronger if used with actual patients, as the pressure from the joints would improve its mechanical properties.

Speaking of potential clinical use, the team is keen to point out that if the process were to be tried out with human cartilage, individual trial participants would have to have their own cells harvested in the first place, ensuring that the resulting 3D-printed artificial cartilage wouldn't be rejected by the body. On the other hand, the process would allow for a high level of flexibility when making implants.

"Because there is no scaffolding, the process of printing the cartilage is scalable, so the patches can be made bigger as well." said Penn State associate professor Ibrahim T. Ozbolat. "We can mimic real articular cartilage by printing strands vertically and then horizontally to mimic the natural structure."

Full details of the study are published online in the journal Scientific Reports. For more on the research project, you can take a look at the video below.

Source: Penn State

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