3D printing can be used to produce parts of the body such as orthopedic joints and prosthetics, as well as portions of bone, skin, and blood vessels. However, the majority of these tissues are created in an apparatus outside of the patient’s body and are then surgically implanted. Such a procedure may involve making large surgical incisions, posing the risk of infection and increased recovery time. To prevent these complications, a team of scientists have developed a technology to print tissues directly in the body.

A collaboration among Ali Khademhosseini, Ph.D., director and CEO of the Terasaki Institute; David J. Hoelzle, Ph.D., from the Ohio State University Department of Mechanical and Aerospace Engineering; and Amir Sheikhi, Ph.D., from the Pennsylvania State University Department of Chemical Engineering has produced a specially formulated bio-ink designed for printing directly in the body.

There are two basic components needed to produce an engineered tissue: a fluid-like bio-ink that consists of a framework material mixed with living cells, and growth factors to help the cells grow and develop into regenerated tissue. When developing tissues for direct implantation into the body, there are other things to consider: The construction of tissue would have to be conducted at body temperature (37 °C); the tissue needs to be attached effectively to soft, live organ tissue; and any procedural steps should not be harmful to the patient. One such harmful step in current methods is the application of UV light necessary to solidify the constructed tissue.

“This bio-ink formulation is 3D printable at physiological temperature, and can be cross-linked safely using visible light inside the body,” said first author Ali Asghari Adib, Ph.D.  To build the tissue, they used robotic 3D printing, which uses robotic machinery affixed with a nozzle. Bio-ink may be dispensed through the nozzle, much like an icing tube squeezes out writing gel, but in a highly precise, programmable manner.

The team also worked on methods to attach pieces of the tissue formed with this bio-ink onto soft surfaces. In experiments attempting to attach the tissue onto pieces of raw chicken strips and agarose, the researchers used a unique interlock technique using the robotic 3D printer and their bio-ink. The nozzle tip was modified to be able to penetrate the soft surfaces and fill the punctured space with bio-ink as it withdrew; this created an anchor for the tissue construct. As the nozzle tip reached the surface, it dispensed an additional blob of bio-ink to “lock in” the anchor.

Additional authors on the article were Melika Shahhosseini; Andrej Simeunovic, Ph.D.; Shuai Wu, Carlos Castro, Ph.D.; and Ruike Zhao, Ph.D. Financial support came from the National Science Foundation.