Engineers at Cornell University used 3D printing techniques to build a new external human ear. The outer ear, also called the auricle, or pinna, was constructed using an extrudable gel made of living cells. Over a 3 month period the ears grew cartilage to replace the collagen base that was used to mold them. Cartilage is an ideal tissue for 3D printed biostructures since it can persist in the absence of vascularization. Formerly, artificial replacement ears had been built from a more styrofoam-like material or sometimes from pieces harvested from a patients rib — a difficult and typically painful procedure, particularly for children.
The pinna is much more than just an ornamental curiosity. Without it, sound localization in the median plane is severely compromised. This is because the pinna, together with the ear canal form a selective filter which imparts direction-selective resonances onto the frequency response of the ear. Specific resonances induced by the pinna may also aid in determining the distance of the sound source.
3D printing has come to prominence only recently and has quickly emerged as a powerful new tool for all kinds of biomedical applications. Earlier this month, a group from Scotland, land of Dolly, the first cloned sheep, was able to 3D print structures using human stem cells. Furthermore, they were able to show that the cells continued to express particular biomarkers that were indicative of pluripotence — the ability to turn into nearly any type of tissue.
The Cornell researchers estimate that the best time to implant a child with the ear would be around age six. At that age the normal ear has already grown to about 80 percent of the adult size, yet the auditory system is still sufficiently plastic to readily adapt itself to its new front end. While the long-term viability of the new ears is obviously still under evaluation, these new printing methods have tremendous potential to transform the field of tissue engineering so that one day we may see entirely printed organs.
Cornell press release: Bioengineers print ears that look and act like the real thing