Biominerals such as nacre of shells, teeth, and bones are organic/inorganic hybrids with complex structures that possess high functionality. In biomineralization, the interactions between biomacromolecules and inorganic ions are essential for the precise control of mineralization. This review focuses on the development of organic/inorganic hybrid materials using polymers through an approach inspired by biomineralization. We have developed the formation of thin-film CaCO₃ by using insoluble polymer matrices in the presence of poly(acrylic acid). Here, the combination of experimentation and molecular simulation is also introduced. Molecular dynamics (MD) simulation of the CaCO₃ precursor suggests that the transition of amorphous calcium carbonate (ACC) to crystals is suppressed in the presence of Mg²⁺ ions. These studies provide useful ideas for the development of hybrid materials through biomimetic approaches.

Generally, mesocrystals are biological and bio-inspired mesoscale structures consisting of oriented nanometric crystalline units. In this article, the mesocrystals are broadly categorized into a new family of crystalline materials as intermediate states between single crystals and polycrystals. Here, the formation routes, the specific properties, and the potential applications of a variety of the mesocrystals and their related structures are described on the basis of their structures and functions.

Magnetotactic bacteria synthesize nano-sized magnetic particles in the cells. The bacterial magnetic particles have a core of magnetite (Fe₃O₄), and are surrounded by a lipid bilayer membrane containing a number of proteins. Since the genetic engineering methodology for magnetotactic bacteria was established, production of recombinant proteins has successfully been performed in which the native proteins in the lipid membrane can serve as anchors for the protein display. These advantages lead to creation of a variety of magnetic particles displaying functional proteins. In this review article, after describing the basic strategy for a protein display on bacterial magnetic particles, we introduce our recent efforts in order to express recombinant proteins, including membrane proteins and disulfide-bonded proteins, which the basic approach cannot match. Due to these efforts, tetracycline-inducible expression system, protease- and anchor protein-deletion mutants, as well as the “in vitro docking method” have been established. The novel systems have shown considerable promise for improving the display efficiency of the difficult-to-express proteins, and thus are expected to contribute to further development of functional magnetic particles.