Biomimetic Synthesis of Sea-Urchin-like Core–Shell Hierarchical Aragonite Calcium Carbonate Induced by Basic Amino Acids

Amino acid residues in biomineralized proteins are related to the formation of otoliths. Although basic amino acid residues are abundant in such proteins, their precise roles in otolith biomineralization remain poorly understood. In this study, we demonstrate that basic amino acids can effectively induce the formation of sea-urchin-like core–shell hierarchical suprastructured calcium carbonate aragonite, which exhibits a high resemblance to fish otoliths. Moreover, this regulatory effect is not confined to specific basic amino acids but can also be extended to other general basic amino molecules. During the aragonite evolution process, hierarchical suprastructures are formed through oriented self-assembly, accompanied by a phase transition from vaterite to aragonite driven by the similarity in the interplanar spacing between these two phases. These findings can advance our understanding of how mineralization-associated proteins utilize their basic amino acid residues to direct biomineral formation. Furthermore, these findings also offer insights into the potential mechanism underlying fish otolith formation.