Investigations on the Silanization of Nanoporous Silicas with 3-APTES and Application for Enzyme Immobilization

Abstract

Abstract In this work, amino-functionalized silicas (AF-NPS) have been successfully synthesized by grafting an organosilane precursor, 3-aminopropyl triethoxysilane (3-APTES), onto the silica surface. The aim of this work is to thoroughly study the effect of the factors such as pH, organosilane precursor concentration, temperature, and reaction time on aqueous silanization of silicas. The study also demonstrates detailed description of the procedure for the preparation of nanoporous silica (NPS), functionalization, and subsequent enzyme immobilization. Sulfuric acid and sodium silicate were used as precursors to synthesize NPS via sol-gel method. The synthesized NPS, which has specific surface area of 133 m2/g, pore size of 36.9 nm, and pore volume of 1.23 cm3/g, is sequentially used as a host material. The performance of the final product was examined by the immobilization of enzyme GL-7-ACA acylase on the activated silicas (AF-NPS-G) obtained by crosslinking of AF-NPS with glutaraldehyde. Nanoporous silicas (before and after modification by 3-APTES and crosslinking by glutaraldehyde) are characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Nitrogen adsorption/desorption methods. The optimal conditions for silanization were found to be pH of 9, 3-APTES concentration of 10 % (dissolved in 25 ml of distilled water for 1 g of silica), temperature of 80 0C, and the reaction time of 2 h.