Several marine organisms, including sponges and diatoms, can produce solid silica structures with well defined nanoscale morphologies, at ambient and neutral pH by peptide mediated condensation of naturally occurring silicic acid.1,2 To date, a number of groups have studied biosilica formation in the laboratory and have successfully developed biological mimics for the condensation of disordered silica structures at ambient conditions.3-6 More recently, polyamines and small bifunctional molecules, including cysteamine and ethanolamine, have been shown to be effective biomimetic catalysts for silica formation.7-10 An application of silica condensation at ambient conditions is the silica immobilization of labile biomolecules (including enzymes, proteins and drugs) which in contrast to most conventional sol-gel routes, would avoid their possible degradation and/or loss of their bioactivity under harsh immobilization conditions.11-14

In this work, two small by-functional catalysts (cysteamine and methionine), were employed as biomimetic catalysts for the simultaneous mesoporous silica formation and acid phosphatase immobilization from tetraethyl orthosilicate (TEOS). Near neutral pH and near physiological temperature conditions were used. The enzyme-loaded silica samples were characterized and quantified using a variety of techniques. Immobilized acid phosphatase activity was determined and compared to free enzyme activity. Results indicated that acid phosphatase entrapped in precipitated silica retained its enzymatic activity. Effects of temperature and catalysts' concentration on silica formation yields and on enzyme activity and immobilization yields were investigated and will be discussed.

References

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