Abstract:Iron oxide magnetic particles were prepared by chemical co-precipitation and the particles were cross-linked to magnetic chitosan microspheres. Afterwards, the magnetic chitosan microspheres were activated by surface modification with epoxy groups for subsequent xanthine oxidase immobilization. Using the epoxy density of the microsphere surface as an activation marker, optimal processing conditions were 40% (V/V) epichlorohydrin, 0.60 g/L sodium borohydrite, and 1.20 mol/L sodium hydroxide. Microsphere structural characterization showed that the iron oxide magnetic particles were successfully wrapped in chitosan and the surfaces of activated microspheres were surrounded by epoxy reactive groups. The diameter of iron oxide magnetic particles, the unactivated magnetic chitosan microspheres, and the activated magnetic chitosan microspheres were 2.16, 20.30, and 24.69 μm, respectively. After activation, xanthine oxidase was immobilized on the magnetic microspheres. Using enzyme activity as an indicator, the optimal immobilization process was conducted at 30 ℃ and pH 8.0 for 1 h. The optimum temperature and pH of the enzyme were 48 ℃ and 8.5, respectively. Moreover, the enzyme possessed good thermal, pH, and operating stability.
