Biogenic silica patterning: simple chemistry or subtle biology?

The importance of solid-state biochemistry was revealed more than twenty years ago by the pioneering work of Lowenstam et al. , and it can now be considered as a field on its own. Among biogenic minerals, silica appears rather singular. Whereas widespread carbonate and phosphate salts are crystalline iono-covalent solids whose precipitation is dictated by solubility equilibria, silica is an amorphous metal oxide formed by more complex inorganic polymerization processes. Biogenic silica has mainly been studied with regard to the diversity of the species that achieve this biomineralization process, and at the level of diversity in the morphology of silica structures. It is only recently that chemists turned their attention to the formation process. One of the triggers was the possibility of designing mesoporous silica materials with a highly ordered network of pores, similar to the siliceous structure found in unicellular diatom algae. Since then, chemists and biologists have learned how to take advantage of each other's knowledge, not only to get new insight into the biochemical processes involved in the natural systems, but also to design materials inspired by nature. As the frontier between these two fields is vanishing, the question arises whether the art of silica chemistry alone is, or will be, enough to understand and mimic the biosilicification reactions that occur in living organisms.