Dissertation > Excellent graduate degree dissertation topics show

Preparation, Characterization and Bioapplication of Multifunctional Organic/Inorganic Polymer Microspheres

Author: GuoJia
Tutor: WangChangChun
School: Fudan University
Course: Polymer Chemistry and Physics
Keywords: magnetic nanoparticles semiconductor nanocrystals poly(N-isopropylacrylamide) chitosan poly(methacrylic acid) magnetic and luminescent microspheres thermosensitive microcapsules hydrothermal method precipitation polymerization sol-gel method
CLC: O631.3
Type: PhD thesis
Year: 2007
Downloads: 1305
Quote: 2
Read: Download Dissertation

Abstract


With the research development in the field of nano-biotechnology, smart microstructures based on organic/inorganic composite polymer microspheres have attracted more and more attention owing to their broaden applications in the biology labeling, biomolecules purifications, cancer therapy and so on. Based on the research background, this thesis has focused on the preparation of multifunctional microspheres, which involves in the following parts. Firstly, the polymer microcapsules with the movable magnetic cores were prepared, and FITC, which is a common organic dye, was attached to the surface of magnetic cores to give the microcapsules with fluorescent function. Secondly, the high-quality thiol-capped CdTe nanocrystals were prepared by the hydrothermal route. As the ideal probes, the as-prepared CdTe nanocrystals were utilized in the cell labeling. Thirdly, the multifunctional microspheres, combining three advances of photoluminescence, magnetic and temperature responses into one single entity, have been prepared. Finally, for improvement of the biocompatibility of multifunctional microspheres, a robust and facile one-pot approach was presented to prepare luminescent/magnetic chitosan-poly(methacrylic acid) microspheres embedded with Fe3O4 and CdTe nanoparticles. The results of each part are listed as follows:(1) Based on the previous work, the magnetic and thermoresponsive microspheres were prepared by coating the Fe3O4@SiO2 particles with the cross-linked poly(N-isopropylacrylamide) (PNIPAM) shells via precipitation polymerization. Since PNIPAM shells have a fast response to the temperature stimuli, the silica shells sandwiched by the PNIPAM shells and magnetic cores can be controllably etched by NaOH solution under the condition of an "open" or "close" state for PNIPAM shells, forming the PNIPAM microcapsules with mobile magnetic cores. For functionalizing the microcapsules, such smart hollow spheres also could serve as microreactors to introduce fluorescence property for them by post-modification of the residue silica on the cores. The organic dyes (FITC) were successfully coupled on the magnetite cores, resulting in forming the desired multifunctions of polymer microcapsules.(2) The high-quality thiol-capped CdTe nanocrystals were prepared by the hydrothermal technique. The growth and photoluminescence dependence of thiol-capped CdTe nanocrystals on the reaction conditions were systematically studied. Through the optimum conditions, including monomer-to-ligand molar ratio, two monomer ratios, precursor concentration and reaction temperatures, the maximum quantum yield of CdTe nanocrystals arrived up to 50%. Meanwhile, it was discussed that both of mono-thiol complexes and dual-thiol complexes significantly affected the nucleation and growth. In addition, it was well demonstrated that the synthesized CdTe nanocrystals have excellent photoluminescence properties and biology compatibleness in the cell labeling experiments. Although the as-prepared CdTe nanocrystals precipitated in a short period under the radiation of a UV lamp, the composite nanoparticles have the better stability with a silica-coating post-treatment. And the core-shell structures can be obtained by the second growth of silica shells on the post-treated CdTe nanoparticles, which is in favor of modification of biomolecules on the surface of silica for the targeted fluorescence probes.(3) Based on the excellent luminescence properties of CdTe nanocrystals, a rational design to prepare luminescent/magnetic composite microspheres with combining advances was discussed in detail. Firstly, the TGA-stabilized CdTe and silica particles can be co-precipitated by adding the Cd2+ ions through electrostatic interactions. Induced by it, magnetite nanoparticles (Fe3O4) were homogeneously incorporated into silica spheres using the modified Stober method, and thiol-capped CdTe nanocrystals were building up a luminescent shell on the surface of magnetic silica spheres. The obtained Fe3O4@SiO2@CdTe particles were coated by an outer shell of silica for avoiding the corrosion of CdTe shells, while providing a robust platform for the covalent binding of specific ligands. The luminescent/magnetic microspheres maintained the photostability and allowed for the surface modification. The subsequent design is that these microspheres were used as seeds to be covered by the crosslinked poly(N-isopropylacrylamide) (PNIPAM). We characterized the particle morphology, size distribution, thermosensitive, magnetic and luminescent properties. For the potential application of intracellular drug delivery, we also demonstrated PNIPAM-covered luminescent/magnetic microspheres were able to be taken up by CHO cells without inducement of any specific ligands. As a result, the designed multifunctional microspheres have much promise in detecting and treating cancer at its earliest stages due to their advances of magnetic targeting, excellent imaging, and drugs-carried matrices, and will be extended to in-vivo systems in the next experiments.(4) In the current study, a facile one-pot approach was presented to prepare luminescent/ magnetic chitosan-poly(methacrylic acid) microspheres with the biodegradable property. The different kinds of -COOH modified nanoparticles (Fe3O4 and CdTe) can be designed to be encapsulated within the chitosan(CS)-based colloids based on the complexation between CS and nanoparticles and subsequent polymerization of methacrylic acid, resulting in formation of the multifunctional organic/inorganic hybrid vectors. The composite microspheres have the narrow size distribution and regular spheric shape. Due to the favorable molar ratio of [methacrylic acid]:[glucosamine units] (4:1), the high envelopment of Fe3O4 nanoparticles allows the controllable magnetic content by calculating the feed amount. Highly luminescent CdTe semiconductor nanocrystals encapsulated in the vectors presented the excellent photoluminescence property as pH was adjusted from 5 to 11. This method would be extended to prepare the various kinds of organic/inorganic composite microspheres in a large scale on the basis of the complexation between CS and inorganic nanoparticles and subsequent polymerization of cationic monomers. Also, PLC/PRF/5 cells were chosen to assess cellular uptake of these multifunctional vectors. The result shows such vectors can significantly improve the rate and extent of transfect into cells under the short-term exposure to the applied magnetic field. This suggests that the luminescent/magnetic CS-based vectors have a great potential to be used as bioactive molecule carriers for gene therapy.

Related Dissertations

  1. Study on the Synthesis Bi3.25La0.75Ti3O12(BLT) Nanotubes and Nano Wires,TB383.1
  2. Cobalt Ferrite and Its Performance,O611.4
  3. The Research on Preparation Technology and Sintering Behavior of Rare Earth Aluminates (Dy3Al5O12、 NdAlO3、LaAl11O18),TB383.3
  4. Studies of High Refractive Index Materials Prepared by Nano ZrO2 and TiO2 Hybrid Silicone Epoxy Resin,TB383.1
  5. Preparation and Characterization of Al2O3/C Hybrid Aerogels and Al2O3 Aerogels,O648.17
  6. The Study on Properties of Desulfurization and Denitrification by Mn/Al Catalysts,X773
  7. Investigation into ZnO Thin Film Transistors Prepared by Sol-gel Method,TN321.5
  8. Sol - gel method p -type ZnO films,O484.1
  9. Storage-stable organic / inorganic hybrid polymers and their light-cured coating application,TQ630.4
  10. Nano- TiO_2 composite photocatalytic oxidation of elemental mercury removal experimental study,X51
  11. Finishing of Cotton Fabric with Vitamin E by Sol-gel Method,TS195.5
  12. Technology and Properties of vanadium oxide thin films,TB383.2
  13. Synthesis and Characterization of Sb-doped SnO2-(CeO2-TiO2) Composite Thin Films Deposited on Substrates for Antistatic Electricity and UV-Shielding,TB383.2
  14. Study on the Structure and Magnetic Properties of K-doped SnO2 and V-doped ZnO Diluted Magnetic Semiconductor Powders,TB383.1
  15. Sol-Gel Synthesis of Nano-sized Phosphors and Their Properties,TB383.1
  16. The synthesis of NZP family mesoporous phosphate materials,O643.36
  17. Catalytic Behaviors for Isobutene Selective Oxidation of MoVBi-AlPO4 Catalysts,O643.32
  18. Study on the NOx Storage and Sulfur Resistance of the Rare-Earth Containing La0.7Sr0.3Co1-xFexO3 Perovskite-type NOx Traps,O643.36
  19. Fabrication and Microwave Absorbing Properties of BaFe12-x (Ni (0.5)Cu0.5Zr)x/2O19 Ferrite,TM277
  20. Preparation and Properties of Li4Ti5O12 as Anode Material of Lithium-Ion Batteries,TM912
  21. Research on Synthesis and Modification of Li3V2(PO43 as Lithium-ion Battery Cathode Material,TM912

CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
© 2012 www.DissertationTopic.Net  Mobile