One of the greatest challenges to clinical use lies in finding a plentiful, reliable source of chondrocytes, Dr. Spector said. He estimates that it will require 250 million cells to properly build an ear. “We’re working on a way of expanding the small number of cartilage cells derived from patient biopsies by mixing them with stem cells or other growth factors to turbo-charge their rates of reproduction.”
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July 2013
The Bionic Ear
Another team of researchers, led by Michael McAlpine, PhD, assistant professor of mechanical and aerospace engineering at Princeton University, has fused biology with electronics to create a structure that not only looks like a human ear but also contains a tiny, coiled antenna that can pick up radiofrequency signals. Like Dr. Spector and his colleagues, Dr. McAlpine and colleagues used calf chondrocytes to make the ear itself. For the antenna, they added a polymer infused with silver nanoparticles. “We used a computer software program that defines the structure in three dimensions and also defines where each material should be placed in a layer-by-layer process,” Dr. McAlpine said. “We then fed nanoelectronics, biological and structural components into the printer.” The result: an ear that can receive signals beyond normal human range.
Their goal was to demonstrate the feasibility of merging electronic and biological systems, said David H. Gracias, PhD, associate professor of chemical and biomolecular engineering at Johns Hopkins University in Baltimore, who collaborated with Dr. McAlpine on this research. “Tissues typically are soft and full of water, and there’s a fundamental mismatch between them and electronics, which are made of metal and are fabricated in a dry vacuum and do not like water. Moreover, it’s a challenge to bridge the interface, because metals don’t adhere well to polymers and biological substrates. This research was a proof-of-concept demonstration of the idea that by printing and embedding the antenna within the tissue structure, it was possible to bridge this divide.”
Dr. Gracias can’t help expressing a note of wonderment at these developments. “It’s quite amazing that you can actually print the cells, that they live, they appear to have the morphology of the ear and the antenna is printed and can receive a signal. The idea that you can keep something alive and fuse it with an electronic device and actually get it to work—that’s really something.”