Enzyme encapsulation in silica particles prepared using enzyme-assisted sol-gel reactions in ionic liquids

Several studies have demonstrated the use of biomimetic approaches in the synthesis of a variety of inorganic materials. In this study, a low-temperature and natural pH procedure for the synthesis of silica was developed using hydrolytic enzymes. For the preparation of silica particles at room temperature and pH 7, a screening test for enzyme-catalyzing direct hydrolysis and polycondensation of tetraethoxysilane by using 5 types of hydrolases; pepsin, trypsin, esterase, and two lipases were chosen as biocatalysts; moreover, these enzymes can promote the precipitation of silica within 3 days. The 29Si nuclear magnetic resonance (NMR) measurements indicated that the enzyme activity in ionic liquids was higher than that in aqueous buffer solutions, and that the obtained silica particles were highly polycondensed. Under ionic liquid conditions, it was observed that enzymes were effectively encapsulated in the sol–gel silica material. In addition, for siloxane bond formation the catalytic activity of silica–enzyme composites was higher than that of free solution enzymes.