Investigation of bifunctional agent potential of tumor targeted silica nanoparticles

Cancer, is an abnormal and uncontrolled proliferation of body cells result of DNA damage or mutation. Pancreatic cancer is the most difficult to diagnose and treatment among cancer types. In addition, survival rate after diagnosis is very low. For this reason, early diagnosis is very important in the treatment of pancreatic cancer. In recent years, it has been seen that alone conventional treatment methods have not been effective. Instead of that, the application of combined treatment methods has increased. Also, using of nanotechnology in the medical field, the development of teranostic agents that enable both diagnosis and treatment has gained pace. In this thesis, mesoporous silica nanoparticles loaded with Zn phthalocyanine (ZnPc) and targeted with cetuximab antibody (MSNP5) were prepared and labeled with 131I radionuclide. ZnPc in nanoparticles allows to carry out the photodynamic therapy (PDT). However, by labeling nanoparticles with 131I, a teranuteric agent was formed which can be used in photodynamic therapy, nuclear imaging and/or nuclear therapy. The size, zeta potential and surface modification analyzes of the synthesized nanoparticles were performed with Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) devices. It was determined with the characterization that the encapsulation of Zn phthalocyanine and the surface modification were successfully carried out. At the same time, the hydrodynamic diameter of MSNP5 nanoparticles was determined to be 185.6±22.6 nm. Photodynamic therapy (PDT) is a non-invasive and an alternative therapy based on the photodynamic effect. In this thesis, we sought to determine the singlet oxygen (1O2) production, radiolabeling efficiency, intracellular uptake and in vitro photodynamic therapy potential of Zn phthalocyanine-loaded mesoporous silica nanoparticles [MSNP4 (without cetuximab) and MSNP5 (with cetuximab)] against pancreatic cancer cells. The 1O2 quantum yield (ΦΔ) value of ZnPc was found to be 0.60 in toluene. In vitro PDT studies were performed to determine the dark and phototoxicity of ZnPc and nanoparticles by using pancreatic cancer cells (MIA PaCa-2, AsPC-1 and PANC-1). According to the results, no dark toxicity was observed for ZnPc and nanoparticles in any cell line. However, MSNP5 nanoparticles showed quite high phototoxic effect, more pronounced than MSNP4 nanoparticles. The highest phototoxic effect was observed at an exposure of 40 J/cm2, namely 16±5%,13±3% and 5±1% cell viability at 5 µM concentrations in MIA PaCa-2, AsPC-1 and PANC-1 cells, respectively. It was observed from the intracellular uptake studies determined by Fluorometric methods that MSNP5 nanoparticles' uptake potential was higher than MSNP4 nanoparticles. Radiolabelling of the nanoparticles with 131I was performed according to the iodogen method. The radiolabeling efficiency of MSNP5 nanoparticles was found to be quite high (95.5±1.2%) in optimum conditions (pH 9 and 60 minutes reaction time). In addition to this, the highest intracellular uptake yields of 131I-MSNP5 in MIA PaCa-2, AsPC-1 and PANC-1cells were determined as 43.9±3.8%, %41.8±0.2 and %37.9±1.3, respectively at 24 hours incubation time. In vivo PDT studies were performed with tumor-bearing Nude mice (AsPC-1 pancreatic cancer cells). MSNP5 nanoparticles were subcutaneously administered under the tumor. For photodynamic therapy, 100 J/cm2 light dose was applied using 685 nm red laser light. Histopathological studies revealed that the ratio of necrosis in tumor tissue was higher in the treatment group treated with MSNP5 nanoparticles than in the control group. In conclusion, MSNP5 nanoparticles with targerting cetuximab antibody appear as suitable a theranostic agent for nuclear imaging/therapy and photodynamic therapy of pancreatic tumors. Keywords: Zn(II) phthalocyanine, mesoporous silica nanoparticles, cetuximab, singlet oxygen, photodynamic therapy.