Magnetism/NIRF Nanoparticles Via Iron Mediated ATRP: Preparation And Application Investigation

ATRP was widely applied in preparation of various materials including pure organicpolymers as well as inorganic/organic hybrid materials which were often achieved bysurface modification of inorganic substrate. Bifunctional material consisting of magnetismand fluorescence has been one of the hottest research topics recently because of itscharming performance. Anumber of strategies for preparing such materials were proposed,nevertheless, preparation of such bifunctional material with application-satisfyingperformance is not an easy work. We, here, study preparing such materials through ironcatalyzed ATRP for consideration of convenient introduction of ATRP initiator on substratewhich facilitates surface modification with polymers, and of improvement of stability ofthe as-obtained products. Detail information about this thesis is as follows:(1) Avariety of transition metals were successfully developed as ATRP catalyst duringits development. Iron, among them, shows unique charm compared to the other transitionmetals because of its non-toxicity and biocompatibility, thus possessing promise inpreparing biomedical related materials. However, iron display inferior activity and poorapplicability towards hydrophilic and functional monomers comparing with the other twofrequently used transition metal catalyst, Cu and Ru. In chapter IV, anenvironment-friendly iron catalyst system was successfully developed in water for theactivator generated by electron transfer for atom transfer radical polymerization (AGETATRP) of water-soluble monomer poly (ethylene glycol) monomethyl ether methacrylate(PEGMA) for the first time. Here, FeCl3·6H2O was used as the catalyst,tris-(3,6-dioxaheptyl) amine (TDA-1) as the ligand, and ascorbic acid as the reducing agent.A kinetic study indicated that the polymerization of PEGMA was a “living”/controlledprocess, where molecular weight increased linearly with monomer conversion. A lowermolecular weight distribution (Mw/Mn<1.5) was maintained. The “living” features of thereaction were further confirmed by a chain-extension reaction. The nontoxic andbiocompatible characteristics of the iron catalyst facilitate its mediated polymerization to be used in the preparation of functional polymer materials for biomedical use and thedeveloped catalyst systems were applied successfully in the preparation of bifunctionalmaterials consisting of magnetism and NIR fluorescence (NIRF).(2) Bifunctional materials with magnetism and fluorescence exhibits applicationprospect in biomedical area because of its combinational advantages of high spatialresolution and sensitivity originating from magnetic resonance imaging (MRI) andfluorescence technique respectively. In chapter V, bifunctional nanoparticles (NPs) capableof emitting NIR fluorescence and generating superpapramagnetism under externalmagnetic field were prepared via AGET ATRP of water-soluble PEGMA and glycidylmethacrylate (GMA) using biocompatible iron as the catalyst on the surface of silicacoated iron oxide (Fe3O4@SiO2) NPs. The prepared NIR organic dye was anchored ontothe polymer shell by chemical reaction afterwards. The different stages of surfacemodification were approved by employing different characterization techniques such asTEM, XRD, XPS, VSM and FT-IR etc., and the properties of the final NPs werethoroughly studied. The ability as dual model imaging agents for MRI and fluorescenceimaging was investigated, indicating a competitive candidate as imaging contrast agents.(3) Multifunctional materials attract wide attention of researchers worldwide becauseit combines different advantages of each individual part of the entirety, therefore it couldbe applied in vast application occasion. In chapter VI, iron-catalyzed AGET ATRP ofPEGMA and2-((ethoxycarbonothioyl)thio)ethyl methacrylate (ETCEMA) followed byreduction were performed to modify Fe3O4@SiO2NPs for introducing thiol groups on thesurface of the NPs. Gold NPs and two NIR organic dyes with different quantum yield werecovalently fixed into the polymer shells independently to afford magnetic NPs withsurface-enhanced Raman spectroscopy (SERS), NIR fluorescence imaging andphoto-thermal therapy (PTT) functionalities, respectively. In addition, all of these NPs areable to display as contrast agents for MRI because of the existence of the paramagneticFe3O4cores. This novel strategy helps building one new approach to fabricatemultifunctional nanomaterials from the same precursor.