Preparation Of Magnetic Microsphere And Immobilization Of BSA And Enzyme

Magnetic polymer microsphere is a novel functional material that has been developed resently. As the carrier of enzyme, cell and drug, it can be widely applied in many fields, such as bio-engineering, cytology, biomedical science and so on. Especially, the application of magnetic microspheres is of great interest for researchers in enzyme immobilization technology. As an important part of immobilized enzymes, the structure and properties of magnetic polymer microspheres affect the activities and operation stabilities of the immobilized enzymes greatly. Therefore, the preparation of carrier materials as well as its surface characteristics will be one of the most significant researches for the development of immobilized enzymes in the future.Here, the magnetic oxide (Fe₃O₄) was prepared by co-precipitation. Using ammonium persulfate as initiator, magnetic functional polymer microsphere P(St/AM/AA) was synthesized by the copolymerization of styrene, acrylamide and acrylic acid in aqueous ethanol medium. In this paper, external shape, size, superficial acrylic acid content of the microspheres and nano-particles of Fe₃O₄ were characterized. FTIR indicated that styrene, acrylamide and acrylic acid were successfully enfolded on the surface of the magnetic particles. SEM was employed to test the microspheres and the result showed that the average diameter was between 0.2-0.5μm. To investigate the effect of microsphere surface property on the immobilization of BSA, a series of microspheres with different hydrophobic/hydrophilic surface characteristics were prepared by adjusting molar percentages of monomers. The results showed that microspheres with different hydrophobicity/hydrophilicity had different immobilized ratio of BSA. Meanwhile, the effects of ester activation, coupling times, temperature and pH value on the immobilized ratio of BSA were discussed.Furthermore, these microspheres were used to immobilize lipase. It was found that the immobilized lipase possessed excellent ability of magnetic separation. When the molar percentage of St was 50 % and the immobilization time was 1 hour, the activity of immobilized enzyme was 2.1 U/mg. These results provided preliminary data for further study on the immobilization of lipase.