Associated Press
This handout photo provided by Cornell University, taken Feb. 13, 2013, shows Cornell University biomedical engineer Lawrence Bonassar holding the scaffolding for an ear his laboratory is creating using a 3-D printer and cartilage-producing cells. Printing out body parts? Cornell University researchers showed it's possible by creating a replacement ear using a 3-D printer and injections of living cells. The work reported Wednesday is a first step toward one day growing customized new ears for children born with malformed ones, or people who lose one to accident or disease. (AP Photo/Lindsay France, Cornell University)

Using injectable living cells and a 3-D printing machine, Cornell biomedical engineers and Weill Cornell Medical College physicians have created ears "practically identical" to a human ear.

The development could be used to help children born with ear deformities or people who lose external ears in accidents or to cancer, co-lead author Dr. Jason Spector, director of the Laboratory for Biogenerative Medicine and Surgery and associate professor of plastic surgery at Weill Cornell, said in a university press release.

To make the ears, engineers and physicians used a digitized 3-D image of an ear (from one of the co-lead author's twin daughters) and converted the image into a digitized "solid" ear, assembling a mold with a 3-D printer.

After injecting the mold with rat-tail-derived collagen, scientists added cartilage cells from the ears of cows, which eventually grew cartilage to replace the collagen.

"It takes half a day to design the mold, a day or so to print it, 30 minutes to inject the gel, and we can remove the ear 15 minutes later. We trim the ear and then let it culture for several days in nourishing cell culture media before it is implanted," said co-lead author Lawrence Bonassar, associate professor of biomedical engineering.

According to scientists, this development could be especially helpful to children born with microtia — a condition in which the external ear is not fully developed, occurring in some 4 per 10,000 births each year. Many of these children have an intact inner ear but experience hearing loss due to the missing external structure.

Spector said replacement ears are usually built with stiffer materials or constructed from harvested rib. The ears rarely look natural or perform well, unlike the ones constructed by the team.

Now used to print everything from guns to footwear, 3-D printing technology has also had benefits for medical innovation. Building ears follows several health breakthroughs involving 3-D printing, including scientists who printed a kidney prototype and the first-ever lower jaw replacement by doctors in the Netherlands.

"This is such a win-win for both medicine and basic science, demonstrating what we can achieve when we work together," said Bonassar.

Spector said if tests work out, it might be possible to try implanting a bioengineered human ear in as little as three years.

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