PAMAM Dendrimer Modified Silica As Carriers For Enzyme Immobilization And Alanine Adsorption

Dendtrimer polyamidoamine (PAMAM) has a large number of terminal functional groups, highly branched and precise molecular structure. PAMAM modified silica has wide range of applications, such as drug carrier and gene transfer.PAMAM modified silica can provide a large amount of amino in surface, which increase the capacity and selectivity of the surface area of silica. PAMAM modified silica was widely used as carriers of immobilized cytochrome C, bovine serum albumin and other biologically active substances. In this work, microwave-assisted method was introduced to the synthesis of the PAMAM-modified silica, which was used as carriers of immobilized enzyme. The main tasks were as follows:1. PAMAM modified silica was prepared by microwave assisted method. Scanning electron microscope, energy spectrum analysis, fourier transform infrared spectroscopy, elemental analysis were used to characterize the structure and composition of the surface of PAMAM modified silica. 2. PAMAM modified silica was applied to trypsin immobilization. The optimum temperature and pH of the reaction of immobilized enzyme were 60℃and 9.0, respectively. The Km value for casein was 7.76 mg/mL3. PAMAM dendrimer modified silica was applied to cellulase immobilization. We used adsorption and cross-linking with glutaraldehyde to immobilize the enzyme, respectively. The optimum temperature and pH of the reaction of immobilized enzyme by adsorption method were 60℃and 4.8, respectively. The Km value was 0.33 mg/mL. The optimum temperature and pH of the reaction of immobilized enzyme by cross-linking method were 60℃and 5.8, respectively. The Km value was 0.41 mg/mL. These results suggest that immobilized enzyme by cross-linking had better tolerance of temperature and pH than adsorption.4. PAMAM modified silica was successfully synthesized by microwave assisted method and used in enzyme immobilization. Compared to the free enzyme, the immobilized enzymes had shown a better thermo-stability, storage stability and reusability. The results indicated that the PAMAM modified silica is a better carrier of enzyme immobilization.