Synthesis and characterisation of silica gels as hosts for biocatalysts

Abstract

Silica gel is an ideal inorganic host material for the encapsulation of biomolecules such as proteins, enzymes and antibodies for applications in catalysis and biosensors. However, the sol gel synthesis of silica gels, with pore diameters below 500, typically takes place under acid or base conditions, which can lead to denaturation of the confined biomolecules.

In this study, silica gels were prepared under neutral pH conditions by using NaF as catalyst due to its compatibility to biomolecules. Various ratios of tetramethylorthosilicate (TMOS) and methyltrimethoxysilane (MTMS) were used to render the surface of the silica gel hydrophobic. Solgel processing parameters (alkoxide chemistry, catalyst type, water to alkoxide ratio, etc) were varied to investigate the structure, morphology of the gels. FTIR, 29Si solid-state NMR techniques were used to elucidate the structure of the silica network, which showed the silica condensation reaction was responsible for gel formation. Silica matrices are various due to the different parameters via SAXS study. The morphology of the gels by FE-SEM shows a dependence on solgel process parameters. BET adsorption reveals the nature of the mesoporous silica network can be modified by the type and amount of silica precursor, the amount of catalyst and the ratio of Si/H20.