The Role of Confinement in Biomineralization.

This review focuses on an important but under-explored biogenic strategy used to control biomineralization processes─confinement─where compartmentalization is fundamental to the organization and function of all organisms. Biominerals combine the functionality of inorganic and organic solid-state materials and are constructed under precise biological control. Often exhibiting desirable properties, such as high strength, toughness, and complex morphologies that surpass those of synthetic materials synthesized under harsher conditions, biomineral formation processes are widely studied. Here we demonstrate the vital role that confinement plays in defining the key structural characteristics of biominerals and in controlling their mechanisms of formation. These range from well-accepted functions, such as stabilizing amorphous phases, isolating the mineralization site, and controlling morphologies, to more speculative roles, including controlling crystal nucleation, orientation and polymorphism. Examples from a range of organisms, mineral types, and length scales are provided, and further insight into potential biogenic mechanisms is gained through comparison with crystallization in complementary confined synthetic systems. Further opportunities for exploring confinement effects in biomineralization systems are discussed throughout, where these will ultimately act as an inspiration for the synthesis of sustainable materials, for medical innovations, as well as providing insights into evolution and environmental change.