Study On Dual-targeted Magneticnanoparticles Applied In Cancer Treatment

Drug delivery systems (DDSs) are becoming more and more important, for playing a vital role to enhance the antitumor efficiency of chemotherapeutics. DDSs based upon superparamagnetic iron oxide nanoparticles (SPIONs) possess a specific function of magnetic targeting, by which the drug-loaded nanocarriers would be largely guided to the lesion location, such enhancing the drug concentration in tumor tissue and reducing the side effect to normal tissue. This dissertation aims to design a series of drug-loaded dual-targeted magnetic nanocarriers to evaluate their anticancer ability under dual-targeting ability both in vitro and in vivo.In chapter 2, according to the difference in the expression of folate receptor (FR)on the surface of different tumor cells, we put forward the innovation idea of controlling the content of ligand on the surface of nanocarriers to realize the optimal pairing of different tumor cell targets.We have combined SPIONs with FA modified Pluronic-F127 (PEO-PPO-PEO), and adjusted the FA content to prepare a series of different FA densities of magnetic nanoparticles SPIONs-F 127-FAx. Prussian blue staining, fluorescence imaging, frozen section, flow cytometry, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) have shown that the optimal FA density is from 2.3×1018 to 2.5×1018 per gram nanoparticles ((g-NPs)-1).The injected SPIONs-F 127-FAx on mouse breast cancer cells (4T1)-bearing BALB/c mice were found to be internalized by 4T1 cells through folate receptor(FR)-mediated endocytosis. The amount of uptake was positively correlated with the amount of the FA densities. Furthermore, this FR-mediated endocytosis can be enhanced by the external magnetic field.In chapter 3, we have designed a phenylo boric acid (PBA)-targeted and redox-responsive star-shaped magnetic micelle. This star-shaped magnetic micelles are formed by self-assembly of four-arm poly(ethylene glycol)(PEG)-poly(?-caprolactone) (PCL) copolymers with disulfide bonds as intermediate linkers. PBA was conjugated on one side of PEG to recognize the sialic acid (SA)receptors overexpressed on tumor cells. Anticancer drug doxorubicin (DOX) and SPIONs are simultaneously encapsulated into the hydrophobic cores by sonication.With lower value of CMC, this star-shaped magnetic DOX-loaded micelle(DOX@M-SPECLss-PBA) is more stable and more redox-responsive than the linear ones (DOX@M-PECLss-PBA). Both qualitative and quantitative analyses of the intracellular uptake of these star-shaped magnetic micelles with dual-targeting ability are performed in vitro by cultured with SA-positive tumor cells (human liver carcinoma cell line HepG2, human cervical cancer cell line HeLa) and SA-negative tumor cells (human breast adenocarcinoma cell line MCF-7, human non-small cell lung cancer cell line A549) in the presence or absence of a permanent magnetic field.In vivo biodistribution studies and anti-tumor effect are carried out in detail after being applied to the mouse-derived hepatocarcinoma cells (H22) bearing BALB/c mice model. Th results demonstrate that a great amount of DOX@M-SPECLss-PBA can be accumulated around the tumor tissues by the magnetic-guiding and in turn internalized by the tumor cells through SA-mediated endocytosis,leading to a high therapeutic efficacy to the artificial solid tumor. TUNEL and CD31 staining showed that the dual-targeted DOX@M-SPECLss-PBA group presented the highest level of cell apoptosis and no tumor angiogenesis, which confirmed its excellent therapeutic effect at tissue level.In chapter 4, mesoporous silica nanoparticles (MSN) were used for its high storage drug loading space to build a redox-responsive crosslinking nanocarrier MMSN-S2-PEI-PEG-PBA to solve the problem of early disclosure of drugs for DDSs.The drug release profile shows that the crosslinking structure are being "closed" in blood circulation and in the extracellular matrix but are being "open" via taking off the coating in cytoplasm under the high concentration of glutathione (GSH). Laser scanning confocal microscopy (CLSM) and z-stacked images illustrated that the final destination of the released drugs are in the nucleus. The frozen section by transmission electron microscope (TEM) proved that the internalization can be enhanced by the external magnetic field, thus killing more HepG2 cells. The anticancer therapy after 21 day illustrated that the inhibition rate of MMSN-S2-PEI-PEG-PBA with dual-targeting to H22-bearing BALB/c mice can reach 93.1% with good biocompatibility. H&E and CD31 staining showed that the dual-targeted MMSN-S2-PEI-PEG-PBA group presented the highest level of cell apoptosis and no tumor angiogenesis, which confirmed its excellent therapeutic effect at tissue level.