Fabrication of a silica coating on magnetic γ-Fe2O3 nanoparticles by an immobilized enzyme

Silicatein, a hydrolytic protein encountered in marine sponges, was immobilized on maghemite (gamma-Fe2O3) nanoparticles that were surface functionalized with a reactive mulfunctional polymer. This polymer carries an anchor group based on dopamine which is capable of binding to the gamma-Fe2O3 Surface and a reactive functional group which allows binding of various biomolecules onto inorganic nanoparticles. This functional nitrilotriacetic acid (NTA) group allows immobilization of His-tagged silicatein on the surface of the gamma-Fe2O3 nanoparticles. The surface-bound protein retains its native hydrolytic activity to catalyze formation of silica through copolymerization of alkoxysilanes Si(OR)(4). Functionalization of the magnetic nanoparticles and the architecture of the SiO2-coated gamma-Fe2O3 nanoparticles was confirmed by TEM studies as well as by FT-IR and optical microscopy.