Dental

Rare mineral from rocks found in mollusk teeth

Researchers discovered a rare mineral hidden inside the teeth of a chiton, a large mollusk found along rocky coastlines. Before this strange surprise, the iron mineral, called santabarbaraite, only had been documented in rocks.

-Northwestern University

Researchers at Northwestern University have identified a hitherto unknown mineral in the teeth of the giant mollusc known as a chiton, which lives near rocky coasts. Santabarbaraite, an iron mineral, has only ever been found in rocks until now. Now we know how the whole Chiton tooth, not just the ultrahard cusp, is adapted to survive feeding by biting on rocks. Researchers created a bio-inspired ink for 3D printing ultrahard, rigid, and long-lasting materials based on minerals found in chiton teeth.

In the past, this mineral has only been found in extremely small quantities in geological specimens, according to Derk Joester, the study’s principal author from Northwestern University. “It’s dense, yet powerful due to its high water content. This may toughen teeth without adding a lot of weight, according to our calculations.” According to the researchers, their findings will be published in the Proceedings of the National Academy of Sciences during the week of May 31. Northwestern University’s McCormick School of Engineering’s Joester is a materials science and engineering associate professor. Former Joester postdoctoral researcher Linus Stegbauer is the primary author of the article. Stegbauer was a primary investigator at Northwestern University throughout the study and is currently at the University of Stuttgart’s Institute of Interfacial Process Engineering and Plasma Technology in Germany. Chiton teeth are made of one of nature’s toughest materials, and they’re connected to a tongue-like radula that scrapes over rocks to gather algae and other food. Having spent years researching chiton teeth, Joester and his colleagues have lately shifted their attention to Cryptochiton stelleri, an enormous reddish-brown chiton known as the “wandering meatloaf.”

Ercan Alper, a senior scientist at the Advanced Photon Source at Argonne National Laboratory, and Paul Smeets at the Northwestern University Atomic and Nanoscale Characterization and Experiment (NUANCE) Center worked together with Joester’s team to examine a tooth from Cryptochiton stelleri using synchrotron Mössbauer spectroscopy at the facility and transmission electron microscopy at NUANCE. In the top stylus of the chiton, a long, hollow structure that links the tooth’s head to the flexible radula membrane, they discovered santabarbarite scattered. Joester compared the stylus to the root of a human tooth, connecting the cusp to the jaw. Biomacromolecules form a fibrous matrix around very tiny nanoparticles, giving the material its toughness.

Joester’s team set a goal of recreating the substance in a 3D printing ink. Iron and phosphate ions were combined with a biopolymer produced from chitin by Stegbauer to create a reactive ink. Graduate student Shay Wallace from Northwestern’s Mark Hersam’s lab, and Stegbauer discovered that the ink printed effectively when combined just before printing using the printers. “To produce nanoparticles, the biopolymer must be heated to a higher temperature. After that, printing may be done with this combination with ease. Final material is firm and stiff as a result of further air drying “Joester was quoted as saying. Using the chiton’s stylus, Joester thinks we may learn from and create new materials inspired by the chiton’s delicate radula.

“For a long time, we’ve been intrigued with the chiton,” he added. “Because mechanical constructions are only as strong as their weakest link, understanding how the chiton connects its very hard teeth to a supple understructure is fascinating. Because this is still a major problem in contemporary production, scientists are turning to organisms like the chiton, which have had hundreds of millions of years to perfect this process.” The National Science Foundation (award numbers DMR-1508399 and DMR-1905982), the National Institutes of Health (award number NIH-DE026952), the Air Force Research Laboratory (award number FA8650-15-2-5518) and Deutsche Forschungsgemeinschaft supported the study “Persistent polyamorphism in chiton tooth: From a new biomaterial to inks for additive manufacturing.”

Journal Reference : Linus Stegbauer, Paul J. M. Smeets, Robert Free, Shay G. Wallace, Mark C. Hersam, Esen E. Alp, Derk Joester. Persistent polyamorphism in the chiton tooth: From a new biomineral to inks for additive manufacturingProceedings of the National Academy of Sciences, 2021; 118 (23): e2020160118 DOI: 10.1073/pnas.2020160118

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