Adsorption of proteins on γ-Fe2O3 and γ-Fe2O3/SiO2 magnetic materials

Abstract

γ-Fe₂O₃–SiO₂ composites are synthesized via the coprecipitation of a γ-Fe₂O₃ magnetic carrier (with specific surface S = 17 m²/g and pore volume V = 0.51 cm³/g) and silicon dioxide from an aqueous glass (sodium silicate) solution. The effect coagulation agent NaCl has on the coprecipitation process and structural characteristics of the composite is discussed. Adding NaCl to the aqueous glass solution prevents the formation of SiO₂ macrogel making it possible to obtain highly porous composites with high adsorption capacity for proteins cytochrome C and hemoglobin. It is established that a composite that is 50% SiO₂ and produced with the addition of 5% NaCl (S = 150 m²/g and V = 0.87 cm³/g) has a sixfold and twofold higher capacity (280 and 175 mg/g) for cytochrome C and hemoglobin, respectively, than the initial ferric oxide (45 and 82 mg/g). The capacity for cytochrome C and hemoglobin of a composite synthesized without NaCl (S = 50 m²/g and V = 0.45 cm³/g) is 19 and 20 mg/g, respectively, which is twofold and fourfold lower than those of the initial γ-Fe₂O₃. The dependence of protein adsorption on pH and the ionic strength of a solution is studied, and the conditions for the maximum adsorption and complete desorption of proteins are established. It is concluded that composites synthesized with additions of NaCl can be used as magnetocontrollable sorbents for the purification, concentration, and immobilization of proteins, and for the preparation of biocatalysts based on immobilized enzymes.