Preparation Of Magnetic Chitosan Microspheres And Study On Immobilized Lipase

The polymer magnetic microspheres are a new type of function material with wideapplications in biochemical industry, cytology, and biomedical engineering. Magneticchitosan microspheres which have been concerned deeply by people were due to theirexcellent biocompatibility, high stability and low toxicity for living body. Also owing to theabundant active groups on surface, chitosan magnetic microspheres can be chosen asimmobilizing carrier. The groups on surface were activated, and then conjugated tobiomolecules such as proteins, antibodies, peptid, DNA or RNA. As a new type of magneticfunctional material, chitosan magnetic microspheres have a broad application perspective inthe fields of enzyme fixation, immunity testing, cell separation and targeted drug, etc.（1） In this paper, the Fe₃O₄nano-particles were prepared by co-precipitation method andmodified by oleic acid. And then using the emulsification cross-linking technique to preparecomposite chitosan magnetic microspheres, which contains dispersed Fe₃O₄nano-particles byadding proper amount of glutaraldehyde into chitosan solution. The results demonstrated thatthe concentration of chitosan solution, NaOH amount and stirring speed of the suspensionmedium were the most effective parameters for the size, size distribution, morphology andmagnetism of magnetic chitosan microspheres. Finally, the preparation conditions areoptimized. The SEM, IR and DLS results indicated that95.4%of the magnetic chitosanmicrospheres concentrated in the332.7nm, the diameter of the microspheres was about348.5nm and dispersion coefficient was0.283. There are abundant hydroxyls, amino and alcoholhydroxyl groups on surface and can be conjugated to biomolecules.（2） Lipase was immobilized onto magnetic chitosan microspheres by cross-linking withglutaldehyde, the optimum conditions of immobilization were investigated, and the physicaland chemical properties, activity recovery, thermal stability and storage stability of lipasewere studied. The result showed that the optimum immobilization time，the optimum pH, theoptimum temperature of immobilized lipase and the optimum lipase amount were respectively7h,8,50℃a nd10mg/100mg （lipase/microspheres）.As compared with free lipase, the thermal and acid-basic stabilities of immobilized lipase were increased appreciably. After5recycle of hydrolyzation, the activity of immobilized lipase remained82.6%of its initialactivity.