Simple and efficient synthesis of copper(II)-modified uniform magnetic Fe₃O₄@SiO₂ core/shell microspheres for immobilization of cellulase

In this paper, we reported a simple and efficient protocol for preparation of Cu²⁺-modified magnetic Fe₃O₄@SiO₂ core/shell microspheres for immobilization of cellulase. The uniform magnetic Fe₃O₄@SiO₂ core/shell microspheres with a thin shell of 20 nm were synthesized through a solvothermal method followed by a sol–gel process. An amino-terminated silane coupling agent of (3-aminopropyl)triethoxysilane (APTS) was then grafted on them for capturing Cu²⁺ ions. The reaction process is very simple, efficient, and economical. Noticeably, the content of Cu²⁺ ions on the magnetic core/shell microspheres can reach 4.6 Wt%, endowing them possess as high immobilization capacity as 225.5 mg/g for cellulase. And the immobilized cellulase can be retained over 90 % on the magnetic microspheres after six cycles. Meanwhile, the magnetic microspheres decorated with Cu²⁺ ions show a superparamagnetic character with a high magnetic saturation of 58.5 emu/g at room temperature, suggesting conveniently and rapidly recycle the enzyme from solution. This facile, recyclable, high immobilization capacity and activity strategy may find potential applications in enzyme catalytic reactions with low cost.