Non-Peptide, Silicatein α Inspired Silica Condensation Catalyst

Introduction A major challenge faced by ceramic chemists today is the production of fully polymerized silica by low temperature (< 50°C) solution routes. Current methods involve high temperature, extreme pH, or both. Biological systems, however, have the ability to produce silica under much more benign conditions. These include near neutral pH and temperatures at or below room temperature. Our goal is to take what has been learned from biology and develop a bioinspired synthetic analog that can be used to produce ceramic materials which are unavailable by current techniques. The protein Silicatein α has been previously shown to catalyze the production of poly(silicate) from tetraethoxysilane (TEOS) monomer. It does this at neutral pH and ambient temperature. The source of Silicatein α for this study was the marine sponge Tethya aurantia. This sponge contains silica needles that constitute up to 75% of its dry weight. Occluded in these silica needles are protein filaments that catalyze their synthesis. About 70% of this protein mass is Silicatein α. Mimicking Silicatein α with synthetic proteins has been shown to be feasible. Proteins were synthesized by a ring opening polymerization method using cyclic amino acid analogs as monomers. Homoand blockproteins were made and tested for catalytic function in the condensation of TEOS. This work showed that the secondary structure of the protein was not critical to its catalytic function. It also provided evidence as to which amino acids, and thus which functional groups, are critical to the protein’s catalytic function. Here, we summarize our work on a purely synthetic, non-peptide copolymer to catalyze the polymerization of silica from a solution of TEOS.