Abstract
Fe3O4 nanoparticles were prepared by a co-precipitation method with the assistance of ultrasound irradiation, and then coated with silica generated by hydrolysis and condensation of tetraethoxysilane. The silica-coated Fe3O4 nanoparticles were further modified with 3-aminopropyltriethoxysilane, resulting in anchoring of primary amine groups on the surface of the particles. Horseradish peroxidase (HRP) was then immobilized on the magnetic core-shell particles by using glutaraldehyde as a crosslinking agent. Immobilization conditions were optimized to obtain the highest relative activity of the immobilized enzyme. It was found the durability of the immobilized enzyme to heating and pH variation were improved in comparison with free HRP. The apparent Michaelis constants of the immobilized HRP and free HRP with substrate were compared, showing that the enzyme activity of the immobilized HRP was close to that of free HRP. The HRP immobilized particles, as an enzyme catalyst, were used to activate H2O2 for degrading 2,4-dichlorophenol. The rapid degradation of 2,4-dichlorophenol indicated that the immobilized enzyme has potential applications for removing organic pollutants.
Highlights
Horseradish peroxidase (HRP), an enzyme isolated from the roots of horseradishes, is the most widely used catalyst in enzymatic reactions [1,2]
As the reaction between amino/glutaraldehyde moieties will occur in a wide range of pH values, primary amino group-modified Fe3O4@SiO2 support molecules may react with HRP besides the intramolecular and intermolecular crosslinking of HRP enzyme by the glutaraldehyde crosslinker during its immobilization
The results indicate that the immobilized enzyme has potential for the removal of organic pollutants from water
Summary
Horseradish peroxidase (HRP), an enzyme isolated from the roots of horseradishes, is the most widely used catalyst in enzymatic reactions [1,2]. The immobilization may block the active center of the enzyme and lead to diffusion problems. Iron oxide nanoparticles have been widely used in many fields such as separation of biochemical products [16], magnetically assisted drug delivery [17] and enzyme immobilization [18]. Iron oxide nanoparticles can be modified with functional groups or inorganic compounds to obtain a magnetic carrier promising for enzyme immobilization [19]. The NH2-modified magnetic silica particles were prepared and HRP were immobilized on the surface of the particles. The HRP-immobilized magnetic silica particles were applied to remove 2,4-dichlorophenol in the presence of H2O2
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