Iron mineral formation using chiton-derived ferritins

The teeth of chitons, a group of marine mollusks, rank among the hardest biomaterials found on earth. These teeth are composed of structurally ordered iron oxide minerals. Ferritin is an iron-storage protein known to regulate iron metabolism across diverse organisms; however, its role in iron biomineralization in chiton teeth remains unclear. Herein, ferritins were isolated from chiton hemolymph. Transcriptome- and proteome-based analysis revealed that the main ferritins in chiton hemolymph are also found in chiton radulae, which is supported by their elevated transcriptional abundance in radular tissues. In vitro assays revealed that these ferritins can bind iron ions and promote the formation of iron-based minerals. Ex vivo experiments using unmineralized radular scaffolds further showed that chiton ferritins facilitate iron oxide biomineralization, although the resulting crystals differed structurally from the native magnetite found in mature teeth. Phylogenetic analysis confirmed the conservation of ferritins among chitons, indicative of their universal role in tooth formation in chitons. Our findings advance the molecular understanding of iron-based biomineralization in chitons and provide insights for the design of synthetic iron-based nanomaterials.