Synthesis and characterization of porous silica particles for bioseparation application

Abstract

Two types of silica particles were synthesized by the sol-gel process. The first type of silica particles was synthesized by neutralization of a highly basic sodium silicate solution. The obtained particles were polydispersed with irregular shapes and a mesoporous structure. The second type of silica particles was prepared by hydrolysis and condensation of tetraethylortosilicate (TEOS). The obtained particles were spherical and monodispersed with a microporous structure. Multimodal size distribution was characteristic of the silica particles obtained from the sodium silicate solution with a particle size distribution between 0.2 and 6 μm. On the other hand, the silica particles obtained from TEOS had a unimodal size distribution with an average particle size of about 0.5 μm. The physical adsorption of Candida rugosa lipase onto the obtained silica particles was investigated at pH=7. The silica particles prepared from TEOS had the lowest adsorption efficiency (2%) while those prepared from the highly basic sodium silicate solution had the highest adsorption efficiency (50%). The isoelectric point of silica particles and Candida rugosa lipase was 2.5 and 2.4, respectively, which suggests that van der Waals’ forces probably play the major role in the process of binding lipase into mesoporous silica when physical adsorption was involved at pH 7.