Silicification and biosilicification : role of macromolecules

Precipitated silica is synthesized commercially by neutralizing sodium silicate solution under harsh conditions of pH and temperature. In contrast, the formation of ornate silica structures in biological systems (biosilicification) occurs at (or close to) pH 7, under ambient conditions and is thought to be mediated by proteins. Determination of the primary sequences of these proteins has led to the identification of various amino acids that have been proposed to be important in biosilicification. The corresponding synthetic polyamino acids are now being successfully used in bioinspired materials chemistry for developing new materials and processes. Here we report the formation of the ordered silica structures in vitro facilitated by various synthetic polypeptides and polymers under ambient conditions and neutral pH. Scanning Electron Microscopy (SEM) was used for studying the silica morphology and Energy Dispersive Spectroscopy (EDS) to verify the formation of silica. These macromolecules are cationically charged at neutral pH and are believed to act as catalysts / templates / scaffolds for the formation of silica in vitro in analogous fashion to certain biomacromolecules that are able to facilitate silicification / biosilicification