Preparetion And Characteration Of Multi-responsive Magnetic Nanospheres

In recent years, environmental responsive materials were applied for drug deliverywhich gives rise to much attention of scholars. Among the many enviroumental responsivematerials, redox responsive, pH responsive and magnetic responsive materials wereespecially favoured by scholars. This is due to the glutathione (GSH) concentration and pHdifference between intracellular and extracellular, and materials with magnetic responsiveare easy to be targeted by magnetic field orientation, which are also easily separated fromthe solution. All of these make redox responsive, pH responsive and magnetic responsivematerials have good application prospect. Compared with the traditional single responsivematerial, multiple responsive nano-drug carriers have more advantages as intelligencematerials.Organic/inorganic nanocomposite particles are of great interest based on the fact thatthe inorganic components enhance the optical, electrical and magnetic properties while theorganic offers the processing and biocompatibility. The introduction of stimuli-responsivefunctional polymers can also extend application of composite nanosphere. And it can beprepared through self-assembly under mild reaction conditions without the usage oforganic solvents.Based on the aforementioned background, SPION and dextran were adopted forprepare organic/inorganic nanocomposite. SPION/dextran composite nanospheres withtriple-responsite properties were prepared by self-assembly, and its structure, morphologyand response were characterized.In chapter1, Superparamagnetic iron oxide nanoparticles (SPION) were prepared bychemical co-precipitation method and then modified with sodium citrate. The magneticnanoparticles were characterized by X-ray diffraction (XRD), Fourier transfprm infreared(FT-IR) and Zeta potential analyzer and so on. The results showed that SPION surface wassuccessfully carboxyl-functioned. In chapter2, epoxy-activated dextran (DEX-EPO) was synthesized via themodification of dextran with an excess quantities of1,4-butanediol diglycidyl ether (BDE).And amino-functionalized dextran (DEX-NH2) was synthesized by ring-opening reactionsof the epoxy groups in the side chains of DEX-EPO, using difunctional cystaminedihydrochloride as the initiator and sodium carbonate as a buffer solution. The structure ofthe products was characterized by1H-NMR and FT-IR. The results showed thatamino-functionalized dextran with terminated amino groups in the side chain weresuccessfully synthesized.In chapter3, a simple approach was presented to prepare composite nonaspheres withtriple-responsive properties. The composite nanospheres were prepared via electrostaticinteraction between the citrate groups of SPION-COOH and the amino groups ofDEX-NH2. By tuning the mass ratio of the DEX-NH2and SPION-COOH, the size of thecomposite nanospheres could be controlled. The DEX-H2/SPION-COOH compositenanospheres were used to encapsulate hydrophilic drugs (DOX). And DOX-loadednanospheres were characterized by transmission electron microscopy (TEM), X-raydiffractometer (XRD), and vibrating sample magnetometer (VSM)，Zeta potential analyzerand so on. In vitro release was conducted in simulated cancerous environment conditionssuch as a high GSH concentration and mild acid. The cytotoxicity of nanosphere andDOX-loaded nanospheres was evaluated on KB cells using MTT assay. The resultsdisplayed that nanospheres exhibited good biocompatibility. In contrast, DOX-loadednanospheres showed a significantly dose-dependent cytotoxicity on KB cells.