The Preparation, Characterization And Primary Application Of Thermo-responsive Hydrogel Nanoparticles And Biodegradable Polymeric Nanoparticles

Polymeric nanoparticles of the diameter in the range of 1~1000nm hold great potential application in the field of biomedicine. There are some basic requirements for the application of polymer nanoparticles in biomedicine, such as narrow particle size distribution, high colloidal stability in aqueous dispersion, no pollution on nanoparticles surface and biocompatibility, but it is difficult to meet these requirements concurrently now. With the development of nanobiomedicine and bioengineering technology, the future developing trend of the polymer nanoparticles for biomedicine could be presented as follows:(l) there are reactive groups or ionizable groups on the polymer nanoparticle surface which can be used to link bioactive species to the nanoparticles by chemical bond or electrostatic attraction; (2) polymer nanoparticles can be responsive to external stimuli, especially in the bioenvironments; (3) polymer nanoparticles of hollow structure can load guest biomolecules of great volume or in large amounts; and (4) polymer nanoparticles of smaller size can play a special role, such as in getting across biological barrier, etc. The research interest of this thesis is concentrated on the synthesis, characterization and application of the polymer nanoparticles for biomedicine, and the research work was carried out to satisfy the basic requirements for their application in biomedicine and cater to their developing trend. Some results have been obtained as follows:(1) Monodisperse, surface-clean and colloidally stable poly(NIPAM-co-DMAEMA) hydrogel nanoparticles with tertiary amine groups on their surface were prepared by surfactant-free copolymerization of dimethylaminoethylmethacrylate (DMAEMA) as functional monomer,N-isopropylacrylamide(NIPAM) and methylene bisacrylamide(MBA). Their volume phase transition temperature was found to be around 32C, and the charge density on their surface is dependent on temperature and pH of the aqueous medium.(2)The establishment of the conventional theory of surfactant-free emulsion polymerization (SFEP) was based on the polymerization of hydrophobic monomers.The kinetic behavior of the SFEP system based on the hydrophilic monomers such as NIPAM, MBA and DMAEMA and temperature-sensitivepolymer(poly(NIPAM-co-DMAEMA)) was investigated in this thesis by the measurements of monomer conversion, particle size and swelling ratio against reaction time, especially by the analysis of the composition of water-soluble polymer produced in the polymerization process.(3)poly(NIPAM-co-DMAEMA) hydrogel nanopartilces are water-swollen colloid particles at room temperature, and their colloidal properties are different from ones of hydrophobic polymer colloidal particles. The effect of several electrolytes on their colloidal properties such as hydrodynamic size, volume phase transition temperature, zeta potential and colloidal stability was studied here. It was found that the hydrodynamic diameter of all hydrogel nanoparticles was found to decrease upon increasing the ionic strength of the dispersion medium, and the ability of the anions to deswell the copolymer microgel has agreement with their position in the Hefmeister series. The volume phase transition temperatures of the hydrogel nanoparticles decrease as NaCl concentration increases, but NaSCN has no the effect, and this phenomena was explained from the view point of thermodynamics. The zeta potentials on the hydrogel nanoparticles surface are reduced by the electrolytes, and the effect becomes more significant as DMAEMA content in the nanoparticles increase. DMAEMA unit in poly(NIPAM-co-DMAEMA) is helpful to the colloidal stability of the hydrogel nanoparticles. The ability of the electrolytes to destabilize the nanoparticle latex is consistent with the Hefmeister series.(4)Monodisperse thermo-responsive polyNIPAM nanocapsules were prepared by template approach. The hollow structure of the nanocapsules was confirmed by TEM, SEM and AFM. The cavity size of the nanocapsules can be controlled by the templ...