Role(s) of synthetic and biological macromolecules in (bio)silicification

Several biological organisms are able to produce patterned and hierarchical biomineral structures. Diatoms, sponges and grasses deposit ornate biogenic silica structures under ambient conditions. These biological systems are able to selectively uptake, store and process soluble silicon (in an as yet unknown form) and mould it with great sophistication into biosilicas. Some aspects of the molecular mechanism(s) controlling biosilicification have recently been elucidated. In order to understand the interactions between these biomolecules and the biosilicas generated in various organisms and also to make use of any understanding so gained, in vitro experiments have been designed that make use of biomimetic analogues for developing bioinspired synthetic schemes for silica synthesis. The results obtained from bioinspired silicification investigations are hypothesised to arise from specific mode of actions of the organic additives and will be presented. Specifically, additives in bioinspired silicification act either as catalysts, aggregation promoting agents or structure-directing agents or more typically, exhibit a combination of these behaviours. Each of these effects will be discussed and representative examples given.