Synthesis Characterization Of Surface-functionalized Paramagnetic Nanoparticles And Their Application To Immobilization Of α-acetolactate Decarboxylase

In the present study, a facile Fe3O4@Si O2–NH2 core-shell nanoparticles have been successfully synthesized, which were applied for α-ALDC immobilization using CDI as a coupling reagent.Firstly, monodisperse, hydrophilic and single-crystalline Fe3O4 paramagnetic(PMN) nanoparticles(NPs) with an average diameter of 100 nm were synthesized by a one-step solvothermal reduction method according to previous report with a little modification. Secondly, PMN Fe3O4@SiO2–OH NPs structure were obtained by encapsulating PMN Fe3O4 NPs in silanols via hydrolysis-condensation of tetraethyl-orthosilicate(TEOS). Thirdly, amine–functional PMN Fe3O4 NPs were obtained by APTES to bind covalently to the free OH groups at the surface of the PMN Fe3O4@SiO2 NPs. Then, α-ALDC was successfully immobilized onto the amino-functionnalized PMN Fe3O4 NPs with water-soluble CDI as the covalent reagent,. The factors affecting the α-ALDC immobilization and the properties of the immobilized α-ALDC were analyzed in detail.The resulting PMN Fe3O4 、Fe3O4@SiO2–OH、Fe3O4@SiO2–NH2 NPs nanomaterials were characterized by means of scanning electron microscope(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared(FT-IR) analysis. The measurements showed that the as-synthesis nanoparticles exhibited satisfactory paramagnetism, good water dispersity, high crystallinity and abundant amine groups on the core-shell. The α-ALDC loading onto the amine-functionalized PMN Fe3O4 NPs amount was found to 48.70±1.25 μg/mg. Compared with the free α-ALDC, the immobilized α-ALDC exhibited good thermal stability and pH stability. Although compared the free enzyme, the rate of immobilized α-ALDC is decrease and the Km is increase, the change of the kinetic parameters between the free α-ALDC and the immobilized α-ALDC was rather near, which indicate that the immobilized α-ALDC still had excellent catalytic capacity. After storage for 14 days, the immobilized α-ALDC retained 65.35% of its initial activity, while the activity of the free α-ALDC just retained 39.22% in the same conditions. After 8 consecutive reused, the residual activity of the immobilized α-ALDC still remained 67.47% of the initial activity. Herein, it has potential value in practical application.