Abstract:

Abstract
BACKGROUND: As carriers of enzymes, cells and drugs, magnetic polymer microspheres have been widely used in the fields of bioengineering, cytology, and biomedicine.
OBJECTIVE: To prepare the magnetic polymer microspheres characterized by small particle size, good dispersion, strong magnetic response, safety, and non-toxicity.
METHODS: Magnetic chitosan microspheres were prepared by reverse phase suspension process using Fe3O4 as core, paraffin as dispersed medium, Span-80 as emulsifier, and glutaraldehyde as cross-linking agent. The effects of factors including crosslinking time (0, 20, 40, 60, 80, 100, 120, 150 and 180 minutes), reaction temperature (20→50 °C, 30→60 °C, 40→70 °C, 50→80 °C), the concentration of chitosan (0.01, 0.02, 0.03, 0.04, 0.05 g/mL), Fe3O4/ chitosan mass ratio (1∶1, 1∶2, 1∶3, 1∶4), the amount of glutaraldehyde (8-10 mL), the
amount of liquid paraffin (40, 60, 80, 100 mL), and stirring speed (0-2 000 r/min) on the properties of magnetic chitosan microspheres. The morphology, particle size, dispersion, and magnetic responsiveness of magnetic chitosan microspheres were characterized.
RESULTS AND CONCLUSION: The optimum conditions for preparing magnetic chitosan microspheres were as follows: starting with glutaraldehyde as crosslinking agent, the reaction was performed at 40 °C for 1 hour and then at 70 °C for 120 minutes. The concentration of chitosan was 0.02 g/mL, the mass ratio of Fe3O4/chitosan was 1∶2, the dosage of liquid paraffin was 80 mL, the stirring speed was 1 200 r/min, and the dosage of glutaraldehyde was 8-10 mL. Magnetic chitosan microspheres had strong magnetic properties under the applied magnetic field and had good suspension stability in the natural state. The Fe3O4/chitosan composites were spherical, and the nanoparticles were encapsulated in the microspheres, which were core-shell structure. The surface of the microspheres was smooth and monodisperse. The magnetic chitosan microspheres prepared had a diameter of 1-15 μm, which is beneficial to the dispersion and magnetic separation of the microspheres in the reaction system.

Key words: magnetic microsphere, polymer microsphere, biomaterials, chitosan, immobilized carrier, magnetic response, reverse phase suspension polymerization, Fe3O4