Hydrophobic mesoporous materials for immobilization of enzymes

Abstract

This study examined the adsorption of lysozyme using three different types of periodic mesoporous organosilicas (PMOs) produced from either bis[3-(trimethoxysilyl)propyl] amine (BTMS-amine), 1,4-bis(triethoxysilyl)benzene (BTES-benzene), or 4-bis(triethoxysilyl) biphenyl (BTES-biphenyl) as precursors. For comparison, the adsorption of lysozyme on mesoporous silica SBA-15 as an absorbent was also investigated. The mesostructure of pristine PMOs and SBA-15 were characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm curves and 29Si and 13C solid state CP MAS NMR spectroscopy. The zeta potential was measured to interpret the dispersive and adsorptive ability of the mesoporous materials. BTES-biphenyl with a more hydrophobic character showed a higher adsorption capacity at the pH near the pI of the organosilica precursor than the other two PMO’s. The maximum amount of enzyme was obtained at pH close to the pI. BTES-benzene and BTES-biphenyl showed high affinity to lysozyme and adsorbed most of the lysozymes. In addition, the adsorption rates of the hydrophobic PMOs were quite fast at pH 10.2; faster than that of SBA-15. Overall, hydrophobic PMO materials are suitable for immobilizing lysozyme at pH 10.2.