Preparation and characterization of surface modified γ-Fe2O3 (maghemite)–silica nanocomposites used for the purification of benzaldehyde lyase Original Research Article

γ-Fe2O3 (maghemite)–silica nanocomposite particles were synthesized using a sol–gel method. The condensation products of 3-glycidoxy propyltrimethoxy silane (GPTMS) and nitrilotriacetic acid (NTA) were introduced onto the surfaces of the γ-Fe2O3–silica nanocomposite particles and subsequently, these modified surfaces were complexed with cobalt (Co+2) metal ions. A possibility of using these surface modified γ-Fe2O3–silica particles for the purification of 6×histidine tagged recombinant benzaldehyde lyase (BAL, EC 4.1.2.38) based on magnetic separation was investigated. X-ray diffraction (XRD), thermal analysis, and vibrating sample magnetometry (VSM) methods were used to characterize the surface modified superparamagnetic γ-Fe2O3 (maghemite)–silica nanoparticles. XRD (Schererʹs equation) results indicate that the primary particle size of maghemite was around 11 nm. Magnetic characterization results confirmed that the γ-Fe2O3 (maghemite)–silica nanoparticles were superparamagnetic. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results, these superparamagnetic nanoparticles specifically capture 6×His-tagged BAL from crude extract of Escherichia coli (E. coli) BL21(DE3)pLysS/BALHIS. This study shows that the surface modified γ-Fe2O3 (maghemite)–silica nanoparticles are eligible for immobilized metal-ion affinity adsorption for histidine tagged recombinant proteins with its high capacity (3.16±0.4 mg/g) and selectivity.