Novel Nanocomposites: Hierarchically ordered porous silica for the immobilization of enzyme as bio-catalyst

摘要

Hierarchically ordered porous silica with porosity in three different lengths (microporosity: pore diameter < 2nm; mesoporosity: 2nm < pore diameter < 50nm; macroporosity: pore diameter > 50nm) has been synthesized using polystyrene latex as colloidal template to generate macroporosity, pluoronic F127 (EO_(107)PO_(70)EO_(107)) as a non-ionic surfactant to generate meso and microporosity in an acidic pH in the presence of tetramethyl orthosilicate as silica source. The calcined material has been functionalized using aminopropyl triethyoxy silane (APTS) in toluene at 50°C in the presence of surface adsorbed water followed by glutaraldehyde treatment. Lipase has been immobilized by chemical conjugation on the surface of functionalized materials in PBS buffer (pH, 7.4). Hydrolysis of 4-nitrophenyl palmitate has been studied using Lipase immobilized hierarchically ordered porous silica and the results have been compared with lipase immobilized non functionalized materials. The rate of hydrolysis was observed to be increased exponentially with time for both materials, however, functionalized materials exhibited a two fold increase in hydrolysis efficiency without loss of catalytic efficiency after 2nd catalytic cycle.