The U.S. Food and Drug Administration (FDA) has released draft guidance, “Technical Considerations for Additive Manufactured Devices,” leapfrogging the administration’s initial thoughts on 3D manufacturing. The draft guidance outlines technical considerations associated with additive manufacturing processes, testing, and characterization for final finished devices fabricated using additive manufacturing.

The draft guidance is broadly organized into two topic areas, design and manufacturing considerations (section V) and device testing considerations (section VI). The design and manufacturing considerations section provides technical considerations that should be addressed as part of fulfilling quality system (QS) requirements for a device, as determined by regulatory classification. While this draft guidance includes manufacturing considerations, it is not intended to comprehensively address all considerations or regulatory requirements to establish a quality system for manufacturing the device.

3D bioprinting produces cartilage from bioink

Strands of cow cartilage substitute for ink in a 3D bioprinting process that may one day create cartilage patches for worn out joints.

A plug of 3D bioprinted cartilage on top of a plug of osteocondral material – bone and cartilage. The bone sits in a bath of nutrient media.
Credit: Ozbolat Lab, Penn State

“Our goal is to create tissue that can be used to replace large amounts of worn out tissue or design patches,” says Ibrahim T. Ozbolat, associate professor of engineering science and mechanics at Penn State, University Park, Pennsylvania.

Because cartilage cannot repair itself, it is a good tissue to target for scale-up bioprinting because it is made up of only one cell type and has no blood vessels within the tissue. Previous attempts at growing cartilage began with cells embedded in a hydrogel – a substance composed of polymer chains and about 90% water – that is used as a scaffold to grow the tissue.

“The hydrogel confines the cells and doesn’t allow them to communicate as they do in native tissues,” says Ozbolat, who is also a member of the Penn State Huck Institutes of the Life Sciences.

Ozbolat and his research team developed a method to produce larger scale tissues without using a scaffold. They create a 0.03" to 0.05" diameter tube made of alginate, an algae extract. They inject cartilage cells into the tube and allow them to grow for about a week and adhere to each other. Because cells do not stick to alginate, they can remove the tube, leaving a strand of cartilage.

A multiarmed bioprinter 3D prints cartilage using a special nozzle for printing bioink.
Credit: Ozbolat Lab, Penn State

The cartilage strand substitutes for ink in the 3D printing process. Using a prototype nozzle that can hold and feed the cartilage strand, the 3D printer lays down rows of cartilage strands in any pattern the researchers choose. After about half an hour, the cartilage patch self-adheres enough to move to a petri dish. The researchers put the patch in nutrient media to allow it to further integrate into a single piece of tissue. Eventually the strands fully attach and fuse together.

The artificial cartilage is very similar to native cow cartilage; however, the mechanical properties are inferior to those of natural cartilage but better than cartilage made using hydrogel scaffolding. Natural cartilage forms with pressure from the joints, and Ozbolat thinks that mechanical pressure on the artificial cartilage will improve the mechanical properties.

If this process is eventually applied to human cartilage, each individual treated would probably have to supply source material to avoid tissue rejection. The source could be existing cartilage or stem cells differentiated into cartilage cells.

Also working on this project were Yin Yu, recent Ph.D. from the University of Iowa now at Harvard University; Kazim K. Moncal, graduate student in engineering science and mechanics and member of the Huck Institute, Penn State; Weijie Peng, visiting scholar in engineering science and mechanics, Penn State; Iris Rivero, associate professor of industrial manufacturing and systems engineering; Jianqiang Li, former student, Iowa State University; and James A. Martin, associate professor of orthopedics and rehabilitation, the University of Iowa.

The National Science Foundation, Grow Iowa Value Funds, and the China Scholarship Fund supported this work.