Preparation And Properties Of Oligosaccharide-modified Magnetic Nanoparticles By Surface Initiated Controlled Polymerization

Magnetic nanoparticles （MNPs） have the advantages ofsuperparamagnetism, high surface area and good dispersibility. Therefore theyhave emerged as excellent materials in many fields, including immobilizedcatalysts, labeling and sorting of biological species, controlled drug delivery,and magnetic resonance imaging. Capping agents such as polymers, inorganiccompounds, and surfactants are always utilized to modify the surfaces of theMNPs, which make the MNPs stable, biocompatible and suitable forfunctionalizations and applications. Oligosaccharides are vital in life and alsohave extensive uses in both industry and science research. Cyclodextrin andmaltose are common in the family of oligosaccharides, owning specialstructures and properties of recognition. They are promising for applicationsin protein recognition, catalysis, and supramolecular assemblies. Thecombination of oligosaccharides and MNPs has attracted increasing attentionand the obtianed hybrid nanoparticles have properties of multifunction,magnetic separation and reuse. Surface initated controlled polymerization iswidely used to produce polymers with controlled molecular weight andnarrow distribution on the surface of solids. Herein theoligosaccharides-modified hybrid magnetic nanoparticles are synthesized bysurface initated controlled polymerization and the study on structure,feasibility and limitation in application are also investigated.In this thesis, nanoparticles Fe₃O₄@SiO₂-PGMA were synthesized by asequence of methods including thermal decomposition, sol-gel process andatom transfer radical polymerization （ATRP）. Cycledextrin and maltose weregrafted by ring-opening reaction of epoxy groups. Compared with the methodof direct surface graft, this approach by controlled polymerization has highergrafting amount of oligosaccharides. The feasibility of usingcyclodextrin-modified hybrid nanoparticles （Fe₃O₄@SiO₂-PGMA-CD） as separable immobilized catalyst and adsorbent was demonstrated. It was foundthe resulting Fe₃O₄@SiO₂-PGMA-CD could be used as catalyst insubstrate-selective oxidation of alcohols system and the catalytic efficiencywas close to pure CD of equal quantity. Meanwhile, compared withFe₃O₄@SiO₂-PGMA, the prepared particles appears remarkably dominantadsorption capacity in removal of bisphenol A from aqueous solutions. Themaltose-modified hybrid nanoparticles were used to immobilize maltosebinding protein fused heparinaseⅠ（MBP-HepA）, but the remains of copper inATRP contributed to the deactivation of enzymes. This system is limited inimmoblizing enzymes which are sensitive to copper. It is hopeful to solve theproblem by using AGET ATRP or eATRP. The results suggest the novelfabricatd nanoparticles could serve as multifunctional materials due to theirproperties of magnetic separation, reuse and facile modification.