Biominerals and Biomineralization on Nanoscale: From Perspective of Mesocrystals

The rise and development of nanogeology lead to exploration of the solid earth materials at the nanoscale, exerting extensive and profound impact on various fields of earth science. As an important branch of nanogeology, nanomineralogy also explores the structure and properties of the minerals including biominerals at the nanoscale, eliminating the limitations of traditional mineralogy which only regards the mineral as ideal crystal lattice, of which mesocrystal is one breakthrough. Mesocrystals represent a class of crystalline nanostructured materials drawing increasing attention from physicists and chemists especially material chemists in recent years. Mesocrystals are the products of non-classical crystallization process with nanoparticles as the basic subunits, sharing the properties of nanoparticles with order on the macroscopic length scale. It has been found that a number of biominerals including vertebrate bones and teeth, nacre, egg shells, sea urchin spines, foraminifera, and corals have the mesocrystals structure. Therefore, re-understanding the biomineralization at the nanoscale and the perspective of mesocrystals will undoubtedly help to reveal the formation mechanisms of hierarchical nanostructures in biominerals and expand the scientific connotation of nanomineralogy. Firstly, the basic concepts of biomineralization and biominerals are introduced. Then, the concept and structural feature of mesocrystals are expounded. Finally, the mesocrystal structure in biominerals and the mechanisms of mesocrystal formation are clarified in detail, referring to several physical and chemical processes such as alignment by the organic matrix, alignment by physical forces, connection by mineral bridges or organic bridges, alignment by spatial constraints, alignment by oriented attachment and alignment by face selective molecules. It is expected that this study may promote the further development of nanomineralogy.