Date

2013

Author

Khodadust, Rouhollah

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Nanotechnology is a promising alternative to overcome the limitations of classical chemotherapy. This technology has enabled the development of particles with nano sizes that can be fabricated from a multitude of materials in a variety of compositions. These nanoparticles include; quantum dots (QDs), polymeric nanoparticles, gold nanoparticles, magnetic nanoparticles and dendrimeric nanoparticles. In first section of this study, superparamagnetic iron oxide nanoparticles were synthesized by coprecipitation method. The nanoparticles were modified with aminopropyltrimethoxysilane and then were coated with PAMAM dendrimer. The detailed characterization of synthesized nanoparticles was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering, and vibrating sample magnetometer (VSM) analyses. TEM images demonstrated that the DcMNPs have mono-disperse size distribution with an average particle diameter of 16 ± 5 nm. DcMNPs were found to be superparamagnetic through VSM analysis. The synthesis, aminosilane modification, and dendrimer coating of iron oxide nanoparticles were validated by FTIR and XPS analyses. Cellular internalization of nanoparticles was studied by inverted light scattering microscopy, and cytotoxicity was determined by XTT analysis. Results demonstrated that the synthesized DcMNPs, with their functional groups, symmetry perfection, size distribution, magnetic properties, and nontoxic characteristics could be suitable nano-carriers for targeted cancer therapy upon loading with various anticancer agents. Poly (I: C), which is a synthetic double-stranded RNA, have significant toxicity on tumor cells. In the second part of this study, Poly (I:C) for the first time was efficiently bound onto the surface of different generations of newly synthesized PAMAM dendrimer coated magnetic nanoparticles (DcMNPs) which can be targeted to the tumor site under magnetic field. Poly (I:C) activation was achieved in the presence of EDC and 1-Methylimidazole. Binding of Poly (I:C) onto DcMNPs was followed by agarose gel electrophoresis. Acidic reaction conditions were found as superior to basic and neutral for binding of Poly (I:C). In addition, having more functional groups at the surface, higher generations (G7, G6, G5) of PAMAM DcMNPs were found more suitable as a delivery system for Poly (I:C). In vitro cytotoxicity study on different breast-cancer cell lines demonstrated that Poly (I:C)-bound DcMNPs are more effective than free Poly (I:C). However, highest cytotoxicity of Poly (I:C)-bound DcMNPs was observed in Doxorubicin resistant MCF7 cells. Therefore, Poly (I:C)-bound DcMNPs seem to be a suitable for the treatment of Doxorubicin resistant cells. In the third part of the study, Doxorubicin loading, release, and stability on nanoparticles (NPs) were analyzed. Doxorubicin could be loaded on G2, G3 and G4DcMNPs with 97% efficiency. The release studies demonstrated that low-generation NPs obtained in this study have pH-sensitive drug release characteristics. G4DcMNPs, which released most of the drug in lower pH, seems to be the most suitable generation for efficient Doxorubicin delivery. In vitro cytotoxicity study on Doxorubicin resistant MCF7 cells demonstrated that application of Doxorubicin-loaded DcMNPs are five times more effective than free Doxorubicin. Therefore, application of Doxorubicin-loaded G4DcMNPs may help to overcome Doxorubicin resistance in MCF7/Dox cells. On the contrary, G2 and G3DcMNPs would be suitable for the delivery of drugs such as Vinca alkaloids and Taxenes, which show their effects in cytoplasm. The results also provide new insights in the development of pH-sensitive targeted drug delivery systems to overcome drug resistance during cancer therapy. In the last section of the research Poly (I:C) binding on Doxorubicin-loaded G4DcMNPs at pH 6 and pH 6.5 were studied. Results demonstrated that Doxorubicin loading on lower generation of DcMNPs make them more suitable for Poly (I:C) binding. Loading of Doxorubicin into the cavities of G4DcMNPs increases the binding efficiency of Poly (I:C) to the surface functional groups up to ten fold. Amine groups at the surface of DcMNPs are the main reasons for the toxicity of these nanoparticles in blood. Binding of Poly (I:C) to amine groups on the surface of Doxorubicin-loaded DcMNPs will decrease the cytotoxicity of the system in the blood and increase its biocompatibility. TEM results demonstrated that Poly (I:C) binding on DcMNPs increases their dispersivity too. When we compared the in vitro cytotoxicity of Doxorubicin, Poly (I:C) and Poly (I:C)-bound Doxorubicin-loaded DcMNPs, it was observed that Poly (I:C)-bound Doxorubicin-loaded DcMNPs show the highest cytotoxic effect on Doxorubicin resistant cells. The results demonstrated that Poly (I:C)-bound, Doxorubicin loaded- G4DcMNPs may be a useful delivery system by the biocompatibility of the complex in blood stream, and by their high toxicity inside tumor cells. These nanoparticles can also be a suitable targeted system to overcome the Doxorubicin resistance in cancer cells.

Subject Keywords

Cancer, Dendrimers in medicine., Doxorubicin., Nanoparticles.

URI

http://etd.lib.metu.edu.tr/upload/12616563/index.pdf
https://hdl.handle.net/11511/22856

Collections

Graduate School of Natural and Applied Sciences, Thesis