Aug.2, 2013

Scientists have created a lifelike artificial human ear using a 3D printer and animal tissue from cows and sheep.

The ears were built by Thomas Cervantes, from Massachusetts General Hospital, and his colleagues.

The artificial ears had both "natural elastic bending" and the shape real ears have. "One, we were able to keep the shape of the ear, after 12 weeks of growth in the rat. And then secondly, we were also able to keep the natural flexibility of the cartilage," Cervantes told BBC.

The ear geometry was designed to have the size and features of an adult human outer ear. A 3D digital model of a human ear was acquired and adapted to an ear-shaped scaffold model using SolidWorks CAD software. The resulting model was 3D printed using stereolithography technology. The 3D printed ear was cast in polydimethylsiloxane (PDMS), a special silicone compound, to create a mould which was then split along the outer contour, resulting in a two-piece cavity mould.

Ear shape design and composite scaffold fabrication process. (a) Initial ear CAD image and (b) the corresponding prototype with plastic surgeon notes. (c) Revised ear prototype with accentuated features to better visualize ear landmarks upon implantation. (d) PDMS negative mould used to cast collagen slurry with embedded wire framework. (e) Titanium wire framework with outer coil sheath; close-up depicts outer coil sheath and an intersection point of skeleton inner wires. (f) Line drawing of inner skeleton path. Dashed lines are overlap regions required for facile construction. (g) Composite collagen ear scaffold with embedded wire framework. Photo credit: Royal Society Publishing

These moulds were filled with collagen from cows and held in shape by titanium wire. The porous collagen was then populated with ear cartilage cells from sheep and the cells grew within the porous collagen fibres.

A key feature of this scaffold was the presence of an embedded titanium wire framework, which had sufficient rigidity to maintain the shape of the ear despite the compressive forces of implantation and contractile forces exerted during neocartilage formation. The wire framework also had sufficient flexibility to permit natural elastic bending of the ear structure, writes the scientists in the study.

Once full-grown, the artificial ears were implanted under the skin of mouses or rats in the lab and all the implants were well tolerated over the 12 weeks in the live rats.

Gross appearance of the engineered ear with embedded wire framework implanted subcutaneously in a nude rat for 12 weeks (a) before and (b) after explant. (c) Gross image of explanted engineered ear without an embedded wire framework. (d) The explanted engineered ear with wire framework maintained its shape and could be elastically deformed. Photo credit: Royal Society Publishing


The scientists hope the artificial ears could be used in transplant operations to replace the damaged or missing body parts of patients.

They said, "The technology is now under development for clinical trials, and thus we have scaled-up and redesigned the prominent features of this scaffold to match the size of an adult human ear and to preserve the aesthetic appearance after implantation."

"We also employed more rigorous methods to analyse the fidelity of the ear geometry after implantation.

"These quantitative shape analysis results have identified opportunities to improve shape fidelity of engineered ear constructs."

"This research is a significant step forward in preparing the tissue-engineered ear for human clinical trials," Dr. Thomas Cervantes, who led the study, told the BBC. He anticipates the application could start in about 5 years.

Their work is featured in a July 31st online issue of the Journal of the Royal Society Interface.

Posted in 3D Printing Applications



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