Preparation Of Different Topologic Structure Copolymer-modified Superparamagnetic Fe₃O₄Nanoparticles And Their Bioapplications

Over the past decade, magnetic nanoparticles (MNPs) have been intensively pursued not only for their fundamental scientific interest but also for rich technological applications. Due to their remarkable magnetic properties and low toxicity, superparamagnetic iron oxide nanoparticles (SPIONs)(usually Fe3O4and Fe2O3) have certainly been and still are the most intensively investigated. In this dissertation, a fashionable route based on the combination of atom transfer radical polymerization and click chemistry is provided to introduce different topological structure copolymers onto the surfaces of Fe3O4nanoparticles and the properties of the surface-modified nanoparticles are in detail investigated. The contents are as follows:1. The dendritic-linear block copolymer-modified surperparamagnetic iron oxide nanoparticles (SPIONs), which consist of a Fe3O4magnetic nanoparticle core and a dendritic-linear block copolymer, the focal point polyamidoamine-type dendron-b-poly(2-dimethylaminoethylmethacrylate)-b-poly(N-isopropylacrylamide)(PAMAM-b-PDMAEMA-b-PNIPAM) shell, were prepared by the combination of Fe3O4nanoparticles were prepared by a high-temperature solution phase reaction in the presence of iron(Ⅲ) acetylacetonate [Fe(acac)3], oleic acid and oleylamine. Then progargyl focal point PAMAM-type dendron (generation2.0, denoted as propargyl-D2.0).with four carboxyl acid end groups as a cap displaced the oleic acid and oleylamine on the surfaces. Subsequently, an initiator for ATRP was introduced onto the propargyl-D2.0-modified Fe3O4nanoparticle surfaces via click chemistry with2’-azidoethyl-2-bromoisobutylate (AEBIB). PDMAEMA and PNIPAM were grown gradually from nanoparticle surfaces using two-step copper-mediated ATRP. Finally, a crosslinking reaction between PDMAEMA block with1,2-bis(2-iodoethoxy)ethane (BIEE) was used to stabilize the nanoparticles and reverse aggregation. The modified nanoparticles were subjected to detailed characterization using FT-IR, DLS, XRD and TGA. Magnetization measurements confirmed the characteristic superparamagnetic behavior of all magnetic nanoparticles under room temperature. In addition, doxorubicin (Dox) as an anticancer drug model was loaded into the dendritic-linear block copolymer shell of the modified nanoparticles, and subsequently the drug release was performed in phosphoric acid buffer solution (pH7.4) at25℃or37℃. The results verify that dendritic-linear block copolymermodified nanoparticles as a drug carrier possess thermosensitive drug release behaviors. Furthermore, a methyl tetrazolium (MTT) assay of Dox-loaded dendritic-linear block copolymer-modified nanoparticles against Hela cells was evaluated. The results show that the modified nanoparticles can be used for drug delivery.2. The water-soluble dendritic-linear-brush-like triblock copolymer, polyamidoamine-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate)(PAMAM-b-PDMAEMA-b-PPEGMA)-grafted superparamagnetic iron oxide nanoparticles (SPIONs) were successfully prepared by click chemistry and two-step copper-mediated ATRP method. The macroinitiators were immobilized on the surface of Fe3O4nanoparticles via effective ligand exchange of oleic acid with the propargyl-D2.0containing four carboxyl acid end groups, following a click reaction with AEBIB. PDMAEMA and PPEGMA were grown gradually from. nanoparticle surfaces using the "grafting from" approach, which rendered the SPIONs soluble in water and reversed aggregation. The modified nanoparticles were systematically studied via TEM, FT-IR, DLS, XRD, NMR, TGA and magnetization measurements. DLS measurement confirmed that the obtained dendritic-linear-brush-like triblock copolymer-grafted SPIONs had a uniform hydrodynamic particle size of average diameter less then30nm. MTT assays indicated that the dendritic-linear-brush-like triblock copolymer-grafted SPIONs had excellent biocompatibility against NIH3T3cells. Furthermore, Dox was loaded into the dendritic-linear-brush-like triblock copolymer-grafted SPIONs, and subsequently the drug releases were performed in phosphoric acid buffer solution pH=11.0,7.4or4.7at37℃. The results verify that the dendritic-linear-brush-like triblock copolymer-grafted SPIONs poccess pH-responsive drug release behaviors. The Hemolysis Assay of copolymer-grafted SPIONs was estimated for the biological applications. The Dox dose of the loaded and free drug required for50%cellular growth inhibition were2.72and0.72μg/mL, respectively, according to MTT assay against a Hella cell line in vitro. Furthermore, The stability of copolymer-modified SPIONs under physiological conditions was evaluated through red blood hemolysis assay, which also served as a model to assess cell membrane toxicity. Therefore, on the basis of its biocompatibility and drug release effect, the modified SPIONs could provide a charming opportunity to design some excellent drug delivery systems for therapeutic applications.