Study On Preparation And Properties Of Natural Polysaccharide Functionalized Magnetic Nanocomposites

Nowadays,nanomaterials as an innovation descipline plays an important role in modern research,among which magnetic nanomaterials are widely concerned because of their unique magnetic properties.However,some inevitable problems of materials,such as poor dispersion,easy agglomeration and instability,restricted to the practical applications.Therefore,development of an appropriate protection strategy is critical for its subsequent application.At present,numbers of studies investigate to improve the stability of magnetic nanoparticles through functional modification.According to the types of modified materials,it can be divided into three categories: inorganic material modification,organic functional molecular modification and high molecular polymer modification.Among them,high molecular polymers include natural and artifical high molecular polymers.Natural macromolecular polymers such as chitosan,gelatin,cellulose,starch and protein,generally present good solubility,biocompatibility,nontoxicity,and widely exist in nature.Moreover,the molecular surface contains a large number of functional groups such as hydroxyl groups and amino groups,which are further coupled to make them widely used in various fields.In this thesis,Fe₃O₄ nanoparticles were modified by two natural polysaccharides: mucilage polysaccharides from Dioscorea opposita Thunb?DOMP?and pullulan?Pn?,and the structural characterization and functional properties of the two prepared nanomaterials were subsquently investigated.The specific research content is divided into the following two parts:1.Fe₃O₄@DOMP prepared successfully was characterized by SEM,zeta-potential,FT-IR,XRD and VSM.Additionally,the catalytic degradation activity of Fe₃O₄@DOMP on basic fuchsin?BF?aqueous solution with different reaction temperature,time,p H and amount of H₂O₂ was investigated by using Fe₃O₄@DOMP as catalyst.Fe₃O₄@DOMP showed good catalytic activity for decolorization of BF in the presence of H₂O₂.The decolorization rate of the dye BF reached over 83% as the system obtained 2.5%H₂O₂ by stirring for 40 min at 60 ? in acidic condition?p H 6?.After 7 cycles of catalytic experiments,the catalytic activity was not significantly reduced.The materials were prepared and achieved to degrade the dye cyclically,quickly and efficiently.Fe₃O₄@DOMP was used as the carrier material to load the antibacterial drug cefalexin?CPX?.Fe₃O₄@DOMP-CPX was successfully synthesized,characterised,drug loading and release,and antibacterial activity were studied.Due to the electrostatic interaction betweenDOMP and CPX,CPX has the strongest absorption at p H 3.5,with 51.33% drug loading rate.According to the release curve,it can be found that approximately 88% of CPX at p H 7.4 in phosphate buffer released within 72 h.Specially,53% of the drug CPX was released explosively at a high rate in the first 2 h,followed by a gradual and sustained release for 70 h.Finally,in vitro antibacterial experiments revealed that the inhibitory activity of pure CPX and released CPX on SA was stronger than that of E.coli.And the inhibitory circle of pure CPX was greater than that of CPX released from drug carriers.2.Fe₃O₄@Pn was successfully synthesized by chemical co-precipitation.The Fe₃O₄@Pn was characterized by SEM,zeta-potential,FT-IR,XRD and VSM,and showed that Fe₃O₄@Pn has superparamagnetic properties.In addition,Fe₃O₄ accounted for 12.29% of Fe₃O₄@Pn by ICP method.After the nanomaterial was irradiated with a near-infrared laser at 808 nm with 3 W/cm2 power for 10 min,the aqueous dispersion of Fe₃O₄@Pn was heated to approximately 50 ?,indicating that the material has a good photothermal effect.Taking the temperature change curve as the index,the laser power and the concentration of the material were investigated at 808 nm.It was found that the heating rate and the maximum temperature increased with the increase of the laser power and material concentration.Furthermore,Fe₃O₄@Pn had better solubility and stability in solution than pure Fe₃O₄ nanoparticles.The material was completely dissolved and stably existed in the dispersion within 7 days,and its photothermal properties showed no significant difference.Finally,cell uptake,in vitro cytotoxicity and in vitro photothermal anti-tumor experiments were performed on Fe₃O₄@Pn,and the results showed that the material has less cytotoxicity to Hep G2 and A549 tumor cells.The activity of tumor cell was significantly reduced after near-infrared laser irradiation,and the material had good photothermal cytotoxicity,which provides a theoratical basis for the application of Fe₃O₄@Pn on photothermal anti-tumor.