3-D Printed Ear
Curator: Larry H. Bernstein, MD, FCAP
Custom 3-D printed ear models help surgeons carve new ears
October 21, 2015
updated – 10/28/2015
A University of Washington (UW) otolaryngology resident and a bioengineering student have used 3-D printing to create a low-cost pediatric rib cartilage model that more closely resembles the feel of real cartilage, which is used in an operation called auricular reconstruction (ear replacement).
The innovation could make it possible for aspiring surgeons to become proficient in the sought-after but challenging procedure. And because the UW models are printed from a CT scan, they mimic an individual’s specific unique anatomy. That offers the opportunity for even an experienced surgeon to practice a particular tricky surgery ahead of time on a patient-specific rib model.
As part of the study, three experienced surgeons practiced carving, bending, and suturing the UW team’s silicone models, which were produced from a 3-D printed mold modeled from a CT scan of an 8-year-old patient. They compared their firmness, feel, and suturing quality to real rib cartilage, and to a more expensive material made out of dental impression material. They preferred the 3-D printed versions.
Co-author Sharon Newman, who graduated from the UW with a bioengineering degree in June, teamed up with lead author Angelique Berens, a UW School of Medicine otolaryngologist, while they both worked in the UW BioRobotics Lab under electrical engineering professor Blake Hannaford.
Newman figured out how to upload and process a CT scan through a series of free, open-source modeling and imaging programs, and ultimately use a 3-D printer to print a negative mold of a patient’s ribs.
Newman had previously tested different combinations of silicone, corn starch, mineral oil and glycerin to replicate human tissue that the lab’s surgical robot could manipulate. She poured them into the molds and let them cure to see which mixture most closely resembled rib cartilage.
The team’s next steps are to get the models into the hands of surgeons and surgeons-in-training, and hopefully to demonstrate that more lifelike practice models can elevate their skills and abilities.
“With one 3-D printed mold, you can make a billion of these models for next to nothing,” said Berens. “What this research shows is that we can move forward with one of these models and start using it.”
Long waiting list
Kathleen Sie, a UW Medicine professor of otolaryngology – head and neck surgery and director of the Childhood Communication Center at Seattle Children’s, said the lack of adequate training models makes it difficult for surgeons to become comfortable performing the delicate technical procedure.
There’s typically a six- to 12-month waiting list for children to have the procedure done at Seattle Children’s, she said.
“It’s a surgery that more people could do, but this is often the single biggest roadblock,” Sie said. “They’re hesitant to start because they’ve never carved an ear before.”
Their study results were presented at the American Academy of Otolaryngology — Head and Neck Surgery conference in Dallas.
Cartilage we can already bioprint with discrete success, as the many images of bioprinted ears circulating around the web clearly seem to demonstrate. But how can we make those ears actually function? For that, we need much more advanced biofabrication processes. What scientists need to do is to find a way to accurately and efficiently 3D print the scaffolds that enable the creation of “end-use”, implantable, complex cartilage implants.
When thinking about cartilaginous parts in our body, very few present more challenges in terms of shape and functionality as the timpanic membrane (aka the eardrum). That is exactly where Lorenzo Moroni and the team from the MERLN Institute for Technology-Inspired Renegarative Medicine at Maastricht University began, in a study titled “Multiscale fabrication of biomimetic scaffolds for tympanic membrane tissue engineering“.
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The timpanic membrane is a thin membrane that basically makes it possible for us to transform vibrations in the air into signals that our brain can elaborate as sounds. If it breaks, we go deaf, making the ability to reproduce it something that would have a significant impact on regenerative medicine. However, the complexity of this task is huge, not only because of the level of miniaturization required (the membrane has a diameter of only a few mm and is as thin as a sheet of paper), but also for the multiplicity of the tissues involved. The malleus is made up of bone tissue, while the membrane has epithelial and neural elements. Recreating it means producing both a physical interface with the malleus and a neural interface with the nervous system.
“What we have been focusing on so far is the 3D printing of the three-dimensional scaffolds, without the part that we wold call bioprinting with the actual cellular materials,” Lorenzo told me when I was finally able to catch up to him. He is always extremely busy, having published over one hundred papers on biotechnology applications, and, currently, he is working on organizing the Biofabrication 2015 conference that will take place in Utrecht next November 7th through the 9th.
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“We actually 3D print the scaffolds with EnvisionTEC’s 3D bioplotter, which is generally considered a bioprinter for cellular materials. Instead, we use polymer based mixtures that are biodegradable and biocompatible,” Lorenzo continued. “We work to engineer the scaffold’s structural properties, as well as those relative to the its surface, with the idea that the scaffold will have to interface with stem cells and, let’s say, ‘persuade them’ to undertake a specific type of activity.” In this case, what we want is for the cells to differentiate into cells of the otoplastic bone or into the cartilaginous cells of the timpanic membrane. This, for example, can be achieved through a differentiation of the sizes of the pores on the scaffold, which determine the concentration of cell nutrients.”
The timpanic membrane is a biological tissue that is made up of collagen, as far as its protein composition goes. Its mechanical properties have to enable the interface with the malleus in order to propagate sounds. Moroni’s team – in collaboration with a team from the University of Pisa – is researching a way to organize the collagen fibers in a way that allows the stem cells to display themselves in specific patterns that seem to facilitate the acoustic propagation.
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The scaffold that would allow this to take place would be implanted together with the membrane and would progressively dissolve and be absorbed by the newly formed cells. In this case, it is extruded in the form of a paste material with thermoplastic properties, meaning that it becomes more fluid with heat and solidifies as it cools down. They are able to do this through the bioplotter and say that they were probably among the first that modified the printer to enable it to extrude thermolastic materials.
These include PCL and PLA; however, one that is now starting to be used more frequently is called PoliActive or PA. Other researchers have begun to introduce new copolymers (which combine polyethylene with other materials) and other interesting materials – especially for soft tissues – such as polymethylcarbonate. The range of available materials has been growing significantly in recent times. For example, there is a family of polyurethanes that are both biocompatible and biodegradable.
This is not the only project that Lorenzo discussed, as he also mentioned current work on pancreatic and neurovascular (capillaries and neural networks together) tissues, which we will further discuss in future talks. Moroni generally agrees that just like – and perhaps even more than – 3D printing in industrial manufacturing, bioprinting is starting to represent an ever more significant segment of all biotechnology. TheBiofabrication 2015 conference in Utrecht is attracting some 250 participants, which is over 100% growth from last year’s event that took place in South Korea. The recent TERMIS also had a larger number of talks on bioprinting than ever before. The technology is here to stay and, soon, even more people will have the opportunity to hear about it.
Davide Sher was born in Milan, Italy and moved to New York at age 14, which is where he received his education, all the way to a BA. He moved back to Italy at 26 and began working as an editor for a trade magazine in the videogame industry. As the market shifted toward new business models Davide started working for YouTech, the first iPad native technology magazine in Italy, where he discovered the world of additive manufacturing and became extremely fascinated by its incredible potential. Davide has since started to work as a freelance journalist and collaborate with many of Italy’s main generalist publications such as Corriere della Sera, Panorama, Focus Italy and Wired Italy: many of his articles have revolved around the different applications of 3D printing.
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Carbon-based small molecules involved in biochemistry and drug design exhibit extraordinary structural diversity. But can we come up with a general set of building blocks from which a machine could put most of them together, in assembly-line fashion? Li et al. present progress toward this goal by showcasing the range of structures available via coupling reactions of fragments bearing a specific type of boronate group. They successfully made complex polycyclic structures by stringing together a linear precursor and then coaxing it to fold back on itself. They also developed a purification method that facilitates automation of the reaction and product isolation.
Science, this issue p. 1221
Vol. 347 no. 6227 pp. 1190-1193
http://dx.doi.org:/10.1126/science.347.6227.1190
The ability to make small organic molecules is at the heart of everything from drug development to the making of new dyes and agricultural chemicals. But ever since the dawn of synthetic organic chemistry in the 1820s, the process has required slow, painstaking effort. Now, however, researchers led by Martin Burke, a chemist at the University of Illinois, Urbana-Champaign, have developed a novel machine that may change all that. The machine automatically synthesizes new small organic molecules by welding together premade building blocks that can be put together in any configuration. Two hundred such building blocks already exist. And thousands of other similar molecules can also be used in the process. As a result, the machine has the ability to make billions of different small organic compounds that can then be tested as new drugs or for other uses. If widely adopted, the synthesis machine could revolutionize organic chemistry, turning it from a slow, painstaking process to a made-for-order business.
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Protecting group-free, selective cross-coupling of alkyltrifluoroborates with borylated aryl bromides via photoredox/nickel dual catalysis
Proc. Natl. Acad. Sci. USA 29 September 2015: 12026–12029.
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