The MedTech Europe blog

From the day I embarked on my journey in the world of medical technology as a Eucomed Communications Intern, I have been impressed by the wide spectrum of technological breakthroughs that surges forward with unprecedented speed. At the same time, I have come to realise that innovation plays a key role in the medtech industry as it helps to improve patients’ lives. And one technology that substantially contributes to driving innovation is three-dimensional printing – also termed ‘additional manufacturing’ – which has already been used for the production of medical devices, bones and, most lately, for a tracheal splint that saved a baby’s life. This printing technique takes on yet another dimension when it comes to producing human tissue and manufacturing human organs. However surreal this may seem, researchers at Princeton University in New Jersey, the United States, have made the impossible possible. The team has conceived a 3-D ‘bionic’ ear, interwoven with electronics and tissue – and capable of hearing radio frequencies by far surpassing the range of a natural human ear. If only Van Gogh and Beethoven were still alive, one would think.

“The design and implementation of bionic organs and devices that enhance human capabilities, known as cybernetics, has been an area of increasing scientific interest“, the researchers stated in an article published in the scholarly journal Nano Letters. But this process is far from being simple.Interfacing electronic materials with biological ones involves mechanical and thermal challenges, according to Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton and the project’s lead researcher. Indeed, “biological structures are soft and squishy, composed mostly of water and organic molecules, while conventional electronic devices are hard and dry, composed mainly of metals, semiconductors and inorganic dielectrics,” explains David Gracias, an associate professor of chemical and biomolecular engineering at Johns Hopkins University in Baltimore, the United States, and co-author of the publication.

While standard tissue engineering employed for bones or cartilage implicates the seeding of cells on a scaffold with the cells excreting their own scaffold as the tissue grows, the Princeton team resorted to computer-aided design (CAD) due to the complex geometry of the ear. After drawing a digital model of a right human ear, the scientists printed it using biological, electronic, and structural components as printer ‘inks’. The latter included a hydrogel matrix containing cartilage-forming calf cells, silicone infused with silver nanoparticles, and structural silicone. The ear was fabricated layer by layer within a few hours – not longer, otherwise the cells would have died – and subsequently placed in a cell culture medium. Over a period of ten weeks, the hydrogel was reabsorbed and the cells developed an extracellular matrix, rendering the ear opaque. Quite fascinating a process, if you ask me.

The finished organ is composed of a cartilage tissue incorporating an electronic receiver coil. The coiled antenna penetrates the ear and connects to a helical cochlea, i.e. the spiral shaped part of the organ that senses sound, with nanoparticle electrodes. In physical appearance, the ear might, for some, bear a slight resemblance to a gag corkscrew from Pylones. But in terms of functionality, it is far from being a joke: the ear can indeed hear signal frequencies ranging from 1 MHz to 5 GHz – far beyond the human range of 20 Hz to 20 KHz. In addition, after having created a second ear by reversing the CAD model, the scientists observed the pair’s ability to hear in stereo. Even if the printed organ only perceives electromagnetic instead of sound waves so far, McAlpine points out that the electrical signals generated by the ear could be connected to a patient’s auditory nerve and that additional material such as electronic pressure-sensitive sensors could be integrated, enabling the ear to register acoustic sounds.

At present, 3-D printing only accounts for a very small share of the medtech industry market, and the first bionic ear implantation on a patient will take a long time before being actually performed. But the manufactured organ already represents an essential first step. It shows that 3-D printing constitutes a technological breakthrough that truly revolutionises the medtech industry: where biology and electronics meet, a new human organ generation arises that could, one day, allow deaf patients to hear – even beyond human capabilities.

Communications Trainee

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