Structural and Proteomic Analyses of Iron Oxide Biomineralization in Chiton Teeth

The denticle caps of chiton teeth exhibit the largest hardness and stiffness among any biological minerals in the world. They consist of a composite structure of highly oriented crystalline nanorods of magnetite surrounded by a veneer of organic. The ultrahard teeth of the chiton are the first reported example of biologically formed magnetite, and its formation mechanisms have been of great interest to researchers for decades. Recently, using modern nanomechanical characterization techniques, it was shown that chiton teeth exhibit the largest hardness and stiffness of any biological mineral. The predicted abrasion resistance of chiton teeth against a blunt contact was reported to be even higher than that of zirconia. Therefore, the elucidation of chiton teeth synthetic processes could help us learn how to develop novel abrasion-resistant materials and environmentally benign processes for the production of iron oxides and other nanostructured materials. In order to understand the chiton teeth formation, proteomic analyses of tooth proteins as well as detailed structural analyses of mature and developing teeth were conducted. Based on the results obtained from these analyses, we discuss the underlying mechanisms of iron oxide biomineralization in chiton teeth.